xref: /honee/src/setupts.c (revision 008ae799015c7852a7858fdacb1bdc82bf96a275)
1 // Copyright (c) 2017-2022, Lawrence Livermore National Security, LLC and other CEED contributors.
2 // All Rights Reserved. See the top-level LICENSE and NOTICE files for details.
3 //
4 // SPDX-License-Identifier: BSD-2-Clause
5 //
6 // This file is part of CEED:  http://github.com/ceed
7 
8 /// @file
9 /// Time-stepping functions for Navier-Stokes example using PETSc
10 
11 #include "../navierstokes.h"
12 #include "../qfunctions/mass.h"
13 
14 // Compute mass matrix for explicit scheme
15 PetscErrorCode ComputeLumpedMassMatrix(Ceed ceed, DM dm, CeedData ceed_data,
16                                        Vec M) {
17   Vec            M_loc;
18   CeedQFunction  qf_mass;
19   CeedOperator   op_mass;
20   CeedVector     m_ceed, ones_vec;
21   CeedInt        num_comp_q, q_data_size;
22   PetscErrorCode ierr;
23   PetscFunctionBeginUser;
24 
25   // CEED Restriction
26   CeedElemRestrictionGetNumComponents(ceed_data->elem_restr_q, &num_comp_q);
27   CeedElemRestrictionGetNumComponents(ceed_data->elem_restr_qd_i, &q_data_size);
28   CeedElemRestrictionCreateVector(ceed_data->elem_restr_q, &m_ceed, NULL);
29   CeedElemRestrictionCreateVector(ceed_data->elem_restr_q, &ones_vec, NULL);
30   CeedVectorSetValue(ones_vec, 1.0);
31 
32   // CEED QFunction
33   CeedQFunctionCreateInterior(ceed, 1, Mass, Mass_loc, &qf_mass);
34   CeedQFunctionAddInput(qf_mass, "q", num_comp_q, CEED_EVAL_INTERP);
35   CeedQFunctionAddInput(qf_mass, "qdata", q_data_size, CEED_EVAL_NONE);
36   CeedQFunctionAddOutput(qf_mass, "v", num_comp_q, CEED_EVAL_INTERP);
37 
38   // CEED Operator
39   CeedOperatorCreate(ceed, qf_mass, NULL, NULL, &op_mass);
40   CeedOperatorSetField(op_mass, "q", ceed_data->elem_restr_q, ceed_data->basis_q,
41                        CEED_VECTOR_ACTIVE);
42   CeedOperatorSetField(op_mass, "qdata", ceed_data->elem_restr_qd_i,
43                        CEED_BASIS_COLLOCATED, ceed_data->q_data);
44   CeedOperatorSetField(op_mass, "v", ceed_data->elem_restr_q, ceed_data->basis_q,
45                        CEED_VECTOR_ACTIVE);
46 
47   // Place PETSc vector in CEED vector
48   CeedScalar *m;
49   PetscMemType m_mem_type;
50   ierr = DMGetLocalVector(dm, &M_loc); CHKERRQ(ierr);
51   ierr = VecGetArrayAndMemType(M_loc, (PetscScalar **)&m, &m_mem_type);
52   CHKERRQ(ierr);
53   CeedVectorSetArray(m_ceed, MemTypeP2C(m_mem_type), CEED_USE_POINTER, m);
54 
55   // Apply CEED Operator
56   CeedOperatorApply(op_mass, ones_vec, m_ceed, CEED_REQUEST_IMMEDIATE);
57 
58   // Restore vectors
59   CeedVectorTakeArray(m_ceed, MemTypeP2C(m_mem_type), NULL);
60   ierr = VecRestoreArrayReadAndMemType(M_loc, (const PetscScalar **)&m);
61   CHKERRQ(ierr);
62 
63   // Local-to-Global
64   ierr = VecZeroEntries(M); CHKERRQ(ierr);
65   ierr = DMLocalToGlobal(dm, M_loc, ADD_VALUES, M); CHKERRQ(ierr);
66   ierr = DMRestoreLocalVector(dm, &M_loc); CHKERRQ(ierr);
67 
68   // Invert diagonally lumped mass vector for RHS function
69   ierr = VecReciprocal(M); CHKERRQ(ierr);
70 
71   // Cleanup
72   CeedVectorDestroy(&ones_vec);
73   CeedVectorDestroy(&m_ceed);
