StackOverflow, ServerFault, and Superuser have ads. (I only see them when I'm not on my own computer where firefox and chrome AdBlock extension is not installed). The new SE 2.0 websites do not seem to have ads. Will this continue for the next couple of years?  I would like to know because ads could be a factor in decisions on whether to migrate existing SE 1.0 communities to SE 2.0 or to use an alternative Q&amp;A platform. There are free-software clones of Stack Exchange (Shapado, possibly others...). I know 1 community (Cheminformatics) that uses a clone and 1 (Bioinformatics) that is considering switching to a free platform. The clones have all the essential features but Stack Exchange software quality and quantity is in the lead.
Some time ago, we announced that . This has gone well and we're extremely thankful to everyone for their support and feedback. Because it has been successful so far, we're going to be extending the program to the majority of our graduated sites. Well, we've pretty much already done that, but there are quite a few sites that have ads enabled, yet still display nothing. The thing is, we don't really have an abundance of clients offering products that a  would find relevant, but Amazon has stand mixers, a selection of super fine chinois, deliciously sharp cutlery and enough cast iron to fill the Gulf Of Mexico with . Beginning as early as this week (week of 5 February 2018), our ad team is going to be hand selecting affiliate ads to be displayed on select sites. The use of inventory will of course depend on the availability of relevant ads to display which means:  Some sites might see very few, if any ads. Some topics simply don't come remotely close to orbiting anything worth advertising. Furthermore, while graduated, some sites simply don't have enough activity for ads to make sense.  Since these are hand-selected, it could take a while for ads to appear initially.  These would of course yield to inventory from clients if clients had products that were relevant to any given topic.   Nothing changes when it comes to the . If you're used to occasionally seeing a community promotion ad, you'll just notice that you'll also occasionally see an ad for something that is likely to be of interest to someone interested in the topic that your site covers. In fact, to be clear, this is simply a continuation of the announcement we made in November of 2016. We just wanted folks to know that we're going to be continuing the program where there's good potential to show relevant advertisements, even if we don't have clients lined up with a demand for it. Where can I give feedback about a certain ad on [site]? Open a meta post on your per-site meta and let us know. Please remember, the bulk of advertisements are an effort to get something small back from folks that hit the sites through search engines and are extremely unlikely to ever become contributors. Their soufflé stopped falling, and we'll probably never see them again. Maybe we can get a few bucks once they realized that copper ions help egg whites stiffen properly and buy a bowl or a proper bloom whisk. However, you're the experts on these topics and we're very likely going to listen to you. What sites, specifically? Are any sites exempt? If you're a former Stack Exchange 1.0 site and / or subsequently joined the network under a special charter, nothing changes - don't panic :) For the rest, we're just extending what we're currently doing with ads on graduated sites to also include those where there's an opportunity to make sensible use of affiliate ads. If a site has less than 15k (average) daily visits, or fewer than roughly 50k combined total posts - it might not yet be time to invest in selecting ads to be shown there. But, part of this exercise is also seeing what works best. I don't really have feedback, just some suggestions Ads aren't just an opportunity to sell stuff, they're an opportunity to really show people that we understand a given topic. That, of course, makes suggestions from people that do that stuff every day quite valuable. Post on your per-site meta and our community / ad critters will take a look. Questions? Comments? Kvetches? Let us know in an answer or comment below. If anything about the plan changes, we'll update this post to let folks know.
