xref: /libCEED/examples/petsc/multigrid.c (revision 3047f7896db8a74672e0eaf4fe2741a47841cabb)
1 // Copyright (c) 2017, Lawrence Livermore National Security, LLC. Produced at
2 // the Lawrence Livermore National Laboratory. LLNL-CODE-734707. All Rights
3 // reserved. See files LICENSE and NOTICE for details.
4 //
5 // This file is part of CEED, a collection of benchmarks, miniapps, software
6 // libraries and APIs for efficient high-order finite element and spectral
7 // element discretizations for exascale applications. For more information and
8 // source code availability see http://github.com/ceed.
9 //
10 // The CEED research is supported by the Exascale Computing Project 17-SC-20-SC,
11 // a collaborative effort of two U.S. Department of Energy organizations (Office
12 // of Science and the National Nuclear Security Administration) responsible for
13 // the planning and preparation of a capable exascale ecosystem, including
14 // software, applications, hardware, advanced system engineering and early
15 // testbed platforms, in support of the nation's exascale computing imperative.
16 
17 //                        libCEED + PETSc Example: CEED BPs 3-6 with Multigrid
18 //
19 // This example demonstrates a simple usage of libCEED with PETSc to solve the
20 // CEED BP benchmark problems, see http://ceed.exascaleproject.org/bps.
21 //
22 // The code uses higher level communication protocols in DMPlex.
23 //
24 // Build with:
25 //
26 //     make multigrid [PETSC_DIR=</path/to/petsc>] [CEED_DIR=</path/to/libceed>]
27 //
28 // Sample runs:
29 //
30 //     multigrid -problem bp3
31 //     multigrid -problem bp4
32 //     multigrid -problem bp5 -ceed /cpu/self
33 //     multigrid -problem bp6 -ceed /gpu/cuda
34 //
35 //TESTARGS -ceed {ceed_resource} -test -problem bp3 -degree 3
36 
37 /// @file
38 /// CEED BPs 1-6 multigrid example using PETSc
39 const char help[] = "Solve CEED BPs using p-multigrid with PETSc and DMPlex\n";
40 
41 #include <stdbool.h>
42 #include <string.h>
43 #include <ceed.h>
44 #include <petsc.h>
45 #include <petscdmplex.h>
46 #include <petscksp.h>
47 #include <petscsys.h>
48 
49 #include "bps.h"
50 #include "include/bpsproblemdata.h"
51 #include "include/petscutils.h"
52 #include "include/petscversion.h"
53 #include "include/matops.h"
54 #include "include/structs.h"
55 #include "include/libceedsetup.h"
56 
57 #if PETSC_VERSION_LT(3,12,0)
58 #ifdef PETSC_HAVE_CUDA
59 #include <petsccuda.h>
60 // Note: With PETSc prior to version 3.12.0, providing the source path to
61 //       include 'cublas_v2.h' will be needed to use 'petsccuda.h'.
62 #endif
63 #endif
64 
65 int main(int argc, char **argv) {
66   PetscInt ierr;
67   MPI_Comm comm;
68   char filename[PETSC_MAX_PATH_LEN],
69        ceed_resource[PETSC_MAX_PATH_LEN] = "/cpu/self";
70   double my_rt_start, my_rt, rt_min, rt_max;
71   PetscInt degree = 3, q_extra, *l_size, *xl_size, *g_size, dim = 3, fine_level,
72            mesh_elem[3] = {3, 3, 3}, num_comp_u = 1, num_levels = degree, *level_degrees;
73   PetscScalar *r;
74   PetscScalar eps = 1.0;
75   PetscBool test_mode, benchmark_mode, read_mesh, write_solution;
76   PetscLogStage solve_stage;
77   PetscLogEvent assemble_event;
78   DM  *dm, dm_orig;
79   KSP ksp;
80   PC pc;
81   Mat *mat_O, *mat_pr, mat_coarse;
82   Vec *X, *X_loc, *mult, rhs, rhs_loc;
83   PetscMemType mem_type;
84   UserO *user_O;
85   UserProlongRestr *user_pr;
86   Ceed ceed;
87   CeedData *ceed_data;
88   CeedVector rhs_ceed, target;
89   CeedQFunction qf_error, qf_restrict, qf_prolong;
90   CeedOperator op_error;
91   BPType bp_choice;
92   CoarsenType coarsen;
93 
94   ierr = PetscInitialize(&argc, &argv, NULL, help);
95   if (ierr) return ierr;
