petsc-3.14.5 2021-03-03
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# KSPSetInitialGuessNonzero

Tells the iterative solver that the initial guess is nonzero; otherwise KSP assumes the initial guess is to be zero (and thus zeros it out before solving).

### Synopsis

    #include "petscksp.h"
    #include "petscmat.h"
    PetscErrorCode  KSPSetInitialGuessNonzero(KSP ksp,PetscBool flg)

Logically Collective on ksp

### Input Parameters

| ksp | - iterative context obtained from KSPCreate()
| flg | - PETSC_TRUE indicates the guess is non-zero, PETSC_FALSE indicates the guess is zero

### Options database keys

| -ksp_initial_guess_nonzero : use nonzero initial guess; this takes an optional truth value (0/1/no/yes/true/false)

### Notes

If this is not called the X vector is zeroed in the call to KSPSolve().

### See Also

KSPGetInitialGuessNonzero(), KSPSetGuessType(), KSPGuessType, KSP

### Level

beginner

### Location

src/ksp/ksp/interface/itfunc.c

### Examples

src/ksp/pc/tutorials/ex1.c.html
src/ksp/pc/tutorials/ex2.c.html
src/ksp/ksp/tutorials/ex3.c.html
src/ksp/ksp/tutorials/ex9.c.html
src/ksp/ksp/tutorials/ex27.c.html
src/ksp/ksp/tutorials/ex51.c.html
src/ksp/ksp/tutorials/ex56.c.html
src/ksp/ksp/tutorials/ex71.c.html
src/ksp/ksp/tutorials/ex72.c.html
src/ksp/ksp/tutorials/ex6f.F90.html
src/tao/pde_constrained/tutorials/parabolic.c.html
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages