http://qs321.pair.com?node_id=1198511


in reply to 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]
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.
In the absence of evidence, opinion is indistinguishable from prejudice. Suck that fhit

Replies are listed 'Best First'.
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.)

[reply]

In Section Seekers of Perl Wisdom