96   comm = PETSC_COMM_WORLD;
97 
98   // Parse command line options
99   ierr = PetscOptionsBegin(comm, NULL, "CEED BPs in PETSc", NULL); CHKERRQ(ierr);
100   bp_choice = CEED_BP3;
101   ierr = PetscOptionsEnum("-problem",
102                           "CEED benchmark problem to solve", NULL,
103                           bp_types, (PetscEnum)bp_choice, (PetscEnum *)&bp_choice,
104                           NULL); CHKERRQ(ierr);
105   num_comp_u = bp_options[bp_choice].num_comp_u;
106   test_mode = PETSC_FALSE;
107   ierr = PetscOptionsBool("-test",
108                           "Testing mode (do not print unless error is large)",
109                           NULL, test_mode, &test_mode, NULL); CHKERRQ(ierr);
110   benchmark_mode = PETSC_FALSE;
111   ierr = PetscOptionsBool("-benchmark",
112                           "Benchmarking mode (prints benchmark statistics)",
113                           NULL, benchmark_mode, &benchmark_mode, NULL);
114   CHKERRQ(ierr);
115   write_solution = PETSC_FALSE;
116   ierr = PetscOptionsBool("-write_solution",
117                           "Write solution for visualization",
118                           NULL, write_solution, &write_solution, NULL);
119   CHKERRQ(ierr);
120   ierr = PetscOptionsScalar("-eps",
121                             "Epsilon parameter for Kershaw mesh transformation",
122                             NULL, eps, &eps, NULL);
123   if (eps > 1 || eps <= 0) SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_ARG_OUTOFRANGE,
124                                      "-eps %D must be (0,1]", eps);
125   degree = test_mode ? 3 : 2;
126   ierr = PetscOptionsInt("-degree", "Polynomial degree of tensor product basis",
127                          NULL, degree, &degree, NULL); CHKERRQ(ierr);
128   if (degree < 1) SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_ARG_OUTOFRANGE,
129                             "-degree %D must be at least 1", degree);
130   q_extra = bp_options[bp_choice].q_extra;
131   ierr = PetscOptionsInt("-q_extra", "Number of extra quadrature points",
132                          NULL, q_extra, &q_extra, NULL); CHKERRQ(ierr);
133   ierr = PetscOptionsString("-ceed", "CEED resource specifier",
134                             NULL, ceed_resource, ceed_resource,
135                             sizeof(ceed_resource), NULL); CHKERRQ(ierr);
136   coarsen = COARSEN_UNIFORM;
137   ierr = PetscOptionsEnum("-coarsen",
138                           "Coarsening strategy to use", NULL,
139                           coarsen_types, (PetscEnum)coarsen,
140                           (PetscEnum *)&coarsen, NULL); CHKERRQ(ierr);
141   read_mesh = PETSC_FALSE;
142   ierr = PetscOptionsString("-mesh", "Read mesh from file", NULL,
143                             filename, filename, sizeof(filename), &read_mesh);
144   CHKERRQ(ierr);
145   if (!read_mesh) {
146     PetscInt tmp = dim;
147     ierr = PetscOptionsIntArray("-cells","Number of cells per dimension", NULL,
148                                 mesh_elem, &tmp, NULL); CHKERRQ(ierr);
149   }
150   ierr = PetscOptionsEnd(); CHKERRQ(ierr);
151 
152   // Set up libCEED
153   CeedInit(ceed_resource, &ceed);
154   CeedMemType mem_type_backend;
155   CeedGetPreferredMemType(ceed, &mem_type_backend);
156 
157   // Setup DM
158   if (read_mesh) {
159     ierr = DMPlexCreateFromFile(PETSC_COMM_WORLD, filename, NULL, PETSC_TRUE,
160                                 &dm_orig);
161     CHKERRQ(ierr);
162   } else {
163     ierr = DMPlexCreateBoxMesh(PETSC_COMM_WORLD, dim, PETSC_FALSE, mesh_elem, NULL,
164                                NULL, NULL, PETSC_TRUE, &dm_orig); CHKERRQ(ierr);
165   }
166 
167   VecType vec_type;
