Date: 2022-03-31T04:48:19+00:00

Actual source code: ex4.c

      2: static char help[] = "Solves a linear system in parallel with KSP and HMG.\n\
      3: Input parameters include:\n\
      4:   -view_exact_sol    : write exact solution vector to stdout\n\
      5:   -m  <mesh_x>       : number of mesh points in x-direction\n\
      6:   -n  <mesh_y>       : number of mesh points in y-direction\n\
      7:   -bs                : number of variables on each mesh vertex \n\n";

      9: /*
     10:   Simple example is used to test PCHMG
     11: */
     12: #include <petscksp.h>

     14: int main(int argc,char **args)
     15: {
     16:   Vec            x,b,u;    /* approx solution, RHS, exact solution */
     17:   Mat            A;        /* linear system matrix */
     18:   KSP            ksp;      /* linear solver context */
     19:   PetscReal      norm;     /* norm of solution error */
     20:   PetscInt       i,j,Ii,J,Istart,Iend,m = 8,n = 7,its,bs=1,II,JJ,jj;
     21:   PetscBool      flg,test=PETSC_FALSE,reuse=PETSC_FALSE,viewexpl=PETSC_FALSE;
     22:   PetscScalar    v;
     23:   PC             pc;

     25:   PetscInitialize(&argc,&args,(char*)0,help);
     26:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
     27:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     28:   PetscOptionsGetInt(NULL,NULL,"-bs",&bs,NULL);
     29:   PetscOptionsGetBool(NULL,NULL,"-test_hmg_interface",&test,NULL);
     30:   PetscOptionsGetBool(NULL,NULL,"-test_reuse_interpolation",&reuse,NULL);
     31:   PetscOptionsGetBool(NULL,NULL,"-view_explicit_mat",&viewexpl,NULL);

     33:   MatCreate(PETSC_COMM_WORLD,&A);
     34:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,m*n*bs,m*n*bs);
     35:   MatSetBlockSize(A,bs);
     36:   MatSetFromOptions(A);
     37:   MatMPIAIJSetPreallocation(A,5,NULL,5,NULL);
     38:   MatSeqAIJSetPreallocation(A,5,NULL);
     39: #if defined(PETSC_HAVE_HYPRE)
     40:   MatHYPRESetPreallocation(A,5,NULL,5,NULL);
     41: #endif

     43:   MatGetOwnershipRange(A,&Istart,&Iend);

     45:   for (Ii=Istart/bs; Ii<Iend/bs; Ii++) {
     46:     v = -1.0; i = Ii/n; j = Ii - i*n;
     47:     if (i>0) {
     48:       J = Ii - n;
     49:       for (jj=0; jj<bs; jj++) {
     50:         II = Ii*bs + jj;
     51:         JJ = J*bs + jj;
     52:         MatSetValues(A,1,&II,1,&JJ,&v,ADD_VALUES);
     53:       }
     54:     }
     55:     if (i<m-1) {
     56:       J = Ii + n;
     57:       for (jj=0; jj<bs; jj++) {
     58:         II = Ii*bs + jj;
     59:         JJ = J*bs + jj;
     60:         MatSetValues(A,1,&II,1,&JJ,&v,ADD_VALUES);
     61:       }
     62:     }
     63:     if (j>0) {
     64:       J = Ii - 1;
     65:       for (jj=0; jj<bs; jj++) {
     66:         II = Ii*bs + jj;
     67:         JJ = J*bs + jj;
     68:         MatSetValues(A,1,&II,1,&JJ,&v,ADD_VALUES);
     69:       }
     70:     }
     71:     if (j<n-1) {
     72:       J = Ii + 1;
     73:       for (jj=0; jj<bs; jj++) {
     74:         II = Ii*bs + jj;
     75:         JJ = J*bs + jj;
     76:         MatSetValues(A,1,&II,1,&JJ,&v,ADD_VALUES);
     77:       }
     78:     }
     79:     v = 4.0;
     80:     for (jj=0; jj<bs; jj++) {
     81:       II = Ii*bs + jj;
     82:       MatSetValues(A,1,&II,1,&II,&v,ADD_VALUES);
     83:     }
     84:   }

     86:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     87:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
     88:   if (viewexpl) {
     89:     Mat E;
     90:     MatComputeOperator(A,MATAIJ,&E);
     91:     MatView(E,NULL);
     92:     MatDestroy(&E);
     93:   }

     95:   MatCreateVecs(A,&u,NULL);
     96:   VecSetFromOptions(u);
     97:   VecDuplicate(u,&b);
     98:   VecDuplicate(b,&x);

    100:   VecSet(u,1.0);
    101:   MatMult(A,u,b);

    103:   flg  = PETSC_FALSE;
    104:   PetscOptionsGetBool(NULL,NULL,"-view_exact_sol",&flg,NULL);
    105:   if (flg) VecView(u,PETSC_VIEWER_STDOUT_WORLD);

    107:   KSPCreate(PETSC_COMM_WORLD,&ksp);
    108:   KSPSetOperators(ksp,A,A);
    109:   KSPSetTolerances(ksp,1.e-2/((m+1)*(n+1)),1.e-50,PETSC_DEFAULT,PETSC_DEFAULT);

    111:   if (test) {
    112:     KSPGetPC(ksp,&pc);
    113:     PCSetType(pc,PCHMG);
    114:     PCHMGSetInnerPCType(pc,PCGAMG);
    115:     PCHMGSetReuseInterpolation(pc,PETSC_TRUE);
    116:     PCHMGSetUseSubspaceCoarsening(pc,PETSC_TRUE);
    117:     PCHMGUseMatMAIJ(pc,PETSC_FALSE);
    118:     PCHMGSetCoarseningComponent(pc,0);
    119:   }

