Hello! I've performed a few simple tests using Haskell and C++ on primitives.I've compilled all Haskell programs with -O2 optimizations, and C++ ones with -O3 ghc version - 7.10.2, gcc version : 5.1.1 I'm sending the codes in the zip file. Time of execution (in seconds): Int pure tail recursion: 6.911011299962411e-2 Int# pure tail recursion : 4.587398100011342e-2 IORef 'tail' recursion 1.0696569040001123 STRef for loop 1.1545546840006864 STRef tail recursion 1.1110019479992843 C++ : 2.7e-07 The llvm version could be as fast as C++ one in this problem. Buuut... then there's problem 2 (using if or case) - 100 000 000 iterations: Int# tail recursion 1.315346227000191 IORef for loop: 2.6442542390004746 STRef for loop: 2.669217500999366 C++: 0.158056 Here haskell is about 9 times slower than C++. Problem 4 - executing the same functionality using bit operations - 100 000 000 iterations: Int# tail recursion: 0.12361123500068061 C++: 0.131141 So, Haskell here is as fast as C++. My question is: can IORefs and STRefs be optimized ? I would like very much to rely on them, but I would like to achieve great speeds. Also, is can one achieve good speeds of execution when using cases or ifs ? If not, what is the other way to do it ? Compiler flags, Cmm optimizations - they are all welcome. And the final question - how hard would it be to implement such optimizations in ghc compiler? Regards, Mateusz Kłoczko _______________________________________________ Glasgow-haskell-users mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users EfficientMutability.zip (6K) Download Attachment |
Hi Mateusz,
IORef and STRef are boxed references. That is, they are a mutable cell that contains a pointer to some immutable Haskell value. When you increment a (STRef Int), you first dereference the pointer, allocate a new immutable heap object to represent the new integer value, then mutate the reference to point to the new object. This costs much more than updating a plain mutable integer. As far as I know there is no particularly popular library that provides mutable references like this. As a workaround, you can create a 1-sized unboxed mutable vector using the vector package, and use it like a reference. On 3 December 2015 at 01:10, Mateusz Kłoczko <[hidden email]> wrote: > Hello! > > I've performed a few simple tests using Haskell and C++ on primitives. > I've compilled all Haskell programs with -O2 optimizations, and C++ ones > with -O3 > ghc version - 7.10.2, gcc version : 5.1.1 > > I'm sending the codes in the zip file. > > Problem1 - 100 000 000 iterations. > > Time of execution (in seconds): > Int pure tail recursion: 6.911011299962411e-2 > Int# pure tail recursion : 4.587398100011342e-2 > IORef for loop 1.1533970820000832 > IORef 'tail' recursion 1.0696569040001123 > STRef for loop 1.1545546840006864 > STRef tail recursion 1.1110019479992843 > C++ : 2.7e-07 On this one, g++ manages to eliminate the loop entirely, but GHC doesn't. > > The llvm version could be as fast as C++ one in this problem. > > Buuut... then there's problem 2 (using if or case) - 100 000 000 iterations: > Int# tail recursion 1.315346227000191 > IORef for loop: 2.6442542390004746 > STRef for loop: 2.669217500999366 > C++: 0.158056 > > > Here haskell is about 9 times slower than C++. The main difference on this comes from the fact that GHC does not optimize (n `remInt#` 2#) into (n `andI#` 1#). There is a ticket [0] that contains some discussion of this issue. [0]: https://ghc.haskell.org/trac/ghc/ticket/5615 Hope this helps, Takano Akio _______________________________________________ Glasgow-haskell-users mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users |
My mutable-containers package has unboxed and storable references actually. On Fri, Dec 11, 2015, 12:26 PM Akio Takano <[hidden email]> wrote: Hi Mateusz, _______________________________________________ Glasgow-haskell-users mailing list [hidden email] http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users |
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