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Added ising2d test for statistics.

This commit is contained in:
tayral 2014-02-13 17:38:01 +00:00 committed by Olivier Parcollet
parent a730f093d6
commit 572053f40d
2 changed files with 192 additions and 0 deletions

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#include <boost/python.hpp>
#include <iostream>
#include <fstream>
#include <triqs/mc_tools/random_generator.hpp>
#include <triqs/mc_tools/mc_generic.hpp>
#include <triqs/utility/callbacks.hpp>
#include <triqs/arrays.hpp>
#include <triqs/statistics.hpp>
#include <vector>
//#define TRIQS_ARRAYS_ENFORCE_BOUNDCHECK
// H = -J \sum_<ij> s_i s_j - h \sum_i s_i
// theoretical T_c = 2/log(1+sqrt(2)) for J = 1.0
using namespace triqs::statistics;
/**************
* config
**************/
struct configuration {
// N is the linear size of spin matrix, M the total magnetization,
// beta the inverse temperature, J the coupling,
// field the magnetic field and energy the energy of the configuration
int N, M;
double beta, J, field, energy;
// the chain of spins: true means "up", false means "down"
triqs::arrays::array<bool,2> chain;
observable<double> M_stack;
// constructor
configuration(int N_, double beta_, double J_, double field_):
N(N_), M(-N*N), beta(beta_), J(J_), field(field_), energy(-J*4*N/2+N*field), chain(N,N) , M_stack(){
chain()=false;
}
};
/**************
* move
**************/
// A move flipping a random spin
struct flip {
configuration * config;
triqs::mc_tools::random_generator &RNG;
struct site { int i,j ;};//small struct storing indices of a given site
site s;
double delta_energy;
// constructor
flip(configuration & config_, triqs::mc_tools::random_generator & RNG_) :
config(&config_), RNG(RNG_) {}
// find the neighbours with periodicity
std::vector<site> neighbors(site s, int N){
std::vector<site> nns(4);
int counter=0;
for(int i=-1;i<=1;i++){
for(int j=-1;j<=1;j++){
if ((i==0) != (j==0)) //xor
nns[counter++] = site{(s.i+i)%N, (s.j+j)%N};
}
}
return nns;
}
double attempt() {
// pick a random site
int index = RNG(config->N*config->N);
s = {index%config->N, index/config->N};
// compute energy difference from field
delta_energy = (config->chain(s.i,s.j) ? 2 : -2) * config->field;
auto nns = neighbors(s,config->N); //nearest-neighbors
double sum_neighbors=0.0;
for(auto & x:nns) sum_neighbors += ((config->chain(x.i,x.j))?1:-1);
// compute energy difference from J
delta_energy += - sum_neighbors * config->J* (config->chain(s.i,s.j)?-2:2);
// return Metroplis ratio
return std::exp(-config->beta * delta_energy);
}
// if move accepted just flip site and update energy and magnetization
double accept() {
config->M += (config->chain(s.i,s.j) ? -2 : 2);
config->chain(s.i,s.j) = !config->chain(s.i,s.j);
config->energy += delta_energy;
return 1.0;
}
// nothing to do if the move is rejected
void reject() {}
};
/**************
* measure
**************/
struct compute_m {
configuration * config;
double Z, M;
compute_m(configuration & config_) : config(&config_), Z(0), M(0) {}
// accumulate Z and magnetization
void accumulate(int sign) {
Z += sign;
M += config->M;
//config->M_stack << double(config->M/(config->N*config->N));
config->M_stack << config->M;
}
// get final answer M / (Z*N)
void collect_results(boost::mpi::communicator const &c) {
double sum_Z, sum_M;
boost::mpi::reduce(c, Z, sum_Z, std::plus<double>(), 0);
boost::mpi::reduce(c, M, sum_M, std::plus<double>(), 0);
if (c.rank() == 0) {
std::cout << "@Beta:\t"<<config->beta<<"\tMagnetization:\t" << sum_M / (sum_Z*(config->N*config->N)) << std::endl ;
std::cout << "average_and_error(M) = " << average_and_error(config->M_stack) << std::endl;
std::cout << "#Beta:\t"<<config->beta<<"\tAutocorr_time:\t" << autocorrelation_time_from_binning(config->M_stack) << std::endl;
std::ofstream outfile("magnetization_series.dat");
for(int i=0;i<config->M_stack.size();i++)
outfile << config->M_stack[i] <<std::endl;
outfile.close();
}
}
};
int main(int argc, char* argv[]) {
// initialize mpi
boost::mpi::environment env(argc, argv);
boost::mpi::communicator world;
double H=0.0,B=0.5;
int N=20;
int nc = 100000;
if(argc==4){
H = atof(argv[1]);//field
B = atof(argv[2]);//inverse temp
N = atoi(argv[3]);//size along one dimension
nc = 1000000 ;
}
if (world.rank() == 0)
std::cout << "2D Ising with field = " << H << ", beta = " << B << ", N = " << N << std::endl;
// Prepare the MC parameters
int n_cycles = nc;
int length_cycle = 100;
int n_warmup_cycles = 100000;
std::string random_name = "";
int random_seed = 374982 + world.rank() * 273894;
int verbosity = (world.rank() == 0 ? 2 : 0);
// Construct a Monte Carlo loop
triqs::mc_tools::mc_generic<double> IsingMC(n_cycles, length_cycle, n_warmup_cycles,
random_name, random_seed, verbosity);
// parameters of the model
int length = N;
double J = 1.0;
double field = H;
double beta = B;
// construct configuration
configuration config(length, beta, J, field);
// add moves and measures
IsingMC.add_move(flip(config, IsingMC.rng()), "spin flip");
IsingMC.add_measure(compute_m(config), "measure magnetization");
// Run and collect results
IsingMC.start(1.0, triqs::utility::clock_callback(-1));
IsingMC.collect_results(world);
return 0;
}

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2D Ising with field = 0, beta = 0.5, N = 20
1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 16% 17% 18% 19% 20% 21% 22% 23% 24% 25% 26% 27% 28% 29% 30% 31% 32% 33% 34% 35% 36% 37% 38% 39% 40% 41% 42% 43% 44% 45% 46% 47% 48% 49% 50% 51% 52% 53% 54% 55% 56% 57% 58% 59% 60% 61% 62% 63% 64% 65% 66% 67% 68% 69% 70% 71% 72% 73% 74% 75% 76% 77% 78% 79% 80% 81% 82% 83% 84% 85% 86% 87% 88% 89% 90% 91% 92% 93% 94% 95% 96% 97% 98% 99% 100%
Total number of measures: 100000
Average sign: 1
@Beta: 0.5 Magnetization: -0.905217
average_and_error(M) = -362.087 +/- 0.0329037
#Beta: 0.5 Autocorr_time: 30.6338