Date: 2022-03-31T04:47:20+00:00

Actual source code: ex12.c

      2: static char help[] = "Reads a PETSc matrix and vector from a file; expands the matrix with the vector\n\n";

      4: /*T
      5:    Concepts: Mat^ordering a matrix - loading a binary matrix and vector;
      6:    Concepts: Mat^loading a binary matrix and vector;
      7:    Concepts: Vectors^loading a binary vector;
      8:    Concepts: PetscLog^preloading executable
      9:    Processors: 1
     10: T*/

     12: /*
     13:   Include "petscmat.h" so that we can use matrices.
     14:   automatically includes:
     15:      petscsys.h       - base PETSc routines   petscvec.h    - vectors
     16:      petscmat.h    - matrices
     17:      petscis.h     - index sets            petscviewer.h - viewers
     18: */
     19: #include <petscmat.h>

     21: /*

     23:    Adds a new column and row to the vector (the last) containing the vector
     24: */
     25: PetscErrorCode PadMatrix(Mat A,Vec v,PetscScalar c,Mat *B)
     26: {
     27:   PetscInt          n,i,*cnt,*indices,nc;
     28:   const PetscInt    *aj;
     29:   const PetscScalar *vv,*aa;

     31:   MatGetSize(A,&n,NULL);
     32:   VecGetArrayRead(v,&vv);
     33:   PetscMalloc1(n,&indices);
     34:   for (i=0; i<n; i++) indices[i] = i;

     36:   /* determine number of nonzeros per row in the new matrix */
     37:   PetscMalloc1(n+1,&cnt);
     38:   for (i=0; i<n; i++) {
     39:     MatGetRow(A,i,&nc,NULL,NULL);
     40:     cnt[i] = nc + (vv[i] != 0.0);
     41:     MatRestoreRow(A,i,&nc,NULL,NULL);
     42:   }
     43:   cnt[n] = 1;
     44:   for (i=0; i<n; i++) {
     45:     cnt[n] += (vv[i] != 0.0);
     46:   }
     47:   MatCreateSeqAIJ(PETSC_COMM_SELF,n+1,n+1,0,cnt,B);
     48:   MatSetOption(*B,MAT_IGNORE_ZERO_ENTRIES,PETSC_TRUE);

     50:   /* copy over the matrix entries from the matrix and then the vector */
     51:   for (i=0; i<n; i++) {
     52:     MatGetRow(A,i,&nc,&aj,&aa);
     53:     MatSetValues(*B,1,&i,nc,aj,aa,INSERT_VALUES);
     54:     MatRestoreRow(A,i,&nc,&aj,&aa);
     55:   }
     56:   MatSetValues(*B,1,&n,n,indices,vv,INSERT_VALUES);
     57:   MatSetValues(*B,n,indices,1,&n,vv,INSERT_VALUES);
     58:   MatSetValues(*B,1,&n,1,&n,&c,INSERT_VALUES);

     60:   MatAssemblyBegin(*B,MAT_FINAL_ASSEMBLY);
     61:   MatAssemblyEnd(*B,MAT_FINAL_ASSEMBLY);
     62:   VecRestoreArrayRead(v,&vv);
     63:   PetscFree(cnt);
     64:   PetscFree(indices);
     65:   return 0;
     66: }

     68: int main(int argc,char **args)
     69: {
     70:   Mat            A,B;
     71:   PetscViewer    fd;                        /* viewer */
     72:   char           file[PETSC_MAX_PATH_LEN];  /* input file name */
     73:   PetscBool      flg;
     74:   Vec            v;

     76:   PetscInitialize(&argc,&args,(char*)0,help);
     77:   /*
     78:      Determine files from which we read the two linear systems
     79:      (matrix and right-hand-side vector).
     80:   */
     81:   PetscOptionsGetString(NULL,NULL,"-f0",file,sizeof(file),&flg);

     84:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);

     86:   MatCreate(PETSC_COMM_WORLD,&A);
     87:   MatSetType(A,MATSEQAIJ);
     88:   MatLoad(A,fd);
     89:   VecCreate(PETSC_COMM_WORLD,&v);
     90:   VecLoad(v,fd);
     91:   MatView(A,PETSC_VIEWER_STDOUT_SELF);
     92:   PadMatrix(A,v,3.0,&B);
     93:   MatView(B,PETSC_VIEWER_STDOUT_SELF);
     94:   MatDestroy(&B);
     95:   MatDestroy(&A);
     96:   VecDestroy(&v);
     97:   PetscViewerDestroy(&fd);

     99:   PetscFinalize();
    100:   return 0;
    101: }

    103: /*TEST

    105:    test:
    106:       args: -f0 ${wPETSC_DIR}/share/petsc/datafiles/matrices/ns-real-int32-float64
    107:       requires: double !complex !defined(PETSC_USE_64BIT_INDICES)

    109: TEST*/