Which language gives better career options: TCL or PERL?

Question: I am an engineer with 1.5 years of experience in Test Automation  in Perl. I am getting chance to work in TCL. I am little worried about my career growth. I don't know whether TCL also has the same growth perspective as Perl or which language has a better market value.
Comment: The best career option is to Learn both.
Answer: For Test Automation purposes, it's always been my belief that once you know 2 scripting languages, you are in very good shape.
Being comfortable with 2 languages means you know how to automate, and that you know how to learn a new scripting language.  As a hiring manager, I will be able to assume that you could easily pick up another new language as needed.
So don't worry about the career growth associated with any one particular language.  In future years neither Perl nor TCL will likely be the high-demand choice anyway - it may well be something that hasn't yet been invented.
Comment: Agreed, Joe.  I certainly hope neither Perl nor TCL is the high-demand choice!
Comment: Thanx Joe for ur comment. I will keep this in mind and work more efficiently
Comment: Good luck, NItesh. Be really good at one or two test automation languages, learn not just how to write code but how to apply it best for testing purposes - and you will go far!
Answer: The programming language you pursue should be predicated on

The technology space you are most interested in (web, platform, mobile, etc)
The market trends in your area (e.g. what language skills are employers most looking for)

 On a side note, I don't know why some people get so focused on a particular "programming langauge." Instead, I recommend learning good programming concepts, data structures, design patterns, etc. Once you understand these concepts moving between languages is relatively easy. During interviews you may be asked a coding question and the answer doesn't necessarily depend on which language you use as much as how you choose to solve the problem (even with pseudo code). If you are a good problems solver, employers will usually give latitude in coming up to speed with a new language. Of course, some employers are simply looking for people to put together basic script-lets that attempt to emulate user events and these employers will likely put more emphasis on a particular language.
Comment: I share your concern about focus on a particular language; however, keep in mind the job listings tend to prioritize particular tech skills. And you often have to get past the HR drone hurdle to be considered for a job; this entails having just enough experience to convince them you "know" this-or-that language.
Answer: Welcome to SQA, Nitesh.
In my market, what you tested and how you tested it would be at least as relevant as what programming language you used.  I think having a variety of experiences will be more useful to you than specializing in one thing.  However, your market might be different.  For example, if you work in short-term contracting projects, expertise in a specific language may be more important because the employer may not want to pay your salary while you get up to speed on a new language.
In any case, 1.5 years is not a lot of experience.  You have time to experiment and make mistakes.
Answer: My advice to someone beginning to do test automation is to look at the organization or company you are working with and if you see that they are using language X or tool Y, then you need to at least learn enough about X and Y to make a contribution.  There are so many languages and tools out there that it cannot hurt to learn any of them.  In the case of TCL versus Perl, I would recommend you focus on what you're doing (or trying to do) and then ask yourself how much "local expertise" is there - if everyone knows Perl, go with it.  If they all know TCL, go with that... but as another answer stated, it's more important to exercise the product and automate your test processes to find more bugs sooner, etc.  If you're still using Perl and TCL but the rest of the organization is using python or ruby or Test Complete or WinRunner or whatever... you might want to move in that direction.  Of course, it depends on the organization too, as it may be that they really need Perl developers but everyone only knows Java, etc. in which case it could be beneficial to be the guy that knows Perl real well.  But between TCL and Perl, I'd have to recommend Perl, since it's bound to be in use in more potential future job situations, and you can learn object-oriented concepts and a lot of other marketable skills.  Then, of course, the ultimate answer is "What is my employer paying me to do?"  If they are paying you to learn X, learn X, and don't complain.  There's a lot of folks out there who would love the chance to get paid to learn something marketable.  So, go with Perl, if your boss says to master Perl.
Answer: either is ok ,  i think. If there is enough libraries available in your company for TCL, it's OK.
The language is not important. What you should learn is the test methodologies and the way you are thinking.
It is more easier for you to learning a new programming language than to have good understanding on testing.


Repeating email notifications

Question: Can email notification sounds be repeated on an HTC Thunderbolt until the message is opened?
Answer: There's a APP that allows you to set custom ring tones and notification sounds. To your particular case, this APP allows you to loop endlessly when you receive an SMS.
SMS Sounds Plus paid
SMS Sounds free
On the APP, you can check the loop when you are in the ringtone picker.
Answer: To the best of my knowledge, no but...
I have created a solution to this problem but it only works while you have a computer, any old computer should work, on the net.
It works by creating calendar appointments for emails. You can do it for any email but that results in way too many notifications for me. I use a collection of Gmail filters.
By creating a Gcal appointment, you get to use programs aimed at calendar notifications. They tend to be much richer than email notification apps. You can search on Google Play for such apps. I can only vouch for Calendar Snooze, the one that I use.
You can read more about Gmail2Gcal or simply test the app my sending an email to firstname.lastname@example.com. The demo will send you an email with additional information.
Gmail2Gcal is open source and free for your use. You can use issue page, found on Gmail2Gcal's main page if you have problems. I'll try to support it as best I can.

Repeating email notifications


2005 chrysler neon clunking noise from front end

Question: My neon has 125000km.  Recently started clunking especially over speed bumps - replaced the the lower bushes and shock absorbers but still continues.  Related is a Brrrrrr sound on hard acceleration from low speed.  Any one give me ideas as to what to try next?  thanks
Comment: Can you identify even generally where the sound is coming from? eg Left, Right, Centre. This would help - and is the vibration from the same area as the clunk?
Answer: Could very well be your motor mounts, if indeed your bushings and shocks needed replacement. The rubber on motor mounts tends to harden and crack and in turn you will get more vibration, movement and noise from the engine. I'd check that before going any further.
Answer: Two things I can think of are the mounts, and loose brakes. When you press the brakes the calipers would smash on the wheel. I have seen this on calipers missing one bolt. The strut mounts could be bad/loose and this would also cause the noise. Also, check you rear drive axle unless you know for sure the sound is coming from the front. You mentioned acceleration, how are your engine mounts?
Answer: I don't know about the clunking noise (I'm hearing something similar in my rear), but the other sound you're describing sounds very much like your exhaust is blowing. Probably just a small hole now, I'd work my way from the back of the car and check for serious rust in the exhaust.


What do gerbes and complex powers of line bundles have to do with each other?

