RE: [Haskell-cafe] -O2 compile option can give speed increase over -O. Fasta shootout program test runs.
| It seems the -O2 option can give a significant speed increase relative | to just the -O option. This is contrary to the documentation which says -O2 switches on SpecConstr, which has improved quite a bit in the last year or so. There's a paper on my home page about it (Constructor specialization for Haskell). Perhaps we should review the documentation you point to! Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] -O2 compile option can give speed increase over -O. Fasta shootout program test runs.
Derek Elkins wrote: Just to add as this was not addressed. -O2 -does not- turn off bounds checking or any other obvious safety mechanism. although even just -O removes GHC's special 'assert'ions (unless you explicitly keep them on?) -- though they shouldn't be used in such a way that they could trigger, assuming that the code/library that employs them is non-buggy (or exports 'unsafe' things in which case a library's client also has to be non-buggy). Bounds checking is turned off iff you use functions named like unsafeAt, regardless of -O0, -O2 or any other optimization flags :) Isaac ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] -O2 compile option can give speed increase over -O. Fasta shootout program test runs.
I have been playing with the Fasta program in the shootout to see if
I can make it umm faster. Starting from dons program on this page and
adding some timing calculations as suggested on this wiki page
http://shootout.alioth.debian.org/gp4/benchmark.php?test=fastalang=ghcid=2
http://www.haskell.org/haskellwiki/Timing_computations
I added different OPTIONS into the top line of the program did a
ghc --make fasta.hs and ran it each time with fasta 250
(This is one tenth of the shootout figure.) These runs all keep the
existing OPTIONS of -fbang-patterns -fexcess-precision
Seconds OPTIONS Added
--- -
40.5
40.5-funbox-strict-fields
40.4 {-# INLINE rand #-}
17.2-O
17.0-O -fvia-C
14.4-O -optc-march=pentium4
11.5-O2
11.2-O3
11.5-O3 {-# INLINE rand #-}
11.3-O2 -optc-march=pentium4
There was a bit of variation, I've averaged over two runs. This is on
an Intel Pentium D 2.66GHz running W2K and GHC 6.6.1.
It seems the -O2 option can give a significant speed increase relative
to just the -O option. This is contrary to the documentation which says
http://www.haskell.org/ghc/docs/latest/html/users_guide/options-optimise.html
http://www.haskell.org/ghc/docs/latest/html/users_guide/faster.html
it won't make any difference. I guess it's program, architecture and
operating system specific, but according to these figures the -O2 option
seems well worth a try for programs that need speed. It may be that
we sacrifice bounds checking or something important with -O2, I don't
know.
Richard.
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Re: [Haskell-cafe] -O2 compile option can give speed increase over -O. Fasta shootout program test runs.
r.kelsall:
I have been playing with the Fasta program in the shootout to see if
I can make it umm faster. Starting from dons program on this page and
adding some timing calculations as suggested on this wiki page
http://shootout.alioth.debian.org/gp4/benchmark.php?test=fastalang=ghcid=2
http://www.haskell.org/haskellwiki/Timing_computations
I added different OPTIONS into the top line of the program did a
ghc --make fasta.hs and ran it each time with fasta 250
(This is one tenth of the shootout figure.) These runs all keep the
existing OPTIONS of -fbang-patterns -fexcess-precision
Seconds OPTIONS Added
--- -
40.5
40.5-funbox-strict-fields
40.4 {-# INLINE rand #-}
17.2-O
17.0-O -fvia-C
14.4-O -optc-march=pentium4
11.5-O2
11.2-O3
11.5-O3 {-# INLINE rand #-}
11.3-O2 -optc-march=pentium4
There was a bit of variation, I've averaged over two runs. This is on
an Intel Pentium D 2.66GHz running W2K and GHC 6.6.1.
It seems the -O2 option can give a significant speed increase relative
to just the -O option. This is contrary to the documentation which says
http://www.haskell.org/ghc/docs/latest/html/users_guide/options-optimise.html
http://www.haskell.org/ghc/docs/latest/html/users_guide/faster.html
it won't make any difference. I guess it's program, architecture and
operating system specific, but according to these figures the -O2 option
seems well worth a try for programs that need speed. It may be that
we sacrifice bounds checking or something important with -O2, I don't
know.
Yes, -O2 is getting better, as new optimisations like SpecConstr are
enabled by it. For shootout problems, I'd selectively test with -O2, and
if it is better, use that.
Good work! And yes, I see that it is currently compiled with:
-O fbang-patterns -fexcess-precision -fglasgow-exts -optc-march=pentium4
if -O2 is consistently better here, then we could happily switch.
-- Don
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Re: [Haskell-cafe] -O2 compile option can give speed increase over -O. Fasta shootout program test runs.
On Tue, 2007-07-17 at 11:24 +1000, Donald Bruce Stewart wrote:
r.kelsall:
I have been playing with the Fasta program in the shootout to see if
I can make it umm faster. Starting from dons program on this page and
adding some timing calculations as suggested on this wiki page
http://shootout.alioth.debian.org/gp4/benchmark.php?test=fasta〈=ghcid=2
http://www.haskell.org/haskellwiki/Timing_computations
I added different OPTIONS into the top line of the program did a
ghc --make fasta.hs and ran it each time with fasta 250
(This is one tenth of the shootout figure.) These runs all keep the
existing OPTIONS of -fbang-patterns -fexcess-precision
Seconds OPTIONS Added
--- -
40.5
40.5-funbox-strict-fields
40.4 {-# INLINE rand #-}
17.2-O
17.0-O -fvia-C
14.4-O -optc-march=pentium4
11.5-O2
11.2-O3
11.5-O3 {-# INLINE rand #-}
11.3-O2 -optc-march=pentium4
There was a bit of variation, I've averaged over two runs. This is on
an Intel Pentium D 2.66GHz running W2K and GHC 6.6.1.
It seems the -O2 option can give a significant speed increase relative
to just the -O option. This is contrary to the documentation which says
http://www.haskell.org/ghc/docs/latest/html/users_guide/options-optimise.html
http://www.haskell.org/ghc/docs/latest/html/users_guide/faster.html
it won't make any difference. I guess it's program, architecture and
operating system specific, but according to these figures the -O2 option
seems well worth a try for programs that need speed. It may be that
we sacrifice bounds checking or something important with -O2, I don't
know.
Yes, -O2 is getting better, as new optimisations like SpecConstr are
enabled by it. For shootout problems, I'd selectively test with -O2, and
if it is better, use that.
Good work! And yes, I see that it is currently compiled with:
-O fbang-patterns -fexcess-precision -fglasgow-exts -optc-march=pentium4
if -O2 is consistently better here, then we could happily switch.
Just to add as this was not addressed. -O2 -does not- turn off bounds
checking or any other obvious safety mechanism.
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