I'm new to PDL, though not new to Perl, and I'm trying to speed my assignment
sub. I've read everything I can find about threading in PDL, and it's all
confused me rather than enlightening.
I have a large 2 dimensional piddle. I also have two piddles which are the X & Y
coordinates in that piddle. I need to update the value of the large piddle but
only if it's non-zero.
This is the code I've come up with, which works, but is quite slow. Any advice?
#!/usr/bin/perl
use Test::Simple tests=>8;
use strict;
use warnings;
use PDL;
my $found = zeroes ushort,10,10;
my $x=pdl (1,1,2,4,5);
my $y=pdl (2,4,3,6,4);
setme($x,$y,10);
#neither 1,1 or 1,3 were mentioned in the list above, so should be 0
#both 1,2 and 1,4 were, so should be 10
ok(at($found,1,1)==0);
ok(at($found,1,2)==10);
ok(at($found,1,3)==0);
ok(at($found,1,4)==10);
$x=pdl (1,1,4,6,2);
$y=pdl (3,4,8,7,5);
setme($x,$y,11);
# This call updated 1,3 and 1,4, but 1,4 was already set, should not change
ok(at($found,1,1)==0);
ok(at($found,1,2)==10);
ok(at($found,1,3)==11);
ok(at($found,1,4)==10);
sub setme {
my $x=shift;
my $y=shift;
my $value=shift;
my ($max)=dims $x;
if($max>0){
foreach my $i (0..$max-1){
if(at($found,at($x,$i), at($y,$i))==0){
set $found, at($x,$i), at($y,$i),$value;
}
}
}
}
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