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Re^3: Nested evals - are they evil? (sample benchmarks)

by cLive ;-) (Parson)
on Jul 31, 2007 at 07:05 UTC ( #629753=note: print w/ replies, xml ) Need Help??


in reply to Re^2: Nested evals - are they evil? (sample benchmarks)
in thread Nested evals - are they evil?

Hmmm, well, I stripped it down further:

use strict; use warnings; use Benchmark 'cmpthese'; cmpthese(-1, { 'eval' => \&eval_code, 'noeval' => \&no_eval_code, }); sub eval_code { eval { some_more_code (); }; if ($@) { error_sub(); } } sub no_eval_code { if (0) { error_sub(); } else { some_more_code (); } } sub some_more_code { } sub error_sub { }
And got this (I think the effectively empty eval is meaningless - see here where I ran it 4 times):
Rate eval noeval eval 1298354/s -- -37% noeval 2066450/s 59% -- Rate eval noeval eval 1316991/s -- -38% noeval 2123851/s 61% -- Rate eval noeval eval 1217925/s -- -21% noeval 1534287/s 26% -- Rate eval noeval eval 1298354/s -- -41% noeval 2205537/s 70% --
I have a feeling an empty eval gets optimized away at compile time (though I am most probably wrong :)

How about if I add in an increment do ensure each eval has to be 'eval'd, ie

use strict; use warnings; use Benchmark 'cmpthese'; my $x; cmpthese(-1, { 'eval' => \&eval_code, 'noeval' => \&no_eval_code, }); sub eval_code { $x=1; eval { some_more_code (); }; if ($@) { error_sub(); } } sub no_eval_code { if ($x==0) { error_sub(); } else { $x=0; some_more_code (); } } sub some_more_code { $x++ } sub error_sub { }
I get this:
Rate eval noeval eval 989400/s -- -23% noeval 1286220/s 30% -- -bash-3.00$ perl tmp.pl Rate eval noeval eval 1092266/s -- -21% noeval 1379705/s 26% -- Rate eval noeval eval 1069351/s -- -19% noeval 1327443/s 24% -- Rate eval noeval eval 1071850/s -- -25% noeval 1435550/s 34% -- Rate eval noeval eval 1071850/s -- -26% noeval 1456355/s 36% --
Either way, I still haven't been able to create a counter example that shows eval to be faster.

But anyway, considering the number of runs a second, I have a feeling my energies are probably better spent focusing on other parts of the code as far as optimizations are concerned :)


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