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# PCModifySubMatricesFn

A prototype of a function used to modify submatrices generated with `PCASM`, `PCBJACOBI`, etc.

## Synopsis

    PETSC_EXTERN_TYPEDEF typedef PetscErrorCode PCModifySubMatricesFn(PC pc, PetscInt nsub, const IS row[], const IS col[], Mat submat[], PetscCtx ctx);

## Calling Sequence

- pc - the `PC` preconditioner context

- nsub - number of index sets

- row - an array of index sets that contain the global row numbers that comprise each local submatrix

- col - an array of index sets that contain the global column numbers that comprise each local submatrix

- submat - array of local submatrices

- ctx - optional user-defined context for private data for the user-defined func routine (may be `NULL`), provided with `PCSetModifySubMatrices()`

## See Also

KSP: Linear System Solvers, `PC`, `PCSetModifySubMatrices()`, `PCModifySubMatrices()`, `PCASM`, `PCBJACOBI`

## Level

beginner

## Location

include/petscpc.h

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