I have read so many blogs for @autorelease pool but I am still not clear about this @autorelease pool concept in objective c or ios development.  So can any one please throw a light on this concept. It would be very helpful to me if any one could provide me with an example of it and when the use of @autorelease pool is required.   How can I measure the memory allocation with use of @autorelease pool and without it.  Please throw a light on this topic might be it is duplicate.
As I understand it, anything created with an alloc, new, or copy needs to be manually released. For example:  int main(void) {     NSString *string;     string = [[NSString alloc] init];     /* use the string */     [string release]; }   My question, though, is wouldn't this be just as valid?:  int main(void) {     NSAutoreleasePool *pool;     pool = [[NSAutoreleasePool alloc] init];     NSString *string;     string = [[[NSString alloc] init] autorelease];     /* use the string */     [pool drain]; }
Generated Frattini Lemma Let $A$ be a normal subgroup of a group $G$. Let $B$ be a subgroup of   $A$ with the property that whenever $B_1 \leq A$ is conjugate to $B$   in $G$ then it is conjugate to $B$ in $A$. Prove that $G=AN_G(B)$   Help me some hints. Animagi (Sirus specifically) and wands? Square roots not on same height This part C\frac{1}{\sqrt{G}}\sqrt{\rho} doesn't seem to be on the same height as this part \sqrt{b}\sqrt{l} when compiled. What am I doing wrong?  \begin{flalign*} T=C\frac{1}{\sqrt{G}}\sqrt{\rho}\sqrt{b}\sqrt{l} &amp;&amp; \end{flalign*} Detect init system using the shell How can I tell hotels exist that aren't on the booking web sites? There are a ton of sites out there to help book hotel rooms and to aggregate all the different sites to book hotel rooms. These companies make enough money to buy ads on TV, so I won't name them here. I normally poke around 3 or 4 of these as part of planning any trip.  I am now starting some very long term planning for a 6 week South Pacific trip, which includes undertstanding what hotels costs on some very small islands. I have paper guidebooks and I've been looking online. But I come across anomalies. For example, a place which has only 9 hotels listed on the sites I use, and prices range from $1000/night down to $200/night, then when I read the reviews on that cheapest one people are saying "it's nothing special, there are 5 or 6 places just like it here for half the price". Well, not on this site there aren't!  My guess is that many of these places don't have web sites, or don't have online booking, and therefore aren't getting into the aggregators. For some islands I have found local tourism boards with lists of "pensions" and such, typically cheaper than what I can find on the aggregators.    But how can I know? I don't want to assume that popular web sites represent reality, and choose only from places listed there. But I don't want to invest 10-20 hours of research per island only to discover the aggregators had everything. How can I know where the coverage is good and where it isn't, what kinds of hotels are more or less likely to be listed at expedia, trivago, booking, hotels, tripadvisor, and the like? (For example, I don't want to stay at a hostel, so I don't mind if they're not included in online sites.) Are there sites like wikitravel that list places without much of an internet presence?  I'm starting my research over a year before the trip, but wading through hotel pages is not the fun part of the planning so tell me how the smart people do it. Identify $P(2014)$ if $P(i)=1/i$ for every positive integer $1\le i\le2013$ Suppose $P(x)$ is a polynomial of degree $2012$ and $P(x) = 1/x$ when $x$ takes the integer values $1\cdots2013$ (inclusive). What is the value of $P(2014)$?   I get $1/1007$ but I'm not sure if it's right, and my method is very inelegant. Change icon on MATE main menu How can I change the default logo icon to a custom icon by the applications menu in Ubuntu MATE without changing the theme? The process substitution &lt;(cat) doesn't work. Why?  head &lt;(cat)  cat: -: Input/output error   I can use an extra file descriptor, but I don't understand why the above doesn't work.  # Using file descriptor 3 to reroute the input (head &lt;(cat &lt;&amp;3)) 3&lt;&amp;0 Solve $f(x)f(2x^2) = f(2x^3+x)$ The full question is to solve $f(x)f(2x^2) = f(2x^3+x)$, prove there are at most one solution per degree of $f(x)$ and then find all the solutions. (Here $f(x)$ is assumed to be polynomial.)  