Skip to main content

Perl Matrix Multiplication

Here's the Perl script for matrix multiplication. It's derived from the RosettaCode site with slight modifications ... I didn't like some things about their way of doing things, but it's much the same in the end.

#! /usr/bin/perl5.20.2

use 5.020;
use warnings; 
use strict;
use English;
use Time::HiRes qw(gettimeofday tv_interval);
use autodie;
use Data::Dumper;

# -------------------------------------------------------
# SUBROUTINES
#
# ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯
# matmult - multiple matrices. Copied from
#    RosettaCode.orgwiki/Matrix_multiplication#Perl.
#
sub matmult {
    my ( $M, $N ) = @_;

    my ( $rows, $cols ) = (scalar @$M, scalar @{$N->[0]} );
    my $prod = [];
    my $k = @$N - 1;

    for my $i ( 0..$rows - 1 ) {
        for my $j ( 0 .. $cols - 1 ) {
            $prod->[$i][$j] += $M->[$i][$_]
                                * $N->[$_][$j]
                for 0..$k;
        }
    }
    return $prod;
}
# ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯
# readMatrix - read file data -> array of array of int.
#
sub readMatrix {
    my ( $filename ) = @_;

    open my $infile, '<', $filename;
    local $/ = undef;
    my ($matrix) = [map { [split / +/, $_] }
                      split / *\n/, <$infile>
                   ];

    return $matrix;
}
# ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯
# main line of processing
#
sub main {
   die( "USAGE: $PROGRAM_NAME reps file1 file1" )
      unless 3 == @ARGV 
          && $ARGV[0] > 0
          && -e $ARGV[1] && -r _
          && -e $ARGV[2] && -r _;

   my ($M, $N) = (readMatrix($ARGV[1]),
                  readMatrix($ARGV[2]));

#    say Data::Dumper::Dumper [$M, $N];

    my $t0 = [ gettimeofday ];
    my $prod;
    for my $reps ( 1 .. $ARGV[0] ) {
        $prod = matmult( $M, $N );
    }
    my $delta = tv_interval($t0);
    say "Multiplying matrices $ARGV[0] times takes ",
        "$delta seconds.";
#    say Data::Dumper::Dumper [$prod];
}
# -----------------------------------------------------

main();



Inverting the numbers to look at millions of multiplications per second, we see that overhead on small matrices degrades performance, but larger matrices enable 5.5 million multiplications per second.


Comments

Popular posts from this blog

Perl5, Moxie and Enumurated Data Types

Moxie - a new object system for Perl5 Stevan Little created the Moose multiverse to upgrade the Perl 5 programming language's object-oriented system more in line with the wonderfull world of Perl 6. Unfortunately, it's grown into a bloated giant, which has inspired light-weight alternatives Moos, Moo, Mo, and others. Now he's trying to create a modern, efficient OO system that can become built into the language. I've seen a few of his presentations at YAPC (Yet Another Perl Conference, now known as TPC, The Perl Conference), among them ‎p5 mop final final v5 this is the last one i promise tar gz While the package provides some POD documentation about the main module, Moxie, it doesn't actually explain the enum package, Moxie::Enum. But delving into the tests directory reveals its secrets. Creating an Enum package Ranks { use Moxie::Enum; enum by_ARRAY => qw( unused 2 3 4 5 6 7 8 9 10 J Q K A ); enum by_HASH => { 2 => 2, 3 =...

AI crap at 100 words a minute

I requested an AI to  create an astable multivibrator that can oscillate at 100KHz with a 50% duty cycle. Of course, this isn't an essay topic, it's a (trivial) electronic circuit. But it set out to provide the required number of words without actually saying anything useful. Here's what came out ... Note the reference to an article from 1968, long before any modern technology. In particular, getting through several paragraphs about oscillators without mentioning the 55 timer ic is unimaginable.

Making a Re-Saw Saw

I made a framing saw from a kit at a Lee Valley workshop, and it was fabulous. It's great as a coping saw, cutting curves, but the thin blade makes it hard to cut a straight line. So I made another one on my own, using a chunk of bandsaw blade, and this was better for straight cuts. But trying to resaw a 1" thick boards into two 1/2" inch boards was impossible. The cut would wander all over the place. I would practically wind up with veneer. I saw a number of articles and YouTube videos about making a re-sawing saw, and I decided to make one. But I'm not keen on kits. For one thing I'm stingy, and don't like giving away the profit. Besides, it doesn't feel like I made it, if someone else provided the challenging parts. So I made my own. The saw blade is cut from one of three rusty handsaw blades I got for $10 off Facebook Marketplace. I used an angle grinder to cut it out, a little over two inches wide, and to grind three-to-the-inch teeth...