Question: We all know how to take integer tensor powers of line bundles.  I claim that one should be able to also take fractional or even complex powers of line bundles.  These might not be line bundles, but they have some geometric life.  They have Chern classes, and one can twist differential operators by them.  How should I think about these?  What do they have to do with gerbes?
Answer: Complex powers of line bundles are classes in $H^{1,1}$, or equivalently sheaves of twisted differential operators (TDO) (let's work in the complex topology). This maps to $H^2$ with $\mathbb{C}$ coefficients, or modding out by $\mathbb{Z}$-cohomology, to $H^2$ with $\mathbb{C}^\times$ coefficients.  The latter classifies $\mathbb{C}^\times$ gerbes, ie gerbes with a flat connection (usual gerbes can be described by $H^2(X,\mathcal{O}^\times)$).  Note that honest line bundles give the trivial gerbe.
In fact the category of modules over a TDO only depends on the TDO up to tensoring with line bundles --- ie it only depends on the underlying gerbe, and can be described as ordinary $\mathcal{D}$-modules on the gerbe. Or if you prefer, regular holonomic modules over a TDO are the same as perverse sheaves on the underlying gerbe. This is explained eg in the encyclopedic Chapter 7 of Beilinson-Drinfeld's Quantization of Hitchin Hamiltonians document, or I think also in a paper of Kashiwara eg in the 3-volume Asterisque on singularities and rep theory (and maybe even his recent $\mathcal{D}$-modules book).
B&D talk in terms of crystalline $\mathcal{O}^\times$ gerbes rather than $\mathbb{C}^\times$ gerbes but the story is the same.
Comment: I took the liberty of TeXifying this answer.
Comment: (for the BD reference, you want 7.10 I think, the crystalline theory of D-modules on stacks).
Answer: To any homomorphism of Lie groups $\phi: G \to H$, and any principal $H$-bundle $P$ over a space $X$, you can associate what I like to call the "gerbe of liftings," namely the stack over $X$ whose objects over $f: Y \to X$ consist of a principal $G$-bundle $Q$ together with an isomorphism $Q_\phi \cong f^* P$.  Here $Q_\phi$ denotes the associated $H$-bundle.  This stack is nothing but $BG \times_{BH} X$.  (Note that it carries a tautological $G$-bundle, pulled back from $BG$.)  If $\phi$ is surjective with kernel $K$, this is a $K$-gerbe with trivial band.  Morally speaking, its isomorphism class comes from the image in the connecting homomorphism $H^1(X,H) \to H^2(X,K)$, and this is literally true if $K$ is abelian.
To relate this to the question, consider the case where $G = H = {\bf C}^\times$ and $\phi$ takes the $k$th power.  Then $K = \mu_k$, a cyclic group of order $k$. The gerbe of liftings measures the failure of a given line bundle on $X$ to be a $k$th power.  (For example, if it is not, then there will be no objects over $f =$ id.)  It coincides with the root stack introduced by Cadman.
It is tempting to regard the $k$th root gerbe $B$ of a line bundle $L$ as $L^{1/k}$.  But it is a gerbe with structure group $\mu_k$, not a bundle with structure group ${\bf C}^\times$.  Topologists should think of it as like an orbifold over $X$, but with orbifold structure spread out all over.  How, then, is $B$ related to a $k$th root of $L$?  As noted above, $B$ carries a tautological line bundle --- and its $k$th power is the pullback of $L$ from $X$!
Moral: fractional line bundles on $X$ can be realized as bona fide line bundles on $\mu_k$-gerbes over $X$.
Answer: If L is any line bundle on a space (scheme, whatever) X, A is any (additive) abelian group, and a an element of A, there is a natural construction of an A-gerbe $L^a$ as follows.  By definition, $L^a$ should be a "sheaf of categories", or stack (not algebraic) on X, and here are its categories of sections.  Identify L with its total space, which is a $\mathbb{G}_m$-bundle on X, and for any open set U in X, let $L^a(U)$ be the category of all A-torsors on $L|_U$ whose monodromy about each fiber of $L|_U \to U$ is a.
One can check that this really is a gerbe: it is locally nonempty, since if L is trivial over U, you can write $L|_U = \mathbb{G}_m \times U$ and then pull back the unique A-torsor on $\mathbb{G}_m$ with monodromy a.  It has a natural action of A-torsors on X, given by pulling up along the bundle map $L \to X$ and tensoring.  And this action is free and transitive, since the difference of two a-monodromic torsors on $L|_U$ has trivial monodromy on each fiber and therefore descends to X.
Why do I call this $L^a$?  Suppose that $L = \mathcal{O}_X(D)$ for a divisor D, where for simplicity let's say that D is irreducible of degree n; then L gets a natural trivialization on $U = X \setminus D$ having a pole of order n along D.  As shown above, this induces a trivialization $\phi$ of $L^a$ on U, and if we pick a small open set V intersecting D and such that D is actually defined by an equation f of degree n, then we get a second (noncanonical) trivialization $\psi$ of $L^a$ on V.  You can check that the difference $\psi^{-1} \phi$, which is an automorphism of the trivial gerbe on $U \cap V$, is in fact described by the A-torsor $\mathcal{T} = f^{-1}(\mathcal{L}_a)$, where $f \colon U \cap V \to \mathbb{G}_m$ and $\mathcal{L}_a$ is the A-torsor of monodromy a.  Since f has degree n, $\mathcal{T}$ has monodromy na about D.  Thus, it is only reasonable to say that the natural trivialization $\phi$ has a pole of order na, which is consistent with the behavior of the trivialization of L itself on U, when raising to integer powers.
What does this have to do with twisting of differential operators?  Suppose we have some kind of sheaves (D-modules, locally constant sheaves, perverse sheaves; technically, they should form a stack admitting an action of A-torsors).  On the one hand, one could mimic the above construction of $L^a$ to describe a-monodromic sheaves on L, and this is what is often called twisting.  On the other hand, there is a natural way to directly twist sheaves by the gerbe $L^a$ without mentioning L at all (that is, you can twist by any A-gerbe).  The procedure is as follows: a twisted sheaf is the assignment, to every open set U in X, of a collection of sheaves on U parameterized by the sections of $L^a(U)$, and compatible with tensoring by A-torsors.  Of course, since if $L^a(U)$ is nonempty this is the same as giving just one sheaf, this is sort of overkill, but the choice of just one such sheaf is noncanonical whereas this description is canonical.  These collections should be compatible with the restriction functors $L^a(U) \to L^a(V)$ when $V \subset U$.  It is an exercise to reader to check that this is the same as the other definition of twisting :)
Man, you asked the right question at the right time.  My thesis is all about this stuff.
Comment: Ah, I see.  Actually, eight months ago was good too :)
Comment:  If I'm not mistaken this gerbe is the pushforward of the Chern class $c_1(L)\in H^2(X,Z)$ to $H^2(X,A)$ under the homomorphism $a:Z\to A$.
Comment: Yes, that's right.  There are a couple of ways to describe it but this one is the most directly related to the definition (that I knew) of twisting.
Comment: Where by "at the right time" you mean eight months ago?  Really, it's Michael Thaddeus who added a new answer at the right time.
Answer: Is this anything more than thinking about the Chern class of the line bundle in H^1(\Omega^1), which can of course be multiplied by any complex number? For example, if you have an elliptic curve E, a complex number alpha and two line bundles L and L' of the same degree, is there any difference between alpha x L and alpha x L'?
Answer: Cadman defined a root stack for line bundles on a scheme, and variations on that theme such as Cartier divisors, in
Cadman, Charles, Using stacks to impose tangency conditions on curves. Amer. J. Math. 129 (2007), no. 2, 405--427.
Maybe this construction was known as folklore beforehand, in any case for a line bundle it gives you a flat gerbe, and might do the job for you for rational powers.


Importing MIDI into Reason 5

Question: I have just upgraded from Reason 3 to Reason 5 (I know, I'm behind the times but I like programs that work).
In Reason 3, I would import a MIDI file (which I create with an external sequencer) then create instruments. Then I would assign the tracks to instruments. Should I need to change the tracks (a frequent need!), I could delete the tracks without deleting the instruments. After reimporting the MIDI file, I would again assign the tracks to the already existing instruments.
In Reason 5, importing a MIDI file causes a combinator to be created automatically for every track. I can set up the combinators or replace them directly with other instruments. Should I wish to change the tracks, I can delete them without deleting the instruments, but when I reimport the MIDI, new combinators are created.
How I can assign the tracks to the already existing instruments?
Answer: You can move-it by drag and drop sequencer clips between tracks. Use "Song Position Pointer tool" to set start point of clips that you wanna move in the beginning of clip.

Importing MIDI into Reason 5


Good reference for homology of $K(\mathbb{Z}, 2n)$?

Question: The homology algebra $H_*( K(\mathbb{Z},2n); \mathbb{Z})$ contains a
divided polynomial algebra on a generator $x$ of dimension $2n$.
I suppose I could read through the Cartan seminar for a proof, but I'm hoping
someone knows of a nice simple argument for this fact.
Comment: @Thomas, well, "Cartan seminar, year 7, exposé 11" is quite precise!
Comment: Jeff -- me too. Otherwise, it is year 7, expos\'e 11. The presentation there is very careful, but it's a bit difficult to follow unless one starts at the beginning of the year.
Comment: @algori: Do you have a more precise reference?
Answer: We need to do three things: (1) show that the homology contains a polynomial algebra, (2) show that powers of the generator are sufficiently divisible, and (3) show that torsion doesn't interfere.
Let me repeat Hatcher's path through (1), since we need the particular generator to show that it is divisible. According to Dold-Thom (Hatcher 4.K; cf Dold-Kan1), a model for $K(Z,m)$ is the free commutative monoid on pointed2 $S^m$. According to James (Hatcher 4.J), the homology of the free associative monoid $JS^m$ on $S^m$ is a polynomial algebra on one generator in degree $m$. Thus there is a map of monoids $JS^m\to K(Z,m)$ so its map on homology is compatible with the ring structure. It is easy to see (eg, by the Serre spectral sequence) that the rational homology of $K(Z,m)$ is the signed-commutative algebra free on a generator in degree $m$, so this map is a rational isomorphism if $m=2n$.
Now for step (2), where we divide the James class by $k!$. If we restrict to words of length $k$ in these monoids, the affect of imposing commutativity is to quotient by the $k$th symmetric group. This piece of the James construction is a pseudo-manifold representing the class in degree $nk$ which is the $k$th power of the generator. The action of the symmetric group is generically free, so this cycle has multiplicity $k!$ when it lands in $K(Z,2n)$. Thus it is divisible. In other words, choose a fundamental domain for the action of the symmetric group on the $k$th filtration of the James construction. This yields is an $kn$-chain which when symmetrized is the whole of the $k$th filtration, and thus a cycle. Projecting it to the quotient is an alternative way of symmetrizing, so it is a cycle for $K(Z,2n)$.
I will leave step (3) as an exercise. What this shows so far is that the integral homology hits the divided power algebra in the rational homology, but the canonical choice of the divided element should make it plausible that these divisions are the right choices, ie, $x^{(k)}x^{(l)}=\binom {k+l}k x^{(k+l)}$.
1If one accepts the fragment of Dold-Kan of the agreement of the two things one can do to a simplicial abelian group (1) homology of (either) associated chain complex and (2) the homotopy groups of the geometric realization; then a version of Dold-Thom follows trivially. Indeed, the very definition of simplicial homology is the free abelian group (ie, simplicial group) on the simplicial set.
2 by "the free (commutative) monoid on a pointed set," I mean that we impose on the free object the relation that the basepoint is the identity for the monoid.
Comment: I think this sounds like the kind of answer I was hoping for.  Thanks!
Answer: Do you want to know the integral homology?
If you are happy with homology with coefficients in $\mathbb{F}_p$, the best way to compute (and describe) the homology of Eilenberg-MacLane spaces is the technique developed in a paper by Ravenel and Wilson (MathSciNet). See also Wilson's "sampler" (MathSciNet). They used the structure called Hopf ring (a collection of Hopf algebras equipped with other operation) to describe $\{H_*(K(\mathbb{Z},n);\mathbb{F}_p)\}_{n\ge 0}$ as a whole.
The point is they worked in homology instead of cohomology so that we can use
$$ K(\mathbb{Z},n)\times K(\mathbb{Z},m) \longrightarrow K(\mathbb{Z},m+n)$$
to "generate" $H_*(K(\mathbb{Z},n);\mathbb{F}_p)$ from $H_*(K(\mathbb{Z},m);\mathbb{F}_p)$ for $m<n$.
It turns out the Hopf ring structure is compatible with the Eilenberg-Moore spectral sequence and we obtain the Hopf algebra structure on the homology of Eilenberg-MacLane spaces easily. It is also important their technique works for generalized homology theories. In fact, their motivation was to compute the Morava $K$-theory of Eilenberg-MacLane spaces.
Comment: I really do want integral homology.
Answer: I am not sure if this qualifies as a simple argument, but to me it is very nice. I did not get the reference in the comments above - so sorry if this is close to that. I dont have an exact reference since this is pieced together from several places.
Let $A$ be any abelian group. Let $X=X(A)$ be the simplicial set defined by:
$X_p = \{$colorings of the $n$ faces of the standard $p$ simplex by elements in $A$ such that when restricted to any $n+1$ face the sum with alternating sign of the colorings of the faces are $0\}$
The face and degeneracy maps are defined by restriction and pull-back (the latter introduces 0's when an $n$ face is degenerate.
with this $X_p$ is a single point when $p < n$ (a single empty coloring), $X_{n}=A$, $X_{n+1}$ is "relations", and $X_p$ for $p>n+1$ is given by its restrictions to the $n+1$ faces. I.e. it is $n+(1 or 2?)$ co-skeletal. This means that its geometric realization $\lvert X \rvert$ is a $K(A,n)$.
In fact this is a simplicial group by adding the colorings, and $X(A)\times X(A)$ is isomorphic as simplicial groups to $X(A\oplus A)$ by definition.
To simplify we now use $A=\mathbb{Z}$ and to understand this product on the $\mathbb{Z}$ span of the simplices, I will assume some familiarity with the Eilenberg-Zilber operator, which appears naturally in the product of simplicial sets. Using this we describe the power map
(1) $H_n(X(A),A)^{\otimes k} \to H_{kn}(X(A)\times\cdots\times X(A),A)=H_{kn}(X(A^{\oplus k}),A) \to H_{kn}(X(A),A)$
$H_n(X(A),A)$ is a single $A$ and it is generated by the $n$ simplex $\alpha$ colored by $1$, the tensor product $\alpha^{\otimes k}$ can when mapped to the middle term of (1) be written as the sum
$\sum_{\sigma \in S(k,n)}$ sgn$(\sigma) \beta_{\sigma}$
where $S(k,N)$ is the permutations on $\{1,\dots,kn\}$ which preserves the order of the $k$ sequences SEQ$\strut_i=\{in+1,\dots,(i+1)n\}, i=0,k-1$ (a generalized shuffle), and $\beta_{\sigma}$ is the associated product of degenerations defined by
(2) $\beta_{\sigma}=(\sigma_1^* \alpha)\times \cdots \times (\sigma_k^* \alpha)$,
where $\sigma_i$ is the order preserving surjective map from $\{0,\dots,kn\}$ to $\{0,\dots,n\}$ defined by increasing one precisely when a number is in the image of $\sigma$ restricted to SEQ$\strut_i$.
In the case of $n$ even it is clear that the sign of the permutations $\sigma$ which simply permutes the sequences SEQ$\strut_i$ (without intertwining them) has sign 1 and thus we may act on the $\sigma$'s in the sum by these with out changing the sign, this action, however, permutes the factors in (2), but when mapped to the last factor in (1), they are the same, so the image of the sum in (1) is divisible by $k!$.
To see injectivity of the product one can see that the power map is injective on rational homology by using a Hopf-algebra argument as in section 3.C of Hatchers book.
Comment: As you say, this is nice;
but it is not as simple as I was hoping for.
Answer: For a reference, you might see this paper of Birgit Richter.  A rough outline follows:
Since $X = K(Z,n)$ can be made a commutative topological monoid per Ben Wieland's answer, its singular chain complex $C_*(X)$ is made into a commutative and associative differential graded algebra via the commutative associative Eilenberg-Zilber shuffle product $C_*(X) \otimes C_*(X) \to C_*(X \times X)$ composed with the multiplication on $X$.
The formula for the shuffle product is slightly involved when you iterate it, but essentially: to multiply $\alpha_1 \cdots \alpha_n$ with $\alpha_i$ of degree $k_i$, you sum over all ways to divide a set of size $\sum k_i$ into subsets of size $k_1, \cdots, k_n$ of a product of certain degeneracy operators, depending on the subdivision, applied to the chains $\alpha_i$.  (With signs.)
If all the $\alpha_i$ are equal and in positive even degree $k$, then the signs don't interfere and we are summing over all ways to divide $nk$ into $n$ equal pieces of size $k$.  However, because the chains are now equal we get the same term if we simply permute the pieces of size $k$, and so each term appears in the sum at least $n!$ times.  (Note that $k > 0$ is necessary here in order for these permutations to actually give different subivisions.)  As a result, the n-fold product chain is divisible by $n!$.
Comment: This is basically Thomas' answer except on the chain level, where you don't have to worry about interference from torsion.
Comment: I really meant mine on the chain level - i write that $\alpha$ is a simplex generating (meant to say a simplex representing a generator).
Answer: Nice question.  Unfortunately the answer I posted an hour ago is wrong because I switched the structures of homology and cohomology for the James reduced product. It is the cohomology that is a divided polynomial ring while the homology is a polynomial ring.
Comment: Yes, that has tantalized me for some time.


