PETSc version 3.15.5
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# 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. For ICC(0) and ILU(0) with the default natural ordering the factorization is done efficiently in-place.

### Synopsis

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

Logically Collective on PC

### Input Parameters

| pc | - the preconditioner context
| flg | - PETSC_TRUE to enable, PETSC_FALSE to disable

### 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
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