[Haskell-cafe] Can Haskell outperform C++?
Manuel M T Chakravarty
chak at cse.unsw.edu.au
Tue May 15 02:55:22 CEST 2012
> But, anyway, it turns out that my example above is easily transformed from a bad GHC performance story into a good one. If you'll bear with me, I'll show how below.
> First, Manuel makes a good point about the LLVM backend. My "6X" anecdote was from a while ago and I didn't use llvm . I redid it just now with 7.4.1+LLVM, results below. (The below table should read correctly in fixed width font, but you can also see the data in the spreadsheet here.)
> Time (ms) Compiled File size Comple+Runtime (ms)
> GHC 7.4.1 O0 2444 1241K
> GHC 7.4.1 O2 925 1132K 1561
> GHC 7.4.1 O2 llvm 931 1133K
> GHC 7.0.4 O2 via-C 684 974K
> So LLVM didn't help . And in fact the deprecated via-C backend did the best!
I would classify that as a bug.
>  P.P.S. Most concerning to me about Haskell/C++ comparisons are David Peixotto's findings that LLVM optimizations are not very effective on Haskell-generated LLVM compared with typical clang-generated LLVM.
There is some work underway to improve the situation, but I am sure more could be done.
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