I would like to fix the fftconvolve() bug for the PDL-2.4.6
release:
http://sourceforge.net/tracker/?func=detail&aid=2630369&group_id=612&atid=100612
but I'm having problems since it appears that our PDL conv1d()
routine actually calculated the 1D correlation of the arguments.
First set up simple arguments:
perldl> $a = zeroes(11);
perldl> $a(5) .= 1;
perldl> p $a
[0 0 0 0 0 1 0 0 0 0 0]
perldl> $b = pdl(2,0,-1);
perldl> p $b
[2 0 -1]
The analytic convolution is calculated to be:
perldl> $ctrue = $a->zeroes;
perldl> $ctrue(4) .= 2;
perldl> $ctrue(6) .= -1;
perldl> p $ctrue
[0 0 0 0 2 0 -1 0 0 0 0]
Here are the various PDL convolution outputs:
perldl> p $c1d = conv1d $a, $b; # wrong!
[0 0 0 0 -1 0 2 0 0 0 0]
perldl> use PDL::Image2D
perldl> p $c2d = conv2d $a, $b; # right!
[
[ 0 0 0 0 2 0 -1 0 0 0 0]
]
perldl> use PDL::ImageND
perldl> p $cNd = convolveND $a, $b; # right!
[0 0 0 0 2 0 -1 0 0 0 0]
The good news is that the conv2d() and convolveND() routines
appear to be calculating a convolution so the only "broken"
routine appears to be the conv1d(). My plan is to add a
test for the bug, fix the code/docs, and update the Release_Notes
--Chris
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