Using a list view to filter another list view

Question: I have two lists; List A and List B. List B has a lookup column to List A.
I want to filter List B based on the value in the field that looks up A. This can of course be done using the default OOTB column filtering. However, I want to create a view/webpart that does this for me using URL filters. Since List A will change from time to time, I won't hardcode the URL's, I want to create a special filtering view of List A I can add to List B's view.
I've managed to do what I'm trying except for one issue. When I filter List B using URL filters (e.g. http://server/site/Lists/Links/AllItems.aspx?FilterField1=DocumentID&FilterValue1=650) it will filter both List A's and List B's views simultaneously. I only want the filtering to be applied to List B. The solution to this could be to add View as an URL attribute, e.g. ?View={GUID}&FilterField1=DocumentID&FilterValue1=650. This will work, but then I need a reference to the View ID of List B from my List A xslt (to apply to the URLs).
Frankly, I could even live with the GUIDs being hardcoded, e.g. that I set them in List B's CAML and in the XSLT of List A. However, they just don't "stick", they are overridden during deployment.
Another option could be to render List A as "unfilterable". if you have any suggestions I'm all ears.
Answer: Use a "Filters » Query String (URL) Filter" webpart on a custom page.
Comment: I don't have an enterprise licence


Can I insulate over 1/2 in. styrofoam?

Question: We have a rec room (basement) from the 60's that we are redoing.  Currently on the outside walls, they have 1 x 2 studding then 1/2 inch white styrofoam then vapour barrier.  WE are wondering if we can remove the plastic vapour barrier and stud over what is there with 2 x 4 then use Roxul Comfort batts?  Wasn't sure if there would be an issue with putting the Roxul over the styrofoam.  As this is the old type of styro I doubt if would have much, if any R value but does anyone know for sure
Answer: 1/2" Styrofoam will give you about R-2.0 to R-2.5 insulation. The best you can expect from any reasonable 1/2" material is R-3.0 to R-3.5, so it's not too bad for what it is. Obviously you will get much better R-values from much thicker material.
Vapor barriers should only be installed closest to the warm side of any insulating assembly and nowhere else. While Roxul is largely water resistant, you still do not want water condensing inside the insulation, it reduces the insulating value and promotes mold growth. You also do not want to block any moisture that gets this far from being able to escape by having additional vapor barriers farther in from the warm side.
So you must remove the existing vapor barrier. Never install insulation on the warm side of a vapor barrier. Unfortunately, styrofoam also serves as a vapor barrier, so you should remove it as well before installing the Roxul. Better to give up that R-2 than risk moisture being trapped in the Roxul. The one and only vapor barrier should be on the warm side of the Roxul.
Note that this is assuming there is no risk of water ingress through the basement walls. If there is any risk, you should be using an insulation impervious to water such as XPS, and some positive drainage scheme must be in place behind the insulation to allow water to drain to a sump for removal.

Can I insulate over 1/2 in. styrofoam?


Can I intercept and interpret the autofocus signals sent to the lens?

Question: I would like to use a Nikon D80 body with a reflecting telescope as the lens to take pictures of bright/textured objects in the night sky (e.g. the moon). The D80 has autofocus capabilities; the telescope does not. From various web searches, I've become aware of people who have fitted motors to their telescope lenses to allow for electronic focusing. However, my question is: if I was able to intercept the SLR body's signals sent to the "lens" is there a standard by which I could interpret them into focal plane movements that could be used to drive the focus motor?
Answer: Yes and no. It's possible, but there is no standard. The lens mount communication protocol for each brand is a proprietary secret. The closest to open is the Four Thirds system, which is still secret but you can buy into it. For everything else, reverse engineering is the only option. (That's how lens makers like Sigma produce AF lenses for other systems.)
It's possible that some DIY reverse-engineering work has been published online, but I'm not aware of any.
Comment: I did consider micro 4/3rds for its openness, but as you say it isn't free.
Answer: I know this is just an idea, but if you get your hand on a broken lens that is compatible with your camera and that still has an active motor, or at least an active driver chip, you may be able to rather intercept the signals that are sent to the motor, that may be easier to reverse engineer.
Consider that there may be lenses that work with just DC motors, Servo motors or piezoelectric motors (I don't know is Ultrasonic motors are a kind on themselves or fit into the piezoelectric category).
By "broken" I mean a lens that has lost its glass, or that has a broken transmission or somehing like that that is still electrically fine.
Comment: This is a cool idea. Check with places such as Lensrental.com, they  go through a lot of lenses, I bet they have some broken ones that are unfixable. Note, they do fix a ton of broken things, rental life is hard on gear.
Comment: I am concerned that the autofocus system requires a fully functioning lens (both electronically and optically) in order to trigger the signals one would be trying to reverse engineer.


Trouble using WUBI to install Xubuntu. Can anyone help?

Question: I am a extremely curious person so I wanted to try Linux, however I have very little knowledge on such a thing. I have successfully installed Ubuntu with WUBI on a newer computer, so I wanted to try it on a slightly older computer. When I installed Ubuntu 12.04 LTS to was incredibly, no sorry UNBEARABLY slow and so I started to think of using 'lightweight Ubuntu flavors' like Xubuntu or Lubuntu (both 12.04 LTS). Using WUBI I tried to install both but both failed the first time they booted up. They would at first load up then work through things like coping the files. Here is where the problem starts. A little over half way through copying files it crashes and comes up with a black screen with white writing and a blurry line through the middle (horizontally). Also the capslock light starts flashing nonstop.I don't have the slightest idea what to do and I am in desperate need of help.
How can I install Xubuntu or Lubuntu using WUBI
and
How can I install (and run of course!) successfully without any of the above problems to occur?
Any answer would be highly appreciated.
Please help me!
(Thank you in advance)
Drew
Answer: First, have you tried booting into the live DVD and selecting the 'Try Ubuntu' option?  If this fails, then 12.04 is not appropriate on your hardware.  Wubi installations do run more slowly that native installations.  The symptoms you are getting suggest that 12.04 is not compatible with your video controller, but booting into 'Try Ubuntu' will test this for you.  If you want to come back to us, please give hardware information including your video controller spec and which version of Microsoft Windows you are running.
Comment: Wubi questions are here if you want to take a look: http://askubuntu.com/questions/tagged/wubi


How to create effective experiences/emotion to change punctured tyres for a car?

