I use the NonlinearProblem solver in Fenicsx to solve my linear problem with mixed elements as Raboynics has done here: Krylov solver's option max_it and a few questions . I also change the convergence criterion.
With solver.convergence_criterion = "residual" I got:
Step 1: num iterations: 1
Step 2: num iterations: 0
Step 3: num iterations: 0
Step 4: num iterations: 0
Step 5: num iterations: 0
Step 6: num iterations: 0
Step 7: num iterations: 0
Step 8: num iterations: 0
Step 9: num iterations: 0
Step 10: num iterations: 0
Step 11: num iterations: 0
Step 12: num iterations: 0
Step 13: num iterations: 0
Step 14: num iterations: 0
Step 15: num iterations: 0
Step 16: num iterations: 0
Step 17: num iterations: 0
Step 18: num iterations: 0
Step 19: num iterations: 0
Step 20: num iterations: 0
Step 21: num iterations: 0
Step 22: num iterations: 0
Step 23: num iterations: 0
Step 24: num iterations: 0
Step 25: num iterations: 0
Step 26: num iterations: 0
Step 27: num iterations: 0
Step 28: num iterations: 0
Step 29: num iterations: 0
Step 30: num iterations: 0
Step 31: num iterations: 0
Step 32: num iterations: 0
Step 33: num iterations: 0
Step 34: num iterations: 0
Step 35: num iterations: 0
Step 36: num iterations: 0
Step 37: num iterations: 0
Step 38: num iterations: 0
Step 39: num iterations: 0
Step 40: num iterations: 0
Step 41: num iterations: 0
Step 42: num iterations: 0
Step 43: num iterations: 0
Step 44: num iterations: 0
Step 45: num iterations: 0
Step 46: num iterations: 0
Step 47: num iterations: 0
Step 48: num iterations: 0
Step 49: num iterations: 0
Step 50: num iterations: 0
2023-12-17 13:02:16.338 ( 7.638s) [ BA8740] vtkTextureObject.cxx:1025 ERR| vtkTextureObject (0x55e487efdac0): Attempt to use a texture buffer exceeding your hardware's limits. This can happen when trying to color by cell data with a large dataset. Hardware limit is 65536 values while 73728 was requested.
ERROR:root:Attempt to use a texture buffer exceeding your hardware's limits. This can happen when trying to color by cell data with a large dataset. Hardware limit is 65536 values while 73728 was requested.
and for solver.convergence_criterion = "incremental'' I got:
DOLFINx version: 0.6.0 based on GIT commit: 30920d400ccb64d190de13509c43b1755d2606cc of https://github.com/FEniCS/dolfinx/
Step 1: num iterations: 2
Step 2: num iterations: 2
Step 3: num iterations: 2
Step 4: num iterations: 2
Step 5: num iterations: 2
Step 6: num iterations: 2
Step 7: num iterations: 2
Step 8: num iterations: 2
Step 9: num iterations: 2
Step 10: num iterations: 2
Step 11: num iterations: 2
Step 12: num iterations: 2
Step 13: num iterations: 2
Step 14: num iterations: 2
Step 15: num iterations: 2
Step 16: num iterations: 2
Step 17: num iterations: 2
Step 18: num iterations: 2
Step 19: num iterations: 2
Step 20: num iterations: 2
Step 21: num iterations: 2
Step 22: num iterations: 2
Step 23: num iterations: 2
Step 24: num iterations: 2
Step 25: num iterations: 2
Step 26: num iterations: 2
Step 27: num iterations: 2
Step 28: num iterations: 2
Step 29: num iterations: 2
Step 30: num iterations: 2
Step 31: num iterations: 2
Step 32: num iterations: 2
Step 33: num iterations: 2
Step 34: num iterations: 2
Step 35: num iterations: 2
Step 36: num iterations: 2
Step 37: num iterations: 2
Step 38: num iterations: 2
Step 39: num iterations: 2
Step 40: num iterations: 2
Step 41: num iterations: 2
Step 42: num iterations: 2
Step 43: num iterations: 2
Step 44: num iterations: 2
Step 45: num iterations: 2
Step 46: num iterations: 2
Step 47: num iterations: 2
Step 48: num iterations: 2
Step 49: num iterations: 2
Step 50: num iterations: 2
2023-12-17 13:19:05.367 ( 46.251s) [ DA8FA740] vtkTextureObject.cxx:1025 ERR| vtkTextureObject (0x555ad4b60cf0): Attempt to use a texture buffer exceeding your hardware's limits. This can happen when trying to color by cell data with a large dataset. Hardware limit is 65536 values while 73728 was requested.
ERROR:root:Attempt to use a texture buffer exceeding your hardware's limits. This can happen when trying to color by cell data with a large dataset. Hardware limit is 65536 values while 73728 was requested.
Note also that the convergence is faster with ‘‘residual’’ than with ‘‘incremental’’.