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
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