74   CeedQFunctionDestroy(&qf_mass);
75   CeedOperatorDestroy(&op_mass);
76 
77   PetscFunctionReturn(0);
78 }
79 
80 // RHS (Explicit time-stepper) function setup
81 //   This is the RHS of the ODE, given as u_t = G(t,u)
82 //   This function takes in a state vector Q and writes into G
83 PetscErrorCode RHS_NS(TS ts, PetscReal t, Vec Q, Vec G, void *user_data) {
84   User           user = *(User *)user_data;
85   PetscScalar    *q, *g;
86   Vec            Q_loc = user->Q_loc, G_loc;
87   PetscMemType   q_mem_type, g_mem_type;
88   PetscErrorCode ierr;
89   PetscFunctionBeginUser;
90 
91   // Get local vector
92   ierr = DMGetLocalVector(user->dm, &G_loc); CHKERRQ(ierr);
93 
94   // Update time dependent data
95   if (user->time != t) {
96     ierr = VecZeroEntries(Q_loc); CHKERRQ(ierr);
97     ierr = DMPlexInsertBoundaryValues(user->dm, PETSC_TRUE, Q_loc, t,
98                                       NULL, NULL, NULL); CHKERRQ(ierr);
99     if (user->phys->solution_time_label) {
100       CeedOperatorContextSetDouble(user->op_rhs, user->phys->solution_time_label, &t);
101     }
102     user->time = t;
103   }
104   if (user->phys->timestep_size_label) {
105     PetscScalar dt;
106     ierr = TSGetTimeStep(ts, &dt); CHKERRQ(ierr);
107     if (user->dt != dt) {
108       CeedOperatorContextSetDouble(user->op_rhs, user->phys->timestep_size_label,
109                                    &dt);
110       user->dt = dt;
111     }
112   }
113 
114   // Global-to-local
115   ierr = DMGlobalToLocal(user->dm, Q, INSERT_VALUES, Q_loc); CHKERRQ(ierr);
116 
117   // Place PETSc vectors in CEED vectors
118   ierr = VecGetArrayReadAndMemType(Q_loc, (const PetscScalar **)&q, &q_mem_type);
119   CHKERRQ(ierr);
120   ierr = VecGetArrayAndMemType(G_loc, &g, &g_mem_type); CHKERRQ(ierr);
121   CeedVectorSetArray(user->q_ceed, MemTypeP2C(q_mem_type), CEED_USE_POINTER, q);
122   CeedVectorSetArray(user->g_ceed, MemTypeP2C(g_mem_type), CEED_USE_POINTER, g);
123 
124   // Apply CEED operator
125   CeedOperatorApply(user->op_rhs, user->q_ceed, user->g_ceed,
126                     CEED_REQUEST_IMMEDIATE);
127 
128   // Restore vectors
129   CeedVectorTakeArray(user->q_ceed, MemTypeP2C(q_mem_type), NULL);
130   CeedVectorTakeArray(user->g_ceed, MemTypeP2C(g_mem_type), NULL);
131   ierr = VecRestoreArrayReadAndMemType(Q_loc, (const PetscScalar **)&q);
132   CHKERRQ(ierr);
133   ierr = VecRestoreArrayAndMemType(G_loc, &g); CHKERRQ(ierr);
134 
135   // Local-to-Global
136   ierr = VecZeroEntries(G); CHKERRQ(ierr);
137   ierr = DMLocalToGlobal(user->dm, G_loc, ADD_VALUES, G); CHKERRQ(ierr);
138 
139   // Inverse of the lumped mass matrix (M is Minv)
140   ierr = VecPointwiseMult(G, G, user->M); CHKERRQ(ierr);
141 
142   // Restore vectors
143   ierr = DMRestoreLocalVector(user->dm, &G_loc); CHKERRQ(ierr);
144 
145   PetscFunctionReturn(0);
146 }
147 
148 // Implicit time-stepper function setup
149 PetscErrorCode IFunction_NS(TS ts, PetscReal t, Vec Q, Vec Q_dot, Vec G,
150                             void *user_data) {
151   User              user = *(User *)user_data;
152   const PetscScalar *q, *q_dot;
153   PetscScalar       *g;
