Re: Qhull test changes

[Ben Abbott]

On Jan 30, 2012, at 3:09 PM, Rik wrote:

> On 01/30/2012 06:39 AM, Ben Abbott wrote:
>>> Rik,
>>> 
>>> I pushed a changeset to fix the tests.
>>> 
>>>       http://hg.savannah.gnu.org/hgweb/octave/rev/2633baa831e2
>>> 
>>> Ben
>>> 
> I now get an error the other direction.  See below.
> 
>  ***** testif HAVE_QHULL
> cube = [0 0 0;1 0 0;1 1 0;0 1 0;0 0 1;1 0 1;1 1 1;0 1 1];
> [h, v] = convhulln (cube, "Qt");
> assert (size (h), [12 3]);
> h = sortrows (sort (h, 2), [1:3]);
> assert (h, [1 2 4; 1 2 6; 1 4 8; 1 5 6; 1 5 8; 2 3 4; 2 3 7; 2 6 7; 3 4 7;
> 4 7 8; 5 6 7; 5 7 8]);
> assert (v, 1, 10*eps);
> [h2, v2] = convhulln (cube); % Test defaut option = "Qt"
> assert (size (h2), size (h))
> h2 = sortrows (sort (h2, 2), [1:3]);
> assert (h2, h);
> assert (v2, v, 10*eps);
> !!!!! test failed
> assert (size (h),[12, 3]) expected
>   12    3
> but got
>   6   4
> values do not match
> 
> Previously the tests were matched to Qhull <= 2010.  Now the tests are
> matched to Qhull >= 2011.  In either case, if Octave is linked against the
> other version then a test error results and users are going to think it is
> Octave's fault.  This is absolutely up-to-date Octave code from Mercurial
> with your changeset, but linked against the default Qhull in Kubuntu 10.04
> which is version 2009.
> 
> A couple of quick ways to solve this.
> 
> 1) Don't check the result.  Check only that h = convhulln (..., "Qt")
> matches h2 = convhulln (...) which shows that Octave is passing Qt as the
> default option.
> 
> 2) Check the size of the result (12 x 3 or 6 x 4) and then compare against
> the appropriate array.
> 
> 3) Embody the test in configure.ac so that Octave can identify which
> version of Qhull it is linking against.  Then you could use two testif
> macros, say HAVE_QHULL or HAVE_QHULL_NEW.
> 
> Cheers,
> Rik

I'm not certain, but doesn't "Qt" imply that the convex hull should be made up 
of triangles ? (perhaps I should study the qhull docs a bit ?)

In any event, I favored the more recent qhull because it matches Matlab's 
result.

Ben