**petsc-master 2019-08-22**

# PCFactorSetUseInPlace

Tells the system to do an in-place factorization. For dense matrices, this enables the solution of much larger problems. For sparse matrices the factorization cannot be done truly in-place so this does not save memory during the factorization, but after the matrix is factored, the original unfactored matrix is freed, thus recovering that space.
### Synopsis

#include "petscpc.h"
PetscErrorCode PCFactorSetUseInPlace(PC pc,PetscBool flg)

Logically Collective on PC

### Input Parameters

### Options Database Key

**-pc_factor_in_place <true,false>** -Activate/deactivate in-place factorization

### Notes

PCFactorSetUseInplace() can only be used with the KSP method KSPPREONLY or when
a different matrix is provided for the multiply and the preconditioner in
a call to KSPSetOperators().
This is because the Krylov space methods require an application of the
matrix multiplication, which is not possible here because the matrix has
been factored in-place, replacing the original matrix.

### See Also

PCFactorGetUseInPlace()

### Level

intermediate

### Location

src/ksp/pc/impls/factor/factor.c
### Implementations

PCFactorSetUseInPlace_Factor in src/ksp/pc/impls/factor/factor.c

Index of all PC routines

Table of Contents for all manual pages

Index of all manual pages