xref: /petsc/src/ts/tutorials/ex4.c (revision 0b4b7b1c20c2ed4ade67e3d50a7710fe0ffbfca5)
1 static char help[] = "Solves a simple time-dependent linear PDE (the heat equation).\n\
2 Input parameters include:\n\
3   -m <points>, where <points> = number of grid points\n\
4   -time_dependent_rhs : Treat the problem as having a time-dependent right-hand side\n\
5   -debug              : Activate debugging printouts\n\
6   -nox                : Deactivate x-window graphics\n\n";
7 
8 /* ------------------------------------------------------------------------
9 
10    This program solves the one-dimensional heat equation (also called the
11    diffusion equation),
12        u_t = u_xx,
13    on the domain 0 <= x <= 1, with the boundary conditions
14        u(t,0) = 0, u(t,1) = 0,
15    and the initial condition
16        u(0,x) = sin(6*pi*x) + 3*sin(2*pi*x).
17    This is a linear, second-order, parabolic equation.
18 
19    We discretize the right-hand side using finite differences with
20    uniform grid spacing h:
21        u_xx = (u_{i+1} - 2u_{i} + u_{i-1})/(h^2)
22    We then demonstrate time evolution using the various TS methods by
23    running the program via
24        mpiexec -n <procs> ex3 -ts_type <timestepping solver>
25 
26    We compare the approximate solution with the exact solution, given by
27        u_exact(x,t) = exp(-36*pi*pi*t) * sin(6*pi*x) +
28                       3*exp(-4*pi*pi*t) * sin(2*pi*x)
29 
30    Notes:
31    This code demonstrates the TS solver interface to two variants of
32    linear problems, u_t = f(u,t), namely
33      - time-dependent f:   f(u,t) is a function of t
34      - time-independent f: f(u,t) is simply f(u)
35 
36     The uniprocessor version of this code is ts/tutorials/ex3.c
37 
38   ------------------------------------------------------------------------- */
39 
40 /*
41    Include "petscdmda.h" so that we can use distributed arrays (DMDAs) to manage
42    the parallel grid.  Include "petscts.h" so that we can use TS solvers.
43    Note that this file automatically includes:
44      petscsys.h       - base PETSc routines   petscvec.h  - vectors
45      petscmat.h  - matrices
46      petscis.h     - index sets            petscksp.h  - Krylov subspace methods
47      petscviewer.h - viewers               petscpc.h   - preconditioners
48      petscksp.h   - linear solvers        petscsnes.h - nonlinear solvers
49 */
50 
51 #include <petscdm.h>
52 #include <petscdmda.h>
53 #include <petscts.h>
54 #include <petscdraw.h>
55 
56 /*
57    User-defined application context - contains data needed by the
58    application-provided call-back routines.
59 */
60 typedef struct {
61   MPI_Comm    comm;             /* communicator */
62   DM          da;               /* distributed array data structure */
63   Vec         localwork;        /* local ghosted work vector */
64   Vec         u_local;          /* local ghosted approximate solution vector */
65   Vec         solution;         /* global exact solution vector */
66   PetscInt    m;                /* total number of grid points */
67   PetscReal   h;                /* mesh width h = 1/(m-1) */
68   PetscBool   debug;            /* flag (1 indicates activation of debugging printouts) */
69   PetscViewer viewer1, viewer2; /* viewers for the solution and error */
70   PetscReal   norm_2, norm_max; /* error norms */
71 } AppCtx;
72 
73 /*
74    User-defined routines
75 */
76 extern PetscErrorCode InitialConditions(Vec, AppCtx *);
77 extern PetscErrorCode RHSMatrixHeat(TS, PetscReal, Vec, Mat, Mat, void *);
78 extern PetscErrorCode RHSFunctionHeat(TS, PetscReal, Vec, Vec, void *);
79 extern PetscErrorCode Monitor(TS, PetscInt, PetscReal, Vec, void *);
80 extern PetscErrorCode ExactSolution(PetscReal, Vec, AppCtx *);
81 
82 int main(int argc, char **argv)
83 {
84   AppCtx        appctx;               /* user-defined application context */
85   TS            ts;                   /* timestepping context */
86   Mat           A;                    /* matrix data structure */
87   Vec           u;                    /* approximate solution vector */
88   PetscReal     time_total_max = 1.0; /* default max total time */
89   PetscInt      time_steps_max = 100; /* default max timesteps */
