Mesh generation (and consequently, timestepping) differs between Linux and Windows.

[ole]

The same script and same ANUGA version generates slightly different meshes on different platforms. The example anuga_work/development/demos/island.py shows this. I have checked in the generated meshes using the names island_linux.msh and island_windows.msh. On either platform the timestepping is dramatically different depending on which mesh is being used. Here's some output:

Using the Linux mesh

Mesh statistics:
  Number of triangles = 7208
  Extent [m]:
    x in [0.000000, 100.000000]
    y in [0.000000, 100.000000]
  Areas [m^2]:
    A in [0.644829, 9.596606]
    number of distinct areas: 7208
    Histogram:
      [0.644829, 1.540006[: 5421
      [1.540006, 2.435184[: 1610
      [2.435184, 3.330362[: 37
      [3.330362, 4.225539[: 35
      [4.225539, 5.120717[: 37
      [5.120717, 6.015895[: 21
      [6.015895, 6.911073[: 18
      [6.911073, 7.806250[: 11
      [7.806250, 8.701428[: 8
      [8.701428, 9.596606]: 10
    Percentiles (10%):
      720 triangles in [0.644829, 0.931708]
      720 triangles in [0.931708, 1.017388]
      720 triangles in [1.017388, 1.096717]
      720 triangles in [1.096717, 1.173627]
      720 triangles in [1.173627, 1.265768]
      720 triangles in [1.265768, 1.367499]
      720 triangles in [1.367499, 1.473311]
      720 triangles in [1.473311, 1.605096]
      720 triangles in [1.605096, 1.788979]
      720 triangles in [1.788979, 9.002288]
      8 triangles in [9.002288, 9.596606]
  Boundary:
    Number of boundary segments == 230
    Boundary tags == ['top', 'right', 'bottom', 'left']
------------------------------------------------

Time = 0.0000, steps=0 (0)
Time = 1.0000, delta t in [0.00490999, 0.02104604], steps=120 (0)
Time = 2.0000, delta t in [0.00488622, 0.00548481], steps=194 (0)

Using the Windows mesh

Mesh statistics:
  Number of triangles = 7210
  Extent [m]:
    x in [0.000000, 100.000000]
    y in [0.000000, 100.000000]
  Areas [m^2]:
    A in [0.629728, 9.479879]
    number of distinct areas: 7210
    Histogram:
      [0.629728, 1.514743[: 5259
      [1.514743, 2.399758[: 1773
      [2.399758, 3.284773[: 40
      [3.284773, 4.169788[: 38
      [4.169788, 5.054803[: 37
      [5.054803, 5.939819[: 16
      [5.939819, 6.824834[: 21
      [6.824834, 7.709849[: 9
      [7.709849, 8.594864[: 10
      [8.594864, 9.479879]: 7
    Percentiles (10%):
      721 triangles in [0.629728, 0.938614]
      721 triangles in [0.938614, 1.023260]
      721 triangles in [1.023260, 1.099714]
      721 triangles in [1.099714, 1.180817]
      721 triangles in [1.180817, 1.270424]
      721 triangles in [1.270424, 1.373040]
      721 triangles in [1.373040, 1.479134]
      721 triangles in [1.479134, 1.602771]
      721 triangles in [1.602771, 1.780142]
      721 triangles in [1.780142, 9.479879]
  Boundary:
    Number of boundary segments == 232
    Boundary tags == ['top', 'right', 'bottom', 'left']
------------------------------------------------

Time = 0.0000, steps=0 (0)
Time = 1.0000, delta t in [0.00046156, 0.02104604], steps=947 (0)
Time = 2.0000, delta t in [0.00040646, 0.00047853], steps=2306 (0)

Can you investigate

1: Why this is? 2: If there is a way of avoiding the mesh condition that creates the degenerate timestepping (194 steps/s to 2306 steps/s)?

This problem was produced in changeset:4725

Ta Ole