How do I calculate the resistor value for a simple LED circuit? I have a simple circuit:    The max rating (current) of the LED is 30mA.  How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be \$3V/0.03A = 100 \Omega\$. However using software called , and trial and error I got the minimum possible resistance to be 36&Omega;. However, if I use a 35&Omega; resistor, then the LED breaks. Is the software wrong, or (more likely) am I doing something wrong? Unable to edit my response to a locked question The image is broken in my  to the "favorite programmer cartoon" question. I'd be happy to fix this, but I can't (not enough rep? not a moderator?).  Here's the image in the Internet Archive: A while back, I read a story in a collection, but I don't remember very much. I know that it was about some missionaries on Mars. Eventually they found a bunch of spheres that apparently have escaped sin by leaving the material world. I don't remember anything else about it. Someone told me that it was in "The Martian Chronicles" by Ray Bradbury, but I checked my copy and couldn't find. I'm pretty sure that it was by Ray Bradbury though. Help would be greatly appreciated. Printer "Filter failed" Upgraded to 18.04 from 16.04. I have a workplace printer connected through appsocket which stopped working.  Printer status is Idle-Filter failed.  Printing queue instantly goes to "stopped".  Right clicking on the printer shows "option finishings has value 3 and cannot be changed". I can't find any info on this error except one pdf to ignore the error.  The printer model Ricoh MP 2555 worked previously with the Ricoh MP C2800 driver. Now it works with neither 2800 or 2555.  The IP address of the printer pings fine. When I try and detect the printer on the network using IP address and I ask it to use the Ricoh MP 2555 driver, it asks for an additional driver which opens Ubuntu software (which never helps) and fails.  I tried changing drivers from "" by providing the ppd file. It still doesn't help. var/log/cups/error.log doesn't tell much, or I don't get it.  Hope someone knows about this error or some kind of a generic solution. Prove that for any piecewise smooth curve it is possible to find the parametrisation $\phi$ that is consistent with its length, ie.  length of a curve segment between $\phi(a)$ and $\phi(b)$ is equal to $|b-a|$.  It seems intuitive, but I don't have any idea how can I show this in the formal way. Convergence of $\sum_{n=1}^\infty\frac{n}{(n+1)!}$ Can someone give an explanation using the definition of convergence in partial sum to show how the above infinite sum converges to 1?  Thanks How to decide if an effect is magical for Magic Resistance? Some creatures have Magic Resistance:     The [...] has advantage on saving throws against spells and other magical effects.   We know from  that this works against Turn Undead, but does it work against Stunning Strike, Death Strike, Fey Presence, etc? How do we decide? Installing from source. How to resolve dependencies without destroying the package manager $G$ a group and $H, K\mathrel{\unlhd}G$. Assuming that $H \cap K = \{1_G\}$ and $G = \langle H, K \rangle$, prove that $G \cong H \times K$ I am trying to prove the following statement:     Let $G$ be a group and $H, K\mathrel{\unlhd}G$. Assuming that $H \cap K =  \{1_G\}$ and $G = \langle H, K \rangle$, prove that $G \cong H \times K$.   From this, we get that $HK \cong H \times K$. Naturally, it would be ideal if I could prove that $HK \cong G$. One issue that I am facing here is the meaning of $G = \langle H, K \rangle$. How is this defined (I mean, more explicitly)? Is my strategy correct or Will my checked luggage freeze in the airplane? I'm taking some freeze-sensitive items in a checked luggage for a short flight. It's cheese, chocolate, toothpaste and wine. I would like to know whether the luggage can get "frozen" in the aircraft. Sometimes it happened to me that my stuff actually was quite cold after the flight, so I'd like to be quite sure. Especially the cheese was really expensive and freezing it would very likely demage it.  Usually I pack everything well in clothes, but this time the things are just too many so it's tough to do more than just protect the wine from breaking.  Some details: It's an A320 flight taking 1.5 hours, with Czech Airlines, from Paris CDG to Prague PRG. I'm working through Exercise 40 from section 1.2.3 of Knuth's The Art of Computer Programming volume 1, but am finding myself unable to produce a rigorous proof, and the one  is suspect and not quite clear enough (for me, at least) in some of the steps; in particular, how to "[identify] the $k$th order coefficient in [the] two polynomials."  The problem is this: given a Vandermonde matrix $[x_j^i]_n$, show that the inverse is given by  $$ [b_{ij}]_n = \left[ \frac{    \sum_{\substack{1 \leq k_1 &lt; \dotsc &lt; k_{n-j} \leq n\\k_1,\dotsc,k_{n-j} \neq i}} (-1)^{j-1} x_{k_1} \dotsc x_{k_{n-j}} }{    x_i \prod_{\substack{1 \leq k \leq n\\k \neq i}} (x_k - x_i) } \right]_n\text{.} $$  The author gives a hint by stating that the sum in the above numerator is just the coefficient of $x^{j-1}$ in the polynomial $(x_1-x)\dotsc(x_n-x)/(x_i-x)$; and he gives an intermediate result showing the explicit multiplication of the matrix and its inverse as  $$    \sum_{1 \leq t \leq n}b_{it}x_j^t    =    \frac{       x_j \prod_{\substack{1 \leq k \leq n\\k \neq i}} (x_k - x_j)    }{       x_i \prod_{\substack{1 \leq k \leq n\\k \neq i}} (x_k - x_i)    }    =    \delta_{ij}\text{.