use strict;
use warnings;
use experimental qw/ say postderef signatures /;
use Time::HiRes 'time';

use PDL;
use PDL::NiceSlice;
use Test::PDL 'eq_pdl';

use constant STEPS => 100;
my $x = zeroes( 200, 200 );
 
# Put in a simple glider.
$x(1:3,1:3) .= pdl ( [1,1,1],
                     [0,0,1],
                     [0,1,0] );
my $backup = $x-> copy;

printf "Game of Life!\nMatrix: %s, %d generations\n", 
    $x-> info, STEPS;

# Tutorial
my $t = time;
my $ct = 0;
for ( 1 .. STEPS ) {
    my $t_ = time;
    # Calculate the number of neighbours per cell.
    my $n = $x->range(ndcoords($x)-1,3,"periodic")->reorder(2,3,0,1);
    $n = $n->sumover->sumover - $x;
    $ct += time - $t_;

    # Calculate the next generation.
    $x = ((($n == 2) + ($n == 3))* $x) + (($n==3) * !$x);
}
printf "Tutorial: %0.3f s (core time: %0.3f)\n",
    time - $t, $ct;

# "Lags"
my $m = $backup-> copy;
$t = time;
$ct = 0;
for ( 1 .. STEPS ) {
    my $t_ = time;
    # Calculate the number of neighbours per cell.
    my $n = sms_GoL_lags( $m ) - $m;
    $ct += time - $t_;

    # Calculate the next generation.
    $m = ((($n == 2) + ($n == 3))* $m) + (($n == 3) * !$m);
}
printf "\"lags\":   %0.3f s (core time: %0.3f)\n",
    time - $t, $ct;
    
die unless eq_pdl( $x, $m );

sub _do_dimension_GoL ( $m ) {
    $m-> slice( -1 )-> glue( 0, $m, $m-> slice( 0 ))
      -> lags( 0, 1, ( $m-> dims )[0] )
      -> sumover
      -> slice( '', '-1:0' )
      -> xchg( 0, 1 )
}

sub sms_GoL_lags ( $m ) {
    _do_dimension_GoL
    _do_dimension_GoL $m 
}

__END__

Game of Life!
Matrix: PDL: Double D [200,200], 100 generations
Tutorial: 1.016 s (core time: 0.835)
"lags":   0.283 s (core time: 0.108)