154   Vec               Q_loc = user->Q_loc, Q_dot_loc = user->Q_dot_loc, G_loc;
155   PetscMemType      q_mem_type, q_dot_mem_type, g_mem_type;
156   PetscErrorCode    ierr;
157   PetscFunctionBeginUser;
158 
159   // Get local vectors
160   ierr = DMGetLocalVector(user->dm, &G_loc); CHKERRQ(ierr);
161 
162   // Update time dependent data
163   if (user->time != t) {
164     ierr = VecZeroEntries(Q_loc); CHKERRQ(ierr);
165     ierr = DMPlexInsertBoundaryValues(user->dm, PETSC_TRUE, Q_loc, t,
166                                       NULL, NULL, NULL); CHKERRQ(ierr);
167     if (user->phys->solution_time_label) {
168       CeedOperatorContextSetDouble(user->op_ifunction,
169                                    user->phys->solution_time_label, &t);
170     }
171     user->time = t;
172   }
173   if (user->phys->timestep_size_label) {
174     PetscScalar dt;
175     ierr = TSGetTimeStep(ts, &dt); CHKERRQ(ierr);
176     if (user->dt != dt) {
177       CeedOperatorContextSetDouble(user->op_ifunction,
178                                    user->phys->timestep_size_label, &dt);
179       user->dt = dt;
180     }
181   }
182 
183   // Global-to-local
184   ierr = DMGlobalToLocal(user->dm, Q, INSERT_VALUES, Q_loc); CHKERRQ(ierr);
185   ierr = DMGlobalToLocal(user->dm, Q_dot, INSERT_VALUES, Q_dot_loc);
186   CHKERRQ(ierr);
187 
188   // Place PETSc vectors in CEED vectors
189   ierr = VecGetArrayReadAndMemType(Q_loc, &q, &q_mem_type); CHKERRQ(ierr);
190   ierr = VecGetArrayReadAndMemType(Q_dot_loc, &q_dot, &q_dot_mem_type);
191   CHKERRQ(ierr);
192   ierr = VecGetArrayAndMemType(G_loc, &g, &g_mem_type); CHKERRQ(ierr);
193   CeedVectorSetArray(user->q_ceed, MemTypeP2C(q_mem_type), CEED_USE_POINTER,
194                      (PetscScalar *)q);
195   CeedVectorSetArray(user->q_dot_ceed, MemTypeP2C(q_dot_mem_type),
196                      CEED_USE_POINTER, (PetscScalar *)q_dot);
197   CeedVectorSetArray(user->g_ceed, MemTypeP2C(g_mem_type), CEED_USE_POINTER, g);
198 
199   // Apply CEED operator
200   CeedOperatorApply(user->op_ifunction, user->q_ceed, user->g_ceed,
201                     CEED_REQUEST_IMMEDIATE);
202 
203   // Restore vectors
204   CeedVectorTakeArray(user->q_ceed, MemTypeP2C(q_mem_type), NULL);
205   CeedVectorTakeArray(user->q_dot_ceed, MemTypeP2C(q_dot_mem_type), NULL);
206   CeedVectorTakeArray(user->g_ceed, MemTypeP2C(g_mem_type), NULL);
207   ierr = VecRestoreArrayReadAndMemType(Q_loc, &q); CHKERRQ(ierr);
208   ierr = VecRestoreArrayReadAndMemType(Q_dot_loc, &q_dot); CHKERRQ(ierr);
209   ierr = VecRestoreArrayAndMemType(G_loc, &g); CHKERRQ(ierr);
210 
211   // Local-to-Global
212   ierr = VecZeroEntries(G); CHKERRQ(ierr);
213   ierr = DMLocalToGlobal(user->dm, G_loc, ADD_VALUES, G); CHKERRQ(ierr);
214 
215   // Restore vectors
216   ierr = DMRestoreLocalVector(user->dm, &G_loc); CHKERRQ(ierr);
217 
218   PetscFunctionReturn(0);
219 }
220 
221 static PetscErrorCode MatMult_NS_IJacobian(Mat J, Vec Q, Vec G) {
222   User user;
223   const PetscScalar *q;
224   PetscScalar       *g;
225   PetscMemType      q_mem_type, g_mem_type;
226   PetscErrorCode    ierr;
227   PetscFunctionBeginUser;
