[Octave-bug-tracker] [bug #50494] griddata loses precision in the linear interpolation of 3 column vectors (using Delaunay triangles)

[John W. Eaton]

Follow-up Comment #5, bug #50494 (project octave):

After 25f914321e7b, I'm seeing the following test failure:


octave:> test griddatan
QH6239 Qhull precision error: Initial simplex is cocircular or cospherical. 
Use option 'Qz' for the Delaunay triangulation or Voronoi diagram of
cocircular/cospherical points.  Option 'Qz' adds a point "at infinity".    Use
option 'Qs' to search all points for the initial simplex.

While executing:  | qhull d Qt Qbb Qc 
Options selected for Qhull 2015.2 2016/01/18:
  run-id 253565979  delaunay  Qtriangulate  Qbbound-last  Qcoplanar-keep
  _pre-merge  _zero-centrum  Qinterior-keep  Pgood  _max-width  1
  Error-roundoff 1.4e-15  _one-merge 9.7e-15  Visible-distance 2.8e-15
  U-coplanar-distance 2.8e-15  Width-outside 5.5e-15  _wide-facet 1.7e-14
***** testif HAVE_QHULL <56515>
 x = [ 0, 0; 1, 1; 0, 1; 1, 0 ];
 y = [ 1; 2; 3; 4 ];
 xi = [ .5, .5 ];
 yi = griddatan (x, y, xi);
!!!!! known bug: https://octave.org/testfailure/?56515
__delaunayn__: qhull failed
PASSES 2 out of 3 tests (1 known bug)



    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?50494>

_______________________________________________
  Message sent via Savannah
  https://savannah.gnu.org/