scipy sparse matrices as an input for petsc4py

petsc, python, scipy

Solution

Your link says that to create a sparse matrix in PETSc, you should use a command like this:

PETSc.Mat().createAIJ(size=(nrows,ncols), csr=(ai,aj,aa))

According to this, the `ai`, `aj` and `aa` are, in PETSc-speak:

> i - row indices
> j - column indices
> a - matrix values

These are equivalent, respectively, to the `.indptr`, `.indices` and `.data` attributes of a `scypy.sparse.csr_matrix`, see the docs for details.

So, if your link is right, the following should work:

>>> from petsc4py import PETSc
>>> import scipy.sparse
>>> csr_mat = scipy.sparse.rand(1000, 1000, density=0.001, format='csr')
>>> petsc_mat = PETSc.Mat().createAIJ(size=csr_mat.shape,
...                                   csr=(csr_mat.indptr, csr_mat.indices,
...                                        csr_mat.data))

Unfortunately, I cannot test it myself.

Problem

I can't seem to find a way how to efficiently load scipy sparse matrices, e.g. `csr_matrix`, into a petsc4py matrix, e.g. `PETSc.Mat().createAIJ`. I found this thread, but I'm not able to apply it. I would also appreciate a pointer where this stuff is actually documented. The examples in the `demo` directory only explain a part, and I can't see any docstrings.

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