[petsc-users] fill matrix using dynamic load balancing code

[Gao Bin]

Hi, all

(1) I am using PETSc to perform, for instance matrix-matrix multiplication. But the numerical values of the matrix are calculated from my integral code. I guess, for matrix-matrix multiplication, it might be better to distribute the rows of matrix uniformly on processors, right?

(2) If yes, I have a problem in my integral code. Since I need dynamic load balancing to calculate the matrix elements and then put them into correct places by using MatSetValues. But I have two questions regarding MatSetValues:

(2.1) If one processor calculated a lot of elements belong to another remote processor, will this become a problem for the performance? Should I make all processors calculate as many local elements as possible?

(2.2) From the manual, I see MatSetValues only caches the values, but MatAssemblyBegin() and MatAssemblyEnd() assembles the matrix. Therefore, is there any memory limit for MatSetValues, or in other words, will it cost a lot of memory before assembling?

Thank you in advance.

Cheers

Gao
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