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I noticed that your fast permutation algorithm passes an arrayref, but then copies the values out. There's no particular savings there compared to passing the array. That and a few other micro-optimizations squeezed 210+% more speed out (if you don't print — the savings are probably less significant with printing turned on.) Code (update: fixed, reducing savings, as expected) follows.
{ my $level = 0; sub permute_new { local @_ = @_; my $index = $level; my $printing = $level == $#_; if ($printing) { do { #print "@_\n"; @_[$index-1, $index] = @_[$index, $index-1] if $index != 0; } while $index-- > 0; } else { do { ++$level; &permute_new; --$level; @_[$index-1, $index] = @_[$index, $index-1] if $index != 0; } while $index-- > 0; } } } sub permute_orig { my ($aref, $level) = (@_, 0); my ($index, $copy, $printing) = ($level, [@$aref], $level+1 == @$a +ref); do { if ($printing) { #print "@$copy\n"; } else { permute_orig($copy, 1+$level); } @$copy[$index-1, $index] = @$copy[$index, $index-1] if $index != 0; } while $index-- > 0; } my $to = shift; use Time::HiRes qw( gettimeofday tv_interval ); my @start_time = gettimeofday(); permute_orig([1..$to]); print "\n"; my @end_time = gettimeofday(); print tv_interval ( \@start_time, \@end_time )," elapsed seconds for o +riginal.\n\n"; @start_time = gettimeofday(); permute_new(1..$to); @end_time = gettimeofday(); print tv_interval ( \@start_time, \@end_time )," elapsed seconds for n +ew.\n\n";

Caution: Contents may have been coded under pressure.

In reply to Re^2: Speed/Efficiency tweaks for a fannkuch benchmark script? by Roy Johnson
in thread Speed/Efficiency tweaks for a fannkuch benchmark script? by thundergnat

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