2: static char help[] = "Tests automatic allocation of matrix storage space.\n\n";

  4:  #include <petscmat.h>

  6: int main(int argc,char **args)
  7: {
  8:   Mat            C;
  9:   PetscInt       i,j,m = 3,n = 3,Ii,J;
 11:   PetscScalar    v;
 12:   MatInfo        info;

 14:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 15:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
 16:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);

 18:   /* create the matrix for the five point stencil, YET AGAIN */
 19:   MatCreate(PETSC_COMM_SELF,&C);
 20:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 21:   MatSetFromOptions(C);
 22:   MatSetUp(C);
 23:   for (i=0; i<m; i++) {
 24:     for (j=0; j<n; j++) {
 25:       v = -1.0;  Ii = j + n*i;
 26:       if (i>0)   {J=Ii-n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 27:       if (i<m-1) {J=Ii+n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 28:       if (j>0)   {J=Ii-1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 29:       if (j<n-1) {J=Ii+1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 30:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 31:     }
 32:   }
 33:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 34:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 35:   MatView(C,PETSC_VIEWER_STDOUT_SELF);

 37:   MatGetInfo(C,MAT_LOCAL,&info);
 38:   PetscPrintf(PETSC_COMM_SELF,"matrix nonzeros = %D, allocated nonzeros = %D\n",(PetscInt)info.nz_used,(PetscInt)info.nz_allocated);

 40:   MatDestroy(&C);
 41:   PetscFinalize();
 42:   return ierr;
 43: }


 46: /*TEST

 48:    test:

 50: TEST*/