90   PetscDraw     draw;                 /* drawing context */
91   PetscInt      steps, m;
92   PetscMPIInt   size;
93   PetscReal     dt, ftime;
94   PetscBool     flg;
95   TSProblemType tsproblem = TS_LINEAR;
96 
97   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
98      Initialize program and set problem parameters
99      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
100 
101   PetscFunctionBeginUser;
102   PetscCall(PetscInitialize(&argc, &argv, NULL, help));
103   appctx.comm = PETSC_COMM_WORLD;
104 
105   m = 60;
106   PetscCall(PetscOptionsGetInt(NULL, NULL, "-m", &m, NULL));
107   PetscCall(PetscOptionsHasName(NULL, NULL, "-debug", &appctx.debug));
108   appctx.m        = m;
109   appctx.h        = 1.0 / (m - 1.0);
110   appctx.norm_2   = 0.0;
111   appctx.norm_max = 0.0;
112 
113   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
114   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Solving a linear TS problem, number of processors = %d\n", size));
115 
116   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
117      Create vector data structures
118      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
119   /*
120      Create distributed array (DMDA) to manage parallel grid and vectors
121      and to set up the ghost point communication pattern.  There are M
122      total grid values spread equally among all the processors.
123   */
124 
125   PetscCall(DMDACreate1d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, m, 1, 1, NULL, &appctx.da));
126   PetscCall(DMSetFromOptions(appctx.da));
127   PetscCall(DMSetUp(appctx.da));
128 
129   /*
130      Extract global and local vectors from DMDA; we use these to store the
131      approximate solution.  Then duplicate these for remaining vectors that
132      have the same types.
133   */
134   PetscCall(DMCreateGlobalVector(appctx.da, &u));
135   PetscCall(DMCreateLocalVector(appctx.da, &appctx.u_local));
136 
137   /*
138      Create local work vector for use in evaluating right-hand-side function;
139      create global work vector for storing exact solution.
140   */
141   PetscCall(VecDuplicate(appctx.u_local, &appctx.localwork));
142   PetscCall(VecDuplicate(u, &appctx.solution));
143 
144   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
145      Set up displays to show graphs of the solution and error
146      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
147 
148   PetscCall(PetscViewerDrawOpen(PETSC_COMM_WORLD, 0, "", 80, 380, 400, 160, &appctx.viewer1));
149   PetscCall(PetscViewerDrawGetDraw(appctx.viewer1, 0, &draw));
150   PetscCall(PetscDrawSetDoubleBuffer(draw));
151   PetscCall(PetscViewerDrawOpen(PETSC_COMM_WORLD, 0, "", 80, 0, 400, 160, &appctx.viewer2));
152   PetscCall(PetscViewerDrawGetDraw(appctx.viewer2, 0, &draw));
153   PetscCall(PetscDrawSetDoubleBuffer(draw));
154 
155   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
156      Create timestepping solver context
157      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
158 
159   PetscCall(TSCreate(PETSC_COMM_WORLD, &ts));
160 
161   flg = PETSC_FALSE;
162   PetscCall(PetscOptionsGetBool(NULL, NULL, "-nonlinear", &flg, NULL));
163   PetscCall(TSSetProblemType(ts, flg ? TS_NONLINEAR : TS_LINEAR));
164 
165   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
166      Set optional user-defined monitoring routine
167      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
168   PetscCall(TSMonitorSet(ts, Monitor, &appctx, NULL));
169 
170   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
171 
172      Create matrix data structure; set matrix evaluation routine.
173      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
174 
175   PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
176   PetscCall(MatSetSizes(A, PETSC_DECIDE, PETSC_DECIDE, m, m));
177   PetscCall(MatSetFromOptions(A));
178   PetscCall(MatSetUp(A));
179 
180   flg = PETSC_FALSE;
181   PetscCall(PetscOptionsGetBool(NULL, NULL, "-time_dependent_rhs", &flg, NULL));
182   if (flg) {
183     /*
184        For linear problems with a time-dependent f(u,t) in the equation
185        u_t = f(u,t), the user provides the discretized right-hand side
186        as a time-dependent matrix.
