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[Octave-bug-tracker] [bug #39314] convn(x, y, "valid") produces results


From: Rik
Subject: [Octave-bug-tracker] [bug #39314] convn(x, y, "valid") produces results that are different from Matlab
Date: Tue, 12 Nov 2013 19:46:12 +0000
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:25.0) Gecko/20100101 Firefox/25.0

Follow-up Comment #18, bug #39314 (project octave):

Octave has been patched so it produces correct results to within a few tens of
eps.  This is far better than producing incorrect values which it was before. 
It should be possible to eliminate even the small difference of a few tens of
eps, but this is rather less urgent.  The problem has, I believe, been
correctly identified by Carne in that the order of summation differs when
doing inner versus outer convolution.

For those interested, the relevant files are 

liboctave/numeric/oct-convn.cc (around line 95, convolve_nd)
liboctave/cruft/blas-xtra/dconv2.f (around line 73, daxpx call)



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