168   switch (mem_type_backend) {
169   case CEED_MEM_HOST: vec_type = VECSTANDARD; break;
170   case CEED_MEM_DEVICE: {
171     const char *resolved;
172     CeedGetResource(ceed, &resolved);
173     if (strstr(resolved, "/gpu/cuda")) vec_type = VECCUDA;
174     else if (strstr(resolved, "/gpu/hip/occa"))
175       vec_type = VECSTANDARD; // https://github.com/CEED/libCEED/issues/678
176     else if (strstr(resolved, "/gpu/hip")) vec_type = VECHIP;
177     else vec_type = VECSTANDARD;
178   }
179   }
180   ierr = DMSetVecType(dm_orig, vec_type); CHKERRQ(ierr);
181   ierr = DMSetFromOptions(dm_orig); CHKERRQ(ierr);
182   ierr = DMViewFromOptions(dm_orig, NULL, "-dm_view"); CHKERRQ(ierr);
183 
184   // Apply Kershaw mesh transformation
185   ierr = Kershaw(dm_orig, eps); CHKERRQ(ierr);
186 
187   // Allocate arrays for PETSc objects for each level
188   switch (coarsen) {
189   case COARSEN_UNIFORM:
190     num_levels = degree;
191     break;
192   case COARSEN_LOGARITHMIC:
193     num_levels = ceil(log(degree)/log(2)) + 1;
194     break;
195   }
196   ierr = PetscMalloc1(num_levels, &level_degrees); CHKERRQ(ierr);
197   fine_level = num_levels - 1;
198 
199   switch (coarsen) {
200   case COARSEN_UNIFORM:
201     for (int i=0; i<num_levels; i++) level_degrees[i] = i + 1;
202     break;
203   case COARSEN_LOGARITHMIC:
204     for (int i=0; i<num_levels - 1; i++) level_degrees[i] = pow(2,i);
205     level_degrees[fine_level] = degree;
206     break;
207   }
208   ierr = PetscMalloc1(num_levels, &dm); CHKERRQ(ierr);
209   ierr = PetscMalloc1(num_levels, &X); CHKERRQ(ierr);
210   ierr = PetscMalloc1(num_levels, &X_loc); CHKERRQ(ierr);
211   ierr = PetscMalloc1(num_levels, &mult); CHKERRQ(ierr);
212   ierr = PetscMalloc1(num_levels, &user_O); CHKERRQ(ierr);
213   ierr = PetscMalloc1(num_levels, &user_pr); CHKERRQ(ierr);
214   ierr = PetscMalloc1(num_levels, &mat_O); CHKERRQ(ierr);
215   ierr = PetscMalloc1(num_levels, &mat_pr); CHKERRQ(ierr);
216   ierr = PetscMalloc1(num_levels, &l_size); CHKERRQ(ierr);
217   ierr = PetscMalloc1(num_levels, &xl_size); CHKERRQ(ierr);
218   ierr = PetscMalloc1(num_levels, &g_size); CHKERRQ(ierr);
219 
220   // Setup DM and Operator Mat Shells for each level
221   for (CeedInt i=0; i<num_levels; i++) {
222     // Create DM
223     ierr = DMClone(dm_orig, &dm[i]); CHKERRQ(ierr);
224     ierr = DMGetVecType(dm_orig, &vec_type); CHKERRQ(ierr);
225     ierr = DMSetVecType(dm[i], vec_type); CHKERRQ(ierr);
226     PetscInt dim;
227     ierr = DMGetDimension(dm[i], &dim); CHKERRQ(ierr);
228     ierr = SetupDMByDegree(dm[i], level_degrees[i], num_comp_u, dim,
229                            bp_options[bp_choice].enforce_bc, bp_options[bp_choice].bc_func);
230     CHKERRQ(ierr);
231 
232     // Create vectors
233     ierr = DMCreateGlobalVector(dm[i], &X[i]); CHKERRQ(ierr);
234     ierr = VecGetLocalSize(X[i], &l_size[i]); CHKERRQ(ierr);
235     ierr = VecGetSize(X[i], &g_size[i]); CHKERRQ(ierr);
236     ierr = DMCreateLocalVector(dm[i], &X_loc[i]); CHKERRQ(ierr);
237     ierr = VecGetSize(X_loc[i], &xl_size[i]); CHKERRQ(ierr);
238 
239     // Operator
240     ierr = PetscMalloc1(1, &user_O[i]); CHKERRQ(ierr);
241     ierr = MatCreateShell(comm, l_size[i], l_size[i], g_size[i], g_size[i],
242                           user_O[i], &mat_O[i]); CHKERRQ(ierr);
243     ierr = MatShellSetOperation(mat_O[i], MATOP_MULT,
244                                 (void(*)(void))MatMult_Ceed); CHKERRQ(ierr);
245     ierr = MatShellSetOperation(mat_O[i], MATOP_GET_DIAGONAL,
246                                 (void(*)(void))MatGetDiag); CHKERRQ(ierr);
247     ierr = MatShellSetVecType(mat_O[i], vec_type); CHKERRQ(ierr);
248 
249     // Level transfers
