Actual source code: ex8.c

  1: /*$Id: ex8.c,v 1.18 2001/08/07 03:03:07 balay Exp $*/

  3: static char help[] = "Tests automatic allocation of matrix storage space.nn";

 5:  #include petscmat.h

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

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

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

 35:   MatGetInfo(C,MAT_LOCAL,&info);
 36:   PetscPrintf(PETSC_COMM_SELF,"matrix nonzeros = %d, allocated nonzeros = %dn",
 37:     (int)info.nz_used,(int)info.nz_allocated);

 39:   MatDestroy(C);
 40:   PetscFinalize();
 41:   return 0;
 42: }