TSP 之基本粒子群算法 cpp实现

 这个求解tsp的粒子群的实现算是最让我满意的一个了

粒子群算法要调的参数不多，这个程序的运行能明显看到路径的收敛

但是距最优解尚有距离

 

速度由交换序表示，那么速度的长度是要控制的参数之一

当速度“长度”长时，收敛较慢，但效果会更好

 

希望精通此道的高人给点意见，主要关于参数的设置

 

完整程序下载

 

/* pso algorithm for TSP * 参考：大连理工大学 谷超 2009年硕士学位论文 “改进的ACO和PSO算法在TSP中的应用” * 郭文忠1，陈国龙1，洪玉玲2 .求解TSP问题的动态邻域粒子群优化算法.漳州师范学院学报(自然科学版) * * @author: [email protected] */ #include <iostream> #include <fstream> #include <vector> #include <algorithm> #include <stdlib.h> #include <time.h> #include <assert.h> #include <math.h> using namespace std; //exchanger struct Exchanger{ int i,j; }; //calculate length of a path double calc_path_len(const vector<int>& path,const vector<vector<double> >& distance) { double dis=0; for (int i=0;i<path.size()-1;i++){ dis+=distance[path[i]][path[i+1]]; } dis+=distance[path[path.size()-1]][path[0]]; return dis; } //generate a integer sequence from 0 to n-1 at random void rand_int_order(vector<int>& randorder,const int n) { assert(n>1); randorder.clear(); randorder.resize(n); vector<int> recoder; for (int i=0;i<n;i++){ recoder.push_back(i); } for(int i=0;i<n;i++){ int sel=rand()%recoder.size(); randorder[i]=recoder[sel]; recoder.erase(recoder.begin()+sel); } assert(randorder.size()==n); } //operation: path add exchanger void exch_add(vector<int>& path,Exchanger speed) { int t=path[speed.i]; path[speed.i]=path[speed.j]; path[speed.j]=t; } //operation: path add exchange_sequences void exch_add(vector<int>& path,const vector<Exchanger>& speed) { for (int i=0;i<speed.size();i++){ exch_add(path,speed[i]); } } //operation: exchange_sequences add exchange_sequences void exch_add(vector<Exchanger>&speed_augend,const vector<Exchanger>& speed_addend,const int len) { for (int i=0;i<speed_addend.size();i++){ speed_augend.push_back(speed_addend[i]); } //if the length of speed is too long,truncate it while(speed_augend.size()>len){ //delete element at random speed_augend.erase(speed_augend.begin()+rand()%len); } } //multiplication for exchange sequences vector<Exchanger> exch_multiply(const vector<Exchanger>&speed,const double accelerator) { vector<Exchanger> exch_v; //if accelerator is bigger than 1,copy (int)accelerator times of initial speed to new speed int dup=(int)accelerator; exch_v.resize(dup*speed.size()); for (int i=0;i<dup;i++){ copy(speed.begin(),speed.end(),exch_v.begin()+i*speed.size()); } // int copyLen=(int)((accelerator-dup)*speed.size()); for (int i=0;i<copyLen;i++){ exch_v.push_back(speed[i]); } //if speed length is too long ,truncate it ////////////////////////////////////////////////////////////////////////// return exch_v; } //subtraction for exchange sequences vector<Exchanger> exch_sub(vector<int>&path_minuend,vector<int>&path_subtrahend) { vector<int> path_subtra=path_subtrahend; vector<Exchanger> exch_sub; for (int s=0;s<path_minuend.size();s++){ if (path_minuend[s]!=path_subtrahend[s]){ Exchanger ex; ex.i=find(path_subtra.begin()+s,path_subtra.end(),path_minuend[s])-path_subtra.begin(); ex.j=s; exch_sub.push_back(ex); exch_add(path_subtra,ex); } } return exch_sub; } //compress speed(exchange sequence),i.e. get the equivalent exchange_sequence //this function is not neccessory,but it might be more high-efficiency void exch_compress(vector<Exchanger>& exch_sequence) { } int main() { srand((unsigned)time(NULL)); //read data from file fstream filein("data/berlin52.tsp.processed",ios::in); if (filein==NULL){ cout<<"cannot open data file"<<endl; return 1; } fstream fileout("data/result.txt",ios::out); if (fileout==NULL){ cout<<"cannot open a file to write data"<<endl; return 1; } //append the best result found in this test to a file named "best.txt" fstream bestout("data/best.txt",ios::app); if (bestout==NULL){ cout<<"cannot open a file to write data"<<endl; return 1; } //number of cities unsigned int cityNum; filein>>cityNum; cout<<cityNum<<endl; //standard path int* standardPath; standardPath=new