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Release Notes for Trilinos Package Ifpack2
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Trilinos 11.4:
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* Relaxation: Use precomputed offsets to extract diagonal

As of this release, Tpetra::CrsMatrix has the ability to to precompute
offsets of diagonal entries, and use them to accelerate extracting a
copy of the diagonal. Relaxation now exploits this feature to speed up
compute() (which extracts a copy of the diagonal of the input matrix).
The optimization only occurs if the input matrix is a CrsMatrix (not
just a RowMatrix) and if it has a const ("static") graph. The latter
is necessary so that we know that the structure can't change between
calls to compute(). (Otherwise we would have to recompute the offsets
each time, which would be no more efficient than what it was doing
before.)
