If you wish to ignore Tanktalus's good advice and sweat the small stuff then a benchmark gives an answer. Normal benchmark caveats apply of course - like the benchmark may not indicate anything at all about your particular situation.
use strict;
use warnings;
use Benchmark qw(cmpthese);
use constant kHalfMax => 509; # Must be odd
my %Contracts = (1..4 * kHalfMax); # kHalfMax * 2 key/value pairs
my $key = kHalfMax;
cmpthese (-1,
{
lookup => \&lookup,
refit => \&refit,
}
);
sub lookup {
return if $Contracts{$key} == 1;
return if $Contracts{$key} == 1;
return if $Contracts{$key} == 1;
return if $Contracts{$key} == 1;
return if $Contracts{$key} == 1;
return if $Contracts{$key} == 1;
return if $Contracts{$key} == 1;
return if $Contracts{$key} == 1;
}
sub refit {
my $ref = \$Contracts{$key};
return if $$ref == 1;
return if $$ref == 1;
return if $$ref == 1;
return if $$ref == 1;
return if $$ref == 1;
return if $$ref == 1;
return if $$ref == 1;
return if $$ref == 1;
}
Result:
Rate lookup refit
lookup 443125/s -- -32%
refit 648621/s 46% --
Note that the result is somewhat sensitive to the number of key/value pairs in the hash. 46% is about the largest difference I've seen.
Note too that at about 200 nano-seconds per access this tweak is unlikely to make much difference to most applications. Code clarity would be a much more important consideration!
DWIM is Perl's answer to Gödel
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