So far I have proven that $(x^2+1)^n$ works for even degree polynomials, and I'm pretty near certain there are no odd solutions.  Is the following a valid argument for there only being at most 1 solution per degree? Let $K$ be the degree of $f(x)$ then $f(x)f(2x^2) = f(2x^3+x)$ produces $3k+1$ linearly independent equations with only $k+1$ independent variables. Therefore for any degree $K$ polynomial there can be at most 1 solution.  Finally, is there any elegant way to prove that no odd solutions exist? What race (species?) is Star Lord's dad? At the end of the new Guardians of the Galaxy Vol. 2 Trailer we meet Star Lord's father:                                  Dad appears to be human. But Peter Quill's mother said in the first film that his father was a      "being made of pure light".    What race (species?) is Star Lord's father in the MCU? How to call shell commands from Ruby What's the difference between asymptotic unbiasedness and consistency? Does each imply the other? If not, does one imply the other? Why/why not?  This issue came up in response to a comment on an answer I posted .  Although google searching the relevant terms didn't produce anything that seemed particularly useful, I did notice  on the math stackexchange. However, I thought that this question was appropriate for this site too.  EDIT after reading the comments  Relative to the math.stackexchange answer I was after something more in depth, covering some of the issues dealt with in . Also, as I see it the math.stackexchange question shows that consistency doesn't imply asymptotically unbiasedness but doesn't explain much if anything about why. The OP there also takes for granted that asymptotic unbiasedness doesn't imply consistency, and thus the sole answerer so far doesn't address why this is. How to prove that $364 \mid n^{91} - n^7$? Beamer - Color of header foreground with AnnArbor theme I use beamer with the theme AnnArbor and colortheme whale.  I tried to use:  \setbeamercolor{section in head/foot}{fg=white, bg=blue}   or  \setbeamercolor{palette tertiary}{fg=white, bg=blue}   But for an unknown reason, the bg works but not the fg... The sections names stay black in the header.    EDIT : the problem comes from the hyperref package.  This code works well :  \documentclass{beamer} \usetheme{AnnArbor} \usecolortheme{whale} \setbeamercolor{frametitle}{fg=white,bg=blue}  \begin{document}     \section{Test 1}     \subsection{Test 1.1}     \begin{frame}         \frametitle{Test}     \end{frame} \end{document}   Whereas this one doesn't works :  \documentclass{beamer} \usetheme{AnnArbor} \usecolortheme{whale} \setbeamercolor{frametitle}{fg=white,bg=blue} \usepackage{hyperref} \hypersetup{     colorlinks=true,     linkcolor=black,     urlcolor=blue,     citecolor=gray,     frenchlinks=false,     pdfborder={0 0 0} }  \begin{document}     \section{Test 1}     \subsection{Test 1.1}     \begin{frame}         \frametitle{Test}     \end{frame} \end{document}   And that's pretty normal because of this line :  linkcolor=black, How to achieve this smudge effect in photoshop? I came across this photo by Jacob Sutton and wanted to know if someone knew how to get this effect in photoshop?    (source: ) Light Presets .exr I would like to install light presets for Blender to automate my lightning in my scenes. I have some .exr files (from Greyscalegorilla) but I don't know how to do it on Blender to make it work. Can someone help me? Thank you If $a$ divides $bc$ and $\gcd(a,b) = d$ then $\frac a d$ divides c I'm trying to prove that if $a$ divides $bc$ and $\gcd(a,b) = d$ then $\frac a d$ divides c. I tried using Bezout identity but couldn't get anywhere. Is it possible to get the ID of a Contact which is part of a Person Account?  I have a custom object which has a custom field referencing the Person Account, though it seems to be referencing the Contact directly. I have created a button which I am using to pass the ID into a Visualforce Page.  With the Insert Field drop-down on the create/edit button page I can put in {!Account.Id} or {!Contact.Id} but neither of these work. The Account ID is placed in the URL but is not the correct ID and the Contact ID is blank, which I assume is because the button is on a Person Account page and not a Contact Page. What's the best way to find the inverse of datetime.isocalendar()? Setting the correct encoding when piping stdout in Python