Actual source code: ex31.c


  2: static char help[] = "Test partition. Reads a PETSc matrix and vector from a file and solves a linear system.\n\
  3: This   Input parameters include\n\
  4:   -f <input_file> : file to load \n\
  5:   -partition -mat_partitioning_view \n\\n";

  7: /*T
  8:    Concepts: KSP^solving a linear system
  9:    Processors: n
 10: T*/

 12: #include <petscksp.h>

 14: int main(int argc,char **args)
 15: {
 16:   KSP            ksp;             /* linear solver context */
 17:   Mat            A;               /* matrix */
 18:   Vec            x,b,u;           /* approx solution, RHS, exact solution */
 19:   PetscViewer    fd;              /* viewer */
 20:   char           file[PETSC_MAX_PATH_LEN];     /* input file name */
 21:   PetscBool      flg,partition=PETSC_FALSE,displayIS=PETSC_FALSE,displayMat=PETSC_FALSE;
 22:   PetscInt       its,m,n;
 23:   PetscReal      norm;
 24:   PetscMPIInt    size,rank;
 25:   PetscScalar    one = 1.0;

 27:   PetscInitialize(&argc,&args,(char*)0,help);
 28:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 29:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 31:   PetscOptionsGetBool(NULL,NULL,"-partition",&partition,NULL);
 32:   PetscOptionsGetBool(NULL,NULL,"-displayIS",&displayIS,NULL);
 33:   PetscOptionsGetBool(NULL,NULL,"-displayMat",&displayMat,NULL);

 35:   /* Determine file from which we read the matrix.*/
 36:   PetscOptionsGetString(NULL,NULL,"-f",file,sizeof(file),&flg);

 39:   /* - - - - - - - - - - - - - - - - - - - - - - - -
 40:                            Load system
 41:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 42:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);
 43:   MatCreate(PETSC_COMM_WORLD,&A);
 44:   MatLoad(A,fd);
 45:   PetscViewerDestroy(&fd);
 46:   MatGetLocalSize(A,&m,&n);

 49:   /* Create rhs vector of all ones */
 50:   VecCreate(PETSC_COMM_WORLD,&b);
 51:   VecSetSizes(b,m,PETSC_DECIDE);
 52:   VecSetFromOptions(b);
 53:   VecSet(b,one);

 55:   VecDuplicate(b,&x);
 56:   VecDuplicate(b,&u);
 57:   VecSet(x,0.0);

 59:   /* - - - - - - - - - - - - - - - - - - - - - - - -
 60:                       Test partition
 61:   - - - - - - - - - - - - - - - - - - - - - - - - - */
 62:   if (partition) {
 63:     MatPartitioning mpart;
 64:     IS              mis,nis,is;
 65:     PetscInt        *count;
 66:     Mat             BB;

 68:     if (displayMat) {
 69:       PetscPrintf(PETSC_COMM_WORLD,"Before partitioning/reordering, A:\n");
 70:       MatView(A,PETSC_VIEWER_DRAW_WORLD);
 71:     }

 73:     PetscMalloc1(size,&count);
 74:     MatPartitioningCreate(PETSC_COMM_WORLD, &mpart);
 75:     MatPartitioningSetAdjacency(mpart, A);
 76:     /* MatPartitioningSetVertexWeights(mpart, weight); */
 77:     MatPartitioningSetFromOptions(mpart);
 78:     MatPartitioningApply(mpart, &mis);
 79:     MatPartitioningDestroy(&mpart);
 80:     if (displayIS) {
 81:       PetscPrintf(PETSC_COMM_WORLD,"mis, new processor assignment:\n");
 82:       ISView(mis,PETSC_VIEWER_STDOUT_WORLD);
 83:     }

 85:     ISPartitioningToNumbering(mis,&nis);
 86:     if (displayIS) {
 87:       PetscPrintf(PETSC_COMM_WORLD,"nis:\n");
 88:       ISView(nis,PETSC_VIEWER_STDOUT_WORLD);
 89:     }

 91:     ISPartitioningCount(mis,size,count);
 92:     ISDestroy(&mis);
 93:     if (displayIS && rank == 0) {
 94:       PetscInt i;
 95:       PetscPrintf(PETSC_COMM_SELF,"[ %d ] count:\n",rank);
 96:       for (i=0; i<size; i++) PetscPrintf(PETSC_COMM_WORLD," %d",count[i]);
 97:       PetscPrintf(PETSC_COMM_WORLD,"\n");
 98:     }

100:     ISInvertPermutation(nis, count[rank], &is);
101:     PetscFree(count);
102:     ISDestroy(&nis);
103:     ISSort(is);
104:     if (displayIS) {
105:       PetscPrintf(PETSC_COMM_WORLD,"inverse of nis - maps new local rows to old global rows:\n");
106:       ISView(is,PETSC_VIEWER_STDOUT_WORLD);
107:     }

109:     MatCreateSubMatrix(A,is,is,MAT_INITIAL_MATRIX,&BB);
110:     if (displayMat) {
111:       PetscPrintf(PETSC_COMM_WORLD,"After partitioning/reordering, A:\n");
112:       MatView(BB,PETSC_VIEWER_DRAW_WORLD);
113:     }

115:     /* need to move the vector also */
116:     ISDestroy(&is);
117:     MatDestroy(&A);
118:     A    = BB;
119:   }

121:   /* Create linear solver; set operators; set runtime options.*/
122:   KSPCreate(PETSC_COMM_WORLD,&ksp);
123:   KSPSetOperators(ksp,A,A);
124:   KSPSetFromOptions(ksp);

126:   /* - - - - - - - - - - - - - - - - - - - - - - - -
127:                            Solve system
128:         - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
129:   KSPSolve(ksp,b,x);
130:   KSPGetIterationNumber(ksp,&its);

132:   /* Check error */
133:   MatMult(A,x,u);
134:   VecAXPY(u,-1.0,b);
135:   VecNorm(u,NORM_2,&norm);
136:   PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %3D\n",its);
137:   PetscPrintf(PETSC_COMM_WORLD,"Residual norm %g\n",(double)norm);
138:   flg  = PETSC_FALSE;
139:   PetscOptionsGetBool(NULL,NULL, "-ksp_reason", &flg,NULL);
140:   if (flg) {
141:     KSPConvergedReason reason;
142:     KSPGetConvergedReason(ksp,&reason);
143:     PetscPrintf(PETSC_COMM_WORLD,"KSPConvergedReason: %D\n", reason);
144:   }

146:   /* Free work space.*/
147:   MatDestroy(&A)); PetscCall(VecDestroy(&b);
148:   VecDestroy(&u)); PetscCall(VecDestroy(&x);
149:   KSPDestroy(&ksp);

151:   PetscFinalize();
152:   return 0;
153: }

155: /*TEST

157:     test:
158:       args: -f ${DATAFILESPATH}/matrices/small -partition -mat_partitioning_type parmetis
159:       requires: datafilespath !complex double !defined(PETSC_USE_64BIT_INDICES) parmetis
160:       output_file: output/ex31.out
161:       nsize: 3

163: TEST*/