228   ierr = MatShellGetContext(J, &user); CHKERRQ(ierr);
229   Vec               Q_loc = user->Q_dot_loc, // Note - Q_dot_loc has zero BCs
230                     G_loc;
231 
232   // Get local vectors
233   ierr = DMGetLocalVector(user->dm, &G_loc); CHKERRQ(ierr);
234 
235   // Global-to-local
236   ierr = DMGlobalToLocal(user->dm, Q, INSERT_VALUES, Q_loc); CHKERRQ(ierr);
237 
238   // Place PETSc vectors in CEED vectors
239   ierr = VecGetArrayReadAndMemType(Q_loc, &q, &q_mem_type); CHKERRQ(ierr);
240   ierr = VecGetArrayAndMemType(G_loc, &g, &g_mem_type); CHKERRQ(ierr);
241   CeedVectorSetArray(user->q_ceed, MemTypeP2C(q_mem_type), CEED_USE_POINTER,
242                      (PetscScalar *)q);
243   CeedVectorSetArray(user->g_ceed, MemTypeP2C(g_mem_type), CEED_USE_POINTER, g);
244 
245   // Apply CEED operator
246   CeedOperatorApply(user->op_ijacobian, user->q_ceed, user->g_ceed,
247                     CEED_REQUEST_IMMEDIATE);
248 
249   // Restore vectors
250   CeedVectorTakeArray(user->q_ceed, MemTypeP2C(q_mem_type), NULL);
251   CeedVectorTakeArray(user->g_ceed, MemTypeP2C(g_mem_type), NULL);
252   ierr = VecRestoreArrayReadAndMemType(Q_loc, &q); CHKERRQ(ierr);
253   ierr = VecRestoreArrayAndMemType(G_loc, &g); CHKERRQ(ierr);
254 
255   // Local-to-Global
256   ierr = VecZeroEntries(G); CHKERRQ(ierr);
257   ierr = DMLocalToGlobal(user->dm, G_loc, ADD_VALUES, G); CHKERRQ(ierr);
258 
259   // Restore vectors
260   ierr = DMRestoreLocalVector(user->dm, &G_loc); CHKERRQ(ierr);
261   PetscFunctionReturn(0);
262 }
263 
264 PetscErrorCode MatGetDiagonal_NS_IJacobian(Mat A, Vec D) {
265   User user;
266   Vec D_loc;
267   PetscScalar *d;
268   PetscMemType mem_type;
269 
270   PetscFunctionBeginUser;
271   MatShellGetContext(A, &user);
272   PetscCall(DMGetLocalVector(user->dm, &D_loc));
273   PetscCall(VecGetArrayAndMemType(D_loc, &d, &mem_type));
274   CeedVectorSetArray(user->g_ceed, MemTypeP2C(mem_type), CEED_USE_POINTER, d);
275   CeedOperatorLinearAssembleDiagonal(user->op_ijacobian, user->g_ceed,
276                                      CEED_REQUEST_IMMEDIATE);
277   CeedVectorTakeArray(user->g_ceed, MemTypeP2C(mem_type), NULL);
278   PetscCall(VecRestoreArrayAndMemType(D_loc, &d));
279   PetscCall(VecZeroEntries(D));
280   PetscCall(DMLocalToGlobal(user->dm, D_loc, ADD_VALUES, D));
281   PetscCall(DMRestoreLocalVector(user->dm, &D_loc));
282   VecViewFromOptions(D, NULL, "-diag_vec_view");
283   PetscFunctionReturn(0);
284 }
285 
286 PetscErrorCode FormIJacobian_NS(TS ts, PetscReal t, Vec Q, Vec Q_dot,
287                                 PetscReal shift, Mat J, Mat J_pre,
288                                 void *user_data) {
289   User user = *(User *)user_data;
290   PetscBool J_is_shell, J_pre_is_shell;
291   PetscFunctionBeginUser;
292   if (user->phys->ijacobian_time_shift_label)
293     CeedOperatorContextSetDouble(user->op_ijacobian,
294                                  user->phys->ijacobian_time_shift_label, &shift);
295   PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY));
296   PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY));
297   Vec coo_vec = NULL;
