Chris Marshall wrote:
> Cliff Sobchuk wrote:
>> 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.)
>
> Try help conv1d to see the computation being performed.
In the perldl shell.
> I just checked the calculation of the convolution again and
> get the same result. This result agrees (now) with conv2d
> and convolutionND.
Meaning to say the current convention for the conv1d()
implementation is consistent with that of conv2d() and
convolveND(). The current implemention is not documented
as to how it kernels with even numbers of elements are
processed.
--Chris
> What do you think the convolution of the $a and $b below
> should be?
>
> --Chris
>
>> 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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