187     */
188     PetscCall(TSSetRHSFunction(ts, NULL, TSComputeRHSFunctionLinear, &appctx));
189     PetscCall(TSSetRHSJacobian(ts, A, A, RHSMatrixHeat, &appctx));
190   } else {
191     /*
192        For linear problems with a time-independent f(u) in the equation
193        u_t = f(u), the user provides the discretized right-hand side
194        as a matrix only once, and then sets a null matrix evaluation
195        routine.
196     */
197     PetscCall(RHSMatrixHeat(ts, 0.0, u, A, A, &appctx));
198     PetscCall(TSSetRHSFunction(ts, NULL, TSComputeRHSFunctionLinear, &appctx));
199     PetscCall(TSSetRHSJacobian(ts, A, A, TSComputeRHSJacobianConstant, &appctx));
200   }
201 
202   if (tsproblem == TS_NONLINEAR) {
203     SNES snes;
204     PetscCall(TSSetRHSFunction(ts, NULL, RHSFunctionHeat, &appctx));
205     PetscCall(TSGetSNES(ts, &snes));
206     PetscCall(SNESSetJacobian(snes, NULL, NULL, SNESComputeJacobianDefault, NULL));
207   }
208 
209   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
210      Set solution vector and initial timestep
211      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
212 
213   dt = appctx.h * appctx.h / 2.0;
214   PetscCall(TSSetTimeStep(ts, dt));
215   PetscCall(TSSetSolution(ts, u));
216 
217   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
218      Customize timestepping solver:
219        - Set the solution method to be the Backward Euler method.
220        - Set timestepping duration info
221      Then set runtime options, which can override these defaults.
222      For example,
223           -ts_max_steps <maxsteps> -ts_max_time <maxtime>
224      to override the defaults set by TSSetMaxSteps()/TSSetMaxTime().
225      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
226 
227   PetscCall(TSSetMaxSteps(ts, time_steps_max));
228   PetscCall(TSSetMaxTime(ts, time_total_max));
229   PetscCall(TSSetExactFinalTime(ts, TS_EXACTFINALTIME_STEPOVER));
230   PetscCall(TSSetFromOptions(ts));
231 
232   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
233      Solve the problem
234      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
235 
236   /*
237      Evaluate initial conditions
238   */
239   PetscCall(InitialConditions(u, &appctx));
240 
241   /*
242      Run the timestepping solver
243   */
244   PetscCall(TSSolve(ts, u));
245   PetscCall(TSGetSolveTime(ts, &ftime));
246   PetscCall(TSGetStepNumber(ts, &steps));
247 
248   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
249      View timestepping solver info
250      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
251   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Total timesteps %" PetscInt_FMT ", Final time %g\n", steps, (double)ftime));
252   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Avg. error (2 norm) = %g Avg. error (max norm) = %g\n", (double)(appctx.norm_2 / steps), (double)(appctx.norm_max / steps)));
253 
254   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
255      Free work space.  All PETSc objects should be destroyed when they
256      are no longer needed.
257      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
258 
259   PetscCall(TSDestroy(&ts));
260   PetscCall(MatDestroy(&A));
261   PetscCall(VecDestroy(&u));
262   PetscCall(PetscViewerDestroy(&appctx.viewer1));
263   PetscCall(PetscViewerDestroy(&appctx.viewer2));
264   PetscCall(VecDestroy(&appctx.localwork));
265   PetscCall(VecDestroy(&appctx.solution));
266   PetscCall(VecDestroy(&appctx.u_local));
267   PetscCall(DMDestroy(&appctx.da));
268 
269   /*
270      Always call PetscFinalize() before exiting a program.  This routine
271        - finalizes the PETSc libraries as well as MPI
272        - provides summary and diagnostic information if certain runtime
273          options are chosen (e.g., -log_view).
