**petsc-dev 2014-07-25**

# KSPQCGGetQuadratic

Gets the value of the quadratic function, evaluated at the new iterate:
### Synopsis

#include "petscksp.h"
PetscErrorCode KSPQCGGetQuadratic(KSP ksp,PetscReal *quadratic)

q(s) = g^T * s + 0.5 * s^T * H * s
which satisfies the Euclidian Norm trust region constraint

|| D * s || <= delta,

where

delta is the trust region radius,
g is the gradient vector, and
H is Hessian matrix,
D is a scaling matrix.

Collective on KSP

### Input Parameter

**ksp ** -the iterative context

### Output Parameter

**quadratic ** -the quadratic function evaluated at the new iterate

**Level:**advanced

Location:src/ksp/ksp/impls/qcg/qcg.c

Index of all KSP routines

Table of Contents for all manual pages

Index of all manual pages