#2670: Performance regression
---------------------------------+------------------------------------------
Reporter: simonmar | Owner: simonpj
Type: bug | Status: new
Priority: normal | Milestone: 6.10.2
Component: Compiler | Version: 6.8.3
Severity: normal | Keywords:
Difficulty: Unknown | Testcase:
Architecture: Unknown/Multiple | Os: Unknown/Multiple
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The attached program performs much worse with HEAD as of today (and
presumably also 6.10.1) than 6.8.3.
{{{
> ghc-6.8.3 --make -O2 bug.hs
[1 of 1] Compiling Main ( bug.hs, bug.o )
Linking bug ...
> time ./bug
1.17s real 1.17s user 0.01s system 99% ./bug
> ghc-6.11 --make -O2 bug.hs
[1 of 1] Compiling Main ( bug.hs, bug.o )
Linking bug ...
> time ./bug
1.58s real 1.58s user 0.01s system 99% ./bug
}}}
The problem appears to be in the code for `delete`, GHC has duplicated two
calls to `next`.
Also note this is a version of the code we have in `eyeball/IOList.lhs`
which illustrates some other problems in the current optimiser (although
the other problems are not regressions, which is why I'm highlighting this
one).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2670>
GHC <http://www.haskell.org/ghc/>
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