250     if (i > 0) {
251       // Interp
252       ierr = PetscMalloc1(1, &user_pr[i]); CHKERRQ(ierr);
253       ierr = MatCreateShell(comm, l_size[i], l_size[i-1], g_size[i], g_size[i-1],
254                             user_pr[i], &mat_pr[i]); CHKERRQ(ierr);
255       ierr = MatShellSetOperation(mat_pr[i], MATOP_MULT,
256                                   (void(*)(void))MatMult_Prolong);
257       CHKERRQ(ierr);
258       ierr = MatShellSetOperation(mat_pr[i], MATOP_MULT_TRANSPOSE,
259                                   (void(*)(void))MatMult_Restrict);
260       CHKERRQ(ierr);
261       ierr = MatShellSetVecType(mat_pr[i], vec_type); CHKERRQ(ierr);
262     }
263   }
264   ierr = VecDuplicate(X[fine_level], &rhs); CHKERRQ(ierr);
265 
266   // Print global grid information
267   if (!test_mode) {
268     PetscInt P = degree + 1, Q = P + q_extra;
269 
270     const char *used_resource;
271     CeedGetResource(ceed, &used_resource);
272 
273     ierr = VecGetType(X[0], &vec_type); CHKERRQ(ierr);
274 
275     ierr = PetscPrintf(comm,
276                        "\n-- CEED Benchmark Problem %d -- libCEED + PETSc + PCMG --\n"
277                        "  PETSc:\n"
278                        "    PETSc Vec Type                     : %s\n"
279                        "  libCEED:\n"
280                        "    libCEED Backend                    : %s\n"
281                        "    libCEED Backend MemType            : %s\n"
282                        "  Mesh:\n"
283                        "    Number of 1D Basis Nodes (p)       : %d\n"
284                        "    Number of 1D Quadrature Points (q) : %d\n"
285                        "    Global Nodes                       : %D\n"
286                        "    Owned Nodes                        : %D\n"
287                        "    DoF per node                       : %D\n"
288                        "  Multigrid:\n"
289                        "    Number of Levels                   : %d\n",
290                        bp_choice+1, vec_type, used_resource,
291                        CeedMemTypes[mem_type_backend],
292                        P, Q, g_size[fine_level]/num_comp_u, l_size[fine_level]/num_comp_u,
293                        num_comp_u, num_levels); CHKERRQ(ierr);
294   }
295 
296   // Create RHS vector
297   ierr = VecDuplicate(X_loc[fine_level], &rhs_loc); CHKERRQ(ierr);
298   ierr = VecZeroEntries(rhs_loc); CHKERRQ(ierr);
299   ierr = VecGetArrayAndMemType(rhs_loc, &r, &mem_type); CHKERRQ(ierr);
300   CeedVectorCreate(ceed, xl_size[fine_level], &rhs_ceed);
301   CeedVectorSetArray(rhs_ceed, MemTypeP2C(mem_type), CEED_USE_POINTER, r);
302 
303   // Set up libCEED operators on each level
304   ierr = PetscMalloc1(num_levels, &ceed_data); CHKERRQ(ierr);
305   for (int i=0; i<num_levels; i++) {
306     // Print level information
307     if (!test_mode && (i == 0 || i == fine_level)) {
308       ierr = PetscPrintf(comm,"    Level %D (%s):\n"
309                          "      Number of 1D Basis Nodes (p)     : %d\n"
310                          "      Global Nodes                     : %D\n"
311                          "      Owned Nodes                      : %D\n",
312                          i, (i? "fine" : "coarse"), level_degrees[i] + 1,
313                          g_size[i]/num_comp_u, l_size[i]/num_comp_u); CHKERRQ(ierr);
314     }
315     ierr = PetscMalloc1(1, &ceed_data[i]); CHKERRQ(ierr);
316     ierr = SetupLibceedByDegree(dm[i], ceed, level_degrees[i], dim, q_extra,
317                                 dim, num_comp_u, g_size[i], xl_size[i], bp_options[bp_choice],
318                                 ceed_data[i], i==(fine_level), rhs_ceed, &target);
319     CHKERRQ(ierr);
