Re: [Haskell-cafe] Diagnose stack space overflow
Max Bolingbroke batterseapo...@hotmail.com writes: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? It's possible that building your program with profiling and then running with +RTS -xc will print a useful call stack. Does this help, really? I've tried that occasionally, but can't really say it's ever helped pinpoint the problem. (Not complaining, stack traces are hard in Haskell.) I generally heap-profile (often with the -hd option), most stack overflows will also retain heap data (i.e. a stack of (+) operations will point to all the numbers as well), which should give you an idea of where to look. -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Diagnose stack space overflow
John Lato jwl...@gmail.com writes: I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? I'd like to point out that a stack-space overflow in Haskell isn't quite the same thing as in other functional languages. In particular, it's possible for tail-recursive functions to overflow the stack because of laziness. ..in fact, you often want to *avoid* tail recursion (e.g. as implemented in foldl) and use something that is not tail recursive (e.g. foldr) but more laziness-friendly. Or use strictness (foldl'). -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Diagnose stack space overflow
On Friday 08 July 2011, 11:29:40, Ketil Malde wrote: Max Bolingbroke batterseapo...@hotmail.com writes: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? It's possible that building your program with profiling and then running with +RTS -xc will print a useful call stack. Does this help, really? I've tried that occasionally, but can't really say it's ever helped pinpoint the problem. (Not complaining, stack traces are hard in Haskell.) It can help. I recently had a stack overflow in some code with ghc-7 (which worked fine in ghc-6) which was a pain to locate. I had forgotten about the -xc way and when (after the fact) I read Max' post, I reverted the fix and tried that. And, hey presto, the printed call stack, although not incredibly informative, revealed the function in which the overflow occurred. It would have been faster to pinpoint with -xc. I generally heap-profile (often with the -hd option), most stack overflows will also retain heap data (i.e. a stack of (+) operations will point to all the numbers as well), which should give you an idea of where to look. The abovementioned didn't reveal anything in the heap profiles, apart from the data that should have been there (in the correct amounts), there were only TSOs and BLACKHOLE in the profiles, not attributed to anything (despite ample SCC pragmas). I have little experience with stack overflows, so I can't tell whether heap profiling is generally more informative than the stack trace to find them or not, it's certainly reasonable to expect that often retained data will show you where to look, but it doesn't always do it. One should be aware of both ways, where the first one tried doesn't help, the other one may. Cheers, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Diagnose stack space overflow
Hi, For the following error: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? Thanks, Loganathan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Diagnose stack space overflow
Profile!! E.g. http://stackoverflow.com/questions/6429085/haskell-heap-issues-with-parameter-passing-style/6429888#6429888 On Mon, Jul 4, 2011 at 11:44 AM, Logo Logo sarasl...@gmail.com wrote: Hi, For the following error: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? Thanks, Loganathan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Diagnose stack space overflow
You can use the heap profiling options in GHC to find out what is using all the memory. You'll want to compile with -prof and -rtsopts, and then invoke the program with +RTS -hx, where x is one of 'c', 'y', or a few others. Then run hp2ps on the resulting .hp file to get a graph of what's using all the memory. -- Chris Smith On Jul 4, 2011 9:46 AM, Logo Logo sarasl...@gmail.com wrote: Hi, For the following error: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? Thanks, Loganathan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Diagnose stack space overflow
On 4 July 2011 16:44, Logo Logo sarasl...@gmail.com wrote: Hi, For the following error: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? It's possible that building your program with profiling and then running with +RTS -xc will print a useful call stack. Cheers, Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Diagnose stack space overflow
Hi Don, I find this answer confusing. The SO question you're linking to is about heap size, not stack overflow. The stack size in this example is 8M. The whole heap size may be much bigger (and increasing the stack size may actually remove the overflow). It would be interesting to learn about success stories of investigation of a stack overflow using heap profiling. * Don Stewart don...@gmail.com [2011-07-04 12:08:05-0400] Profile!! E.g. http://stackoverflow.com/questions/6429085/haskell-heap-issues-with-parameter-passing-style/6429888#6429888 On Mon, Jul 4, 2011 at 11:44 AM, Logo Logo sarasl...@gmail.com wrote: Hi, For the following error: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? -- Roman I. Cheplyaka :: http://ro-che.info/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Diagnose stack space overflow
From: Logo Logo sarasl...@gmail.com Hi, For the following error: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually? I'd like to point out that a stack-space overflow in Haskell isn't quite the same thing as in other functional languages. In particular, it's possible for tail-recursive functions to overflow the stack because of laziness. Consider this tail-recursive sum function: trSum :: [Int] - Int trSum l = go 0 l where go acc [] = acc go acc (x:xs) = go (acc+x) xs It's tail-recursive. But if you enter this in ghci and run it, you'll find that it uses increasing stack space, and will likely cause a stack overflow for large enough inputs. The problem is that the accumulator 'acc' isn't strict and builds up a thunk of the form: 0+n1+n2+...+nn The solution is to add strictness. For this example, a '!' on the accumulator will do. GHC will sometimes spot cases where extra strictness is helpful (it'll figure this one out when compiled with -O), but it often needs help. I'd recommend Edward Yang's series of blog posts about debugging, space leaks, and the Haskell heap. One useful article is http://blog.ezyang.com/2011/05/anatomy-of-a-thunk-leak/ , but you may want to start at the beginning of the heap series. John L. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
