1: static char help[] = "Tests TS time span \n\n";

  3: #include <petscts.h>

  5: static PetscErrorCode RHSFunction(TS ts, PetscReal t, Vec X, Vec F, void *ctx)
  6: {
  7:   PetscInt           i, n;
  8:   const PetscScalar *xx;
  9:   PetscScalar       *ff;

 11:   PetscFunctionBeginUser;
 12:   PetscCall(VecGetLocalSize(X, &n));
 13:   PetscCall(VecGetArrayRead(X, &xx));
 14:   PetscCall(VecGetArray(F, &ff));
 15:   if (n >= 1) ff[0] = 1;
 16:   for (i = 1; i < n; i++) ff[i] = (i + 1) * (xx[i - 1] + PetscPowReal(t, i)) / 2;
 17:   PetscCall(VecRestoreArrayRead(X, &xx));
 18:   PetscCall(VecRestoreArray(F, &ff));
 19:   PetscFunctionReturn(PETSC_SUCCESS);
 20: }

 22: int main(int argc, char *argv[])
 23: {
 24:   TS               ts;
 25:   Vec              X, *Xs;
 26:   PetscInt         i, n, N = 9;
 27:   PetscReal        tspan[8] = {16.0, 16.1, 16.2, 16.3, 16.4, 16.5, 16.6, 16.7};
 28:   const PetscReal *tspan2;

 30:   PetscFunctionBeginUser;
 31:   PetscCall(PetscInitialize(&argc, &argv, NULL, help));
 32:   PetscCall(TSCreate(PETSC_COMM_SELF, &ts));
 33:   PetscCall(TSSetType(ts, TSRK));
 34:   PetscCall(TSSetRHSFunction(ts, NULL, RHSFunction, NULL));
 35:   PetscCall(VecCreateSeq(PETSC_COMM_SELF, N, &X));
 36:   PetscCall(VecZeroEntries(X));
 37:   PetscCall(TSSetTimeStep(ts, 0.001));
 38:   PetscCall(TSSetTimeSpan(ts, 8, tspan));
 39:   PetscCall(TSSetExactFinalTime(ts, TS_EXACTFINALTIME_MATCHSTEP));
 40:   PetscCall(TSSetFromOptions(ts));
 41:   PetscCall(TSSolve(ts, X));
 42:   PetscCall(TSGetTimeSpanSolutions(ts, &n, &Xs));
 43:   PetscCall(TSGetTimeSpan(ts, &n, &tspan2));
 44:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Time Span: "));
 45:   for (i = 0; i < n; i++) PetscCall(PetscPrintf(PETSC_COMM_WORLD, " %g", (double)tspan2[i]));
 46:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "\n"));
 47:   PetscCall(TSDestroy(&ts));
 48:   PetscCall(VecDestroy(&X));
 49:   PetscCall(PetscFinalize());
 50:   return 0;
 51: }

 53: /*TEST

 55: testset:
 56:   test:
 57:     suffix: 1
 58:     args: -ts_monitor
 59:   test:
 60:     suffix: 2
 61:     requires: !single
 62:     args: -ts_monitor -ts_adapt_type none
 63: TEST*/