2: static char help[] = "Tests converting a parallel AIJ formatted matrix to the parallel Row format.\n\
  3:  This also tests MatGetRow() and MatRestoreRow() for the parallel case.\n\n";

  5:  #include <petscmat.h>

  7: int main(int argc,char **args)
  8: {
  9:   Mat               C,A;
 10:   PetscInt          i,j,m = 3,n = 2,Ii,J,rstart,rend,nz;
 11:   PetscMPIInt       rank,size;
 12:   PetscErrorCode    ierr;
 13:   const PetscInt    *idx;
 14:   PetscScalar       v;
 15:   const PetscScalar *values;

 17:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 18:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 19:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 20:   n    = 2*size;

 22:   /* create the matrix for the five point stencil, YET AGAIN*/
 23:   MatCreate(PETSC_COMM_WORLD,&C);
 24:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 25:   MatSetFromOptions(C);
 26:   MatMPIAIJSetPreallocation(C,5,NULL,5,NULL);
 27:   MatSeqAIJSetPreallocation(C,5,NULL);
 28:   for (i=0; i<m; i++) {
 29:     for (j=2*rank; j<2*rank+2; j++) {
 30:       v = -1.0;  Ii = j + n*i;
 31:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 32:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 33:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 34:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 35:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 36:     }
 37:   }
 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);

 45:   MatGetOwnershipRange(C,&rstart,&rend);
 46:   for (i=rstart; i<rend; i++) {
 47:     MatGetRow(C,i,&nz,&idx,&values);
 48:     PetscSynchronizedFPrintf(PETSC_COMM_WORLD,stdout,"[%d] get row %D: ",rank,i);
 49:     for (j=0; j<nz; j++) {
 50:       PetscSynchronizedFPrintf(PETSC_COMM_WORLD,stdout,"%D %g  ",idx[j],(double)PetscRealPart(values[j]));
 51:     }
 52:     PetscSynchronizedFPrintf(PETSC_COMM_WORLD,stdout,"\n");
 53:     MatRestoreRow(C,i,&nz,&idx,&values);
 54:   }
 55:   PetscSynchronizedFlush(PETSC_COMM_WORLD,stdout);

 57:   MatConvert(C,MATSAME,MAT_INITIAL_MATRIX,&A);
 58:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO);
 59:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 60:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 61:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 63:   MatDestroy(&A);
 64:   MatDestroy(&C);
 65:   PetscFinalize();
 66:   return ierr;
 67: }