in reply to Re: Kronecker Product
in thread Kronecker Product
I was inspired to copy the recently (as of 2.077) added dupN to make inflateN, which does the converse of dupN, suitable for Kronecker products.
The above will broadcast nicely over any number of dimensions, not just 2. inflateN has been added and will be in the next PDL release (2.081).sub PDL::inflateN { my ($this, @times) = @_; return $this->copy if !grep $_ != 1, @times; my $sl = join ',', map "*$_,:", @times; $this = $this->slice($sl); $this = $this->clump($_, $_+1) for 0..$#times; $this; } pdl> p $a = pdl '[[1 2][3 4]]' [ [1 2] [3 4] ] pdl> p $b = pdl '[[5 6][7 8][9 10]]' [ [ 5 6] [ 7 8] [ 9 10] ] pdl> p $a->inflateN($b->dims) [ [1 1 2 2] [1 1 2 2] [1 1 2 2] [3 3 4 4] [3 3 4 4] [3 3 4 4] ] pdl> p $b->dupN($a->dims) [ [ 5 6 5 6] [ 7 8 7 8] [ 9 10 9 10] [ 5 6 5 6] [ 7 8 7 8] [ 9 10 9 10] ] sub kron { my ($x,$y) = @_; $x->inflateN($y->dims) * $y->dupN($x->dims +) } pdl> p kron($a,$b) [ [ 5 6 10 12] [ 7 8 14 16] [ 9 10 18 20] [15 18 20 24] [21 24 28 32] [27 30 36 40] ]
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