[petsc-users] petsc4py getVecArray magic

[Gianluca Meneghello]

Dear all,

I just discovered that

x = da.getVecArray(X)

does not return a numpy array but rather a _DMDA_Vec_array, which has (I
guess) the great advantage of allowing for a starting index which is not
zero. So x[87] makes sense even if the actual length of x is only 50.

What I would like to do is to split the _DMDA_Vec_array x into multiple
variables, e.g.

x1,x2,x3 = x[:,0:12] , x[:,12:16], x[:,16:28]

which, written in this way, returns x1,x2,x3 as numpy view() arrays
starting from zero and of length equal to the length of the global X
divided by the number of processors. The arrays x1,x2,x3 thus becomes
unaccessible when using global indices. Using local indices does not look
like a good idea because of the presence of ghost entries.

I was wondering if there is any good way to address this situation besides
not splitting x in x1,x2,x3.

Thanks for your help,

Gianluca
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