Hi Richard,
I do have approx. the same numbers, but on 4 cores (see screenshot).
Fortunately, I was able to adapt our little program here with success
- which I append here just for the sake of completeness, since I went on
github and tried my best to propose that change, see
https://github.com/dealii/dealii/pull/10838
<https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fdealii%2Fdealii%2Fpull%2F10838&data=02%7C01%7CWolfgang.Bangerth%40colostate.edu%7Cda1531178e7b4705abac08d843a89035%7Cafb58802ff7a4bb1ab21367ff2ecfc8b%7C0%7C0%7C637333738540558308&sdata=1VdEvclgxPPonuEzf1nrSpc0TGmge9QTTXlkJ1snjPk%3D&reserved=0>
I hope that worked out, but I used git for the first time.
It's the first time at some time for everyone -- but we hope it won't be your
last patch!
Nonetheless, some concerns of mine remain:
(i) if I allow in my application-code to actually change the row scaling of
the right matrix in the product (assuming the vector has all nonzero entries),
I will actually get away with only 1 additional matrix being the product
instead of 2 including the product and a temporary one (which was the one not
destroyed)
by the cost of scaling and rescaling the right matrix in the product.
Right. You might not actually need this function, but it's still worth fixing
:-)
(ii) The documentation says, that both Trilinos and PETSc actually rebuilding
the sparsity pattern of the product,
so using compute_mmult_pattern in the setup of the product would be of no use,
right?
For the moment that's correct. But the PETSc documentation provides a way how
one could re-use a previously computed sparsity pattern. One could add a flag
to the mmult function that switches between either telling PETSc to create a
new sparsity pattern, or re-using the existing one.
If you only call the function once, I have no doubt that there is not much of
a difference between using the deal.II and PETSc ways of creating sparsity
patterns. It's a different story if you plan on calling this function multiple
times using the same sparsity pattern.
Best
W.
--
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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