274   */
275   PetscCall(PetscFinalize());
276   return 0;
277 }
278 /* --------------------------------------------------------------------- */
279 /*
280    InitialConditions - Computes the solution at the initial time.
281 
282    Input Parameter:
283    u - uninitialized solution vector (global)
284    appctx - user-defined application context
285 
286    Output Parameter:
287    u - vector with solution at initial time (global)
288 */
289 PetscErrorCode InitialConditions(Vec u, AppCtx *appctx)
290 {
291   PetscScalar *u_localptr, h = appctx->h;
292   PetscInt     i, mybase, myend;
293 
294   PetscFunctionBeginUser;
295   /*
296      Determine starting point of each processor's range of
297      grid values.
298   */
299   PetscCall(VecGetOwnershipRange(u, &mybase, &myend));
300 
301   /*
302     Get a pointer to vector data.
303     - For default PETSc vectors, VecGetArray() returns a pointer to
304       the data array.  Otherwise, the routine is implementation dependent.
305     - You MUST call VecRestoreArray() when you no longer need access to
306       the array.
307     - Note that the Fortran interface to VecGetArray() differs from the
308       C version.  See the users manual for details.
309   */
310   PetscCall(VecGetArray(u, &u_localptr));
311 
312   /*
313      We initialize the solution array by simply writing the solution
314      directly into the array locations.  Alternatively, we could use
315      VecSetValues() or VecSetValuesLocal().
316   */
317   for (i = mybase; i < myend; i++) u_localptr[i - mybase] = PetscSinScalar(PETSC_PI * i * 6. * h) + 3. * PetscSinScalar(PETSC_PI * i * 2. * h);
318 
319   /*
320      Restore vector
321   */
322   PetscCall(VecRestoreArray(u, &u_localptr));
323 
324   /*
325      Print debugging information if desired
326   */
327   if (appctx->debug) {
328     PetscCall(PetscPrintf(appctx->comm, "initial guess vector\n"));
329     PetscCall(VecView(u, PETSC_VIEWER_STDOUT_WORLD));
330   }
331   PetscFunctionReturn(PETSC_SUCCESS);
332 }
333 /* --------------------------------------------------------------------- */
334 /*
335    ExactSolution - Computes the exact solution at a given time.
336 
337    Input Parameters:
338    t - current time
339    solution - vector in which exact solution will be computed
340    appctx - user-defined application context
341 
342    Output Parameter:
343    solution - vector with the newly computed exact solution
344 */
345 PetscErrorCode ExactSolution(PetscReal t, Vec solution, AppCtx *appctx)
346 {
347   PetscScalar *s_localptr, h = appctx->h, ex1, ex2, sc1, sc2;
348   PetscInt     i, mybase, myend;
349 
350   PetscFunctionBeginUser;
351   /*
352      Determine starting and ending points of each processor's
353      range of grid values
354   */
355   PetscCall(VecGetOwnershipRange(solution, &mybase, &myend));
356 
357   /*
358      Get a pointer to vector data.
359   */
360   PetscCall(VecGetArray(solution, &s_localptr));
361 
362   /*
363      Simply write the solution directly into the array locations.
364      Alternatively, we culd use VecSetValues() or VecSetValuesLocal().
365   */
366   ex1 = PetscExpReal(-36. * PETSC_PI * PETSC_PI * t);
367   ex2 = PetscExpReal(-4. * PETSC_PI * PETSC_PI * t);
368   sc1 = PETSC_PI * 6. * h;
369   sc2 = PETSC_PI * 2. * h;
370   for (i = mybase; i < myend; i++) s_localptr[i - mybase] = PetscSinScalar(sc1 * (PetscReal)i) * ex1 + 3. * PetscSinScalar(sc2 * (PetscReal)i) * ex2;
371 
372   /*
373      Restore vector
374   */
375   PetscCall(VecRestoreArray(solution, &s_localptr));
376   PetscFunctionReturn(PETSC_SUCCESS);
377 }
378 /* --------------------------------------------------------------------- */
379 /*
380    Monitor - User-provided routine to monitor the solution computed at
381    each timestep.  This example plots the solution and computes the
382    error in two different norms.
