From 864e288c5cb51ae94ac09db8597714c605344c3d Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Fri, 19 Oct 2018 11:42:27 -0400
Subject: added standalone ising example

---
 examples/CMakeLists.txt       |  2 +
 examples/ising_standalone.cpp | 99 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+)
 create mode 100644 examples/ising_standalone.cpp

diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index a4a4a5c..c64bb06 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -1,11 +1,13 @@
 
 add_executable(ising ising.cpp)
 add_executable(ising_animation ising_animation.cpp)
+add_executable(ising_standalone ising_standalone.cpp)
 add_executable(xy On.cpp)
 
 add_compile_definitions(xy WOLFF_N=2)
 
 target_link_libraries(ising wolff)
 target_link_libraries(ising_animation wolff GL GLU glut)
+target_link_libraries(ising_standalone wolff)
 target_link_libraries(xy wolff)
 
diff --git a/examples/ising_standalone.cpp b/examples/ising_standalone.cpp
new file mode 100644
index 0000000..c958777
--- /dev/null
+++ b/examples/ising_standalone.cpp
@@ -0,0 +1,99 @@
+
+#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);
+    }
+};
+
+class measure_clusters : public measurement<ising_t, ising_t> {
+  public:
+    v_t C;
+    double Ctotal;
+
+    measure_clusters() {
+      Ctotal = 0;
+    }
+
+    void pre_cluster(N_t, N_t, const system<ising_t, ising_t>&, v_t, const ising_t&) {
+      C = 0;
+    }
+
+    void plain_bond_visited(const system<ising_t, ising_t>&, v_t, const ising_t&, v_t, double dE) {}
+
+    void ghost_bond_visited(const system<ising_t, ising_t>&, v_t, const ising_t& s_old, const ising_t& s_new, double dE) {}
+
+    void plain_site_transformed(const system<ising_t, ising_t>&, v_t, const ising_t&) {
+      C++;
+    }
+
+    void ghost_site_transformed(const system<ising_t, ising_t>&, const ising_t&) {}
+
+    void post_cluster(N_t, N_t, const system<ising_t, ising_t>&) {
+      Ctotal += C;
+    }
+};
+
+int main(int argc, char *argv[]) {
+
+  // set defaults
+  N_t N = (N_t)1e3;
+  D_t D = 2;
+  L_t 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
+  graph G(D, L);
+
+  // initialize the system
+  system<ising_t, ising_t> S(G, T, Z, B);
+
+  // define function that generates self-inverse rotations
+  std::function <ising_t(std::mt19937&, const system<ising_t, ising_t>&, v_t)> gen_R = [] (std::mt19937&, const system<ising_t, ising_t>&, v_t) -> 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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