Question: Keeping climate, location and gender into consideration, the mechanism of changing punctured tyres have not seen greater changes? Still it takes energy,effort and time, moreover awful experience around it! Cars & Passengers are interlinked by aesthetics, dashboard and comfort. But what has been done to core problem areas when you are stuck in a cyclone and mending a car tyre with high turn-around time to fix -Is'nt that a strategical experience point for businesses? Your thoughts?
Answer: Certainly there are great tools to accelerate the process, but those are not suitable to take with you in the car. If you also consider that the wheels have to be securely attached to the structure, there are not many options.
Although, there are some patents for products not commercialized yet or for systems like the ones in use for race cars, those involve traction or locking instead of pure friction. But those are complex and expensive mechanisms that are not available for your average car.
It will be great to have something like the quick release of bicycles, but it seems far in the futures for most cars.
And situations like the one you mention are not common for the majority of users, so it's not specially interesting, even as an option. How much extra would you pay for a system that lets you change the tire in a short time instead of the actual normal time and effort?
Also, even if you consider punctured tires, they happen less and less, so for the very few occasions that it happens, it doesn't look to be worth the money invested in solving the situation from the rim perspective.
But, there are some interesting works with the tire itself, to make it self repair and to deflate more slowly.
Answer: There actually have been made changes over the last years. In my new car (as of 2010) there were no spare tyre, just a tyre inflator. I'm still looking suspicious at it while taking the car for a longer spin, but it works (I'm told).
Works in a few seconds and you don't have to change tyres, getting dirty and oily, saying things to the surroundings you later regret. Just inflate - and drive to the nearest tyre shop.

Tyre Inflator


On the location of zeros of L functions from modular forms

Question: I understand that the Mellin transform of a modular form is expected to satisfy RH when it is an eigenform of all Hecke operators, in which case it has an Euler product. Now about when the form is not an eigenform: Is it known a case where the zeros are all in the critical strip?
Answer: When it is not a Hecke-Eigen form, the Hecke L-series connected with the modular form does not have an Euler product. However it can still be written as a linear combination of Hecke L-series that have Euler-products. Thus the situation will resemble the case of linear combinations of Dirichlet L-series. In particular we can use joint Voronin universality to obtain $\gg T$ zeroes in any strip $1/2<\sigma_1<\Re(s)<\sigma_2 < 1$, $-T < \Im(s)< T.$ These results follows from the analytic properties of the Rankin-Selberg zeta-function (which gives "independence results" for Hecke eigenvalues of primes attached to different cusp forms). You should be able to find results of this kind in Steuding's SLN "Value Distribution of L-functions".
Also the results of Davenport-Heilbronn for the Hurwitz zeta-function can be proved, i.e. For any $\epsilon>0$ there exists $\gg T$ zeroes with $1<\Re(s)<1+\epsilon$ and $-T < \Im(s) < T $.
Stronger results corresponding to results of Karatsuba, Bombieri, Hejhal and Selberg for Dirichlet L-function that holds close to the critical line likely also holds. I think the russian school (Irina Rezvyakova) has proved results in this direction.
Comment: Am I right that you only give an argument for RH is not true for that kind of function? This is not the question.
Comment: In the first section I state that. In the second section I mention the analogue of the Davenport-Heilbronn theorem that there are zeroes for Re(s)>1. It should follow in a similar way as the case of the Hurwitz zeta-function for rational parameter.
Answer: Perhaps I don't understand the question, but in its current form the answer is no.
A general modular form of fixed weight will be a linear combination of Hecke eigenforms of that weight. The Gamma factors will imply that there are trivial zeros outside the critical stripe.
But I guess you have an L-function with symmetric functional equation in mind? The Mellin transform is a linear operator, so the result is a linear combination of Hecke L functions times a Gamma factors. Assuming that you find some combination non-vanishing out the complement of closure of the critical stripe via some estimates I don't know, you will need a good argument for non-vanishing on the boundary of the critical stripe, where the function is expected to be universal.
What is the motivation for the question?
Comment: I was thinking if the following may be true:
if L is the Mellin transform of a modular form , and L has all its zeros in the critical strip, then the modular form is an eigenform.
Comment: Okay, that it was Johan Andersson's answer seems to imply.


Why does randomness work in numerical algorithms?