298   PetscCall(PetscObjectTypeCompare((PetscObject)J, MATSHELL, &J_is_shell));
299   PetscCall(PetscObjectTypeCompare((PetscObject)J_pre, MATSHELL,
300                                    &J_pre_is_shell));
301   if (!user->matrices_set_up) {
302     if (J_is_shell) {
303       PetscCall(MatShellSetContext(J, user));
304       PetscCall(MatShellSetOperation(J, MATOP_MULT,
305                                      (void (*)(void))MatMult_NS_IJacobian));
306       PetscCall(MatShellSetOperation(J, MATOP_GET_DIAGONAL,
307                                      (void (*)(void))MatGetDiagonal_NS_IJacobian));
308       PetscCall(MatSetUp(J));
309     }
310     if (!J_pre_is_shell) {
311       PetscCount ncoo;
312       PetscInt *rows, *cols;
313       PetscCall(CeedOperatorLinearAssembleSymbolic(user->op_ijacobian, &ncoo, &rows,
314                 &cols));
315       PetscCall(MatSetPreallocationCOOLocal(J_pre, ncoo, rows, cols));
316       free(rows);
317       free(cols);
318       CeedVectorCreate(user->ceed, ncoo, &user->coo_values);
319       user->matrices_set_up = true;
320       VecCreateSeq(PETSC_COMM_WORLD, ncoo, &coo_vec);
321     }
322   }
323   if (!J_pre_is_shell) {
324     CeedMemType mem_type = CEED_MEM_HOST;
325     const PetscScalar *values;
326     MatType mat_type;
327     PetscCall(MatGetType(J_pre, &mat_type));
328     if (strstr(mat_type, "kokkos")
329         || strstr(mat_type, "cusparse")) mem_type = CEED_MEM_DEVICE;
330     CeedOperatorLinearAssemble(user->op_ijacobian, user->coo_values);
331     CeedVectorGetArrayRead(user->coo_values, mem_type, &values);
332     if (coo_vec) {
333       VecPlaceArray(coo_vec, values);
334       VecViewFromOptions(coo_vec, NULL, "-coo_vec_view");
335       VecDestroy(&coo_vec);
336     }
337     PetscCall(MatSetValuesCOO(J_pre, values, INSERT_VALUES));
338     CeedVectorRestoreArrayRead(user->coo_values, &values);
339   }
340   PetscFunctionReturn(0);
341 }
342 
343 // User provided TS Monitor
344 PetscErrorCode TSMonitor_NS(TS ts, PetscInt step_no, PetscReal time,
345                             Vec Q, void *ctx) {
346   User           user = ctx;
347   Vec            Q_loc;
348   char           file_path[PETSC_MAX_PATH_LEN];
349   PetscViewer    viewer;
350   PetscErrorCode ierr;
351   PetscFunctionBeginUser;
352 
353   // Print every 'output_freq' steps
354   if (step_no % user->app_ctx->output_freq != 0)
355     PetscFunctionReturn(0);
356 
357   // Set up output
358   ierr = DMGetLocalVector(user->dm, &Q_loc); CHKERRQ(ierr);
359   ierr = PetscObjectSetName((PetscObject)Q_loc, "StateVec"); CHKERRQ(ierr);
360   ierr = VecZeroEntries(Q_loc); CHKERRQ(ierr);
361   ierr = DMGlobalToLocal(user->dm, Q, INSERT_VALUES, Q_loc); CHKERRQ(ierr);
362 
363   // Output
364   ierr = PetscSNPrintf(file_path, sizeof file_path,
365                        "%s/ns-%03" PetscInt_FMT ".vtu",
366                        user->app_ctx->output_dir, step_no + user->app_ctx->cont_steps);
367   CHKERRQ(ierr);
368   ierr = PetscViewerVTKOpen(PetscObjectComm((PetscObject)Q), file_path,
369                             FILE_MODE_WRITE, &viewer); CHKERRQ(ierr);
370   ierr = VecView(Q_loc, viewer); CHKERRQ(ierr);