320   }
321 
322   // Gather RHS
323   CeedVectorTakeArray(rhs_ceed, MemTypeP2C(mem_type), NULL);
324   ierr = VecRestoreArrayAndMemType(rhs_loc, &r); CHKERRQ(ierr);
325   ierr = VecZeroEntries(rhs); CHKERRQ(ierr);
326   ierr = DMLocalToGlobal(dm[fine_level], rhs_loc, ADD_VALUES, rhs); CHKERRQ(ierr);
327   CeedVectorDestroy(&rhs_ceed);
328 
329   // Create the restriction/interpolation QFunction
330   CeedQFunctionCreateIdentity(ceed, num_comp_u, CEED_EVAL_NONE, CEED_EVAL_INTERP,
331                               &qf_restrict);
332   CeedQFunctionCreateIdentity(ceed, num_comp_u, CEED_EVAL_INTERP, CEED_EVAL_NONE,
333                               &qf_prolong);
334 
335   // Set up libCEED level transfer operators
336   ierr = CeedLevelTransferSetup(ceed, num_levels, num_comp_u, ceed_data,
337                                 level_degrees,
338                                 qf_restrict, qf_prolong); CHKERRQ(ierr);
339 
340   // Create the error QFunction
341   CeedQFunctionCreateInterior(ceed, 1, bp_options[bp_choice].error,
342                               bp_options[bp_choice].error_loc, &qf_error);
343   CeedQFunctionAddInput(qf_error, "u", num_comp_u, CEED_EVAL_INTERP);
344   CeedQFunctionAddInput(qf_error, "true_soln", num_comp_u, CEED_EVAL_NONE);
345   CeedQFunctionAddOutput(qf_error, "error", num_comp_u, CEED_EVAL_NONE);
346 
347   // Create the error operator
348   CeedOperatorCreate(ceed, qf_error, CEED_QFUNCTION_NONE, CEED_QFUNCTION_NONE,
349                      &op_error);
350   CeedOperatorSetField(op_error, "u", ceed_data[fine_level]->elem_restr_u,
351                        ceed_data[fine_level]->basis_u, CEED_VECTOR_ACTIVE);
352   CeedOperatorSetField(op_error, "true_soln",
353                        ceed_data[fine_level]->elem_restr_u_i,
354                        CEED_BASIS_COLLOCATED, target);
355   CeedOperatorSetField(op_error, "error", ceed_data[fine_level]->elem_restr_u_i,
356                        CEED_BASIS_COLLOCATED, CEED_VECTOR_ACTIVE);
357 
358   // Calculate multiplicity
359   for (int i=0; i<num_levels; i++) {
360     PetscScalar *x;
361 
362     // CEED vector
363     ierr = VecZeroEntries(X_loc[i]); CHKERRQ(ierr);
364     ierr = VecGetArray(X_loc[i], &x); CHKERRQ(ierr);
365     CeedVectorSetArray(ceed_data[i]->x_ceed, CEED_MEM_HOST, CEED_USE_POINTER, x);
366 
367     // Multiplicity
368     CeedElemRestrictionGetMultiplicity(ceed_data[i]->elem_restr_u,
369                                        ceed_data[i]->x_ceed);
370     CeedVectorSyncArray(ceed_data[i]->x_ceed, CEED_MEM_HOST);
371 
372     // Restore vector
373     ierr = VecRestoreArray(X_loc[i], &x); CHKERRQ(ierr);
374 
375     // Creat mult vector
376     ierr = VecDuplicate(X_loc[i], &mult[i]); CHKERRQ(ierr);
377 
378     // Local-to-global
379     ierr = VecZeroEntries(X[i]); CHKERRQ(ierr);
380     ierr = DMLocalToGlobal(dm[i], X_loc[i], ADD_VALUES, X[i]);
381     CHKERRQ(ierr);
382     ierr = VecZeroEntries(X_loc[i]); CHKERRQ(ierr);
383 
384     // Global-to-local
385     ierr = DMGlobalToLocal(dm[i], X[i], INSERT_VALUES, mult[i]);
386     CHKERRQ(ierr);
387     ierr = VecZeroEntries(X[i]); CHKERRQ(ierr);
388 
389     // Multiplicity scaling
390     ierr = VecReciprocal(mult[i]);
391   }
392 
393   // Set up Mat
394   for (int i=0; i<num_levels; i++) {
395     // User Operator
396     user_O[i]->comm = comm;
397     user_O[i]->dm = dm[i];
398     user_O[i]->X_loc = X_loc[i];
399     ierr = VecDuplicate(X_loc[i], &user_O[i]->Y_loc); CHKERRQ(ierr);
400     user_O[i]->x_ceed = ceed_data[i]->x_ceed;
401     user_O[i]->y_ceed = ceed_data[i]->y_ceed;
402     user_O[i]->op = ceed_data[i]->op_apply;
403     user_O[i]->ceed = ceed;
404 
405     if (i > 0) {
