[petsc-users] Question about TSSetRHSJacobian for linear time dependent problem

[Sajid Ali]

Hi,

If I have a linear time dependent equation I'm trying to solve using TS, I
can use :
TSSetProblemType(ts,TS_LINEAR);
TSSetRHSFunction(ts,NULL,TSComputeRHSFunctionLinear,NULL);
TSSetRHSJacobian(ts,A,A,YourComputeRHSJacobian, &appctx);

If the matrix that's being evaluated by YourComputeRHSJacobian is such that
the non-zero structure stays the same and only the diagonal changes with
time, is there a way to optimize the function so that it doesn't create the
whole matrix from scratch each time ?

Naively I can make a dummy matrix and store the copy from t=0 and change
the diagonal at each iteration but that unnecessarily doubles the memory
consumption, is there a better way?


Thank You,
Sajid Ali
Applied Physics
Northwestern University
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