/*
    Context for conjugate gradient method (unconstrained minimization)
 */


#ifndef __TAO_CG_H
#define __TAO_CG_H

#include <petsc/private/taoimpl.h>

typedef struct {
    Vec G_old;
    Vec X_old;
    Vec W; /*  work vector */

    PetscReal eta;         /*  Restart tolerance */
    PetscReal delta_max;   /*  Minimum value for scaling */
    PetscReal delta_min;   /*  Maximum value for scaling */


    /*  The algorithm restarts when the gradient at the current point g_k,
       and the gradient of the previous point, g_{k-1}, satisfy the
       following inequality:

            abs(inner(g_k, g_{k-1})) > eta * norm(g_k, 2)^2. */

    PetscInt ngradsteps;              /*  Number of gradient steps */
    PetscInt nresetsteps;               /*  Number of reset steps */

    PetscInt cg_type;           /*  Formula to use */
} TAO_CG;

#endif /* ifndef __TAO_CG_H */