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

#include <petscts.h>

static PetscErrorCode RHSFunction(TS ts, PetscReal t, Vec X, Vec F, PetscCtx ctx)
{
  PetscInt           i, n;
  const PetscScalar *xx;
  PetscScalar       *ff;

  PetscFunctionBeginUser;
  PetscCall(VecGetLocalSize(X, &n));
  PetscCall(VecGetArrayRead(X, &xx));
  PetscCall(VecGetArray(F, &ff));
  if (n >= 1) ff[0] = 1;
  for (i = 1; i < n; i++) ff[i] = (i + 1) * (xx[i - 1] + PetscPowReal(t, i)) / 2;
  PetscCall(VecRestoreArrayRead(X, &xx));
  PetscCall(VecRestoreArray(F, &ff));
  PetscFunctionReturn(PETSC_SUCCESS);
}

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

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  PetscCall(TSCreate(PETSC_COMM_SELF, &ts));
  PetscCall(TSSetType(ts, TSRK));
  PetscCall(TSSetRHSFunction(ts, NULL, RHSFunction, NULL));
  PetscCall(VecCreateSeq(PETSC_COMM_SELF, N, &X));
  PetscCall(VecZeroEntries(X));
  PetscCall(TSSetTimeStep(ts, 0.001));
  PetscCall(TSSetTimeSpan(ts, 8, tspan));
  PetscCall(TSSetExactFinalTime(ts, TS_EXACTFINALTIME_MATCHSTEP));
  PetscCall(TSSetFromOptions(ts));
  PetscCall(TSSolve(ts, X));
  PetscCall(TSGetEvaluationSolutions(ts, &n, &sol_times, &Xs));
  PetscCall(TSGetEvaluationTimes(ts, &n, &tspan2));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Time Span: "));
  for (i = 0; i < n; i++) PetscCall(PetscPrintf(PETSC_COMM_WORLD, " %g", (double)tspan2[i]));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "\n"));
  for (PetscInt i = 0; i < n; i++) {
    PetscCheck(PetscIsCloseAtTol(tspan2[i], sol_times[i], 1e-6, 1e2 * PETSC_MACHINE_EPSILON), PetscObjectComm((PetscObject)ts), PETSC_ERR_PLIB, "Requested solution at time %g, but received time at %g", (double)tspan[i], (double)sol_times[i]);
  }
  PetscCall(TSDestroy(&ts));
  PetscCall(VecDestroy(&X));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

testset:
  test:
    suffix: 1
    args: -ts_monitor
  test:
    suffix: 2
    requires: !single
    args: -ts_monitor -ts_adapt_type none
TEST*/