Hello,
I’m writing a Python extension module to expose various classes, functions in
my C PETSc-based application code. I’ve taken a lot of inspiration from
petsc4py and borrowed bits of code from it. Everything works but one niggling
issue I’m facing is how to automatically inherit the data-types used to build
PETSc in my Cython code. Specifically, I want to make sure that if PETSc is
built with 64-bit ints then I use the correct type when I call my PETSc C
functions or create Numpy arrays with PyArray_SimpleNewFromData, etc.
I tried to understand how petsc4py does it, but looking at PETSc/PETSc.pyx it
seems that PetscInt is hardwired:
cdef extern from * nogil:
ctypedef long PetscInt
ctypedef double PetscReal
ctypedef double PetscScalar
PetscInt is then used elsewhere Ωin petsc4py (e.g., in Mat.pyx) when calling
PETSc functions. But wouldn’t this be incompatible with the PetscInt defined in
petscsystypes.h if PETSc were built with --with-64-bit-indices?
On the other hand, I see (sort of; the code is very complicated!) that
arraynpy.pxi correctly picks up (via numpy.h) the mappings between PETSc and
Numpy arrays and these are used in the few places where an enumerated data type
is required as an argument (e.g., in DMSwarm.pyx).
I don’t believe there’s any incompatibility with PetscInt in petsc4py so I’m
likely missing something here. Could someone please explain how PetscInt, etc
pick up their correct values and how I can do the same in my code?
Thanks very much!
Best,
Samar
