On 3/14/21 3:23 PM, Andrey Volkov wrote:
The system_matrix.block(0,0) gives access to a single block, namely *M
*(correct?). However, is there a way to access/extract _multiple blocks as a
whole block matrix_, let us say { [M B], [B 0] } or { [D E], [F G] }?
Sure, I looked at step-20/22, as all I have done so far is based on these
tutorials.
Not quite so easily, but ASPECT does this: It simply defines its own 2x2 block
matrix class that points to sub-blocks of a larger matrix. See here:
https://github.com/geodynamics/aspect/blob/master/source/simulator/solver.cc#L47-L105
Of course, if you don't actually need access to the M and B blocks
individually, you don't have to structure your matrix that way. The
structuring of the matrix based on solution variables is your choice, and you
can have a 2x2 block pattern for a matrix even if you have 3 solution
variables, and then you can put [[M, B],[B, 0]] all into one block.
Best
W.
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