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Re^3: Too much SQL not enough perl

by InfiniteSilence (Curate)
on Oct 10, 2005 at 15:10 UTC ( [id://498838]=note: print w/replies, xml ) Need Help??


in reply to Re^2: Too much SQL not enough perl
in thread Too much SQL not enough perl

Nor, is it fair that in the 'slow' one, you use a temporary array...

EvanCarroll is right about the slight differences in the routines, so I commented out some things in code and made them both use the same array (note, I increased the number of elements to look for as well as the number of iterations for more meaningful results):

#!/usr/bin/perl -w use strict; use Benchmark qw(:all); my @choices = qw|a b c z m p t l c f g|; my %choices = map{$_=>1}@choices; my @cData = <DATA>; timethese(50_000,{'Damn Slow'=>\&parseData1, 'Much Better'=>\&parseData2}); sub parseData1 { foreach (@cData){ chomp; my @items = split/,/,$_; #slow way, foreach my $item (@items){ if(grep {$item eq $_} @choices){ #print qq|FOUND $item|; } } } } sub parseData2 { foreach(@cData){ chomp; # foreach my $item (split/,/,$_){ my @items = split/,/,$_; #slow way, foreach my $item (@items){ if ($choices{$item}){ #print qq|FOUND $item\n|; } } } } __DATA__ z,t,m,u,a,b,c s,t,l,m,z,a,s c,b,a,m,u,t,n k,l,t,s,z,r,t

Which still produces:

perl seediff.pl Benchmark: timing 50000 iterations of Damn Slow, Much Better... Damn Slow: 6 wallclock secs ( 6.12 usr + 0.00 sys = 6.12 CPU) @ 81 +72.61/s (n=50000) Much Better: 3 wallclock secs ( 2.96 usr + 0.00 sys = 2.96 CPU) @ 1 +6874.79/s (n=50000)

I think the above changes were 'fair' since the performance of a function like SQL in() in an actual database should not decrease noticeably with the number of elements.

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