[petsc-users] MatSetValues on same column multiple times

[John Mousel]

If I'm adding to a particular column in multiple passes, do I need to
preallocate enough memory for each pass, or just 1 for each column in the
row?
Right now I'm drastically over-allocating, and I'm trying to reduce this.
If I give the true number of columns in the row, I keep getting new entry
errors.

New nonzero at (8045,60) caused a malloc!

I have it spit into phases where I set zeros in the non-zero pattern, then
I come back and fill in entries in a bulk pass, and then do a second pass
to clean up entries in special rows.
Could someone clarify how this works.

John
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