/*
   Context for using preconditioned conjugate gradient method to minimized a
   quadratic function subject to a trust region constraint.  If the matrix
   is indefinite, a direction of negative curvature may be encountered.  If
   a direction of negative curvature is found, then we follow it to the
   boundary of the trust region.

   This method is described in:
     T. Steihaug, "The Conjugate Gradient Method and Trust Regions in Large
       Scale Optimization", SIAM Journal on Numerical Analysis, 20,
       pages 626-637, 1983.
*/

#pragma once

#include <petsc/private/kspimpl.h>

typedef struct {
  PetscReal radius;
  PetscReal norm_d;
  PetscReal o_fcn;
  PetscInt  dtype;
} KSPCG_STCG;