Yet another solution using FFT

1 files changed, 16 insertions, 0 deletions

diff --git a/challenge-248/wlmb/perl/ch-2b.pl b/challenge-248/wlmb/perl/ch-2b.pl
new file mode 100755
index 0000000000..1640bcddd7
--- /dev/null
+++ b/challenge-248/wlmb/perl/ch-2b.pl
@@ -0,0 +1,16 @@
+#!/usr/bin/env perl
+use v5.36;
+use PDL;
+use PDL::FFT;
+my $matrix=pdl(shift);
+my $width=my $w=shift;
+my $height=my $h=shift;
+my $small=ones($w%2?$w:$w+1, $h%2?$h:$h+1);
+$small->slice(-1).=0, ++$w unless $w%2; # zero row and/or column for even kernels
+$small->slice([],-1).=0, ++$h unless $h%2;
+my $kernel=kernctr($matrix, $small); #full kernel
+my $result=$matrix->copy;
+$result->fftconvolve($kernel);
+say "$matrix $width $height -> ",
+$result->slice([floor(($width-1)/2),floor(-($width+1)/2)],
+	       [floor(($height-1)/2),floor(-($height+1)/2)]);