Surface refinement node-vertex consistency error on Icelake-client

[inducer]

Continued from the end of #118.

test$  rm *vtu;pycl test_refinement.py 'test_refine_surfaces(_acf,  "icosphere", True)' 
Traceback (most recent call last):
  File "/home/andreas/src/meshmode/test/test_refinement.py", line 360, in <module>
    exec(sys.argv[1])
  File "<string>", line 1, in <module>
  File "/home/andreas/src/meshmode/test/test_refinement.py", line 349, in test_refine_surfaces
    refined_mesh = refine_uniformly(mesh, 1)
  File "/home/andreas/src/meshmode/meshmode/mesh/refinement/__init__.py", line 991, in refine_uniformly
    refiner.refine_uniformly()
  File "/home/andreas/src/meshmode/meshmode/mesh/refinement/no_adjacency.py", line 61, in refine_uniformly
    return self.refine(flags)
  File "/home/andreas/src/meshmode/meshmode/mesh/refinement/no_adjacency.py", line 227, in refine
    new_mesh = Mesh(new_vertices, new_el_groups, is_conforming=(
  File "/home/andreas/src/meshmode/meshmode/mesh/__init__.py", line 779, in __init__
    assert _test_node_vertex_consistency(
  File "/home/andreas/src/meshmode/meshmode/mesh/__init__.py", line 983, in _test_node_vertex_consistency
    assert _test_node_vertex_consistency_resampling(mesh, mgrp, tol)
  File "/home/andreas/src/meshmode/meshmode/mesh/__init__.py", line 971, in _test_node_vertex_consistency_resampling
    assert max_el_vertex_error < tol*size, max_el_vertex_error
AssertionError: 9.901371953343942

Quite likely a numpy behavior change.

• numpy 1.20 wheel: fine
• numpy 1.20.1 wheel: fine
• pip install --no-binary ":all:" numpy cython: (resulting in 1.20.1) error (only on my laptop, not on dunkel)

cc @alexfikl because it feels less lonely that way. :)

[alexfikl]

Just tried it locally with the newer numpy and can confirm I still can't get it to fail. This is on Comet Lake (and probably many OS differences).

Do the wheels use a different blas or something?

[inducer]

Looks like my numpy has bigger problems. It even fails modepy's

python test_nodes.py 'test_simp_nodes(3, 6)'  

specifically

assert (unodes >= -1-eps).all()

(And not by a little. One of those node coordinates is -1.03.)

[inducer]

I could probably chase this further, but I doubt it's worth it. It'll be some crappy BLAS bug. FWIW, it also fails

python -c 'import numpy; numpy.linalg.test()'  

[inducer]

OK, fine. Feeling charitable: numpy/numpy#18471

And, I'm not falling for this nonsense again: https://gitlab.tiker.net/inducer/akprojects-bin/-/commit/ad245e404813e70a52129544911549918590ca77