Question: There are successful numerical algorithms that involves a sequence of random numbers, like Monte Carlo methods or simulated annealing.  I can follow the lines of proofs of their convergence, and actually see them work. However I sometimes find it paradoxical that it is useful to deliberately add an unpredictable factor into a process, while we have the opportunity to have the full control over it.  Could you give an intuitive explanation for this?
Comment: It might be a good idea to rephrase the title of the question; as is, it's kind of overly broad...
Comment: Perhaps "Why use randomness in numerical analysis?" or "How does randomness work in numerical analysis?"
Answer: If one had infinite computing capacity, then you would be right that randomness would not be useful (unless an adversary also had access to randomness - see below), and it would always be better to maintain full control of one's parameters.  ("God does not need to play dice".) However, our computing capacity is limited, and randomness offers a way to stretch that capacity further (though it is an important open problem to quantify exactly how much randomness actually stretches our capacity; see the discussion on P=BPP in other comments).
Let's give a simple example.  Suppose one is playing the following game with a computer.  This computer uses some (deterministic) algorithm to generate 1000 "bad" numbers from 1 to 1 million.  Meanwhile, you pick your own number from 1 to 1 million.  If you pick one of the bad numbers, you lose; otherwise, you win.  You get to see the computer's algorithm in advance.
With infinite computing capacity, you have a strategy which is 100% guaranteed to succeed: you run the computer's algorithm, find all the bad numbers, and pick a number not chosen by the computer.
But there is a much lazier strategy that requires no computing power: just pick a number randomly, and one has a 99.9% chance of winning.
[Note also that if the computer used a randomised algorithm instead of a deterministic one, then there is no longer any 100% winning strategy for you, even with infinite computing power, though the random strategy works just fine.  This is another indication of the power of randomness.]
Many randomised algorithms work, roughly speaking, by reducing the given problem to some version of the above game.  For instance, Monte Carlo integration using a set of points to sample the function might give satisfactory levels of accuracy for all but a tiny fraction  of the possible choices of sample points.  With infinite computing capacity, one could locate all the bad configurations of sample points and then find a configuration which is guaranteed to give a good level of accuracy, but this is a lot of work - more work, in fact, than just doing classical numerical integration.  Instead, one takes the lazy way out and picks the sample points randomly.  (Well, in practice, one picks the points pseudorandomly instead of randomly, because true randomness is very hard to capture by a computer; this is a subtle issue - again related to P=BPP - that I don't want to get into here.)
Answer: Imagine you are looking for a structure with certain properties, within a universe of possible structures. It is sometimes (perhaps "often"?) the case that the structures you can actually explicitly build form a tiny fraction of that universe, but on the other hand they all fail to have the property you seek.
So, if you wanted to write a program to generate "good" structures, you could either work really hard and find a way of explicitly constructing them, or you could simply choose a structure at random (assuming you have a good way of doing this), check if it "good", and repeat if not.
A classic example: expander graph. It's ridiculously easy to create one by just choosing a graph at random. Explicit constructions, on the other hand, are far from trivial.
It is an open problem whether this really helps, from the perspective of complexity theory. People have found clever "derandomization" schemes that essentially convert a random algorithm to a deterministic one. It is still not known if what you can do in a reasonable time with randomization (RP) is really more than what you can do in a reasonable time without access to randomness (P), and I think most people believe that it's not - in other words, randomness doesn't really "work".
Comment: Shouldn't that be "work" in the asymptotic sense?
Comment: Of course - the last paragraph is all about asymptotics, and ignoring all constants and powers. The recent proof that primality testing can be done in polynomial time is extremely interesting from a theoretical perspective, but in practice I suspect most implementations still use the random variants which are simpler and more efficient.
Comment: Interesting! And thanks for the clarification
Answer: I'm not sure whether this is the kind of answer you are looking for, but in some cases, you are guaranteed a certain probability of success if you choose your parameter randomly, but there is no known procedure to choose a good parameter. The best example of this is Primality testing, where you can prove that at least 1/2 of the possible witnesses for primality work.
Answer: In addition to various reasonable general things described by other people, you might want to learn about the formalization of the notion of randomness: the BPP complexity class.
It's interesting that most computer scientists believe P = BPP. This equality means that (at least theoretically) one can rewrite all algorithms using randomness as the algorithms not using randomness. But it's not proven.
For example, existence of strong pseudorandom generators (link to my MO question) implies P = BPP. But that is in itself a big problem.
So it's very hard to prove the theorem eiher way. Of course, when people tried to prove P = BPP or its converse, they had lots of explanations as to why their theorem is true. None of those explanations is completely successful but they could answer your question about the idea of randomness.
Comment: I think most computer scientists believe that P = BPP is very likely.
Comment: Seconding what Rune said -- it's known that if NP-complete problems are either very easy or very hard, P = BPP. What's generally believed (and I want to say actually known, although I can't find the reference) is that DTIME(n^c) is strictly contained in BPTIME(n^c) for some (and in fact probably most) c > 1.
Comment: Thanks! I missed it, even though I knew it from the answer to my other question. Corrected now.
Answer: This isn't a complete answer, but I've found it useful to think in this way in the past. Part of the reason that randomness is "better" -- though, again, certainly not all of it -- is just due to the way that we quantify how good or bad algorithms are.
So it should be a familiar fact that there are algorithms that do really well most of the time, but which don't do well in the worst case. Two everyday examples are quicksort and the simplex algorithm. The reason for this is that these algorithms aren't as sensitive as they could be to certain kinds of changes in the data, so an adversary who's trying to make your algorithm run slow has a lot of "room to work." But a uniform distribution (or something morally equivalent, or lots of distributions that arise in the real world) isn't adversarial.
So what random algorithms let you do is take a single instance of a problem, and instead sample from a distribution of a bunch of instances of another, related problem, so you get to work (to a certain degree) with average-case complexity instead of with worst-case. Another way of thinking about it: your adversary from before could create hard instances since he knew what your algorithm would do in advance, and he had sneaky ways of making the problem harder without your algorithm noticing until it was too late. But now he doesn't know what the algorithm will do -- it's random! So creating a hard instance seems pretty much hopeless.
Most of the rest of the advantage of random algorithms -- the "real advantage," if you will -- comes from what Alon said above. There are certain desirable properties which seem to be correlated with "high-complexity" strings or distributions, which by definition can't be reached quickly and deterministically. This is closely related to the efficacy of the probabilistic method in combinatorics.
Comment: For example, using the probabilistic method one can prove theorems of the form "a random graph G has property P with probability q," but in several cases it's not known how to find large graphs with property P deterministically.
Answer: There are alternatives to random methods that try to keep the advantages of random methods and improve on them.
Quasi-Monte Carlo methods are deterministic.  They depend on sequences that are more evenly distributed than truly random sequences.  (Ironically, they look more like what most people expect from randomness. True randomness looks too clumpy to untrained eyes.  See these graphs.)
For some numerical integration problems, QMC methods outperform MC methods.  Art Owen published some papers on this.  QMC works best when a the effective dimension of a problem is lower than the full dimension.  For example, a problem that depends 500 variables but 20 of those variables are much more important than the rest.
QMC methods don't easily provide error estimates.  To get around this, sometimes people combine QMC with MC.  They may take a QMC grid of points and jiggle it randomly.  On some problems, this hybrid approach works better than either approach separately.
Answer: There are many reasons that randomness is associated with some numerical algorithms. An example I can think of off the top, that is of particular interest to me, is optimization through genetic algorithms (which involve a significant amount of randomness, I can give further description if necessary, for now I'll keep things succinct).
These algorithms are often used for optimization problems where the space of solutions is either
A) very large
B) hard to compute known successful optimization algorithms, either because of high dimension or because the algorithm is NP-Complete or something to that effect.
Granted, if the problem is NP-Complete, asymptotically the genetic algorithm is also NP-complete, but in certain cases these methods do particularly well.
Are there particular algorithms you were interested in? That's just the first example I thought of and can explain in a bit of detail.
EDIT: Response to a Comment:
While it is true that we have machines that can compute functions explicitly, and so if we had infinite time and infinite resources probabilistic methods would not be particularly helpful, we are in fact limited by speed and resources of a computer.
One example: Tracking facial feature change and movement is a problem that has come up in computer science. This can be restated as determining the intrinsic dimension of a high dimensional space, thus producing a low dimensional manifold embedded in the high dimensional space. However, it turns out that the randomly checking certain parts of the expected manifold for certain characteristics actually is faster (in practice, not asymptotically) then doing the full calculation on the manifold.
A Note: We always need to remember that in numerical analysis we are working in discrete spaces, and there is often no way to make purely analytical checks to speed up matters, AND we may not have an analytical model for our particular situation. Thus in order to completely calculate something it often requires iteration over every point in the space, or quite a few of them. Any process which can reduce this amount of computation, and do so with relatively good accuracy, is a definite bonus.
Hope that helps!
Comment: Thanks for the reply.  I don't have a particular example, I just  find it paradoxical in general. We have a machine that is ready to precisely do whatever computation we ask.  But we choose it to act in a random fashion.
Answer: The clue of success of Monte Carlo method and other probabilistic algorithms is, that after You consider proper bounds ( for example You control that Your parameters describing are on hipersurface of constant energy) then other possibilities are fully exchangeable and equivalent from te point of view of the target of the problem formulation. That means: all system states You drawing are in fact equivalent if on surface of bounds. So if You want to compute some quantity for them, You may pick it in probabilistic way, and You only should take care about bounds.
For example if You construct expander graph for given graph family ( which is bound condition) then You may replace deterministic search algorithm by stochastic motion on it and results will be as good as deterministic search on beginning graph. That is because every vertex in our graph family is "near" some expander graph vertex so all of them are not-so-far-placed vertexes as counting from expander graph. If some of them would be to-far-placed Your algorithm will have lack of efficiency but expander graph definition protect You from that situation! So every vertex in computable equivalent, comparable distance from some edges of expander graphs.
Another example: If You want to compute some minima in optimisation problem, You may try to search by deterministic algorithm but when You find a way to produce by probabilistic way points on proper surface, then  it will work as well as deterministic one. That is because If You draws starting points for computing gradients, for every point on "surface" there is a set of near points which are "typical" and may give You better solution that first one. The only point for which it is not true is this You are looking for! Of course, You may consider case when for given starting point every point in its neighbourhood is wrong-one but here regularity conditions for function You try to optimise protect You from that situation. Of course in general case it may be not so easy, for example trying to find minima of function which is non-deferential everywhere is not so easy, but even then it is easier in probabilistic way b betting the points....


Programmatically read both per-tab Terminal.app titles

Question: When bringing up the Inspector (⌘I) in Terminal.app to edit the title (⇧⌘I), there are actually two titles that can be entered. The first is known as the Tab Title and affects the terminal window title (but only when that tab is selected). The second is the Tab Subtitle and affects the text in the tab header only. [The naming seems strange, with Tab Title affecting the title of the window, and Tab Subtitle affecting the title of the tab.]
Preferring osascript, but open to other approaches, I wish to programmatically get both of these titles for each tab. In going through AppleScript dictionaries, Cocoa framework docs, etc., I have only found how to read the Tab Title, surfaced as the "custom title" (custom_title) property of the tab. This is the one that all search hits on getting/setting the title via osascript refer to. Even though there are other title properties in the window and tab.current_settings it seems that they all reference only this first title field and there is therefore some redundancy.
I am setting each title programmatically using terminal escape sequences, as I similarly do not know how to set the Tab Subtitle.
Although it is possible to use UI scripting, I expect that such an approach will have to visibly cycle through all Terminal windows/tabs in order to read them all when producing the overall output that I desire. I would prefer something that can get at the data without causing selection/focus changes.
My last option seems a little heavyweight (though may still be preferable to UI scripting) which is to export the settings (Shell > Export Settings...) which produces a large XML file which does include both fields. Surprisingly the data structures in this file match the AppleScript structures almost identically, except that it includes the field I'm otherwise missing.
Being quite new to programming on the Apple platform, can anyone enlighten me to how I can get at this data that seems it should exist in the place I am looking but that I am unable to find?
Answer: Try:
<code>tell application "Terminal"
    set myTabs to every tab of window 1
    set myData to {}
    repeat with aTab in myTabs
        set aTab's selected to true
        delay 0.2
        set windowTitle to name of window 1
        set customTitle to aTab's custom title
        set end of myData to "Window:" & windowTitle & return & "Custom Title:" & customTitle & return & return
    end repeat
    display dialog (myData as text)
end tell
</code>


What considerations are important for initial placements in Kingdom Builder?

Question: I've only played Kingdom Builder a few times.  What should I be looking for when placing my first couple settlements?  Are there synergies between the scoring rules and bonus abilities to consider?  How much should I avoid being adjacent to multiple terrains?
Answer: The first turn is basically a trade-off between getting the best bonus tile (given the scoring goals in play) and minimising the risk of getting trapped, by avoiding placing in a large area of one terrain and making as few adjacencies as possible. It's often possible to do this in such a way that the bonus tile you claim guarantees you another tile next turn, regardless of your card draw.
Answer: Place according to the 3 endgame win cards. But generally keep your options open for expansion by starting with small areas you can fill up quick.


My Herokuapp is inaccessible from custom domain name

Question: I have a Heroku app that is located at myapp.herokuapp.com. I have mapped a domain name to this app, using the A properties. I followed the instructions on Heroku's website to the letter, and it worked for a few days. Now when I try to access the site from the custom domain, it's timing out!
On Chrome, I am getting "Oops! Google Chrome could not find that page!" message.
I tried pinging the name as well, but I got this error:

ping: cannot resolve yourhostname.org: Unknown host

The app itself is working and I don't see any error messages from Heroku. Or from new Relic. What's going on here?
Also tried running host and this was the error message:

;; connection timed out; no servers could be reached
Answer: Turns out it was the GoDaddy outage of 2012. Scary times.


How long will questions and answers be stored at stackoverflow?

