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You need a huge number of keys to make pre-allocation worth it. Running this several times:
use warnings; use strict; use Benchmark; my $start = new Benchmark; my $size = 10000000; my %hash; keys(%hash) = $size; for my $i (1..$size) { my $key = "key$i"; $hash{$key} = $key; } my $end = new Benchmark; my $diff = timediff ($end, $start); print "The code ran for \n",timestr($diff),"\n";
With 10,000,000 keys, typical numbers for pre-allocated hash keys was:
19 wallclock secs (17.36 usr + 0.94 sys = 18.30 CPU)
Typical numbers with the pre-allocation commented out:
21 wallclock secs (21.23 usr + 0.63 sys = 21.86 CPU)

I had to use 100,000 keys to even measure a difference, which was typically 0.03 seconds.

It ain't worth it.

In reply to Re: Minimum Hash keys allocated? by cdarke
in thread Minimum Hash keys allocated? by flexvault

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