[petsc-users] Petsc direct solver

[Satish Balay]

On Sat, 10 Sep 2011, amrit poudel wrote:

>  All right, got it. I must specify -pc_type to lu if I want to use
> mumps and there is no way around it. This basically means I will
> need astronomical amount of memory :( as noted in my previous email.

Yes - direct solvers can need lot of memory.

> [1]PETSC ERROR: Error reported by MUMPS in numerical factorization phase: Cannot allocate required memory
> 2022169721 megabytes

As the message says - MUMPS needs that much memory to solve your
problem.

 Your attempt to work arround 'lu' and to call mumps directly - and
save memory is based on the false notion that 'lu' in PETSc is
something different [from direct solver] - and comsumes its own
memory. [which is incorrect]

LU in PETSc is an iterface to direct solver implemneations. [who do
their own factiorizations - and need memory for that work]

Satish