Hi Chris,
I am looking at the outputs that you provided, and they all look
incorrect to me. The convolution shouldn't be 0 for the first 5
elements, then element 6 = 2, element 7 = 0, element 8 = -1, element
9..11 = 0.
Comments? (btw, I am on vacation until Jan.4 so you might get an ooo
alert, but every couple of days I check my email.)
Cliff Sobchuk esn 361-8169, 403-262-4010 ext: 361-8169
Fax: 403-262-4010 ext: 361-8170
Core RF Support Engineer
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-----Original Message-----
From: Chris Marshall [mailto:[email protected]]
Sent: December 19, 2009 12:33 PM
To: [email protected]
Cc: perldl
Subject: [Perldl] conv1d or corr1d
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&ati
d=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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