int[cityNum]; for (int i=0;i<cityNum;i++){ filein>>standardPath[i]; } //distance between cities vector<vector<double> > distance; for (int i=0;i<cityNum;i++){ vector<double> v; for (int j=0;j<cityNum;j++){ double d; filein>>d; v.push_back(d); } distance.push_back(v); } ////////////////////////////////////////////////////////////////////////// //parameters //partical number int partical_num=100; //partical swarm vector<vector<int> > swarm(partical_num); //accelerator double alpha=2;//if it equals to 1,accelerators will make no sense double beta=2; //inertia double inertia=1; //speed length int speed_len=cityNum/4; //global best partical vector<int> best_global(partical_num); //length of global best partical double best_global_len; //partial best particals vector<vector<int> > best_partial; //length of partial best particals vector<double> best_partial_len(partical_num); //speed of every partical vector<vector<Exchanger> >speed(partical_num); //initilization //particals for (int i=0;i<partical_num;i++){ rand_int_order(swarm[i],cityNum); } //initialize best partical length int l=1<<(8*sizeof(int)-2); best_global_len=l; for (int i=0;i<partical_num;i++){ best_partial_len[i]=l; } //best partial particals best_partial=swarm; //initialize speed for (int i=0;i<partical_num;i++){ int init_speed_len=rand()%speed_len; for (int j=0;j<init_speed_len;j++){ Exchanger ex; ex.i=rand()%cityNum; ex.j=ex.i; while(ex.i=ex.j){ ex.j=rand()%cityNum; } speed[i].push_back(ex); } } //generation int generation=3000; for (int g=0;g<generation;g++){ //update speed and best particals and length of these particals double length; //find best of last generation int best_index_this=0; double best_len_this=1<<(8*sizeof(int)-2); for (int i=0;i<partical_num;i++){ length=calc_path_len(swarm[i],distance); if (length<best_global_len){ //update global best partical best_global=swarm[i]; best_global_len=length; best_partial[i]=swarm[i]; best_partial_len[i]=length; }else if (length<best_partial_len[i]){ //update partical best particals best_partial[i]=swarm[i]; best_partial_len[i]=length; } if (length<best_len_this){ best_len_this=length; best_index_this=i; } } fileout<<"generation "<<g<<" "<<endl <<"best path found in this generation:"<<endl; for (int i=0;i<cityNum;i++){ fileout<<swarm[best_index_this][i]<<" "; } fileout<<endl; fileout<<"best path length in this generation : "<<best_len_this<<endl; fileout<<"best path length found for the moment: "<<best_global_len<<endl; fileout<<endl; cout<<"generation :"<<g<<endl <<"length in this generation :"<<best_len_this<<endl; <<"length found for the moment:"<<best_global_len<<endl; //shorten exchange sequences,i.e. speed for (int i=0;i<partical_num;i++){ exch_compress(speed[i]); } for (int i=0;i<partical_num;i++){ //update speed exch_add(exch_multiply(speed[i],inertia),exch_multiply(exch_sub(best_partial[i],swarm[i]),alpha*rand()/RAND_MAX),speed_len); exch_add(speed[i],exch_multiply(exch_sub(best_global,swarm[i]),beta*rand()/RAND_MAX),speed_len); //update particals exch_add(swarm[i],exch_multiply(speed[i],inertia)); } } //write best result found into a file bestout<<best_global_len<<endl; for (int i=0;i<cityNum;i++){ bestout<<best_global[i]<<" "; } bestout<<endl; //record time time_t currenttime; time(¤ttime); bestout<<ctime(¤ttime); //show standard path and distance fileout<<"standard path:"<<endl; double standardbestlen=0; for (int i=0;i<cityNum;i++){ fileout<<standardPath[i]<<" "; } for (int i=0;i<cityNum-1;i++){ standardbestlen+=distance[standardPath[i]][standardPath[i+1]]; } standardbestlen+=distance[standardPath[cityNum-1]][standardPath[0]]; fileout<<endl<<"length of standard path: "<<endl<<" "<<standardbestlen<<endl; //free memory///////////////////////////////////////////////////////////// filein.close(); fileout.close(); bestout.close(); delete[] standardPath; return 0; }