#3586: Initialisation of unboxed arrays is too slow
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Reporter: simonpj | Owner:
Type: run-time performance bug | Status: new
Priority: high | Milestone: 6.12.2
Component: libraries (other) | Version: 6.10.4
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Comment (by int-e):
Replying to [comment:12 simonpj]:
> Both versions yield identical code. So why do you think one is better
than t'other?
I'm afraid I must have imagined that. In any case, I'm unable to reproduce
my measurements although I remember a distinct decrease in runtime with a
variant of dons' testcase, from 0.090 to 0.060 seconds, with multiple
measurements. Perhaps I mixed up user and total execution time? Oh well.
So that part of the patch should be left out.
On to more serious matters - the explicitely inlined worker trick works
for ghc 6.10.4, but is not sufficient for the 6.12 RC, so that will need a
different fix. One idea that works is to add
{{{
newArray = newArrayImpl
}}}
to all {{{MArray (STUArray ...) ...}}} instances. Of course getting
inlining for default methods to work would be preferable. In fact, for
default method it would be nice to have a special form of the SPECIALIZE
pragma as well, one that duplicates the definition for all instances and
optimizes it in that context.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3586#comment:13>
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