Actual source code: ex9.c

petsc-3.4.2 2013-07-02
  2: static char help[] = "Tests MPI parallel matrix creation.\n\n";

  4: #include <petscmat.h>

  8: int main(int argc,char **args)
  9: {
 10:   Mat            C;
 11:   MatInfo        info;
 12:   PetscMPIInt    rank,size;
 13:   PetscInt       i,j,m = 3,n = 2,low,high,iglobal;
 14:   PetscInt       Ii,J,ldim;
 16:   PetscBool      flg;
 17:   PetscScalar    v,one = 1.0;
 18:   Vec            u,b;

 20:   PetscInitialize(&argc,&args,(char*)0,help);
 21:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 22:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 23:   n    = 2*size;

 25:   MatCreate(PETSC_COMM_WORLD,&C);
 26:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 27:   MatSetFromOptions(C);
 28:   MatSetUp(C);

 30:   /* Create the matrix for the five point stencil, YET AGAIN */
 31:   for (i=0; i<m; i++) {
 32:     for (j=2*rank; j<2*rank+2; j++) {
 33:       v = -1.0;  Ii = j + n*i;
 34:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 35:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 36:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 37:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 38:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 39:     }
 40:   }

 42:   /* Add extra elements (to illustrate variants of MatGetInfo) */
 43:   Ii   = n; J = n-2; v = 100.0;
 44:   MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);
 45:   Ii   = n-2; J = n; v = 100.0;
 46:   MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);

 48:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 49:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 51:   /* Form vectors */
 52:   VecCreate(PETSC_COMM_WORLD,&u);
 53:   VecSetSizes(u,PETSC_DECIDE,m*n);
 54:   VecSetFromOptions(u);
 55:   VecDuplicate(u,&b);
 56:   VecGetLocalSize(u,&ldim);
 57:   VecGetOwnershipRange(u,&low,&high);
 58:   for (i=0; i<ldim; i++) {
 59:     iglobal = i + low;
 60:     v       = one*((PetscReal)i) + 100.0*rank;
 61:     VecSetValues(u,1,&iglobal,&v,INSERT_VALUES);
 62:   }
 63:   VecAssemblyBegin(u);
 64:   VecAssemblyEnd(u);

 66:   MatMult(C,u,b);

 68:   VecView(u,PETSC_VIEWER_STDOUT_WORLD);
 69:   VecView(b,PETSC_VIEWER_STDOUT_WORLD);

 71:   VecDestroy(&u);
 72:   VecDestroy(&b);

 74:   PetscOptionsHasName(NULL,"-view_info",&flg);
 75:   if (flg)  {PetscViewerSetFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO);}
 76:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);

 78:   MatGetInfo(C,MAT_GLOBAL_SUM,&info);
 79:   PetscPrintf(PETSC_COMM_WORLD,"matrix information (global sums):\n\
 80:      nonzeros = %D, allocated nonzeros = %D\n",(PetscInt)info.nz_used,(PetscInt)info.nz_allocated);
 81:   MatGetInfo (C,MAT_GLOBAL_MAX,&info);
 82:   PetscPrintf(PETSC_COMM_WORLD,"matrix information (global max):\n\
 83:      nonzeros = %D, allocated nonzeros = %D\n",(PetscInt)info.nz_used,(PetscInt)info.nz_allocated);

 85:   MatDestroy(&C);
 86:   PetscFinalize();
 87:   return 0;
 88: }