[petsc-users] Reading matrices into PETSc

[Tomasz Jankowski]

> Matlab pseudo code
> A = diag([1 1 1])
>
> So table is sth like this
> i  j  val
> 0 0 1
> 1 1 1
> 2 2 1
>
> see this
>
> Mat A; // of course, A should be created first and assembled after the set 
> operation
> int m =3;
> int n = 3;
> PetscInt indxm [] ={0, 1, 2};
> PetscInt indxn [] = {0, 1, 2};
> PetscScalar vals[] = {1.,1.,1.}
> MatSetValues(A, m, idxm, n, idxn, vals, INSERT_VALUES);


you example doen't work
the result matrix is:

row 0: (0, 1.1)  (1, 1.2)  (2, 1.3)
row 1: (0, 2.07356e-317)  (1, 2.122e-314)  (2, 9.88131e-324)
row 2: (0, 2.122e-314)  (1, 9.88131e-324)  (2, 1.40122e-316)

tom

here is the code for this example

   Mat xx;
   PetscInitialize(&argc,&argv,(char *)0,help);

   MatCreateSeqAIJ(PETSC_COMM_SELF,3,3,1,PETSC_NULL,&xx);

   int m =3;
   int n = 3;
   PetscInt indxm [] ={0, 1, 2};
   PetscInt indxn [] = {0, 1, 2};
   PetscScalar vals[] = {1.1,1.2,1.3};

   MatSetValues(xx,m,indxm,n,indxn,vals,INSERT_VALUES);

   MatAssemblyBegin(xx,MAT_FINAL_ASSEMBLY);
   MatAssemblyEnd(xx,MAT_FINAL_ASSEMBLY);

   MatView(xx,PETSC_VIEWER_STDOUT_WORLD);
   PetscFinalize();

return EXIT_SUCCESS;