Re: Faster alternative to Math::Combinatorics

I think this is doing the same thing in

C:\test>1198509.pl >nul
Took 0.064547 seconds
[download]

with output redirected; or if not:

C:\test>1198509.pl
0
2
3
0 0
0 2
0 3
2 0
2 2
2 3
3 0
...
3 3 3 3 3 3 2 3
3 3 3 3 3 3 3 0
3 3 3 3 3 3 3 2
3 3 3 3 3 3 3 3
Took 6.103125 seconds
[download]

#! perl -slw
use strict;
use Time::HiRes qw[ time ];
use Algorithm::Combinatorics qw[ variations_with_repetition ];

my @data = ( 0, 2, 3 );

my $start = time;
for my $k ( 1 .. 8 ) {
    my $iter = variations_with_repetition( \@data, $k );
    print "@$_" while $_ = $iter->next;
}
printf STDERR "Took %f seconds\n", time() - $start;
[download]

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Comment on Re: Faster alternative to Math::Combinatorics Select or Download Code

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Re^2: Faster alternative to Math::Combinatorics
by AppleFritter (Vicar) on Sep 01, 2017 at 16:54 UTC

Funny that not redirecting the output makes such a big difference on your machine. For me, your code takes ~0.06 seconds to run when redirecting to /dev/nul, and ~0.11 seconds if not.

Be that as it may, thanks for the pointer to Algorithm::Combinatorics and the code snippet, this looks like a very useful module! And (redirecting to /dev/nul, again) I'm getting running times of ~0.5s, ~2.9s, ~12.1s, ~40.6s for @data sizes of 4, ..., 7, which is very reasonable.

EDIT: Of course, what I was actually looking for was multisets, not ordered tuples (did you read my post?), but fortunately Algorithm::Combinatorics also offers a combinations_with_repetition function for that. Funny that I completely missed this module when looking at CPAN earlier today, too.)

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