[petsc-users] unable to set type "agg" in GAMG preconditioner

[A.L. Siahaan]

Hi, 
I am experimenting with GAMG by changing some of its parameters. 
I tried to set the GAMG type into "agg" using : 
PCGAMGSetType(pc,"agg");

and I get the following error : 

========================================================================== 
Solving linear system of size 108972 x 108972 (PETSc Krylov solver). 
demo_elasticity: 
/usr/local/packages/src/petsc-3.3/src/ksp/pc/impls/gamg/agg.c:1522: 
PCCreateGAMG_AGG: Assertion `!pc_gamg->subctx' failed. 
==========================================================================

Is there any other parameter which needs to be set to enable "agg" ?
And what is the default type if I don't set to either "agg" or "geo" ?

Thanks,
Antony