Re: [OctDev] griddata / delaunay

[David B. <Dav...@mo...>]

According to Jonathan Stickel <jjs...@sb...> (on 09/01/04):
> I have encountered a problem with griddata when using semi-regular input 
> points.  The issue has to do with facet merging when running delaunay, 
> via qhull, with defualt options.  To avoid this, delaunay should be run 
> with the "QJ" option.  Perhaps this should be mentioned explicitly in 
> the delaunay help.  For the worst case of a rectangular grid, a 
> segmentation fault occcurs:
> 
> octave:1> [x,y]=meshgrid(1:10,1:10);
> octave:2> delaunay(x(:),y(:),"QJ")
> (plot of triangles)
> octave:3> delaunay(x(:),y(:))
> panic: Segmentation fault -- stopping myself...
> attempting to save variables to `octave-core'...
> save to `octave-core' complete
> Segmentation fault
> 
> Attached is a patch for griddata which calls delaunay with the "QJ" option.

Not sure if this is the right approach. What is the real reason for the
seg fault. If it is in the underlying qhull code, it might be better to
surround the calls to the qhull stuff with

      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE_1;

      error ("delaunay: Internal qhull error. Please try the 'QJ' option.");
      octave_throw_interrupt_exception ();

      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE_2;

      <QHULL CODE HERE>

      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;

and inform the author of qhull of the problem within their code. At least
this way octave won't crash for qhulls problems....

D.


> 
> Regards,
> Jonathan


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David Bateman                                Dav...@mo...
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