[petsc-users] Slepc reading distributed matrix from files

[errabii sohaib]

Hi everyone,

I am trying to use Mat.view and Mat.load that you suggested. Regardless of
the fact that the matrix i get is not what i had initially, my question is
about how Mat.load reads the matrix in Parallel. Am i able to read the
matrix in parallel regardless how it was written with Mat.view() ? My
second question is about the difference between PETSc.COMM_WORLD and
MPI.COMM_WORLD, i have read in the user's manual that they are the
practically the same, but creating a viewer with MPI.COMM_WORLD returns an
error and it works with PETSc.COMM_WORLD.

ps:
*Here is the code i am using to write the matrix*

comm = PETSc.COMM_WORLD
rank = comm.Get_rank()
size = comm.Get_size()

sizeGlob,nnzGlob,size,nnz,I,J,A=readMat('jacobian/matJ%i'%rank)

M=PETSc.Mat()
M.create()
M.setSizes(size=(sizeGlob,sizeGlob))
M.setType('aij')
M.setUp()
for i in range(nnz):            #each proc holds different I,J,A and i
simply fill in the matrix
    M[I[i]-1,J[i]-1]=A[i]
M.assemblyBegin()
M.assemblyEnd()


vi = PETSc.Viewer()
vi.createBinary('matJacobian',mode=1,comm=comm)
M.view(viewer=vi)

*And the code i am using to read it:*

comm = PETSc.COMM_WORLD
rank = comm.Get_rank()
size = comm.Get_size()

A = PETSc.Mat(comm)
vi = PETSc.Viewer()
vi.createBinary('matJacobian',mode=0,comm=comm)
A.load(vi)

Checking the matrix after reading it with A.getType returns seqaij as if it
wasn't distributed on each proc!

Thank you so much for your time,
Sohaib
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