**-pc_use_amat ** -use the matrix that defines the linear system, Amat as the matrix for the
inner solver, otherwise by default it uses the matrix used to construct
the preconditioner, Pmat (see PCSetOperators())

Notes: Using a Krylov method inside another Krylov method can be dangerous (you get divergence or
the incorrect answer) unless you use KSPFGMRES as the other Krylov method

Developer Notes: PCApply_KSP() uses the flag set by PCSetInitialGuessNonzero(), I think this is totally wrong, because it is then not
using this inner KSP as a preconditioner (that is a linear operator applied to some vector), it is actually just using
the inner KSP just like the outer KSP.

### See Also

PCCreate(), PCSetType(), PCType (for list of available types), PC,

PCSHELL, PCCOMPOSITE, PCSetUseAmat(), PCKSPGetKSP()

**Level:**intermediate

Location:src/ksp/pc/impls/ksp/pcksp.c

Index of all PC routines

Table of Contents for all manual pages

Index of all manual pages