oldgeezer wrote:
Hi all,
Hello,
Last week I discovered this perl.beginners group.
Good stuff here, albeit many times hard to grasp
the answers. But I'm learning.
If you have any questions just ask (the list.)
What I would like to understand is why looping
2 times through 5000 lines takes less time than
looping 5000 times through 2 lines.
Because that is just the way things work. Keep that in mind if you ever
have to optimise nested loops. And don't forget to benchmark any code
to be sure that you have an objective metric.
To show what I mean, I wrote a snippet that
does nothing with the data and yet the first
part is 5 times faster than the second part
(in my pc anyway).
On my PC it is 3 times faster.
#!/usr/bin/perl
use strict;
use warnings;
use POSIX qw(clock);
#just create a small array for this test
my @few=();
for my $i(1...2){push @few, $i};
That is usually written as:
my @few = 1 .. 2;
#just create a big array for this test
my @many=();
for my $i(1...500000){push @many, $i};
That is usually written as:
my @many = 1 .. 500_000;
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
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