Question: Having some interesting questions in my favorite list that could help me if I stumble over them in the future, I wondered about how long the questions and answers will be stored (so, if I should save some of my favorites offline to still have access to them in a year). Of course there can't be a guarantee that SO will still be available, but if it is, will my favorite question also be? Or is there some sort of "timeout" and questions/answers get deleted from the database after some time?
Comment: They will be stored at stackoverflow until Google Code eats it up :p
Answer: https://stackoverflow.com/questions/228462/how-can-a-question-or-answer-be-deleted says:

There are three ways posts can be deleted:

You can delete your own post
Moderators can delete your post
The post reaches the 5-vote offensive threshold and is deleted
Posts aren't physically deleted -- just hidden. (aka soft delete)

I'm fairly sure your question will not be deleted because it's "old" :) .
Answer: One issue is that "correct answers" for many problems may no longer be the best answer down the line. Even if someone posts a new, updated, even more correct answer on a post later on (unlikely, there's 60k questions now, so old questions will be found by people looking for answers, not looking to give answers) it is unlikely that they will be scored up, or accepted.
So the site needs to ensure that old questions are "rebubbled" to the top occasionally - in a year or two at least, to get updated answers and keep them alive, maybe get some more upvotes for still correct answers.
Answer: SO is desiged to be the knowledge warehouse of all technical questions and all questions will stay forever.
Answer: In hundreds of years future generations will browse Stackoverflow in a Minority Report stylish way like we do it today looking at historical version of Encyclopedia Britannica on the intarweb. ;-)
There could only be one problem: the Stackoverflow content could be too small for the minimum size of 1 Petabyte of "data objects" on future computers.
alt text http://blog.wired.com/photos/uncategorized/2007/08/13/minorityreport.jpg
Comment: Don't worry, peoples' arms will be genetically engineered not to get tired.
Comment: Hahaha.. Fantastic comment. :-)
Answer: The posts remain in stackoverflow untill unless they are deleted.
Answer: As far as I know, they are here to stay, so we create a piece of programmer reference on the internet.
But I can imagine that there will be cleanup sessions in the future.
Answer: Some cleanup of low score, zero answers questions is done monthly.
(And as an aside: low use tags are cleaned up too.)
Answer: I thought all the questions and reputation points are going to be zero-ed when stackOverflow comes out of BETA....
straight up - honest ;-)
Tony
Answer: I wouldn't worry too much about the data being lost any time soon. It has been created for developers by developers, and even if, at some point in the future, they decide to shut the whole thing down, I couldn't imagine that anyone (especially our lovable overlords J & J) wouldn't at least offer the database to someone else to host: even as a static archive.
Answer: If sh*t happens, hopefully there's still the archive.org version of Stackoverflow.
Did you know that the site existed back in 2000? ;-)


Google multiple sign-in fails to switch users!

Question: I'm in Gmail with 3 Google accounts signed-in.  When I choose to switch to a different user account from the drop-down menu in the upper right of Gmail, it pops open a new Gmail window for the same user as before.  What gives?
Comment: Which browser are you using? Have you tried other browsers?
Comment: Try using the following answer: http://webapps.stackexchange.com/a/36090/29140
Answer: This seems to happen from time to time in my experience (4 accounts), especially if I try to log into two accounts at once from the same domain (examples: firstname.lastname@example.com and firstname.lastname@example.com)
Just restarting the browser works much of the time.
If not, logging out and starting over usually works. Starting over = logging into each account again.
Rare cases I have to log out and wait 30 minutes to try again.
To log into another account from the same domain use the generic GMail login screen and enter the full email address as the user id.
Comment: Logging out and then back in did 'work' for me as a workaround.
Answer: This still happens to me all the time. I find that I need to do the following:

Switch to the account I want to sign in to.
When the password screen comes up I enter the WRONG password and submit the page.(I'm assumming it just cleared the cookies)
Now enter the correct password and it should work.

It then takes me to the correct account. If I just enter the correct password it always takes me to the wrong account.
Comment: This doesn't work for me because when I choose to sign in with a different account, then choose UserB, it loads the login page for UserA again. Grr. Logging out and then back in did 'work' as a workaround.
Answer: I meet same problem many times and trust its authorisation scripts problem. Google try to make accounts switching easy - just this brings some small problems with so many services they offering using same authorisation data.

I use iGoogle which loads for specific account and sometimes it ask me to re-enter account password to be able to bring me mail messages inside iGoogle. In other words to access my iGoogle account the password is ok, but NOT to access the same account mail messages. Authorisation scripts used in iGoogle and on Gmail gadget on it are different authorising on different ways - but trust they write in same variables in my browser to keep my login data for all further cases when account authorisation will be required.
Every account have own number in the list of all available accounts inside current browser.
The primary account have id 0, then all other have own number depending of the order of signups. When you switch google accounts the account id is passed through URL:
https://mail.google.com/mail/u/0/
Changing the number from 0 to 1, 2, 3 allows you to easy switch between accounts (no pop-up).
If this not works the sign-out is the only available option, which must clear all authorisation problems.


Can I use spray paint to touch up my car?

Question: I have several really small nicks and major scuffs on my car; the nicks from driving on the highway (flying debris hitting chassis) and the scuffs from two fender benders. The nicks have started to rust and the scuffs are just annoying, so I'd like to get rid of them. A body repair shop charges me for each body piece, so that doesn't make for a good deal. I was wondering if I can resolve it with something like DAP Touch'n'Tone multipurpose spray paint?
Comment: even touch up paint wont match exactly do to sun exposure to your existing paint.
Answer: You can, but probably not in the way you're thinking.  You can't just go out and buy a can of "red spray paint", unless you are prepared to re-paint the whole car in that color or you really don't care about the results.  This is because your car isn't "red" (for example), it's "Sierra Red (L D3V)".
However, if you go to a professional paint supply shop you can get them to inject the specific color for your car into a spray can.  You can often get "touch up" bottles of paint in the exact color from your dealer.
The rust is another matter though...  If it's surface rust, you may be able to get away with just using primer that reacts with and neutralizes the rust, and then paint over that.  However, if the rust is "flaking" or working behind other parts of the paint, you're probably going to have to clean that out, for example with a wire wheel on a tool, possibly making the area you have to paint much larger.  It's either that or risk having to deal with a larger area (or a hole clean through) later.
These rust-reacting primers, like certain models of Rustoleum, work extremely well in my experience.  When I was younger I had a couple of cars that had varying degrees of paint damage near the wheel wells or on the front end, and was very happy with the rust-stopping results of Rustoleum.
In my experience though, if you want something that looks good, you need to do the whole panel.  And if you want something that looks really good, you have to do it with the right tools in a booth.
Comment: Thanks @Sean, and yeah, I REALLY don't care about the results. My car is plain white color, so I guess I can get away with touch up.
Answer: Consider going to a detailer. It's amazing how much they can do without actually painting anything.
Comment: Yeah well, as I mentioned in my question, this is not an option right now.
Answer: You can buy touch up paint that matches the paint color of your car. This can be used to fill in the nicks in the paint.
Not sure if this would help with the scuffs, depends on how large and deep they are.
Answer: Normal spray paint may likely chip off in a few days.
Here's an instructable about painting your car with Rustoleum.
Answer: You should be able to buy colour-matched automotive spray paint for your car in most larger car-parts shops (in the UK, Halfords sell a wide range, and their larger stores can match considerably more from manufacturer's paint codes).
However, as others have said, it can be very tricky to get a good match as your paint will have faded, and the new will be matched to the original factory colour. You might be able to get away with it by using t-cut or similar to restore the original paint (they effectively work by removing the top layer of the paint, so don't try it too often!), then carefully blending in the new paint, but it's not easy - it depends how good you want the result to look!
If you've got scratches strarting to rust you'll need to take them back to bare metal and paint with an etch primer first, otherwise the rust will spread under the new paint.


Is SEO the most important part on making a website good?

Question: Can SEO be the only major part in making a website good? Cmon there are lots of facts, design, functionality, user friendly, efficient.
Answer: Perhaps indirectly SEO can improve a website. It encourages you to think about quality content, good navigation and site usability.
But no, SEO itself does not make a website good or bad at all. In other words, good SEO is a side-effect of a good website.
Comment: Your last sentence is spot on
Comment: Nice reply, congrats.
Answer: SEO is mostly:

quality content
usability
accessibility
semantic markup

If your site is built with the four principles in mind your site will be optimized for the search engines. If you have to go back and "SEO your website" then you made mistakes when you first built it and only are fixing it (or making it worse if your changes are only being made with the search engines in mind).
Once a properly built website is launched the only real SEO to be done is to utilize tools like Google Webmaster Tools to help facilitate the indexing of your site and find potential errors or problems that the search engines have with your site. Then from there it's continually adding new quality content (if applicable) and marketing (seeking links is marketing).
Answer: A good website has, IMHO:

Good content
Good accessibility
Good design
Good usability

Make site findable is important, but making visitors like a site after find it depends on other things.
On page SEO basically depends on 2 of four factors I listed (content and accessibility), plus semantic markup, plus friendly URLs. Except content, other points are technical.
Content, usability and design are the factors that make your site interesting and pleasant. Without them, your site can be find, but can't achieve goals or help out people, thus making it a bad website.
So, I think SEO is important, but content (be it a copy text, an idea or a service) and usability are more important than findability as measure to a good website.-
Answer: No it's not, but If you try to sell something on the web, SEO is the most important part!!!
Nowdays even if you have super efficent server and well designed, with great functionality and user friendlysness, efficient website, but you do not appear in 1st Google page, you won't get any orders!!!
This said, it's absolutely true that it's easier to do SEO on well designed, with great functionality and user friendlysness, efficient, full of rich interesting contents  websites rather than doing SEO on poorly designed, slow, poor contents, websites.
So a well designed webiste can be considered a necessary start conditon for good SEO, but not sufficient. You might still find poor designed webistes that ranks higher that your well designed website on Google and they will sell more than your website.
Answer: Short answer no. But what do you mean by 'good'. Not a great question. A website has many aspects all of which should be attended well to make a superior quality site.
Answer: SEO does not 'make a website good', per se.
SEO can help a good website get better exposure via search engines, obviously. But a 'bad' website can equally benefit from SEO.
However, SEO is improved by many of the techniques that feature in good websites: appropriate, valid semantic markup, good content, accessibility, etc.
So good design improves SEO, but SEO doesn't necessarily improve the website.
Answer: I'm relatively new in SEO, and my knowledge is based on forums such as this and some articles I found over the web - but I want to share an interesting fact from my experience.
I have an ecommerce website that didn't do so good. There is LOTS of sense in the way Google ranks and promotes your website. The Google bots are actually good quite human, if they would like your site then humans would like it.
The SEO knowledge got me to completely change the design of my website making it a lot more user friendly. Besides for the fact that I do get a lot more traffic (but never enough :) ), the users are actually buying since it is easier to find their way around the site. Before the site was pretty and now it is effective!


What is a dice pool mechanic?

