Re^2: How expensive is eval { }?

This benchmark result seems to vary strongly with the platform and/or perl version.

Debian GNU/Linux i386 (32 bit, SMP):

$ perl5.8.8 foo.pl
            Rate ForExcept   BareFor ExceptFor
ForExcept 2511/s        --      -34%      -34%
BareFor   3794/s       51%        --       -1%
ExceptFor 3829/s       52%        1%        --
$ perl5.10.0 foo.pl
            Rate ForExcept   BareFor ExceptFor
ForExcept 2393/s        --      -29%      -30%
BareFor   3350/s       40%        --       -2%
ExceptFor 3429/s       43%        2%        --
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That's quite different from the 2% .. 13%.

Any idea why the differences between the perl versions and platforms are that big?

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Re^3: How expensive is eval { }? by GrandFather (Saint) on Apr 17, 2008 at 10:05 UTC
No real idea, but bear in mind that most likely we are looking at only a few instructions' execution time difference between each case so they could be highly sensitive to optimization or modest differences in instruction timing between different processors (I ran my tests on a Turion⁶⁴ powered laptop btw). Beyond indicating that the eval overhead is small enough to be discounted in most practical contexts, the benchmark really doesn't tell us very much - except that you can't trust benchmarks very much for this sort of fine grain comparison. The important thing to note is that the eval costs much less than 1 micro-second. Perl is environmentally friendly - it saves trees	[reply]

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Re^3: How expensive is eval { }?
by GrandFather (Saint) on Apr 17, 2008 at 10:05 UTC

No real idea, but bear in mind that most likely we are looking at only a few instructions' execution time difference between each case so they could be highly sensitive to optimization or modest differences in instruction timing between different processors (I ran my tests on a Turion⁶⁴ powered laptop btw).

Beyond indicating that the eval overhead is small enough to be discounted in most practical contexts, the benchmark really doesn't tell us very much - except that you can't trust benchmarks very much for this sort of fine grain comparison. The important thing to note is that the eval costs much less than 1 micro-second.

Perl is environmentally friendly - it saves trees

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