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simple_tasep_ring.cpp
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simple_tasep_ring.cpp
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/***********************************************************
* Copyright (C) 2014
* Authors: Hamid Teimouri & Daniel Celis
* Rice university--Department of Chemistry
* This file is distributed under the terms of the
* GNU General Public License as published by the
* Free Software Foundation; either version 3 of the
* License, or (at your option) any later version.
* http://www.gnu.org/copyleft/gpl.txt
***********************************************************/
//==============================================================================================================//
// Monte Carlo Siumulation of totally asymmetric simple exclusion process (TASEP) for periodic boundaries (ring)//
//==============================================================================================================//
#include <iostream>
#include <fstream>
#include <sstream>
#include <math.h>
#include <time.h>
#include <numeric>
#include <cstdlib>
#include <vector>
#include <valarray>
#include <algorithm>
#include <cstddef>
#include <iomanip>
#include <ctime>
#include "ran3.h"
#include <cmath>
#pragma hdrstop
#define MBIG 1000000000
#define MSEED 161803398
#define MZ 0
#define FAC (1.0/MBIG)
using std::vector;
using namespace std;
long int dum;
const int L = 100;
long double T = 1e4;
long double Teq = T * 0.2;
long double Tdif = T-Teq;
long double dt = 0.01;
long double t;
int site;
int nextsite;
long double J;
long double SiteDens;
long double AvgDens;
long double hop;
long double rho;
double densprof[L+1], lattice[L+1], p[L+1], possibleEnter[L+1];
long int j, num, k, i, N;
//////////////////////////////////////// Functions ///////////////////////////////////////
void possible_enter()
{
i = 1;
k = 1;
while (i < L)
{
if (lattice[i] == 0)
{
possibleEnter[k] = i;
i++;
k++;
}
else
{
i++;
}
}
}
void initialise() // Initialize lattice.
{
t=0.0; // Initial time.
J=0.0; // Initial current
AvgDens = 0.0;
num = 0;
for (j = 1; j <= L; j++)
{
lattice[j]=0; densprof[j]=0; p[j]=1;
}
hop = dt * p[L/2]; // The probability of hopping.
while (num < N)
{
possible_enter();
site = possibleEnter[rand()%k + 1];
lattice[site] = 1;
num++;
}
}
void move()
{
for (j = 1;j <= L; j++) // Goes through as many iterations as the array's length.
{
site = rand()%L + 1; // Picks out a random site in the array.
nextsite = site + 1; // Defines the next site. Saves the program from unecessary calculations.
if (site == L && lattice[site] == 1 && lattice[1] == 0 && ran3(&dum) <= hop) // Exit last site.
{
lattice[site] = 0; // If the citeria are met, the site is emptied.
lattice[1] = 1;
}
if (lattice[site] == 1 && lattice[nextsite] == 0 && site < L && ran3(&dum) <= hop) // Bulk of the array.
{
lattice[site] = 0; // If the criteria are met the particle leave site.
lattice[nextsite] = 1; // And enters the next site.
if(site == L/2 && t >= Teq) // Measuring current. It's measured when a particle crosses the midpoint of the array.
{
J++;
}
}
} // End of loop through array. J-loop.
}
void update()
{
dum=-time(NULL);
ran3(&dum);
for (t = 0.0; t <= T; t += dt)
{
move(); // Move function.
if (t >= Teq) // Building the density profile after the system has reached steady state. Not averaged yet.
{
for (j = 1; j <= L; j++) // Sweeps throught the array.
{
if (lattice[j] == 1) // If it finds a site which contains a particle.
{
densprof[j] += dt; // It adds one to its density counter. In reality this can be >1, it will be time-averaged later.
}
}
}
} // End of time loop.
}
double cputime ( )
{
double time;
time = ( double ) clock ( ) / ( double ) CLOCKS_PER_SEC;
return time;
}
//===================================================================//
//============================ MAIN CODE ============================//
//===================================================================//
int main()
{
double cputime0;
double cputime1;
double cputime2;
const string program ="Monte Carlo Siumulation of totally asymmetric simple exclusion process (TASEP)";
const string spaces(program.size(), '*');
const string stars = spaces;
cout<<"\n"<<endl;
cout<<stars<<endl;
cout<< program <<endl;
cout<< "for periodic boundary conditions (ring)." <<endl;
cout<<stars<<endl;
cout<< "\nrho = ";
cin>> rho;
cin.ignore();
N = int(L*rho);
cout<< "\n" << stars <<endl;
cout<< "Parameters:\n" <<endl;
cout<< " L = " << L << endl;
cout<< " T = " << T << endl;
cout<< " dt = " << dt <<endl;
cout<< " rho = " << rho <<endl;
cout<< " N = " << N <<endl;
cout<< "\n" << stars <<endl;
cout<< "Exact Solution:\n" <<endl;
cout<< " J = rho(1-rho) = "<< rho*(1-rho) <<endl;
cout<< " Density = rho = "<< rho <<endl;
cout<< "\n" << stars <<endl;
std::ostringstream fileNameStreamD("");
fileNameStreamD << "R_Densprof" << "_rho="<< rho <<".txt";
std::string fileNameD = fileNameStreamD.str();
ofstream q1(fileNameD.c_str());
#pragma omp parallel
#pragma omp for lastprivate(lattice, J)
initialise();
update();
for (j = 1; j <= L; j++) // Time averaging of the density.
{
SiteDens = densprof[j]/Tdif;
q1<<j<<" "<< SiteDens <<endl;
AvgDens += SiteDens;
}
q1.close();
cputime2 = cputime ();
cputime0 = cputime2 - cputime1;
cout<< "Simulation Results:\n" <<endl;
cout<<" J = "<< J/Tdif <<endl;
cout<<" Density = "<< AvgDens/L <<endl;
cout<< "\n";
cout<< " Elapsed cpu time for main computation:\n";
cout<< " " << cputime2 << " seconds" <<endl;
cout<< "\n" << stars <<endl;
std::ostringstream fileNameStreamL("");
fileNameStreamL << "R_Log" << "_rho="<< rho <<".txt";
std::string fileNameL = fileNameStreamL.str();
ofstream q2(fileNameL.c_str());
q2<< stars <<endl;
q2<< "Parameters:\n" <<endl;
q2<< " L = " << L << endl;
q2<< " T = " << T << endl;
q2<< " dt = " << dt <<endl;
q2<< " rho = " << rho <<endl;
q2<< " N = " << N <<endl;
q2<< stars <<endl;
q2<< "Exact Solution:\n" <<endl;
q2<< " J = rho(1-rho) = "<< rho*(1-rho) <<endl;
q2<< " Density = rho = "<< rho <<endl;
q2<< "\n" << stars <<endl;
q2<< "Simulation Results:\n" <<endl;
q2<<" J = "<< J/Tdif <<endl;
q2<<" Density = "<<AvgDens/L<<endl;
q2<< "\n";
q2<< " Elapsed cpu time for main computation:\n";
q2<< " " << cputime2 << " seconds" <<endl;
q2<< "\n" << stars <<endl;
q2.close();
}