} $$  The only other hint as to the type of solution he was expecting is a reference to A. de Moivre's The Doctrine of Chances, 2nd edition, pp. 197-199, which deals with polynomial recurrence relations and difference products (available ).  At the least, I was just hoping someone could either verify the proof is correct at proofwiki and possibly fill in exactly how one identifies the $k$th order coefficient in the proof; or perhaps explain a proof strategy as to what steps to take where the intermediate result is obtained at some point before the final result.  Thanks so much for any help. Is there a Raster Equivalent of the Split tool? I can't solve this problem:  Suppose $f$ is polynomial function of even degree $n$ with always $f\geq0$.  Prove that $f+f'+f''+\cdots+f^{(n)}\geq 0$. As things stand, will House Stark go extinct? According to the family tree in A World of Ice and Fire Ned Stark's children are in fact the only surviving Starks. And as of S06E09;      Bran is the only legitimate, male Stark.   In the Season Six Finale it is revealed that;      Jon is in fact the Son of Lyanna Stark and most likely, Rhaegar Targaryen.   This means that if Jon was legitimised and there was record of his birth in the Citadel;      He would become a Targaryen.   So I guess my big question is: Can Bran father children? I find it to be quite an important issue considering House Stark's long term survival depends on it.  In season 4 (I can't remember which episode) Locke Bolton gives Bran a cut on the leg to confirm his identity. Bran reacts only with fear and not pain, indicating that he has no feeling below his waist.  Does this mean that he wouldn't be able to...get it up? And if so, why hasn't the show addressed House Stark's impending doom? Persistent Dummy Output The soundcard I want to use is detected and works (it only recently switched to dummy output and didn't allow me to go back). HDMI is no longer listed under Audio and Video - KDE Control Module; everything under audio module is set to dummy output and its the only 'soundcard' on the list now. I can view my previous sound cards in alsamixer, but changing the settings from there does nothing. How can I get my real soundcards to work again? I have already tried the following answers without success:  EDIT: name@name-desktop:~$ lspci -vvv | grep -A8 Audio 00:01.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Kaveri HDMI/DP Audio Controller         Subsystem: ASRock Incorporation Kaveri HDMI/DP Audio Controller         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast &gt;TAbort- &lt;TAbort- &lt;MAbort- &gt;SERR- &lt;PERR- INTx-         Latency: 0, Cache Line Size: 64 bytes         Interrupt: pin B routed to IRQ 43         Region 0: Memory at ff764000 (64-bit, non-prefetchable) [size=16K]         Capabilities: &lt;access denied&gt;         Kernel driver in use: snd_hda_intel         Kernel modules: snd_hda_intel -- 00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD] FCH Azalia Controller (rev 01)         Subsystem: ASRock Incorporation FCH Azalia Controller         Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-         Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=slow &gt;TAbort- &lt;TAbort- &lt;MAbort- &gt;SERR- &lt;PERR- INTx-         Latency: 32, Cache Line Size: 64 bytes         Interrupt: pin A routed to IRQ 16         Region 0: Memory at ff760000 (64-bit, non-prefetchable) [size=16K]         Capabilities: &lt;access denied&gt;         Kernel driver in use: snd_hda_intel  Could this image possibly help?:  There is another soundcard but I'm unsure of what its for because it never outputs sound, but it does have a lot of settings: that sound card is labelled as &quot;HD-Audio Generic&quot;.   So I went into Software &amp; Updates under the Additional drivers tab and I see this:  It was on Do not use the device so I changed it and applied the settings but unfortunately the soundcard isn't back even after reboot. Are InnoDB Deadlocks exclusive to INSERT/UPDATE/DELETE? I am interested in comparing the computational cost of grid search vs. random search algorithm for hyperparameter tuning. Is random search computationally less expensive then grid search? Is there an article/paper that talks about this topic? Thank you, I was reading an example about describing homomorphisms and I'm having a bit of trouble with this one.  Show there is no group homomorphism $f : \mathbb{Z}_{10} \to \mathbb{Z}_{25}$ such that $f(1) = 3$. The first step of the proof is  $|1| = 10$ in $\mathbb{Z}_{10}$, so $|f(1)| \in\{ 1, 2, 5, 10\}$.  Does this mean that $|f(1)|$ can be $1$, $2$, $5$ or $10$? I see that $|1| = 10$ since $1$ is a generator of $\mathbb{Z}_{10}$, and that $|f(1)|$ seems to be a factor of $10$. If $f(1)$ is the image of $1$ under $f$, how would I find the order of $f(1)$?  Thanks for your help. E.g.  I know that I can browse the chat when I'm not logged on. But what if I am logged on and want to spare the inconvenience of logging off/multiple browsers? I am always really hesitant to mess around with $IFS because it's clobbering a global.   But often it makes loading strings into a bash array nice and concise, and for bash scripting, conciseness is hard to come by.   So I figure it might be better than nothing if I try to "save" the starting contents of $IFS to another variable and then restore it immediately after i am done using $IFS for something.   Is this practical? Or is it essentially pointless and I should just directly set IFS back to whatever it needs to be for its subsequent uses?