Don Stewart ha scritto:
dons:
bulat.ziganshin:
Hello Achim,
Friday, February 20, 2009, 11:44:49 PM, you wrote:
Turning this into a ticket with associated test will: but why you think that this is untypical and needs a ticket? ;)
Bulat, you are right in every aspect. You never did anything wrong. Achim, this is simplest code one can imagine. so when Simon will go to check ghc optimizations, he will try it without any reports. but Simon, unlike Don, never said that ghc may be compared to gcc. Don, on the other hand, say this everyday. when he is asked for code that shows this, he declined to answer. so - why YOU think that ghc generates fast code and this example is something unusual? can you provide any *technical* arguments or will continue to make personal attacks together with Don? Bulat, you misunderstand, it is not personal! We just want something to work on. Something specific.
For example, you've identified loop unrolling as something that could very profitably be improved in GHC, and Claus even wrote a prototype to see what kind of speedups to guess.
This is a great contribution! Now we know where to hunt.
And just to summarise what we have seen:
ghc -O2 naive left fold 15.680 gcc -O0 4.500 ghc manual recursion -fasm 1.328 ghc manual recursion 1.035 ghc naive left fold "stream fusion" 0.967 gcc -O1 0.892 ghc "-funroll-loops" -D8 0.623 gcc -O3 -funroll-loops 0.318 ghc "-funroll-loops" -D64 0.088
As a full comparison I would like to see time for ghc -O0 naive left fold Manlio Perillo