406       // Prolongation/Restriction Operator
407       user_pr[i]->comm = comm;
408       user_pr[i]->dmf = dm[i];
409       user_pr[i]->dmc = dm[i-1];
410       user_pr[i]->loc_vec_c = X_loc[i-1];
411       user_pr[i]->loc_vec_f = user_O[i]->Y_loc;
412       user_pr[i]->mult_vec = mult[i];
413       user_pr[i]->ceed_vec_c = user_O[i-1]->x_ceed;
414       user_pr[i]->ceed_vec_f = user_O[i]->y_ceed;
415       user_pr[i]->op_prolong = ceed_data[i]->op_prolong;
416       user_pr[i]->op_restrict = ceed_data[i]->op_restrict;
417       user_pr[i]->ceed = ceed;
418     }
419   }
420 
421   // Assemble coarse grid Jacobian for AMG (or other sparse matrix) solve
422   ierr = DMCreateMatrix(dm[0], &mat_coarse); CHKERRQ(ierr);
423 
424   ierr = PetscLogEventRegister("AssembleMatrix", MAT_CLASSID, &assemble_event);
425   CHKERRQ(ierr);
426   {
427     // Assemble matrix analytically
428     PetscCount num_entries;
429     CeedInt *rows, *cols;
430     CeedVector coo_values;
431     CeedOperatorLinearAssembleSymbolic(user_O[0]->op, &num_entries, &rows, &cols);
432     ISLocalToGlobalMapping ltog_row, ltog_col;
433     ierr = MatGetLocalToGlobalMapping(mat_coarse, &ltog_row, &ltog_col);
434     CHKERRQ(ierr);
435     ierr = ISLocalToGlobalMappingApply(ltog_row, num_entries, rows, rows);
436     CHKERRQ(ierr);
437     ierr = ISLocalToGlobalMappingApply(ltog_col, num_entries, cols, cols);
438     CHKERRQ(ierr);
439     ierr = MatSetPreallocationCOO(mat_coarse, num_entries, rows, cols);
440     CHKERRQ(ierr);
441     free(rows);
442     free(cols);
443     CeedVectorCreate(ceed, num_entries, &coo_values);
444     ierr = PetscLogEventBegin(assemble_event, mat_coarse, 0, 0, 0); CHKERRQ(ierr);
445     CeedOperatorLinearAssemble(user_O[0]->op, coo_values);
446     const CeedScalar *values;
447     CeedVectorGetArrayRead(coo_values, CEED_MEM_HOST, &values);
448     ierr = MatSetValuesCOO(mat_coarse, values, ADD_VALUES); CHKERRQ(ierr);
449     CeedVectorRestoreArrayRead(coo_values, &values);
450     ierr = PetscLogEventEnd(assemble_event, mat_coarse, 0, 0, 0); CHKERRQ(ierr);
451     CeedVectorDestroy(&coo_values);
452   }
453 
454   // Set up KSP
455   ierr = KSPCreate(comm, &ksp); CHKERRQ(ierr);
456   {
457     ierr = KSPSetType(ksp, KSPCG); CHKERRQ(ierr);
458     ierr = KSPSetNormType(ksp, KSP_NORM_NATURAL); CHKERRQ(ierr);
459     ierr = KSPSetTolerances(ksp, 1e-10, PETSC_DEFAULT, PETSC_DEFAULT,
460                             PETSC_DEFAULT); CHKERRQ(ierr);
461   }
462   ierr = KSPSetFromOptions(ksp); CHKERRQ(ierr);
463   ierr = KSPSetOperators(ksp, mat_O[fine_level], mat_O[fine_level]);
464   CHKERRQ(ierr);
465 
466   // Set up PCMG
467   ierr = KSPGetPC(ksp, &pc); CHKERRQ(ierr);
468   PCMGCycleType pcmg_cycle_type = PC_MG_CYCLE_V;
469   {
470     ierr = PCSetType(pc, PCMG); CHKERRQ(ierr);
471 
472     // PCMG levels
473     ierr = PCMGSetLevels(pc, num_levels, NULL); CHKERRQ(ierr);
474     for (int i=0; i<num_levels; i++) {
475       // Smoother
476       KSP smoother;
477       PC smoother_pc;
478       ierr = PCMGGetSmoother(pc, i, &smoother); CHKERRQ(ierr);
479       ierr = KSPSetType(smoother, KSPCHEBYSHEV); CHKERRQ(ierr);
480       ierr = KSPChebyshevEstEigSet(smoother, 0, 0.1, 0, 1.1); CHKERRQ(ierr);
481       ierr = KSPChebyshevEstEigSetUseNoisy(smoother, PETSC_TRUE); CHKERRQ(ierr);
482       ierr = KSPSetOperators(smoother, mat_O[i], mat_O[i]); CHKERRQ(ierr);
483       ierr = KSPGetPC(smoother, &smoother_pc); CHKERRQ(ierr);
484       ierr = PCSetType(smoother_pc, PCJACOBI); CHKERRQ(ierr);
485       ierr = PCJacobiSetType(smoother_pc, PC_JACOBI_DIAGONAL); CHKERRQ(ierr);
486 
487       // Work vector
488       if (i < num_levels - 1) {
