371 lines
9.3 KiB
C++
371 lines
9.3 KiB
C++
// vim: set ts=2 sw=2 et tw=80:
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// compile with
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// c++ -O2 -lpthread --std=c++11 -o c_prob/aco aco.cc opt.cc
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include <pthread.h>
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#include <vector>
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#include <set>
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#include <iostream>
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#include <algorithm>
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#include <unistd.h>
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#include "opt.h"
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#define SINGLE_CORE 1
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using namespace std;
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typedef unsigned int uint;
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const uint MAX_NODES = 1577;
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// alpha >= 0
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double alpha;
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// beta >= 1
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double beta;
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double pheromone_evaporation_coeff;
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double pheromone_constant;
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uint n_iterations;
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uint n_ants;
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uint n_nodes;
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double dist_matrix[MAX_NODES][MAX_NODES];
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double pheromone_map[MAX_NODES][MAX_NODES];
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double ant_updated_pheromone_map[MAX_NODES][MAX_NODES];
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double sh_dist;
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vector<uint> sh_route;
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bool first_pass;
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uint start;
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struct ant {
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uint seed;
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uint idx;
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uint iter;
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pthread_t t_handle;
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uint location;
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double distance_travelled;
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set<uint> possible_locations;
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vector<uint> route;
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bool tour_complete = false;
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uint select_random(const set<uint> &s) {
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auto n = rand_r(&seed) % s.size(); // not _really_ random
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auto it = begin(s);
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advance(it, n); // 'advance' the iterator n times
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return *it;
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}
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void init() {
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this->seed = this->idx * 1000 + this->iter;
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this->distance_travelled = 0.0;
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this->route.clear();
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this->possible_locations.clear();
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for (size_t i = 0; i < n_nodes; i++) {
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this->possible_locations.insert(i);
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}
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this->location = start;
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this->update_route(start);
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this->tour_complete = false;
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};
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void update_route(uint new_loc) {
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this->route.push_back(new_loc);
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this->possible_locations.erase(new_loc);
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};
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uint pick_path() {
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if (first_pass) {
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return select_random(this->possible_locations);
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} else {
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double toss = (double) rand_r(&seed) / (double) RAND_MAX;
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double attractiveness[n_nodes];
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double sum_total = 0.0;
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vector<uint> idxs;
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for (uint loc : this->possible_locations) {
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idxs.push_back(loc);
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double pheromone_amount = pheromone_map[this->location][loc];
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double distance = dist_matrix[this->location][loc];
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if (distance == 0) { distance = 0.000000001; };
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attractiveness[loc] = pow(pheromone_amount, alpha) *
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pow(1 / distance, beta);
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sum_total += attractiveness[loc];
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if (isnan(sum_total)) { cerr << "nanalert " << attractiveness[loc] <<
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" " << pheromone_amount << " " << distance << endl; }
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}
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// it is possible to have small values for pheromone amount / distance,
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// such that with rounding errors this is equal to zero
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if (sum_total == 0.0) {
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// increment all zero's, such that they are the smallest non-zero
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// values supported by the system
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// source: http://stackoverflow.com/a/10426033/5343977
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for (uint loc : idxs) {
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attractiveness[loc] = nextafter(attractiveness[loc],
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std::numeric_limits<double>::infinity());
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}
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sum_total = nextafter(sum_total, std::numeric_limits<double>::infinity());
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}
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double cumulative = 0.0;
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for (uint loc : idxs) {
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double weight = (attractiveness[loc] / sum_total);
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if (toss <= (weight + cumulative)) {
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return loc;
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}
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cumulative += weight;
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}
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return idxs[idxs.size() - 1];
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}
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};
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void traverse(uint next) {
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this->update_route(next);
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this->distance_travelled += dist_matrix[this->location][next];
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this->location = next;
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}
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void run() {
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while (!this->possible_locations.empty()) {
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uint next = this->pick_path();
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this->traverse(next);
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}
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this->distance_travelled += dist_matrix[this->route[this->route.size() - 1]]
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[this->route[0]];
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this->tour_complete = true;
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}
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};
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void *ant_thread (void *ant_ptr) {
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ant& ant = *((struct ant *) ant_ptr);
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ant.run();
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return NULL;
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}
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ant* ants;
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void init_ants(size_t it) {
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for (size_t i = 0; i < n_ants; i++) {
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ants[i].idx = i;
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ants[i].iter = it;
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ants[i].init();
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}
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}
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pthread_mutex_t mut;
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void init_aco() {
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pthread_mutex_init(&mut, NULL);
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start = 0;
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first_pass = true;
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memset(pheromone_map, 0, sizeof(pheromone_map));
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memset(ant_updated_pheromone_map, 0, sizeof(ant_updated_pheromone_map));
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init_ants(0);
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sh_dist = -1.0;
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}
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void populate_ant_updated_pheromone_map(ant& ant) {
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for (size_t i = 0; i < ant.route.size(); i++) {
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size_t j = (i + 1) % n_nodes;
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double current_ph = ant_updated_pheromone_map[ant.route[i]][ant.route[j]];
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double new_ph = pheromone_constant / ant.distance_travelled;
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ant_updated_pheromone_map[ant.route[i]][ant.route[j]] =
