#2416: Optimization defeated by merging module into main
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Reporter: sedillard | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.8.3 | Severity: normal
Keywords: | Testcase:
Architecture: x86_64 (amd64) | Os: Linux
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I have a library, `TheModule`, and an application that uses `TheModule`,
called `Main`. When `TheModule` lives in `TheModule.hs` and `Main` lives
in `Main.hs`, optimization works as expected. When I copy all of
`TheModule`'s definitions and all of `Main`'s definitions into `Both.hs`,
much less optimization occurs, as can be seen from -ddump-simpl, as well
as the drastic difference in running times.
The program performs a lot of small matrix-vector multiplications. The
single command line argument tells how many to do.
{{{
time ./Main 1000000
20.0 :. (59.0 :. (100.0 :. (137.0 :. ())))
real 0m0.389s
user 0m0.152s
sys 0m0.232s
time ./Both 100000
20.0 :. (59.0 :. (100.0 :. (137.0 :. ())))
real 0m3.462s
user 0m3.368s
sys 0m0.068s
}}}
So that makes Both about 100 times slower. Compiled with -O2 and -fexcess-
precision
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2416>
GHC <http://www.haskell.org/ghc/>
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