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# PCREDUNDANT

Runs a `KSP` solver with preconditioner for the entire problem on subgroups of processors

## Options Database Key

- -pc_redundant_number n - number of redundant solves, for example if you are using 64 MPI processes and use an n of 4 there will be 4 parallel solves each on 16 = 64/4 processes.

## Notes

Options for the redundant preconditioners can be set using the options database prefix -redundant_

The default `KSP` is preonly and the default `PC` is `PCLU` or `PCCHOLESKY` if Pmat is of type `MATSBAIJ`.

`PCFactorSetShiftType()` applied to this `PC` will convey they shift type into the inner `PC` if it is factorization based.

## Developer Note

`PCSetInitialGuessNonzero()` is not used by this class but likely should be.

## See Also

KSP: Linear System Solvers, `PCCreate()`, `PCSetType()`, `PCType`, `PCRedundantSetScatter()`, `PCRedundantGetKSP()`, `PCRedundantGetOperators()`, `PCRedundantSetNumber()`, `PCREDISTRIBUTE`

## Level

intermediate

## Location

src/ksp/pc/impls/redundant/redundant.c

Index of all PC routines
Table of Contents for all manual pages
Index of all manual pages