ants.h

/*

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######################################################
##########    ACO algorithms for the TSP    ##########
######################################################

      Version: 1.0
      File:    ants.h
      Author:  Thomas Stuetzle
      Purpose: implementation of procedures for ants' behaviour
      Check:   README and gpl.txt
      Copyright (C) 2002  Thomas Stuetzle
*/

/***************************************************************************

    Program's name: acotsp

    Ant Colony Optimization algorithms (AS, ACS, EAS, RAS, MMAS, BWAS) for the 
    symmetric TSP 

    Copyright (C) 2004  Thomas Stuetzle

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    email: stuetzle no@spam ulb.ac.be
    mail address: Universite libre de Bruxelles
                  IRIDIA, CP 194/6
                  Av. F. Roosevelt 50
                  B-1050 Brussels
		  Belgium

***************************************************************************/



#define HEURISTIC(m,n)     (1.0 / ((double) instance.distance[m][n] + 0.1))
/* add a small constant to avoid division by zero if a distance is 
zero */

#define EPSILON            0.00000000000000000000000000000001

#define MAX_ANTS       1024    /* max no. of ants */
#define MAX_NEIGHBOURS 512     /* max. no. of nearest neighbours in candidate set */

/* Note that *tour needs to be allocated for length n+1 since the first city of 
a tour (at position 0) is repeated at position n. This is done to make the 
computation of the tour length easier 
*/
typedef struct {
  long int  *tour;
  char      *visited;
  long int  tour_length;
} ant_struct;

extern ant_struct *ant;      /* this (array of) struct will hold the colony */
extern ant_struct *best_so_far_ant;   /* struct that contains the best-so-far ant */
extern ant_struct *restart_best_ant;  /* struct that contains the restart-best ant */

extern double   **pheromone; /* pheromone matrix, one entry for each arc */
extern double   **total;     /* combination of pheromone times heuristic information */

extern double   *prob_of_selection;


extern long int n_ants;      /* number of ants */
extern long int nn_ants;     /* length of nearest neighbor lists for the ants'
                                solution construction */

extern double rho;           /* parameter for evaporation */
extern double alpha;         /* importance of trail */
extern double beta;          /* importance of heuristic evaluate */
extern double q_0;           /* probability of best choice in tour construction */


extern long int as_flag;     /* = 1, run ant system */
extern long int eas_flag;    /* = 1, run elitist ant system */
extern long int ras_flag;    /* = 1, run rank-based version of ant system */
extern long int mmas_flag;   /* = 1, run MAX-MIN ant system */
extern long int bwas_flag;   /* = 1, run best-worst ant system */
extern long int acs_flag;    /* = 1, run ant colony system */

extern long int elitist_ants;    /* additional parameter for elitist ant system, 
				    it defines the number of elitist ants */

extern long int ras_ranks;       /* additional parameter for rank-based version of ant
				    system */

extern double   trail_max;       /* maximum pheromone trail in MMAS */
extern double   trail_min;       /* minimum pheromone trail in MMAS */
extern long int u_gb;            /* every u_gb iterations update with best-so-far ant;
				    parameter used by MMAS for scheduling best-so-far update
				 */

extern double   trail_0;         /* initial pheromone trail level in ACS  and BWAS */

/* Pheromone manipulation etc. */

void init_pheromone_trails ( double initial_trail );

void evaporation ( void );

void evaporation_nn_list ( void );

void global_update_pheromone ( ant_struct *a );

void global_update_pheromone_weighted ( ant_struct *a, long int weight );

void compute_total_information( void );

void compute_nn_list_total_information( void );

/* Ants' solution construction */

void ant_empty_memory( ant_struct *a );

void place_ant( ant_struct *a , long int phase );

void choose_best_next( ant_struct *a, long int phase );

void neighbour_choose_best_next( ant_struct *a, long int phase );

void choose_closest_next( ant_struct *a, long int phase );

void neighbour_choose_and_move_to_next( ant_struct *a , long int phase );

/* Auxiliary procedures related to ants */

long int find_best ( void );

long int find_worst( void );

void copy_from_to(ant_struct *a1, ant_struct *a2);

void allocate_ants ( void );

long int nn_tour( ant_struct *a1, long int empty_mem_after_gen );

long int distance_between_ants( ant_struct *a1, ant_struct *a2);

/* Procedures specific to MAX-MIN Ant System */

void mmas_evaporation_nn_list( void );

void check_nn_list_pheromone_trail_limits( void );

void check_pheromone_trail_limits( void );

/* Procedures specific to Ant Colony System */

void global_acs_pheromone_update( ant_struct *a );

void local_acs_pheromone_update( ant_struct *a, long int phase );

/* Procedures specific to Best Worst Ant System */

void bwas_worst_ant_update( ant_struct *a1, ant_struct *a2);

void bwas_pheromone_mutation( void );