Question: A very basic question, I know. What is a dice pool mechanic and how is it different from a roll vs. target number mechanic?
Comment: Is it worth noting for this question that the term really means different things in different games? Recently I've come across a game where your "Dice pool" meant the amount of dice you got to roll for any purpose during a round. You "spended" them.
Answer: In a "dice pool," one considers each die individually, rather than as a collection of components to be summed. As an example, an attack in the HERO System might do 8d6 damage; to resolve it, you'd roll eight six-sided dice and add them up to produce a number between 8 and 48. In a die pool system, you might see how many of the dice showed a 5 or a 6 on the top face, and count those as "successes" toward a benchmark.
Rolling vs. a target number can be used in both die pool systems and otherwise. In HERO, for example, you roll 3d6 and sum them, trying to stay below 11 (or an otherwise modified target). In Deadlands, you use your die pool and select the highest rolled die, comparing it with a target number modified by the difficulty of the task at hand.
Answer: In recent usage, a "Dice Pool" system means each die is individually compared to a TN, while a  "roll vs target number" mechanic usually means to total all the thrown dice.
In older usage, dice pool simply meant those dice being grabbed to be rolled, and didn't limit it to counting individual dice. This was the case especially for some systems where skill determines number of dice thrown, and they are all totaled, such as the d6 system or L5R, and in the text of some recent editions of L5R and in Houses of the Blooded. Note that EABA and L5R, the dice totaled are usually a subset of the dice in the pool.
Dice pool is almost never used to refer to games where all rolls are made with a specific number and type of dice. Examples of this are 2300AD, MegaTraveller, D&D, and Palladium. For example purposes, 2300AD always uses 3d6 and 1d10; the D10 is used for success, the 3d6 for time, but it's almost never called a dice pool system, even by those who call Star Wars d6 a dice pool system.
The classic "dice pool - count successes" systems are Shadowrun (through 3rd ed) and Vampire 1st Ed - the number of dice are determined by stats and skills, while the TN is set by difficulty. Each game uses a single type of die.
More modern "dice pool - count successes" systems often use a single TN, and difficulty is the number of dice required to succeed in order for the action to succeed. Examples include most of the old StoryTeller system games, and all the newer StoryTeller system games, as well as Burning Wheel and Mouse Guard. Again, a single type of die is used.
Vincent Baker's Dogs in the Vineyard uses a dice pool of multiple types of dice; and does some strange math with them... while I've read it, I don't quite grasp it, other than you pull dice from the pool to be counted individually.
Greg Stoltze's Reign uses a pool of dice by ability, with the number of dice that match each other determining one element of success, and the face showing another element of success.
Answer: Simply put, the dice pool is a bit of a squishy word that describes any time you roll a  handful of dice instead of a single die to determine the result of an action.
Usually it describes any mechanic where you roll dice and compare against a target number.  Since you have more dice rolling, it's less random than mechanics like D&D, and theoretically it makes it much harder for a Zen Swordmaster who's been studying the sword for 50 years to be taken down in a single swing by Cleetus the farmboy (don't laugh, I've seen something like this happen at a gaming table).
In shadowrun, you use 6 sided dice.  If your Pistol skill is 5, you roll 5 6-sided dice to see if you shoot the bad guy or not.  There are also other pools of dice (notably combat, astral, hacking, and control pools) that enable you to add dice to the test.

For example, you are in a very tense situation, and NEED to hit the bad guy.  Your Pistol Skill is 5, and you have a Combat Pool of 5.  You could then use some (or all) of your Combat Pool dice to try to make a more impossible shot; or since Shadowrun lets you use extra success dice to increase damage, you could take a small gun, use all your pool dice and (if you are lucky) get enough successes to guarantee a deadly wound to the bad guy.

Other examples of mechanics that use dice pools include:
Old World of Darkness, (I believe New World of Darkness, but don't quote me on that), and if anyone else knows of any, I'll happy edit to list them in here.
Comment: New WoD uses a dice pool mechanic indeed. It's a bit different than old WoD, but the concept is the same.
Comment: @Cthos, how do OWoD and NWoD's mechanics differ?
Comment: Lots of little things, this sums it up pretty well: http://en.wikipedia.org/wiki/World_of_Darkness#New_rule_system, but in general You only can botch on a chance roll (when your dice pool is 0 or less), Target number is an 8 instead of varying, 10-again rule was introduced, etc.
Comment: @Cthos, wow, we used about half of the changes as house-rules in our long running OWoD chronicle.  Thanks much!
Answer: Dice pools are used either to describe that you have a bunch of dice which will not be added up but scored individually or that you have a flexible reserve of dice that you can apply to certain actions.
Amusingly, both terms have been used in the Shadowrun game.  In SR4, the basic mechanic is a dice pool of the first type; you have a certain number of dice (perhaps adjusted by bonuses and penalties), and you roll them against a target number of 5.  In SR3, in contrast, certain actions had dice pools of the second sort: combat pool, for instance, was a flexible reserve of dice that you could use to assist in combat actions, so you could switch between, say, more offensive and more defensive approaches (by applying those dice to one or the other).
Comment: Isn't the latter better known as Dice Spending?

What is a dice pool mechanic?


Grilling burgers: flip once, or keep flipping?

Question: When grilling burgers I usually flip several times, but have recently been advised to cook forever on once side, flip once, cook and be done.
Is that the best way to do it?
How do you know when a burger is ready to flip?
Answer: I'm solidly in the flip as often as you want camp.  As long as it's not over (or under) cooked I find that you get better results flipping often. Plus you can rearrange things to make more room as you flip.
To tell how cooked a burger is poke it with a finger or something else that's not too sharp; just like a steak the more cooked it is the more firm it will be.  You just need to learn how "squishy" you like them.
Also, as fun as it is, don't press the whole burger into the grill!  All that happens is that the delicious juices are forced out.
Comment: I believe the flip once advice is mainly for getting better grill marks on the burger (or steak), although there's also "less handling = less temptation to squish the burger".
Answer: Harald McGee says flipping more often will help the meat inside the burger (or steak) to warm without burning the outside.
Answer: Multiple flipping: more even cooking, thin crust
Flip once: uneven cooking, thick crust
(Note: by 'uneven' I mean that you will have a much wider range of doneness from crust at the outside to possibly raw in the middle; more crust=less unevenness)
So it's a matter of taste really. I personally prefer multiple flipping, in a pan and not on the grill.
Comment: I prefer even cooking as well, but my father-in-law likes to put his steaks on the grill from frozen, specifically to enhance the bullseye effect. To each his own? I guess that's a +1 for pointing out the different effects each method gives and that it's a matter of preference
Answer: i feel flipping any thing on the grill once for best results juices stay in side place the burger or steak on the grill few minutes or so depending on temp turn it weight 3-5 minutes then flip it once better diamonds juicier steak or burger is
Answer: I'm in the flip-turn-flip camp to sear in the juices and for some sweet looking grill marks. FWIW, I used to be a high volume grill cook. After a while you can tell when it needs the flip or turn just by looking at it. It's also really weak to cut into the meat to check the temp since you'll lose all the juices.
Answer: I prefer "flip once".   Assuming you've got the heat right...

put them on the grill or pan
as soon as they're all on the heat, give each one a little nudge to make sure it's not stuck
finish messing with condiments or have a beer or something else for 3-5 minutes
flip the burgers, and give them the same "unsticking" nudge as before and wait another 3-5 minutes
get the buns toasted
serve and eat

I think the meat done-ness method I heard was to compare it to each of your "earlobe" (rare), "cheek", "side of nose", and "tip of nose" (well or medium well), going from least to most done.   The more firm the meat is, the more done it is.
or you can do what my mother does, and get out a knife and cut into one of the burgers and see how pink it is on the inside.


How to set up SAMBA / CUPS print server?

Question: I am using 13.04 on an old laptop hooked up to a printer that I would like to access from my Windows 8 PC. I have been working on this for hours and I cannot seem to get the right configuration of SAMBA and CUPS to make it work. I had it working once before but I had to re-install for an unrelated reason. Did not think of backing up the configuration files...
Anyways, I would like to be able to go onto my windows computer open up the network folder and see the server show up. Then when I open the server, for it to show me all the printers connected to that computer. And finally, to be able to install and print right from there.
I have searched hours and tried multiple solutions but none seem to work. As soon as I get a reasonable answer, I will wipe my current configuration and start from scratch, so that none of my work will interfere with the solution.
Please when you answer make sure to start from the beginning. As I will not have a single thing set up. (e.g.  list all commands, program requirements, etc)
Thanks for the help!
Answer: There is a Ubuntu based equivalent -if not better called Zentyal and can be either installed as an appliance or on top of a Ubuntu installation (Zentyal-Samba and Zentyal-Printers)
More details Here


Will vacuum sealing an open bottle of wine make it like it was never opened?

Question: I have a professional vacuum sealer, which removes the air, and seals the bottle, or container.
Will this work with wine, or does the wine degrade once it has been exposed to air, no matter how well the vacuum sealer works?
Answer: The only way to get "like it was never opened" is not to open it.  But storing an opened wine bottle isn't a new question.  There are a whole range of products, which will keep the wine varying lengths of time.  From simple hand-vacuum pumps which can hold a day or two, to as-decanted nitrogen or argon replacement systems, which can add a week or two.
See http://www.wineenthusiast.com/serve-preserve/wine-preservation.asp?AfID=CJ for some product examples.  The longest holding I've personally played with is something like http://www.wineenthusiast.com/nitrotap-single-bottle-wine-service-preservation-system.asp, which prevents oxygen ever getting into the bottle.  However, even the bit of air between pulling the cork and inserting the spigot causes the wine to degrade within a week or two.
If you're looking to set up a bar, the nitrogen replacement systems can be found in multi-spigot configurations.  So you can have 4 or 8 bottles "open" at a time.
Answer: The problem is the cork. One you pull it, you damage it. If you put a new cork of the correct size and "weight" for your bottle it will seal properly again and the wine will last many years
The small amount of air at the top of the bottle does not seriously affect the wine. A vacuum sealer will not remove that much air anyway (otherwise the cork would just get sucked in)
If you remove a sample of wine you should top it up with either distilled water, or wine from the same batch
Good vintage wineries offer services to open you r wine every 20 years or so, check them, top them up, and re-cork them. If done properly it will keep another 20 years!
Some wineries use carbon dioxide or nitrogen as an air replacement, but in history this was not done, and there are many records of wine lasting many decades
Screw caps cannot be easily replaced, you will need a screw capping machine, and I don't think they make domestic versions of these!
Answer: As far as I know, it will still degrade a bit, but not that fast. Always keep in mind that "degrading" means oxidation which will kick in as soon as air gets into the bottle. So even if you remove the air after pouring, there was some air in the bottle, which means a tiny amount is oxidated.
To put that into practice: As long as you don't try to store the bottle for weeks, most people won't notice a difference. But still, the wine will change, depending on how good the bottle is sealed and how long it was left open.


