[BUG] Writing a mesh using meshio results in KeyError: dtype('uint64') in _ansys.py

[mildblimp]

Describe the bug
Creating a simple rectangle mesh using pygmsh results in the following error

Traceback (most recent call last):
  File "/.../rectangle.py", line 7, in <module>
    mesh.write("rectangle.msh")
  File "/usr/local/lib/python3.10/dist-packages/meshio/_mesh.py", line 241, in write
    write(path_or_buf, self, file_format, **kwargs)
  File "/usr/local/lib/python3.10/dist-packages/meshio/_helpers.py", line 188, in write
    return writer(filename, mesh, **kwargs)
  File "/usr/local/lib/python3.10/dist-packages/meshio/ansys/_ansys.py", line 442, in write
    key = binary_dtypes[values.dtype] if binary else "12"
KeyError: dtype('uint64')

It can be circumvented by using pygmsh's internal write function.

To Reproduce
Run the following script

import pygmsh

with pygmsh.geo.Geometry() as geom:
    rec = geom.add_rectangle(0, 1, 0, 2, 0, mesh_size=0.05)
    mesh = geom.generate_mesh()

mesh.write("rectangle.msh")

Diagnose

meshio==5.3.4
pygmsh==7.1.17

[shinstra]

Just hit this issue myself. Looks like it is expecting the dtypes of mesh.cells[...].data to be int32/int64.

[shinstra]

Looks like the simplest workaround is to use the gmsh write method as from here.

import gmsh
import pygmsh

with pygmsh.geo.Geometry() as geom:
    rec = geom.add_rectangle(0, 1, 0, 2, 0, mesh_size=0.05)
    mesh = geom.generate_mesh()

    gmsh.write("rectangle.msh")
    gmsh.clear()

Doesn't solve the underlying issue with mesh.write(...), but appears to be a clean solution in the interim.

[Social-Mean]

Looks like the simplest workaround is to use the gmsh write method as from here.

import gmsh
import pygmsh

with pygmsh.geo.Geometry() as geom:
    rec = geom.add_rectangle(0, 1, 0, 2, 0, mesh_size=0.05)
    mesh = geom.generate_mesh()

    gmsh.write("rectangle.msh")
    gmsh.clear()

Doesn't solve the underlying issue with mesh.write(...), but appears to be a clean solution in the interim.

@shinstra
Hi! I use you code but:

Traceback (most recent call last):

  File ~\.conda\envs\pygmsh\lib\site-packages\spyder_kernels\py3compat.py:356 in compat_exec
    exec(code, globals, locals)

  File d:\tmp\测试他人有限元库\test.py:28
    gmsh.write("test.msh")

  File ~\.conda\envs\pygmsh\lib\site-packages\gmsh.py:370 in write
    raise Exception(logger.getLastError())

  File ~\.conda\envs\pygmsh\lib\site-packages\gmsh.py:10614 in getLastError
    raise Exception('Could not get last error')

Exception: Could not get last error


Error   : Gmsh has not been initialized
Error   : Gmsh has not been initialized

Did you omit some details?
How gmsh know which mesh to write? (that means the variable mesh is not a param for gmsh)