1 files changed, 110 insertions, 0 deletions
diff --git a/examples/potts.cpp b/examples/potts.cpp
new file mode 100644
index 0000000..84494e2
--- /dev/null
+++ b/examples/potts.cpp
@@ -0,0 +1,110 @@
+
+#include <getopt.h>
+#include <iostream>
+#include <chrono>
+
+#include "simple_measurement.hpp"
+
+#include <wolff/models/potts.hpp>
+#include <wolff/models/symmetric.hpp>
+#include <wolff/finite_states.hpp>
+
+#include <wolff.hpp>
+
+using namespace wolff;
+
+int main(int argc, char *argv[]) {
+
+  // set defaults
+  N_t N = (N_t)1e4;
+  D_t D = 2;
+  L_t L = 128;
+  double T = 2.26918531421;
+  vector_t<WOLFF_POTTSQ, double> H;
+  H.fill(0.0);
+  q_t Hi = 0;
+
+  int opt;
+
+  // take command line arguments
+  while ((opt = getopt(argc, argv, "N:D:L:T:H:")) != -1) {
+    switch (opt) {
+    case 'N': // number of steps
+      N = (N_t)atof(optarg);
+      break;
+    case 'D': // dimension
+      D = atoi(optarg);
+      break;
+    case 'L': // linear size
+      L = atoi(optarg);
+      break;
+    case 'T': // temperature
+      T = atof(optarg);
+      break;
+    case 'H': // external field
+      H[Hi] = atof(optarg);
+      Hi++;
+      break;
+    default:
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  // define the spin-spin coupling
+  std::function <double(const potts_t<WOLFF_POTTSQ>&, const potts_t<WOLFF_POTTSQ>&)> Z = [] (const potts_t<WOLFF_POTTSQ>& s1, const potts_t<WOLFF_POTTSQ>& s2) -> double {
+    if (s1.x == s2.x) {
+      return 1.0;
+    } else {
+      return 0.0;
+    }
+  };
+
+  // define the spin-field coupling
+  std::function <double(const potts_t<WOLFF_POTTSQ>&)> B = [=] (const potts_t<WOLFF_POTTSQ>& s) -> double {
+    return H[s.x];
+  };
+
+  // initialize the lattice
+  graph G(D, L);
+
+  // initialize the system
+  system<symmetric_t<WOLFF_POTTSQ>, potts_t<WOLFF_POTTSQ>> S(G, T, Z, B);
+
+  // initialize the random number generator
+  auto seed = std::chrono::high_resolution_clock::now().time_since_epoch().count();
+  std::mt19937 rng{seed};
+
+  // define function that generates self-inverse rotations
+  std::function <symmetric_t<WOLFF_POTTSQ>(std::mt19937&, const system<symmetric_t<WOLFF_POTTSQ>, potts_t<WOLFF_POTTSQ>>&, v_t)> gen_r = [] (std::mt19937& r, const system<symmetric_t<WOLFF_POTTSQ>, potts_t<WOLFF_POTTSQ>>& S, v_t i0) -> symmetric_t<WOLFF_POTTSQ> {
+    symmetric_t<WOLFF_POTTSQ> rot;
+
+    std::uniform_int_distribution<q_t> dist(0, WOLFF_POTTSQ - 2);
+    q_t j = dist(r);
+    q_t swap_v;
+    if (j < S.s[i0].x) {
+      swap_v = j;
+    } else {
+      swap_v = j + 1;
+    }
+
+    rot[S.s[i0].x] = swap_v;
+    rot[swap_v] = S.s[i0].x;
+
+    return rot;
+  };
+
+  // initailze the measurement object
+  simple_measurement A(S);
+
+  // run wolff N times
+  S.run_wolff(N, gen_r, A, rng);
+
+  // print the result of our measurements
+  std::cout << "Wolff complete!\nThe average energy per site was " << A.avgE() / S.nv
+    << ".\nThe average magnetization per site was " << A.avgM() / S.nv
+    << ".\nThe average cluster size per site was " << A.avgC() / S.nv << ".\n";
+
+  // exit
+  return 0;
+}
+