[Octave-bug-tracker] [bug #33292] trapz on matrices does not allow a vector as first argument

[Rik]

Update of bug #33292 (project octave):

                  Status:         Patch Submitted => Fixed                  
             Open/Closed:                    Open => Closed                 

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Follow-up Comment #5:

I checked in changes to the stable branch
(http://hg.savannah.gnu.org/hgweb/octave/rev/d8aff843a9e9) which correct this
bug.  To access the changes you will need to download from the Mercurial
archives and build from source, or wait for the 3.4.1 release.  Instructions
for downloading the source code are here
(http://www.gnu.org/software/octave/download.html)

For Jordi, I took a slightly different approach from your patch.  In your
patch the pseudocode was

unwind_protect block
{
  expand x to size of y with bsxfun
  recursively call trapz with new x, old y matrices
}

If y is a large ND-array, then reproducing x to be the same size as y can be
wasteful of memory.  I also guessed that the overhead of an unwind_protect
block and an extra function call might be heavy.  Instead I tried something
like this

extra_input_validation (which obviates unwind_protect)
{
  reshape x vector to point along correct dimension
  use bsxfun to implement trapz computation between a vector and a matrix
}

Benchmarking showed the new approach to take 84% less time.  I didn't
investigate further, so I still don't know which code construct is actually
responsible for the slowdown.

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