489         ierr = PCMGSetX(pc, i, X[i]); CHKERRQ(ierr);
490       }
491 
492       // Level transfers
493       if (i > 0) {
494         // Interpolation
495         ierr = PCMGSetInterpolation(pc, i, mat_pr[i]); CHKERRQ(ierr);
496       }
497 
498       // Coarse solve
499       KSP coarse;
500       PC coarse_pc;
501       ierr = PCMGGetCoarseSolve(pc, &coarse); CHKERRQ(ierr);
502       ierr = KSPSetType(coarse, KSPPREONLY); CHKERRQ(ierr);
503       ierr = KSPSetOperators(coarse, mat_coarse, mat_coarse); CHKERRQ(ierr);
504 
505       ierr = KSPGetPC(coarse, &coarse_pc); CHKERRQ(ierr);
506       ierr = PCSetType(coarse_pc, PCGAMG); CHKERRQ(ierr);
507 
508       ierr = KSPSetOptionsPrefix(coarse, "coarse_"); CHKERRQ(ierr);
509       ierr = PCSetOptionsPrefix(coarse_pc, "coarse_"); CHKERRQ(ierr);
510       ierr = KSPSetFromOptions(coarse); CHKERRQ(ierr);
511       ierr = PCSetFromOptions(coarse_pc); CHKERRQ(ierr);
512     }
513 
514     // PCMG options
515     ierr = PCMGSetType(pc, PC_MG_MULTIPLICATIVE); CHKERRQ(ierr);
516     ierr = PCMGSetNumberSmooth(pc, 3); CHKERRQ(ierr);
517     ierr = PCMGSetCycleType(pc, pcmg_cycle_type); CHKERRQ(ierr);
518   }
519 
520   // First run, if benchmarking
521   if (benchmark_mode) {
522     ierr = KSPSetTolerances(ksp, 1e-10, PETSC_DEFAULT, PETSC_DEFAULT, 1);
523     CHKERRQ(ierr);
524     ierr = VecZeroEntries(X[fine_level]); CHKERRQ(ierr);
525     my_rt_start = MPI_Wtime();
526     ierr = KSPSolve(ksp, rhs, X[fine_level]); CHKERRQ(ierr);
527     my_rt = MPI_Wtime() - my_rt_start;
528     ierr = MPI_Allreduce(MPI_IN_PLACE, &my_rt, 1, MPI_DOUBLE, MPI_MIN, comm);
529     CHKERRQ(ierr);
530     // Set maxits based on first iteration timing
531     if (my_rt > 0.02) {
532       ierr = KSPSetTolerances(ksp, 1e-10, PETSC_DEFAULT, PETSC_DEFAULT, 5);
533       CHKERRQ(ierr);
534     } else {
535       ierr = KSPSetTolerances(ksp, 1e-10, PETSC_DEFAULT, PETSC_DEFAULT, 20);
536       CHKERRQ(ierr);
537     }
538   }
539 
540   // Timed solve
541   ierr = VecZeroEntries(X[fine_level]); CHKERRQ(ierr);
542   ierr = PetscBarrier((PetscObject)ksp); CHKERRQ(ierr);
543 
544   // -- Performance logging
545   ierr = PetscLogStageRegister("Solve Stage", &solve_stage); CHKERRQ(ierr);
546   ierr = PetscLogStagePush(solve_stage); CHKERRQ(ierr);
547 
548   // -- Solve
549   my_rt_start = MPI_Wtime();
550   ierr = KSPSolve(ksp, rhs, X[fine_level]); CHKERRQ(ierr);
551   my_rt = MPI_Wtime() - my_rt_start;
552 
553 
554   // -- Performance logging
555   ierr = PetscLogStagePop();
556 
557   // Output results
558   {
559     KSPType ksp_type;
560     PCMGType pcmg_type;
561     KSPConvergedReason reason;
562     PetscReal rnorm;
563     PetscInt its;
564     ierr = KSPGetType(ksp, &ksp_type); CHKERRQ(ierr);
565     ierr = KSPGetConvergedReason(ksp, &reason); CHKERRQ(ierr);
566     ierr = KSPGetIterationNumber(ksp, &its); CHKERRQ(ierr);
567     ierr = KSPGetResidualNorm(ksp, &rnorm); CHKERRQ(ierr);
568     ierr = PCMGGetType(pc, &pcmg_type); CHKERRQ(ierr);
569     if (!test_mode || reason < 0 || rnorm > 1e-8) {
570       ierr = PetscPrintf(comm,
571                          "  KSP:\n"
572                          "    KSP Type                           : %s\n"
573                          "    KSP Convergence                    : %s\n"
574                          "    Total KSP Iterations               : %D\n"
575                          "    Final rnorm                        : %e\n",
576                          ksp_type, KSPConvergedReasons[reason], its,
577                          (double)rnorm); CHKERRQ(ierr);
578       ierr = PetscPrintf(comm,
579                          "  PCMG:\n"
580                          "    PCMG Type                          : %s\n"