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ant_updated_pheromone_map[ant.route[j]][ant.route[i]] =
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current_ph + new_ph;
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}
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}
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void update_pheromone_map() {
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for (size_t i = 0; i < n_nodes; i++) {
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for (size_t j = 0; j < n_nodes; j++) {
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pheromone_map[i][j] = (1 - pheromone_evaporation_coeff) *
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pheromone_map[i][j] + ant_updated_pheromone_map[i][j];
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}
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}
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}
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double mainloop(size_t i) {
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#if SINGLE_CORE
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for (uint j = 0; j < n_ants; j++) {
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ant_thread(&(ants[j]));
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}
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#else
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for (uint j = 0; j < n_ants; j++) {
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pthread_create(&(ants[j].t_handle), NULL, ant_thread, &(ants[j]));
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}
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for (uint j = 0; j < n_ants; j++) {
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pthread_join(ants[j].t_handle, NULL);
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}
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#endif
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unsigned long sum = 0L;
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for (uint j = 0; j < n_ants; j++) {
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populate_ant_updated_pheromone_map(ants[j]);
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sum += ants[j].distance_travelled;
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if (ants[j].iter > 200 && n_nodes == 76) { // eil76 after 200th iteration
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three_opt(ants[j].route, dist_matrix, ants[j].distance_travelled);
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}
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if (sh_dist < 0 || ants[j].distance_travelled < sh_dist) {
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sh_dist = ants[j].distance_travelled;
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sh_route = ants[j].route;
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cerr << "new short distance is " << sh_dist << " ant " << j << endl;
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}
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}
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update_pheromone_map();
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first_pass = false;
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init_ants(i+1);
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memset(ant_updated_pheromone_map, 0, sizeof(ant_updated_pheromone_map));
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return (double) sum / (double) n_ants;
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}
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uint two_five_opt() {
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uint swaps = 0;
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for (int i = 0; i < n_nodes - 2; i++) {
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for (int j = i+2; j < n_nodes; j++) {
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size_t ip = i == 0 ? (n_nodes - 1) : (i - 1);
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size_t x1 = sh_route[ip];
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size_t x2 = sh_route[i];
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size_t x3 = sh_route[i+1];
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size_t y3 = sh_route[j-2];
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size_t y1 = sh_route[j-1];
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size_t y2 = sh_route[j];
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double var_a = sh_dist - dist_matrix[x2][x1] - dist_matrix[y2][y1]
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+ dist_matrix[x1][y1] + dist_matrix[y2][x2];
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double var_b = sh_dist - dist_matrix[x2][x1] - dist_matrix[y2][y1]
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- dist_matrix[x2][x3] + dist_matrix[x2][y2]
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+ dist_matrix[y1][x2] + dist_matrix[x1][x3];
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double var_c = sh_dist - dist_matrix[x2][x1] - dist_matrix[y2][y1]
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- dist_matrix[y1][y3] + dist_matrix[x1][y1]
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+ dist_matrix[y1][x2] + dist_matrix[y3][y2];
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if (var_a < sh_dist && var_a < var_b && var_a < var_c) {
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sh_dist = var_a;
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reverse(sh_route.begin() + i, sh_route.begin() + j);
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swaps++;
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} else if (var_b < sh_dist && var_b < var_a && var_b < var_c) {
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for (int k = i; k < j - 1; k++) {
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sh_route[k] = sh_route[k + 1];
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}
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sh_route[j - 1] = x2;
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sh_dist = var_b;
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swaps++;
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} else if (var_c < sh_dist && var_c < var_a && var_c < var_b) {
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for (int k = j - 2; k >= i; k--) {
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sh_route[k + 1] = sh_route[k];
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}
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sh_route[i] = y1;
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sh_dist = var_c;
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swaps++;
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}
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}
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}
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return swaps;
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}
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#define buffersize 100000
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int main(int argc, char** argv) {
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unsigned started = time(NULL);
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int optruns;
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if (argc < 9) {
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cerr << argv[0] << " [n_nodes] [n_iter] [n_ants] [alpha] [beta] [evap] [weight] [optruns]" << endl;
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return 1;
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}
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n_nodes = atoi(argv[1]);
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n_iterations = atoi(argv[2]);
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n_ants = atoi(argv[3]);
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sscanf(argv[4], "%lf", &alpha);
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sscanf(argv[5], "%lf", &beta);
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sscanf(argv[6], "%lf", &pheromone_evaporation_coeff);
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sscanf(argv[7], "%lf", &pheromone_constant);
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sscanf(argv[8], "%d", &optruns);
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ant ants_arr[n_ants];
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ants = ants_arr;
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cerr << n_nodes << endl;
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char * pch;
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int row = 0, column = 0;
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char buffer[buffersize];
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for (size_t i = 0; i < n_nodes; i++) {
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fgets(buffer, buffersize, stdin);
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pch = strtok(buffer, " ");
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column = 0;
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while (pch != NULL) {
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sscanf(pch, "%lf", &(dist_matrix[row][column]));
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pch = strtok(NULL, " ");
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column++;
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}
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row++;
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}
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cerr << "reading done" << endl;
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init_aco();
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unsigned limit = 175;
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unsigned last_time = started;
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unsigned last_delta = 0;
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for (size_t i = 0; i < n_iterations; i++) {
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double d = mainloop(i);
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unsigned now = time(NULL);
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cerr << "iter: " << i << " - dist: " << sh_dist << " - avg: "
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<< d << " - elapsed: " << now - started << endl;
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if ((now - started) + last_delta > limit) {
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cerr << "out of time" << endl;
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break;
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}
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last_delta = now - last_time;
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last_time = now;
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}
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cerr << "pre-optimization length: " << sh_dist << endl;
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cerr << sh_route << endl;
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for (uint j = 0; j < optruns; j++) {
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two_five_opt();
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three_opt(sh_route, dist_matrix, sh_dist);
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cerr << "optimized length " << j << " : " << sh_dist << endl;
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}
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cout << sh_route << endl;
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}
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