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;
 11:   PetscInt       i,j,m = 5,n = 4,Ii,J;
 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(PETSC_COMM_WORLD,1,"Use np <= 2");

 24:   /* Create the matrix for the five point stencil, YET AGAIN */
 25:   MatCreate(PETSC_COMM_WORLD,&C);
 26:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 27:   MatSetFromOptions(C);
 28:   MatSetUp(C);
 29:   for (i=0; i<m; i++) {
 30:     for (j=2*rank; j<2*rank+2; j++) {
 31:       v = -1.0;  Ii = j + n*i;
 32:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 33:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 34:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 35:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 36:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 37:     }
 38:   }

 40:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 41:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 42:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO);
 43:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);
 44:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 45:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);

 47:   PetscStrcpy(mtype,MATSAME);
 48:   PetscOptionsGetString(NULL,NULL,"-conv_mat_type",mtype,256,NULL);
 49:   MatConvert(C,mtype,MAT_INITIAL_MATRIX,&A);
 50:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO);
 51:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 52:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 53:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_IMPL);
 54:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 55:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 56: 
 57:   /* Free data structures */
 58:   MatDestroy(&A);
 59:   MatDestroy(&C);

 61:   PetscFinalize();
 62:   return 0;
 63: }