383 
384    Input Parameters:
385    ts     - the timestep context
386    step   - the count of the current step (with 0 meaning the
387              initial condition)
388    time   - the current time
389    u      - the solution at this timestep
390    ctx    - the user-provided context for this monitoring routine.
391             In this case we use the application context which contains
392             information about the problem size, workspace and the exact
393             solution.
394 */
395 PetscErrorCode Monitor(TS ts, PetscInt step, PetscReal time, Vec u, void *ctx)
396 {
397   AppCtx   *appctx = (AppCtx *)ctx; /* user-defined application context */
398   PetscReal norm_2, norm_max;
399 
400   PetscFunctionBeginUser;
401   /*
402      View a graph of the current iterate
403   */
404   PetscCall(VecView(u, appctx->viewer2));
405 
406   /*
407      Compute the exact solution
408   */
409   PetscCall(ExactSolution(time, appctx->solution, appctx));
410 
411   /*
412      Print debugging information if desired
413   */
414   if (appctx->debug) {
415     PetscCall(PetscPrintf(appctx->comm, "Computed solution vector\n"));
416     PetscCall(VecView(u, PETSC_VIEWER_STDOUT_WORLD));
417     PetscCall(PetscPrintf(appctx->comm, "Exact solution vector\n"));
418     PetscCall(VecView(appctx->solution, PETSC_VIEWER_STDOUT_WORLD));
419   }
420 
421   /*
422      Compute the 2-norm and max-norm of the error
423   */
424   PetscCall(VecAXPY(appctx->solution, -1.0, u));
425   PetscCall(VecNorm(appctx->solution, NORM_2, &norm_2));
426   norm_2 = PetscSqrtReal(appctx->h) * norm_2;
427   PetscCall(VecNorm(appctx->solution, NORM_MAX, &norm_max));
428   if (norm_2 < 1e-14) norm_2 = 0;
429   if (norm_max < 1e-14) norm_max = 0;
430 
431   /*
432      PetscPrintf() causes only the first processor in this
433      communicator to print the timestep information.
434   */
435   PetscCall(PetscPrintf(appctx->comm, "Timestep %" PetscInt_FMT ": time = %g 2-norm error = %g max norm error = %g\n", step, (double)time, (double)norm_2, (double)norm_max));
436   appctx->norm_2 += norm_2;
437   appctx->norm_max += norm_max;
438 
439   /*
440      View a graph of the error
441   */
442   PetscCall(VecView(appctx->solution, appctx->viewer1));
443 
444   /*
445      Print debugging information if desired
446   */
447   if (appctx->debug) {
448     PetscCall(PetscPrintf(appctx->comm, "Error vector\n"));
449     PetscCall(VecView(appctx->solution, PETSC_VIEWER_STDOUT_WORLD));
450   }
451   PetscFunctionReturn(PETSC_SUCCESS);
452 }
453 
454 /* --------------------------------------------------------------------- */
455 /*
456    RHSMatrixHeat - User-provided routine to compute the right-hand-side
457    matrix for the heat equation.
458 
459    Input Parameters:
460    ts - the TS context
461    t - current time
462    global_in - global input vector
463    dummy - optional user-defined context, as set by TSetRHSJacobian()
464 
465    Output Parameters:
466    AA - Jacobian matrix
467    BB - optionally different preconditioning matrix
468 
469   Notes:
470   RHSMatrixHeat computes entries for the locally owned part of the system.
471    - Currently, all PETSc parallel matrix formats are partitioned by
472      contiguous chunks of rows across the processors.
473    - Each processor needs to insert only elements that it owns
474      locally (but any non-local elements will be sent to the
475      appropriate processor during matrix assembly).
476    - Always specify global row and columns of matrix entries when
477      using MatSetValues(); we could alternatively use MatSetValuesLocal().
