Test failure for fftfilt.m

[Daniel J Sebald]

Below seems to be the fftfilt accuracy issue cropping up again.  I seem 
to recall we went through all these tests and reworked them somewhat by 
increasing the tolerance value somewhat larger than eps (many multiples) 
and adding more tests to really check the fftfilt routine beyond the few 
degenerate cases.  None of that seems to be in the fftfilt.m file.  Was 
some changes set lost or reverted along the way?  In the repository, the 
most recent changeset is:

http://hg.savannah.gnu.org/hgweb/octave/file/72c96de7a403/scripts/signal/fftfilt.m
Mon, 02 Jan 2012 14:25:41 -0500 (14 months ago)

It seems like the group examined this since then, sometime in early 
September of last year according to my old emails.

Dan


> > > > > processing /usr/local/src/octave/octave-dialog/octave/scripts/signal/fftfilt.m
  ***** test
 r = sqrt (1/2) * (1+i);
 b = b*r;
 assert (fftfilt (b, x  ), r*[1 1 0 0 0 0 0 0 0 0]  , eps);
 assert (fftfilt (b, r*x), r*r*[1 1 0 0 0 0 0 0 0 0], eps);
 assert (fftfilt (b, x.'), r*[1 1 0 0 0 0 0 0 0 0].', eps);
!!!!! test failed
assert (fftfilt (b, r * x),r * r * [1, 1, 0, 0, 0, 0, 0, 0, 0, 0],eps) 
expected
 Columns 1 through 3:
   0.00000 + 1.00000i   0.00000 + 1.00000i   0.00000 + 0.00000i
 Columns 4 through 6:
   0.00000 + 0.00000i   0.00000 + 0.00000i   0.00000 + 0.00000i
 Columns 7 through 9:
   0.00000 + 0.00000i   0.00000 + 0.00000i   0.00000 + 0.00000i
 Column 10:
   0.00000 + 0.00000i
but got
 Columns 1 through 3:
   0.00000 + 1.00000i   0.00000 + 1.00000i   0.00000 - 0.00000i
 Columns 4 through 6:
  -0.00000 + 0.00000i  -0.00000 + 0.00000i   0.00000 + 0.00000i
 Columns 7 through 9:
  -0.00000 + 0.00000i   0.00000 - 0.00000i  -0.00000 + 0.00000i
 Column 10:
  -0.00000 + 0.00000i
maximum absolute error 2.22478e-16 exceeds tolerance 2.22045e-16
shared variables   scalar structure containing the fields:
    b =
       1   1
    x =
       1   0   0   0   0   0   0   0   0   0
    r = [](0x0)