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Re^2: does perl have branch prediction

by david2008 (Scribe)
on Jan 29, 2014 at 06:38 UTC ( #1072440=note: print w/ replies, xml ) Need Help??


in reply to Re: does perl have branch prediction
in thread does perl have branch prediction

Good point Here is my code

use strict; use warnings; use Benchmark; use List::Util qw /shuffle/; use feature 'say'; my $n = 10**7; my @sorted = 1..$n; my @random = shuffle @sorted; my $t0 = Benchmark->new; say sum_this(\@sorted); my $t1 = Benchmark->new; my $td1 = timediff($t1, $t0); say "sorted:",timestr($td1); my $t2 = Benchmark->new; say sum_this(\@random); my $t3 = Benchmark->new; my $td2 = timediff($t3, $t2); say "random:",timestr($td2); sub sum_this { my ($arr) = @_; my $sum; foreach (my $i=0;$i<=$#$arr;$i++) { my $x = $arr->[$i]; if($x>$n/2) { $sum+= $x; } } return $sum; }
The output is
37500002500000
sorted: 6 wallclock secs ( 5.61 usr +  0.00 sys =  5.61 CPU)
37500002500000
random: 6 wallclock secs ( 5.81 usr +  0.00 sys =  5.81 CPU)
There is a difference but not as dramatic as in java or c++ (from the stack overflow post) What is the correct interpretation of the results?


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