# MatSNESMFSetHHistory

Sets an array to collect a history of the differencing values (h) computed for the matrix-free product.

### Synopsis

    #include "petscsnes.h"
    PetscErrorCode PETSCSNES_DLLEXPORT MatSNESMFSetHHistory(Mat J,PetscScalar history[],PetscInt nhistory)

Collective on Mat

### Input Parameters

| J | - the matrix-free matrix context
| histroy | - space to hold the history
| nhistory | - number of entries in history, if more entries are generated than nhistory, then the later ones are discarded

### Notes

Use MatSNESMFResetHHistory() to reset the history counter and collect a new batch of differencing parameters, h.

### Keywords

SNES, matrix-free, h history, differencing history

### See Also

MatSNESMFGetH(), MatCreateSNESMF(),
MatSNESMFResetHHistory(), MatSNESMFKSPMonitor(), MatSNESMFSetFunctionError()

Level:advanced
Location:src/snes/mf/snesmfj.c
Index of all SNESMF routines
Table of Contents for all manual pages
Index of all manual pages