Dual FireWire External HDD and second port performance

Question: Backstory: There is a drive that comes to mind out there that has two FireWire 800 ports.  My question is related to performance of the second port.  In my case, I would like to hook up an external sound card to my MacBook Pro.  I am already maxing out my USB ports with other devices and I and using Thunderbolt to power another display.  So my only option is to use FireWire, which is the choice anyways.
Question: Will using a dual FireWire 5400 RPM HDD with the additional port (daisy chain) affect the stability, quality or bus speed to the external sound card?
Answer: It shouldn't. FireWire is a peer to peer technology


How do I fill holes around a newly fitted ceiling light socket?

Question: I'm replacing a ceiling light that when fitted will leave gaps / holes in the ceiling where the existing socket hole is.  The previous light was bigger and had a sensible amount of room for the wiring to be comfortably housed.
The new fitting is effectively the shape of a polo mint about 200cm diameter and about 30cm thick.  In other words very awkward to mount and doesn't cover the previous hole.
I have two problems.  The hole in the ceiling and the recess in the light fitting means it's the wiring is going to be pretty cramped by the time its fitted but the biggest issue is how do I fill the hole so I can make a decent finish.
Hope someone can help??
Comment: Can you provide a photo? (See the [faq] for how to add your photo before you have the rep.)
Comment: Can you putty it? Thats what I have done in the past.
Comment: this [question](http://diy.stackexchange.com/q/10168/33) might be helpful.
Answer:
You could use something like this. They come in various sizes and styles, can be painted and are usually held in place with a little glue or drywall screws.

Something like this is much more decorative.
Comment: Where did you find the first image? I'm searching for a very simple, plain white medallion and I can't find one anywhere.
Answer: If you don't want to cover it with a medallion as the other answer suggests (a great answer, and popular practice in old houses) you will end up having to paint, so you might as well just fix the drywall properly. Cut a square around the fixture using a utility knife (scoring it repeatedly) or a drywall saw (being careful to avoid the wires).
Ideally you should cut it so you expose a half a joist on two sides, e.g. cut all the way back to the edges of the nearest joists on either side. This is a pretty good example, but you only need to open up one joist bay.
Then cut a piece of drywall the same size, and measure the location of your fixture, and cut that out precisely. Reinstall the square, tape, mud & sand.
While the ceiling is open, you could replace the box with something bigger to solve your other problem.

Picture from knoji.com which provides more detail on general drywall repair.
Answer: Depends on the gaps involved, I replaced the electrical boxes in our ceilings as the old nail-on 70s boxes were flimsy, the holes through the ceiling were either off center or had broken edges where the plasterboard had chipped out due to poor cutting technique. The new boxes were flush mounted to the ceiling surface and unmovable once fastened down.
I used mesh joint tape to bridge the gaps on the attic side and mixed up Plaster of Paris, pressing it through the joint tape to completely fill the gaps. After letting it set, I attacked it from the room side with more Plaster of Paris and a narrow putty knife to create a smooth surface that feathered into the ceiling. It filled gaps up to 1/2" very well and was necessary as the new suspended glass ceiling lamps I'd chosen covered the box with an escutcheon plate 1/4 inch larger than the electrical box and would have left unsightly gaps with attendant heat loss had I retained the old boxes.
Comment: I know this has been in this website for 3 years, but may I add another tip? BE VERY, VERY PATIENT IN APPLYING, THEN SANDING (SMOOTHING) WHERE THE INSERTED PATCHED IN DRY WALL MEETS THE ORIGINAL CEILING............TOOK ME MAYBE SIX TO EIHGHT TIMES OF SANDING, REAPEATING THE CYCLE OVER AND OVER AGAIN. YOU DO NOT WANT THE LIGHT IN THE ROOM TO CATCH THE JOINTED AREA! I did two rooms like this, and several years later, you cannot find the jointed areas. Be sure to use finer and finer grits (or sanding sponges) as you near the final finish.


Why are the Shabbat additions to Pesukei D'zimra added before the every-day parts?

Question: In the Pesukei D'zimra of Shabbat, why are the Shabbat-specific portions added before most of the every-day portions? Shouldn't they be said after according to the rule: Tadir V'she'eino Tadir, Tadir Kodem (when there's a common requirement and a rare requirement, the common requirement comes first)?
Answer: The purpose and structure of Pesukei D'Zimra is outlined in Shulchan Aruch, but the basic idea is that it all leads up to Ashrei, and specifically the Posuk פותח את ידך. The things that come after that have a specific purpose (finishing until the end of tehillim, and so on - but mainly about providing praise to Hashem and the types of praises, leading up to Yishtabach which expresses that concept).
So in terms of the structure of Pesukei D'Zimra, some of the things that we add on Shabbos are additional meditations intended to be before Ashrei (broadly - about Hashem's creation and control of the world), whereas what is added afterwards (before Yishtabach) is about the idea of praising Hashem. So within their respective sections of Pesukei D'Zimra, they are at the end, following the principle of Tadir Vshe'eino Tadir, Tadir Kodem.
Comment: Where exactly in Shulchan Aruch is this thematic schema laid out?


Light Day-Hiking with Newborn-- baby carrier or offroad stroller?

Question: Baby is due in late June, and we hope to continue our normal habit of light day hikes (<4 miles, no major elevation changes) with her later in the summer and into early fall. Does it make sense to carry her in a front baby carrier, or should we look for a carseat carrier which will fit the offroad stroller we already purchased? The stroller warns it cannot be used without an infant carrier until baby is 6 months old.
We'd like to just use the front baby carrier, and switch off between Mom & Dad if one of us gets tired, but need to know if this is practical or not... thank you!
Comment: I liked using a front carrier, but everyone's different. Try borrowing something from a friend to see what you like.
Answer: I'd recommend checking out a baby wrap instead of a carrier.  Especially in the infant stage.
You can either get one online (my wife got one here and loved it) or make one yourself.  They are pretty easy.  My wife made one out of lighter material for the hot summer months.
Answer: If you already have purchased the baby carrier, or were going to purchase it anyway - I'd try out the baby carrier first. If you deem that it does not work for you, then you can look into purchasing a car seat that fits in your off-road stroller.
With a baby carrier, you are not as restricted by the terrain or small spaces. However, you do have to be a lot more careful with the baby - a slip or a fall could be deadly for the baby. Baby carrier also allows you to easily feed the baby while in the sling. Be careful about not over-dressing the baby. Babies can get very warm from your body heat in a sling. Keep an eye on the baby's temperature.
With a baby in a car seat in the stroller, the baby is relatively safe - after all, car seats are designed to sustain the damage of car accidents. You'd have to stop and take out the baby for feeding it. Strollers are more of a nuisance, however, and restrict the spaces you can enter.
I would think that a baby carrier would be preferred until the baby is a little - but every family is different, and every baby is different. What works for one family, might not work for yours.
Answer: The front baby carrier is very hard for your back, but seem to be nicer for baby's neck... We had a carrier that could be switched from front to back position, that was very useful. I would buy a carrier in any case because even if you don't use during hiking, it will be useful when baby is crying: they love it and get asleep very fast in this position.
Answer: I would recommend a wrap or an Ergo backpack-they have newborn inserts for it.  We had an ergo that I LOVED!  It is a soft backpack, that can also be worn in front... it holds them as though they are sitting-which helps their hip joints develop correctly... as opposed to holding them from their crotch.  It is comfortable when worn and holds kids up to 60+ lbs, at least, I think.  If I still had ours (I lost it 6 months ago), I'd take it for in the airport for our preschooler... to keep her with us instead of running around.  In lieu of the Ergo, I'd recommend a sling or other wrap, also-it's not as cumbersome and more versatile than a metal framed backpack carrier for carrying the baby in a position they will also be happy in.
If that is the only stroller you own, I'd recommend getting the infant seat that fits in it, anyway-as you will use it when you go to a mall or a store that doesn't have shopping carts.. or walk around a park or....
Answer: I'll buck the trend here and say if you have a jogging/offroad stroller (something with inflatable tires that will stand up to a gravel trail), get a carrier for that stroller and use that.
We have a Baby Trends system (Expedition ELX) that has a jogging stroller, carrier and car seat base. I love it; it rolls around effortlessly, maneuvers like a dream, and cushions the bumps and pits in the parking lot and sidewalk much better than a standard stroller. The one thing I wished it had that it doesn't (and I can't find it on any jogging stroller) is a trigger for the front wheel lock up on the handlebars; if you want to start jogging, you have to bend down to the front wheel and flip the latch; to round that sharp corner, you have to release the lock (or raise the front wheel off the ground; not an easy thing to do smoothly).
The advantage of putting the baby in a car carrier and stroller is protection. The car carrier is designed to protect your baby in a car crash. If you're hiking with the baby in a front carrier, and stumble and fall, you can seriously injure yourself and your baby. By contrast, even if the stroller tips over your baby will be relatively safe.
Answer: Have you walked the same paths with a stroller before? Will you be only use tracks that can be navigated by car or at least by bike? Our only offroad hike with a stroller ended with carrying the thing a lot, even though we did know the area somewhat. Somehow we had never really noticed how many stairs there were in this area.