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#include <iostream>
#include <chrono>
#include <wolff.hpp>
using namespace wolff;
class ising_t {
public:
int s;
ising_t() : s(1) {};
ising_t(int i) : s(i) {};
ising_t act(const ising_t& x) const {
return ising_t(s * x.s);
}
ising_t act_inverse(const ising_t& x) const {
return this->act(x);
}
};
typedef graph<> G_t;
typedef wolff::system<ising_t, ising_t> sys;
class measure_clusters : public measurement<ising_t, ising_t> {
private:
unsigned C;
public:
double Ctotal;
measure_clusters() { Ctotal = 0; }
void pre_cluster(unsigned, unsigned, const sys&, const G_t::vertex&, const ising_t&) override { C = 0; }
void plain_site_transformed(const sys&, const G_t::vertex&, const ising_t&) override { C++; }
void post_cluster(unsigned, unsigned, const sys&) override { Ctotal += C; }
};
int main(int argc, char *argv[]) {
// set defaults
unsigned N = (unsigned)1e3;
unsigned D = 2;
unsigned L = 128;
double T = 2.26918531421;
double H = 0.01;
// define the spin-spin coupling
std::function <double(const ising_t&, const ising_t&)> Z =
[](const ising_t& s1, const ising_t& s2) -> double {
return (double)(s1.s * s2.s);
};
// define the spin-field coupling
std::function <double(const ising_t&)> B =
[=](const ising_t& s) -> double {
return H * s.s;
};
// initialize the lattice
G_t G(D, L);
// initialize the system
sys S(G, T, Z, B);
// define function that generates self-inverse rotations
std::function <ising_t(std::mt19937&, const sys&, const G_t::vertex&)> gen_R =
[] (std::mt19937&, const sys&, const G_t::vertex&) -> ising_t {
return ising_t(-1);
};
// initailze the measurement object
measure_clusters A;
// initialize the random number generator
auto seed = std::chrono::high_resolution_clock::now().time_since_epoch().count();
std::mt19937 rng(seed);
// run wolff N times
S.run_wolff(N, gen_R, A, rng);
// print results
std::cout << "The average cluster size per site was " << (A.Ctotal / N) / S.nv << ".\n";
// exit
return 0;
}
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