PETSc version 3.15.5
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# SNESSetInitialFunction

Sets the function vector to be used as the function norm at the initialization of the method. In some instances, the user has precomputed the function before calling SNESSolve. This function allows one to avoid a redundant call to SNESComputeFunction in that case.

### Synopsis

    #include "petscsnes.h"
    PetscErrorCode  SNESSetInitialFunction(SNES snes, Vec f)

Logically Collective on SNES

### Input Parameters

| snes | - the SNES context
| f | - vector to store function value

### Notes

This should not be modified during the solution procedure.

This is used extensively in the SNESFAS hierarchy and in nonlinear preconditioning.

### See Also

SNESSetFunction(), SNESComputeFunction(), SNESSetInitialFunctionNorm()

### Level

developer

### Location

src/snes/interface/snes.c
Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages