# TSSetRHSMatrix

Sets the function to compute the matrix A, where U_t = A(t) U. Also sets the location to store A.

### Synopsis

    #include "petscts.h"
    PetscErrorCode PETSCTS_DLLEXPORT TSSetRHSMatrix(TS ts,Mat A,Mat B,PetscErrorCode (*f)(TS,PetscReal,Mat*,Mat*,MatStructure*,void*),void *ctx)

Collective on TS

### Input Parameters

| ts | - the TS context obtained from TSCreate()
| A | - matrix
| B | - preconditioner matrix (usually same as A)
| f | - the matrix evaluation routine; use PETSC_NULL (PETSC_NULL_FUNCTION in fortran) if A is not a function of t.
| ctx | - [optional] user-defined context for private data for the matrix evaluation routine (may be PETSC_NULL)

### Calling sequence of func

        func (TS ts,PetscReal t,Mat *A,Mat *B,PetscInt *flag,void *ctx);

| t | - current timestep
| A | - matrix A, where U_t = A(t) U
| B | - preconditioner matrix, usually the same as A
| flag | - flag indicating information about the preconditioner matrix structure (same as flag in KSPSetOperators())
| ctx | - [optional] user-defined context for matrix evaluation routine

### Notes

See KSPSetOperators() for important information about setting the flag output parameter in the routine func(). Be sure to read this information!

The routine func() takes Mat * as the matrix arguments rather than Mat. This allows the matrix evaluation routine to replace A and/or B with a completely new new matrix structure (not just different matrix elements) when appropriate, for instance, if the nonzero structure is changing throughout the global iterations.

### Important

The user MUST call either this routine or TSSetRHSFunction().

### Keywords

TS, timestep, set, right-hand-side, matrix

### See Also

TSSetRHSFunction()

Level:beginner
Location:src/ts/interface/ts.c
Index of all TS routines
Table of Contents for all manual pages
Index of all manual pages

### Examples

src/ts/examples/tutorials/ex3.c.html
src/ts/examples/tutorials/ex4.c.html
src/ts/examples/tutorials/ex5.c.html
src/ts/examples/tutorials/ex6.c.html