581                          "    PCMG Cycle Type                    : %s\n",
582                          PCMGTypes[pcmg_type],
583                          PCMGCycleTypes[pcmg_cycle_type]); CHKERRQ(ierr);
584     }
585     if (!test_mode) {
586       ierr = PetscPrintf(comm,"  Performance:\n"); CHKERRQ(ierr);
587     }
588     {
589       PetscReal max_error;
590       ierr = ComputeErrorMax(user_O[fine_level], op_error, X[fine_level], target,
591                              &max_error); CHKERRQ(ierr);
592       PetscReal tol = 5e-2;
593       if (!test_mode || max_error > tol) {
594         ierr = MPI_Allreduce(&my_rt, &rt_min, 1, MPI_DOUBLE, MPI_MIN, comm);
595         CHKERRQ(ierr);
596         ierr = MPI_Allreduce(&my_rt, &rt_max, 1, MPI_DOUBLE, MPI_MAX, comm);
597         CHKERRQ(ierr);
598         ierr = PetscPrintf(comm,
599                            "    Pointwise Error (max)              : %e\n"
600                            "    CG Solve Time                      : %g (%g) sec\n",
601                            (double)max_error, rt_max, rt_min); CHKERRQ(ierr);
602       }
603     }
604     if (benchmark_mode && (!test_mode)) {
605       ierr = PetscPrintf(comm,
606                          "    DoFs/Sec in CG                     : %g (%g) million\n",
607                          1e-6*g_size[fine_level]*its/rt_max,
608                          1e-6*g_size[fine_level]*its/rt_min);
609       CHKERRQ(ierr);
610     }
611   }
612 
613   if (write_solution) {
614     PetscViewer vtk_viewer_soln;
615 
616     ierr = PetscViewerCreate(comm, &vtk_viewer_soln); CHKERRQ(ierr);
617     ierr = PetscViewerSetType(vtk_viewer_soln, PETSCVIEWERVTK); CHKERRQ(ierr);
618     ierr = PetscViewerFileSetName(vtk_viewer_soln, "solution.vtu"); CHKERRQ(ierr);
619     ierr = VecView(X[fine_level], vtk_viewer_soln); CHKERRQ(ierr);
620     ierr = PetscViewerDestroy(&vtk_viewer_soln); CHKERRQ(ierr);
621   }
622 
623   // Cleanup
624   for (int i=0; i<num_levels; i++) {
625     ierr = VecDestroy(&X[i]); CHKERRQ(ierr);
626     ierr = VecDestroy(&X_loc[i]); CHKERRQ(ierr);
627     ierr = VecDestroy(&mult[i]); CHKERRQ(ierr);
628     ierr = VecDestroy(&user_O[i]->Y_loc); CHKERRQ(ierr);
629     ierr = MatDestroy(&mat_O[i]); CHKERRQ(ierr);
630     ierr = PetscFree(user_O[i]); CHKERRQ(ierr);
631     if (i > 0) {
632       ierr = MatDestroy(&mat_pr[i]); CHKERRQ(ierr);
633       ierr = PetscFree(user_pr[i]); CHKERRQ(ierr);
634     }
635     ierr = CeedDataDestroy(i, ceed_data[i]); CHKERRQ(ierr);
636     ierr = DMDestroy(&dm[i]); CHKERRQ(ierr);
637   }
638   ierr = PetscFree(level_degrees); CHKERRQ(ierr);
639   ierr = PetscFree(dm); CHKERRQ(ierr);
640   ierr = PetscFree(X); CHKERRQ(ierr);
641   ierr = PetscFree(X_loc); CHKERRQ(ierr);
642   ierr = PetscFree(mult); CHKERRQ(ierr);
643   ierr = PetscFree(mat_O); CHKERRQ(ierr);
644   ierr = PetscFree(mat_pr); CHKERRQ(ierr);
645   ierr = PetscFree(ceed_data); CHKERRQ(ierr);
646   ierr = PetscFree(user_O); CHKERRQ(ierr);
647   ierr = PetscFree(user_pr); CHKERRQ(ierr);
648   ierr = PetscFree(l_size); CHKERRQ(ierr);
649   ierr = PetscFree(xl_size); CHKERRQ(ierr);
650   ierr = PetscFree(g_size); CHKERRQ(ierr);
651   ierr = VecDestroy(&rhs); CHKERRQ(ierr);
652   ierr = VecDestroy(&rhs_loc); CHKERRQ(ierr);
653   ierr = MatDestroy(&mat_coarse); CHKERRQ(ierr);
654   ierr = KSPDestroy(&ksp); CHKERRQ(ierr);
655   ierr = DMDestroy(&dm_orig); CHKERRQ(ierr);
656   CeedVectorDestroy(&target);
657   CeedQFunctionDestroy(&qf_error);
658   CeedQFunctionDestroy(&qf_restrict);
659   CeedQFunctionDestroy(&qf_prolong);
660   CeedOperatorDestroy(&op_error);
661   CeedDestroy(&ceed);
662   return PetscFinalize();
663 }
664