Actual source code: ex31.c

petsc-3.7.5 2017-01-01
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  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*/


 13: #include <petscksp.h>

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

 31:   PetscInitialize(&argc,&args,(char*)0,help);
 32:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 33:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 35:   PetscOptionsGetBool(NULL,NULL,"-partition",&partition,NULL);
 36:   PetscOptionsGetBool(NULL,NULL,"-displayIS",&displayIS,NULL);
 37:   PetscOptionsGetBool(NULL,NULL,"-displayMat",&displayMat,NULL);

 39:   /* Determine file from which we read the matrix.*/
 40:   PetscOptionsGetString(NULL,NULL,"-f",file,PETSC_MAX_PATH_LEN,&flg);
 41:   if (!flg) SETERRQ(PETSC_COMM_WORLD,1,"Must indicate binary file with the -f option");

 43:   /* - - - - - - - - - - - - - - - - - - - - - - - -
 44:                            Load system
 45:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 46:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);
 47:   MatCreate(PETSC_COMM_WORLD,&A);
 48:   MatLoad(A,fd);
 49:   PetscViewerDestroy(&fd);
 50:   MatGetLocalSize(A,&m,&n);
 51:   if (m != n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ, "This example is not intended for rectangular matrices (%d, %d)", m, n);

 53:   /* Create rhs vector of all ones */
 54:   VecCreate(PETSC_COMM_WORLD,&b);
 55:   VecSetSizes(b,m,PETSC_DECIDE);
 56:   VecSetFromOptions(b);
 57:   VecSet(b,one);

 59:   VecDuplicate(b,&x);
 60:   VecDuplicate(b,&u);
 61:   VecSet(x,0.0);

 63:   /* - - - - - - - - - - - - - - - - - - - - - - - -
 64:                       Test partition
 65:   - - - - - - - - - - - - - - - - - - - - - - - - - */
 66:   if (partition) {
 67:     MatPartitioning mpart;
 68:     IS              mis,nis,is;
 69:     PetscInt        *count;
 70:     Mat             BB;

 72:     if (displayMat) {
 73:       if (!rank) printf("Before partitioning/reordering, A:\n");
 74:       MatView(A,PETSC_VIEWER_DRAW_WORLD);
 75:     }

 77:     PetscMalloc1(size,&count);
 78:     MatPartitioningCreate(PETSC_COMM_WORLD, &mpart);
 79:     MatPartitioningSetAdjacency(mpart, A);
 80:     /* MatPartitioningSetVertexWeights(mpart, weight); */
 81:     MatPartitioningSetFromOptions(mpart);
 82:     MatPartitioningApply(mpart, &mis);
 83:     MatPartitioningDestroy(&mpart);
 84:     if (displayIS) {
 85:       PetscPrintf(PETSC_COMM_WORLD,"mis, new processor assignment:\n");
 86:       ISView(mis,PETSC_VIEWER_STDOUT_WORLD);
 87:     }

 89:     ISPartitioningToNumbering(mis,&nis);
 90:     if (displayIS) {
 91:       PetscPrintf(PETSC_COMM_WORLD,"nis:\n");
 92:       ISView(nis,PETSC_VIEWER_STDOUT_WORLD);
 93:     }

 95:     ISPartitioningCount(mis,size,count);
 96:     ISDestroy(&mis);
 97:     if (displayIS && !rank) {
 98:       PetscInt i;
 99:       printf("[ %d ] count:\n",rank);
100:       for (i=0; i<size; i++) printf(" %d",count[i]);
101:       printf("\n");
102:     }

104:     ISInvertPermutation(nis, count[rank], &is);
105:     PetscFree(count);
106:     ISDestroy(&nis);
107:     ISSort(is);
108:     if (displayIS) {
109:       PetscPrintf(PETSC_COMM_WORLD,"inverse of nis - maps new local rows to old global rows:\n");
110:       ISView(is,PETSC_VIEWER_STDOUT_WORLD);
111:     }

113:     MatGetSubMatrix(A,is,is,MAT_INITIAL_MATRIX,&BB);
114:     if (displayMat) {
115:       if (!rank) printf("After partitioning/reordering, A:\n");
116:       MatView(BB,PETSC_VIEWER_DRAW_WORLD);
117:     }

119:     /* need to move the vector also */
120:     ISDestroy(&is);
121:     MatDestroy(&A);
122:     A    = BB;
123:   }

125:   /* Create linear solver; set operators; set runtime options.*/
126:   KSPCreate(PETSC_COMM_WORLD,&ksp);
127:   KSPSetOperators(ksp,A,A);
128:   KSPSetFromOptions(ksp);

130:   /* - - - - - - - - - - - - - - - - - - - - - - - -
131:                            Solve system
132:         - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
133:   KSPSolve(ksp,b,x);
134:   KSPGetIterationNumber(ksp,&its);

136:   /* Check error */
137:   MatMult(A,x,u);
138:   VecAXPY(u,-1.0,b);
139:   VecNorm(u,NORM_2,&norm);
140:   PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %3D\n",its);
141:   PetscPrintf(PETSC_COMM_WORLD,"Residual norm %g\n",(double)norm);
142:   flg  = PETSC_FALSE;
143:   PetscOptionsGetBool(NULL,NULL, "-ksp_reason", &flg,NULL);
144:   if (flg) {
145:     KSPConvergedReason reason;
146:     KSPGetConvergedReason(ksp,&reason);
147:     PetscPrintf(PETSC_COMM_WORLD,"KSPConvergedReason: %D\n", reason);
148:   }

150:   /* Free work space.*/
151:   MatDestroy(&A); VecDestroy(&b);
152:   VecDestroy(&u); VecDestroy(&x);
153:   KSPDestroy(&ksp);

155:   PetscFinalize();
156:   return 0;
157: }