371   ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);
372   if (user->dm_viz) {
373     Vec         Q_refined, Q_refined_loc;
374     char        file_path_refined[PETSC_MAX_PATH_LEN];
375     PetscViewer viewer_refined;
376 
377     ierr = DMGetGlobalVector(user->dm_viz, &Q_refined); CHKERRQ(ierr);
378     ierr = DMGetLocalVector(user->dm_viz, &Q_refined_loc); CHKERRQ(ierr);
379     ierr = PetscObjectSetName((PetscObject)Q_refined_loc, "Refined");
380     CHKERRQ(ierr);
381     ierr = MatInterpolate(user->interp_viz, Q, Q_refined); CHKERRQ(ierr);
382     ierr = VecZeroEntries(Q_refined_loc); CHKERRQ(ierr);
383     ierr = DMGlobalToLocal(user->dm_viz, Q_refined, INSERT_VALUES, Q_refined_loc);
384     CHKERRQ(ierr);
385     ierr = PetscSNPrintf(file_path_refined, sizeof file_path_refined,
386                          "%s/nsrefined-%03" PetscInt_FMT ".vtu", user->app_ctx->output_dir,
387                          step_no + user->app_ctx->cont_steps);
388     CHKERRQ(ierr);
389     ierr = PetscViewerVTKOpen(PetscObjectComm((PetscObject)Q_refined),
390                               file_path_refined, FILE_MODE_WRITE, &viewer_refined); CHKERRQ(ierr);
391     ierr = VecView(Q_refined_loc, viewer_refined); CHKERRQ(ierr);
392     ierr = DMRestoreLocalVector(user->dm_viz, &Q_refined_loc); CHKERRQ(ierr);
393     ierr = DMRestoreGlobalVector(user->dm_viz, &Q_refined); CHKERRQ(ierr);
394     ierr = PetscViewerDestroy(&viewer_refined); CHKERRQ(ierr);
395   }
396   ierr = DMRestoreLocalVector(user->dm, &Q_loc); CHKERRQ(ierr);
397 
398   // Save data in a binary file for continuation of simulations
399   ierr = PetscSNPrintf(file_path, sizeof file_path, "%s/ns-solution.bin",
400                        user->app_ctx->output_dir); CHKERRQ(ierr);
401   ierr = PetscViewerBinaryOpen(user->comm, file_path, FILE_MODE_WRITE, &viewer);
402   CHKERRQ(ierr);
403   ierr = VecView(Q, viewer); CHKERRQ(ierr);
404   ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);
405 
406   // Save time stamp
407   // Dimensionalize time back
408   time /= user->units->second;
409   ierr = PetscSNPrintf(file_path, sizeof file_path, "%s/ns-time.bin",
410                        user->app_ctx->output_dir); CHKERRQ(ierr);
411   ierr = PetscViewerBinaryOpen(user->comm, file_path, FILE_MODE_WRITE, &viewer);
412   CHKERRQ(ierr);
413   #if PETSC_VERSION_GE(3,13,0)
414   ierr = PetscViewerBinaryWrite(viewer, &time, 1, PETSC_REAL);
415   #else
416   ierr = PetscViewerBinaryWrite(viewer, &time, 1, PETSC_REAL, true);
417   #endif
418   CHKERRQ(ierr);
419   ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);
420 
421   PetscFunctionReturn(0);
422 }
423 
424 // TS: Create, setup, and solve
425 PetscErrorCode TSSolve_NS(DM dm, User user, AppCtx app_ctx, Physics phys,
426                           Vec *Q, PetscScalar *f_time, TS *ts) {
427   MPI_Comm       comm = user->comm;
428   TSAdapt        adapt;
429   PetscScalar    final_time;
430   PetscErrorCode ierr;
431   PetscFunctionBeginUser;
432 
433   ierr = TSCreate(comm, ts); CHKERRQ(ierr);
434   ierr = TSSetDM(*ts, dm); CHKERRQ(ierr);
435   if (phys->implicit) {
