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Re: 2% speedup with Duff's device

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Jarkko Hietaniemi
January 23, 2001 07:03
Re: 2% speedup with Duff's device
Message ID:
> > That is true, the timing of the whole suite is to be taken with a
> > biiig grain of salt -- but a test of consisting of, say, 1 second of
> > actual test (CPU time being burned) and 1 second of sleep gets sped up
> > by, say, 10%, it means that the CPU time really got slashed by 20%,
> > which is actually *more* significant than without the sleep.
> But in
> u=1.33  s=0.46  cu=62.27  cs=10.54  scripts=273  tests=21120
> real    2m16.388s
> user    1m3.610s
> sys     0m11.000s
> (which is from time ./perl TEST)
> I was under the impression that real is wallclock, and the other two
> are user and system call CPU time, not elapsed time.

Correct.  I was in the above talking more about the timings for one
test, not the whole suite.

> > I think the most dubious element of the test suite as a whole is the
> > large number of separate and relatively small scripts, the operating
> > system (and filesystem, and networking, and ...) dependent startup
> > time may taint the results quite a lot.
> Lots of lovely perl symbols, all being put into symbol tables lots of
> times, all being hashed each time?

Very possible.  But how about them op/numconvert and op/int failures, eh? :-)

> If so, that might explain it unfairly favouring faster hash algorithms
> Nicholas Clark

$jhi++; #
        # There is this special biologist word we use for 'stable'.
        # It is 'dead'. -- Jack Cohen

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