#3629: Code compiled WITHOUT profiling many times slower than compiled WITH
profiling on
---------------------------+------------------------------------------------
Reporter: gchrupala | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.12 branch
Component: Compiler | Version: 6.13
Resolution: | Keywords:
Difficulty: Unknown | Os: Unknown/Multiple
Testcase: | Architecture: Unknown/Multiple
Failure: None/Unknown |
---------------------------+------------------------------------------------
Changes (by aruiz):
* cc: aruiz (added)
* failure: => None/Unknown
Comment:
I have a similar problem using foreign calls (in the hmatrix library). A
program is 10x slower without profiling (and in ghci) than compiled with
profiling on.
This happens in ghc-6.12.1 (ghc-6.12.1-i386-unknown-linux-n.tar.bz2 on
Ubuntu ), but not in ghc-6.10. I include a small test case.
We need:
$ sudo apt-get install libgsl0-dev liblapack-dev
$ cabal install hmatrix -p
$ cat slow.hs
{{{
import Numeric.LinearAlgebra
m = ident 2000 :: Matrix Double
main = print $ vectorMax (takeDiag (m <> m))
}}}
With ghc-6.12.1
{{{
$ ghc -V
The Glorious Glasgow Haskell Compilation System, version 6.12.1
$ ghc --make slow.hs -fforce-recomp
[1 of 1] Compiling Main ( slow.hs, slow.o )
Linking slow ...
$ time ./slow
1.0
real 1m15.790s
user 1m15.489s
sys 0m0.228s
$ ghc --make slow.hs -prof -fforce-recomp
[1 of 1] Compiling Main ( slow.hs, slow.o )
Linking slow ...
$ time ./slow
1.0
real 0m7.366s
user 0m7.264s
sys 0m0.100s
}}}
With ghc-6.10.3
{{{
$ ghc -V
The Glorious Glasgow Haskell Compilation System, version 6.10.3
$ ghc --make slow.hs -fforce-recomp
[1 of 1] Compiling Main ( slow.hs, slow.o )
Linking slow ...
$ time ./slow
1.0
real 0m7.142s
user 0m7.060s
sys 0m0.072s
$ ghc --make slow.hs -prof -fforce-recomp
[1 of 1] Compiling Main ( slow.hs, slow.o )
Linking slow ...
$ time ./slow
1.0
real 0m7.242s
user 0m7.132s
sys 0m0.096s
}}}
Thanks,
Alberto Ruiz
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3629#comment:3>
GHC <http://www.haskell.org/ghc/>
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