Actual source code: ex20.c

  2: static char help[] = "Tests converting a matrix to another format with MatConvert().\n\n";

 4:  #include petscmat.h

  8: int main(int argc,char **args)
  9: {
 10:   Mat               C,A = PETSC_NULL;
 11:   PetscInt          i,j,m = 5,n = 4,I,J;
 12:   PetscErrorCode    ierr;
 13:   PetscMPIInt       rank,size;
 14:   PetscScalar       v;
 15:   char              mtype[256];

 17:   PetscInitialize(&argc,&args,(char *)0,help);
 18:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 20:   /* This example does not work correctly for np > 2 */
 21:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 22:   if (size > 2) SETERRQ(1,"Use np <= 2");

 24:  /* Create the matrix for the five point stencil, YET AGAIN */
 25:   MatCreate(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n,&C);
 26:   MatSetFromOptions(C);
 27:   for (i=0; i<m; i++) {
 28:     for (j=2*rank; j<2*rank+2; j++) {
 29:       v = -1.0;  I = j + n*i;
 30:       if (i>0)   {J = I - n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 31:       if (i<m-1) {J = I + n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 32:       if (j>0)   {J = I - 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 33:       if (j<n-1) {J = I + 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 34:       v = 4.0; MatSetValues(C,1,&I,1,&I,&v,INSERT_VALUES);
 35:     }
 36:   }

 38:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 39:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 40:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO);
 41:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);
 42:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 43:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);
 44: 
 45:   PetscStrcpy(mtype,MATSAME);
 46:   PetscOptionsGetString(PETSC_NULL,"-conv_mat_type",mtype,256,PETSC_NULL);
 47:   MatConvert(C,mtype,&A);
 48:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO);
 49:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 50:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 51:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_IMPL);
 52:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 54:   /* Free data structures */
 55:   MatDestroy(A);
 56:   MatDestroy(C);

 58:   PetscFinalize();
 59:   return 0;
 60: }