[petsc-users] MatNullSpaceCreate

[Shao-Ching Huang]

Hi,

I have two linear systems:

A1*x1=b1
A2*x2=b2

Each of A1 and A2 has a null space with a constant vector (like [1 1
... 1]') in it, so I currently use MatNullSpaceCreate(with
n=0,has_cnst=PETSC_TRUE).

Now I want to solve these two systems in one solve, i.e.

A*x = b

where A = [A1 0; 0 A2] and x=[x1 x2]', b=[b1 b2]'

Can I just put two vectors

[1 1 1 ... 1 0 0 ... 0]' (i.e. null space from A1)
[0 0 0 ... 0 1 1 ... 1]' (i.e. null space from A2)

into MatNullSpaceCreate (with n=2,has_cnst=PETSC_FALSE) to span the null space?

Thanks.

Shao-Ching