436     ierr = TSSetType(*ts, TSBDF); CHKERRQ(ierr);
437     if (user->op_ifunction) {
438       ierr = TSSetIFunction(*ts, NULL, IFunction_NS, &user); CHKERRQ(ierr);
439     } else { // Implicit integrators can fall back to using an RHSFunction
440       ierr = TSSetRHSFunction(*ts, NULL, RHS_NS, &user); CHKERRQ(ierr);
441     }
442     if (user->op_ijacobian) {
443       ierr = DMTSSetIJacobian(dm, FormIJacobian_NS, &user); CHKERRQ(ierr);
444     }
445   } else {
446     if (!user->op_rhs) SETERRQ(comm, PETSC_ERR_ARG_NULL,
447                                  "Problem does not provide RHSFunction");
448     ierr = TSSetType(*ts, TSRK); CHKERRQ(ierr);
449     ierr = TSRKSetType(*ts, TSRK5F); CHKERRQ(ierr);
450     ierr = TSSetRHSFunction(*ts, NULL, RHS_NS, &user); CHKERRQ(ierr);
451   }
452   ierr = TSSetMaxTime(*ts, 500. * user->units->second); CHKERRQ(ierr);
453   ierr = TSSetExactFinalTime(*ts, TS_EXACTFINALTIME_STEPOVER); CHKERRQ(ierr);
454   ierr = TSSetTimeStep(*ts, 1.e-2 * user->units->second); CHKERRQ(ierr);
455   if (app_ctx->test_mode) {ierr = TSSetMaxSteps(*ts, 10); CHKERRQ(ierr);}
456   ierr = TSGetAdapt(*ts, &adapt); CHKERRQ(ierr);
457   ierr = TSAdaptSetStepLimits(adapt,
458                               1.e-12 * user->units->second,
459                               1.e2 * user->units->second); CHKERRQ(ierr);
460   ierr = TSSetFromOptions(*ts); CHKERRQ(ierr);
461   user->time = -1.0; // require all BCs and ctx to be updated
462   user->dt   = -1.0;
463   if (!app_ctx->cont_steps) { // print initial condition
464     if (!app_ctx->test_mode) {
465       ierr = TSMonitor_NS(*ts, 0, 0., *Q, user); CHKERRQ(ierr);
466     }
467   } else { // continue from time of last output
468     PetscReal   time;
469     PetscInt    count;
470     PetscViewer viewer;
471     char        file_path[PETSC_MAX_PATH_LEN];
472     ierr = PetscSNPrintf(file_path, sizeof file_path, "%s/ns-time.bin",
473                          app_ctx->output_dir); CHKERRQ(ierr);
474     ierr = PetscViewerBinaryOpen(comm, file_path, FILE_MODE_READ, &viewer);
475     CHKERRQ(ierr);
476     ierr = PetscViewerBinaryRead(viewer, &time, 1, &count, PETSC_REAL);
477     CHKERRQ(ierr);
478     ierr = PetscViewerDestroy(&viewer); CHKERRQ(ierr);
479     ierr = TSSetTime(*ts, time * user->units->second); CHKERRQ(ierr);
480   }
481   if (!app_ctx->test_mode) {
482     ierr = TSMonitorSet(*ts, TSMonitor_NS, user, NULL); CHKERRQ(ierr);
483   }
484 
485   // Solve
486   double start, cpu_time_used;
487   start = MPI_Wtime();
488   ierr = PetscBarrier((PetscObject) *ts); CHKERRQ(ierr);
489   ierr = TSSolve(*ts, *Q); CHKERRQ(ierr);
490   cpu_time_used = MPI_Wtime() - start;
491   ierr = TSGetSolveTime(*ts, &final_time); CHKERRQ(ierr);
492   *f_time = final_time;
493   ierr = MPI_Allreduce(MPI_IN_PLACE, &cpu_time_used, 1, MPI_DOUBLE, MPI_MIN,
494                        comm); CHKERRQ(ierr);
495   if (!app_ctx->test_mode) {
496     ierr = PetscPrintf(PETSC_COMM_WORLD,
497                        "Time taken for solution (sec): %g\n",
498                        (double)cpu_time_used); CHKERRQ(ierr);
499   }
500   PetscFunctionReturn(0);
501 }
502