478    - Here, we set all entries for a particular row at once.
479    - Note that MatSetValues() uses 0-based row and column numbers
480      in Fortran as well as in C.
481 */
482 PetscErrorCode RHSMatrixHeat(TS ts, PetscReal t, Vec X, Mat AA, Mat BB, void *ctx)
483 {
484   Mat         A      = AA;            /* Jacobian matrix */
485   AppCtx     *appctx = (AppCtx *)ctx; /* user-defined application context */
486   PetscInt    i, mstart, mend, idx[3];
487   PetscScalar v[3], stwo = -2. / (appctx->h * appctx->h), sone = -.5 * stwo;
488 
489   PetscFunctionBeginUser;
490   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
491      Compute entries for the locally owned part of the matrix
492      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
493 
494   PetscCall(MatGetOwnershipRange(A, &mstart, &mend));
495 
496   /*
497      Set matrix rows corresponding to boundary data
498   */
499 
500   if (mstart == 0) { /* first processor only */
501     v[0] = 1.0;
502     PetscCall(MatSetValues(A, 1, &mstart, 1, &mstart, v, INSERT_VALUES));
503     mstart++;
504   }
505 
506   if (mend == appctx->m) { /* last processor only */
507     mend--;
508     v[0] = 1.0;
509     PetscCall(MatSetValues(A, 1, &mend, 1, &mend, v, INSERT_VALUES));
510   }
511 
512   /*
513      Set matrix rows corresponding to interior data.  We construct the
514      matrix one row at a time.
515   */
516   v[0] = sone;
517   v[1] = stwo;
518   v[2] = sone;
519   for (i = mstart; i < mend; i++) {
520     idx[0] = i - 1;
521     idx[1] = i;
522     idx[2] = i + 1;
523     PetscCall(MatSetValues(A, 1, &i, 3, idx, v, INSERT_VALUES));
524   }
525 
526   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
527      Complete the matrix assembly process and set some options
528      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
529   /*
530      Assemble matrix, using the 2-step process:
531        MatAssemblyBegin(), MatAssemblyEnd()
532      Computations can be done while messages are in transition
533      by placing code between these two statements.
534   */
535   PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
536   PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
537 
538   /*
539      Set and option to indicate that we will never add a new nonzero location
540      to the matrix. If we do, it will generate an error.
541   */
542   PetscCall(MatSetOption(A, MAT_NEW_NONZERO_LOCATION_ERR, PETSC_TRUE));
543   PetscFunctionReturn(PETSC_SUCCESS);
544 }
545 
546 PetscErrorCode RHSFunctionHeat(TS ts, PetscReal t, Vec globalin, Vec globalout, void *ctx)
547 {
548   Mat A;
549 
550   PetscFunctionBeginUser;
551   PetscCall(TSGetRHSJacobian(ts, &A, NULL, NULL, &ctx));
552   PetscCall(RHSMatrixHeat(ts, t, globalin, A, NULL, ctx));
553   /* PetscCall(MatView(A,PETSC_VIEWER_STDOUT_WORLD)); */
554   PetscCall(MatMult(A, globalin, globalout));
555   PetscFunctionReturn(PETSC_SUCCESS);
556 }
557 
558 /*TEST
559 
560     test:
561       args: -ts_view -nox
562 
563     test:
564       suffix: 2
565       args: -ts_view -nox
566       nsize: 3
567 
568     test:
569       suffix: 3
570       args: -ts_view -nox -nonlinear
571 
572     test:
573       suffix: 4
574       args: -ts_view -nox -nonlinear
575       nsize: 3
576       timeoutfactor: 3
577 
578     test:
579       suffix: sundials
580       requires: sundials2
581       args: -nox -ts_type sundials -ts_max_steps 5 -nonlinear
582       nsize: 4
583 
584     test:
585       suffix: sundials_dense
586       requires: sundials2
587       args: -nox -ts_type sundials -ts_sundials_use_dense -ts_max_steps 5 -nonlinear
588       nsize: 1
589 
590 TEST*/
591