    121:   KSPSetFromOptions(ksp);
    122:   KSPSolve(ksp,b,x);

    124:   if (reuse) {
    125:     MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    126:     MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    127:     KSPSolve(ksp,b,x);
    128:     MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    129:     MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    130:     KSPSolve(ksp,b,x);
    131:     /* Make sparsity pattern different and reuse interpolation */
    132:     MatSetOption(A,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_FALSE);
    133:     MatSetOption(A,MAT_IGNORE_ZERO_ENTRIES,PETSC_FALSE);
    134:     MatGetSize(A,&m,NULL);
    135:     n = 0;
    136:     v = 0;
    137:     m--;
    138:     /* Connect the last element to the first element */
    139:     MatSetValue(A,m,n,v,ADD_VALUES);
    140:     MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    141:     MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    142:     KSPSolve(ksp,b,x);
    143:   }

    145:   VecAXPY(x,-1.0,u);
    146:   VecNorm(x,NORM_2,&norm);
    147:   KSPGetIterationNumber(ksp,&its);

    149:   PetscPrintf(PETSC_COMM_WORLD,"Norm of error %g iterations %D\n",(double)norm,its);

    151:   KSPDestroy(&ksp);
    152:   VecDestroy(&u);
    153:   VecDestroy(&x);
    154:   VecDestroy(&b);
    155:   MatDestroy(&A);

    157:   PetscFinalize();
    158:   return 0;
    159: }

    161: /*TEST

    163:    build:
    164:       requires: !complex !single

    166:    test:
    167:       suffix: hypre
    168:       nsize: 2
    169:       requires: hypre !defined(PETSC_HAVE_HYPRE_DEVICE)
    170:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type hypre

    172:    test:
    173:       suffix: hypre_bs4
    174:       nsize: 2
    175:       requires: hypre !defined(PETSC_HAVE_HYPRE_DEVICE)
    176:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type hypre -bs 4 -pc_hmg_use_subspace_coarsening 1

    178:    test:
    179:       suffix: hypre_asm
    180:       nsize: 2
    181:       requires: hypre !defined(PETSC_HAVE_HYPRE_DEVICE)
    182:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type hypre -bs 4 -pc_hmg_use_subspace_coarsening 1 -mg_levels_3_pc_type asm

    184:    test:
    185:       suffix: hypre_fieldsplit
    186:       nsize: 2
    187:       requires: hypre !defined(PETSC_HAVE_HYPRE_DEVICE)
    188:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type hypre -bs 4 -mg_levels_4_pc_type fieldsplit

    190:    test:
    191:       suffix: gamg
    192:       nsize: 2
    193:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type gamg

    195:    test:
    196:       suffix: gamg_bs4
    197:       nsize: 2
    198:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type gamg -bs 4 -pc_hmg_use_subspace_coarsening 1

    200:    test:
    201:       suffix: gamg_asm
    202:       nsize: 2
    203:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type gamg -bs 4 -pc_hmg_use_subspace_coarsening 1 -mg_levels_1_pc_type asm

    205:    test:
    206:       suffix: gamg_fieldsplit
    207:       nsize: 2
    208:       args: -ksp_monitor -pc_type hmg -ksp_rtol 1e-6 -hmg_inner_pc_type gamg -bs 4 -mg_levels_1_pc_type fieldsplit

    210:    test:
    211:       suffix: interface
    212:       nsize: 2
    213:       args: -ksp_monitor -ksp_rtol 1e-6 -test_hmg_interface 1 -bs 4

    215:    test:
    216:       suffix: reuse
    217:       nsize: 2
    218:       args: -ksp_monitor -ksp_rtol 1e-6   -pc_type hmg -pc_hmg_reuse_interpolation 1 -test_reuse_interpolation 1 -hmg_inner_pc_type gamg

    220:    test:
    221:       suffix: component
    222:       nsize: 2
    223:       args: -ksp_monitor -ksp_rtol 1e-6 -pc_type hmg -pc_hmg_coarsening_component 2  -pc_hmg_use_subspace_coarsening 1 -bs 4 -hmg_inner_pc_type gamg

    225:    testset:
    226:       output_file: output/ex4_expl.out
    227:       nsize: {{1 2}}
    228:       filter: grep -v "MPI processes" | grep -v " type:" | grep -v "Mat Object"
    229:       args: -ksp_converged_reason -view_explicit_mat -pc_type none -ksp_type {{cg gmres}}
    230:       test:
    231:         suffix: expl_aij
    232:         args: -mat_type aij
    233:       test:
    234:         suffix: expl_hypre
    235:         requires: hypre
    236:         args: -mat_type hypre

    238:    test:
    239:       suffix: hypre_device
    240:       nsize: {{1 2}}
    241:       requires: hypre defined(PETSC_HAVE_HYPRE_DEVICE)
    242:       args: -mat_type hypre -ksp_converged_reason -pc_type hypre -m 13 -n 17

    244:    test:
    245:       suffix: hypre_device_cusparse
    246:       output_file: output/ex4_hypre_device.out
    247:       nsize: {{1 2}}
    248:       requires: hypre cuda defined(PETSC_HAVE_HYPRE_DEVICE)
    249:       args: -mat_type {{aij aijcusparse}} -vec_type cuda -ksp_converged_reason -pc_type hypre -m 13 -n 17

    251: TEST*/