bug in conv()

[Ben Abbott]

On Sep 29, 2008, at 8:46 AM, Ben Abbott wrote:

>
> On Sep 29, 2008, at 2:14 AM, Jaroslav Hajek wrote:
>
>> On Mon, Sep 29, 2008 at 2:59 AM, Ben Abbott <bpabbott at mac.com> wrote:
>>>
>>> On Sep 28, 2008, at 4:47 PM, dph.work wrote:
>>>
>>>> According to http://www.gnu.org/software/octave/FAQ.html#MATLAB-compatibility
>>>> differences in Matlab and Octave are considered bugs.  The attached
>>>> m file
>>>> illustrates how conv() produces a column vector in Matlab and a row
>>>> vector in
>>>> Octave.
>>>>
>>>> Hope this helps.
>>>> Dan
>>>>
>>>> % In Matlab the variable c ends up a column vector, while in
>>>> Octave it
>>>> % ends up a row vector.
>>>> %
>>>> % octave:9> conv_bug.m
>>>> % ans =
>>>> %
>>>> %    1   29
>>>> %octave:9> ver
>>>> %
>>>> %
>>>> ----------------------------------------------------------------------
>>>> % GNU Octave Version 3.0.1
>>>> % GNU Octave License: GNU General Public License
>>>> % Operating System: Linux 2.6.18-4-amd64 #1 SMP Mon Mar 26 11:36:53
>>>> % CEST 2007 x86_64
>>>> %
>>>> ----------------------------------------------------------------------
>>>>
>>>> % matlab>> conv_bug
>>>> %
>>>> % ans =
>>>> %
>>>> %    29     1
>>>> %
>>>> %matlab>> ver
>>>> %
>>>> -----------------------------------------------------------------------
>>>> % MATLAB Version 7.3.0.298 (R2006b)
>>>> % MATLAB License Number:
>>>> % Operating System: Linux 2.6.18-4-amd64 #1 SMP Mon Mar 26 11:36:53
>>>> % CEST 2007 x86_64
>>>> % Java VM Version: Java is not enabled
>>>> %
>>>> -----------------------------------------------------------------------
>>>> % MATLAB                                     Version 7.3
>>>> (R2006b)
>>>> % Signal Processing Toolbox                  Version 6.6
>>>> (R2006b)
>>>>
>>>> a = blackman(10);
>>>> b = blackman(20);
>>>> c = conv(a,b);
>>>>
>>>> size(c)
>>>
>>> The default branch (3.1.51+) respects Matlab's behavior. However,
>>> 3.0.2 fails.
>>>
>>> Question for the list; As 3.0.3 is soon to be released, should that
>>> be
>>> fixed?
>>>
>>> Ben
>>>
>>
>> The conv.m sources are not differing betheen the two branches.
>> Apparently the problem is in DLD-FUNCTIONS/filter.cc, but according  
>> to
>> ChangeLog, the only relevant patch missing from 3.0.x is John's 7967,
>> adding single precision type, which apparently fixes the problem as a
>> side effect. So this will stay unfixed until someone isolates the fix
>> for 3.0.x.
>
> ok. I did a bit more testing. Matlab's output vector respects the
> input vector of greatest length. I'm also confused was to what I did
> yesterday. Today, I don't detect any difference between 3.0.2 and
> 3.1.51+ :-(
>
> In any event, I've added the following tests to my local version of
> conv.m
>
> %!test
> %! a = 1:10;
> %! b = 1:3;
> %! c = conv (a, b);
> %! assert (size(c), [1, numel(a)+numel(b)-1])
> %!test
> %! a = (1:10).';
> %! b = 1:3;
> %! c = conv (a, b);
> %! assert (size(c), [numel(a)+numel(b)-1, 1])
> %!test
> %! a = 1:10;
> %! b = (1:3).';
> %! c = conv (a, b);
> %! assert (size(c), [1, numel(a)+numel(b)-1])
>
> In 3.0.2 I get
>
>> octave:26> test conv
>>  ***** xtest
>> a = (1:10).';
>> b = 1:3;
>> c = conv (a, b);
>> assert (size(c), [numel(a)+numel(b)-1, 1])
>> !!!!! known failure
>> error: assert (size (c),[numel(a) + numel(b) - 1, 1]) expected
>>   12    1
>> but got
>>    1   12
>> values do not match
>> PASSES 9 out of 9 tests (1 expected failures)
>
> In 3.1.51+ I get
>
>> octave-3.1.51+:21> test conv
>>  ***** xtest
>> a = (1:10).';
>> b = 1:3;
>> c = conv (a, b);
>> assert (size(c), [numel(a)+numel(b)-1, 1])
>> !!!!! known failure
>> assert (size (c),[numel(a) + numel(b) - 1, 1]) expected
>>   12    1
>> but got
>>    1   12
>> values do not matchPASSES 9 out of 9 tests (1 expected failures)
>
>
> So it appears that the orientation is a bug in all versions. I'm
> unfamiliar with filter(), I'll look to see if the problem is there or
> local to conv.m.
>
> Also, notice the output of "test" for 3.1.51+ ... the last two lines
> are missing a LF.
>
> Ben

filter() appears to work properly.

 > filter(1:3,1,[1:5,0,0])
ans =

     1    4   10   16   22   22   15

 > filter(1:3,1,[1:5,0,0]')
ans =

     1
     4
    10
    16
    22
    22
    15

However, conv() does not

 > conv(1:3,1:5)
ans =

     1    4   10   16   22   22   15

 > conv(1:3,(1:5)')
ans =

     1    4   10   16   22   22   15

Patch to follow.

Ben