Actual source code: ex16.c
petsc-3.12.4 2020-02-04
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      2: static char help[] = "Tests MatDenseGetArray() and MatView_SeqDense_Binary(), MatView_MPIDense_Binary().\n\n";

      4:  #include <petscmat.h>
      5:  #include <petscviewer.h>

      7: int main(int argc,char **args)
      8: {
      9:   Mat            A;
     10:   PetscInt       i,j,m = 3,n = 2,rstart,rend;
     12:   PetscScalar    v,*array;
     13:   PetscViewer    view;

     15:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
     16:   /*
     17:       Create a parallel dense matrix shared by all processors
     18:   */
     19:   MatCreateDense(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,m,n,NULL,&A);

     21:   /*
     22:      Set values into the matrix
     23:   */
     24:   for (i=0; i<m; i++) {
     25:     for (j=0; j<n; j++) {
     26:       v = 9.0/(i+j+1); MatSetValues(A,1,&i,1,&j,&v,INSERT_VALUES);
     27:     }
     28:   }
     29:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     30:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

     32:   /*
     33:        Print the matrix to the screen
     34:   */
     35:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

     38:   /*
     39:       Print the local portion of the matrix to the screen
     40:   */
     41:   MatDenseGetArray(A,&array);
     42:   MatGetOwnershipRange(A,&rstart,&rend);
     43:   for (i=rstart; i<rend; i++) {
     44:     for (j=0; j<n; j++) {
     45:       PetscSynchronizedPrintf(PETSC_COMM_WORLD,"%6.4e ",(double)PetscRealPart(array[j*(rend-rstart)+i-rstart]));
     46:     }
     47:     PetscSynchronizedPrintf(PETSC_COMM_WORLD,"\n");
     48:   }
     49:   PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT);
     50:   MatDenseRestoreArray(A,&array);

     52:   /*
     53:       Store the binary matrix to a file
     54:   */
     55:   PetscViewerBinaryOpen(PETSC_COMM_WORLD, "matrix.dat", FILE_MODE_WRITE, &view);
     56:   PetscViewerPushFormat(view,PETSC_VIEWER_NATIVE);
     57:   MatView(A,view);
     58:   PetscViewerPopFormat(view);
     59:   PetscViewerDestroy(&view);
     60:   MatDestroy(&A);

     62:   /*
     63:      Now reload the matrix and view it
     64:   */
     65:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,"matrix.dat",FILE_MODE_READ,&view);
     66:   MatCreate(PETSC_COMM_WORLD,&A);
     67:   MatSetType(A,MATMPIDENSE);
     68:   MatLoad(A,view);
     69:   PetscViewerDestroy(&view);
     70:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

     73:   PetscMalloc1((rend-rstart)*n,&array);
     74:   for (i=0; i<(rend-rstart)*n; i++) array[i] = 1.;
     75:   MatDensePlaceArray(A,array);
     76:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
     77:   MatDenseResetArray(A);
     78:   PetscFree(array);
     79:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
     80:   MatDestroy(&A);

     82:   PetscFinalize();
     83:   return ierr;
     84: }

     87: /*TEST

     89:    test:
     90:       nsize: 2

     92: TEST*/