# MatSNESMFWPSetComputeNormU

Sets whether it computes the ||U|| used by the WP PETSc routine for computing h. With any Krylov solver this need only be computed during the first iteration and kept for later.
### Synopsis

#include "petscsnes.h"
PetscErrorCode PETSCSNES_DLLEXPORT MatSNESMFWPSetComputeNormU(Mat A,PetscTruth flag)

### Input Parameters

### Options Database Key

**-snes_mf_compute_normu <true,false> ** -true by default, false can save calculations but you
must be sure that ||U|| has not changed in the mean time.

### Notes

See the manual page for MATSNESMF_WP for a complete description of the
algorithm used to compute h.

### See Also

MatSNESMFSetFunctionError(), MatCreateSNESMF()

**Level:**advanced

Location:src/snes/mf/wp.c

Index of all SNESMF routines

Table of Contents for all manual pages

Index of all manual pages