[petsc-users] non-contiguous parallel block of the coefficient matrix and AO functions

[M. Scot Breitenfeld]

  I'm a little unclear how to use the AO functions if the global nodal 
numbering results in a non-contiguous parallel block of the coefficient 
matrix.

For example, if I have 1D (1 dof per node) problem (2 processors), for 
this case node number = row position in vector:

0    3   4   7       2   5   6   1 (Apps)
o    o   o   o  ||  o   o   o  o
0    1    2   3      4   5   6  7 (Petsc)

First I call,

CALL AOCreateBasic(PETSC_COMM_WORLD,  n, mappings, PETSC_NULL_INTEGER, 
ao, ierr)

where

n = 4, mappings=P0:{0,3,4,7}, P1:{2,5,6,1}
Petsc will be continuous P0:{0,1,2,3}, P1:{4,5,6,7} so I used NULL.

CALL AOApplicationToPetsc(ao,n,mappings, ierr)

Now if I want to add a value at the global 7th row (Application row) on 
processor 0, do I use the Application's numbering 7, or petsc numbering 3.

If it's the global Application id:
CALL VecSetValues(b, 1, 7 , value, ADD_VALUES, ierr)
Does Petsc know if I specify row 7 to put it in row 3 of petsc numbering?

Or is the numbering always Petsc's numbering?

If I then solve the solution
CALL KSPSolve(ksp,b,b,ierr)

and I want to get the values back

CALL VecGetValues(b,1,row, value, ierr)

is 'row' the Application row (7) or Petsc row (3)

Thanks,
Scot