From 6b8448e5f80a7fa623678c532d1cceba0d19ac11 Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Sat, 21 Jul 2018 13:47:01 -0400
Subject: made wolff-ising header files more pedogogical

---
 lib/ising.h         | 55 +++++++++++++++++++++++++++++------------------------
 lib/z2.h            | 25 ++++++++++++------------
 src/wolff_ising.cpp | 36 ++++++++++++++++++++++++++++++-----
 3 files changed, 74 insertions(+), 42 deletions(-)

diff --git a/lib/ising.h b/lib/ising.h
index 4e5164b..e09b39e 100644
--- a/lib/ising.h
+++ b/lib/ising.h
@@ -1,10 +1,28 @@
 #pragma once
 
 #include <cmath>
-#include <stdlib.h>
 
 #include "types.h"
 
+/* The following is the minimum definition of a spin class.
+ *
+ * The class must contain an M_t and an F_t for holding the sum of an
+ * integer number of spins and a double-weighted number of spins,
+ * respectively.
+ *
+ * void init(X_t *p);
+ * void free_spin(X_t p);
+ * void free_spin(M_t p);
+ * void free_spin(F_t p);
+ * X_t copy(X_t x);
+ * void add(M_t *x1, int factor, X_t x2);
+ * void add(F_t *x1, double factor, X_t x2);
+ * M_t scalar_multiple(int factor, X_t x);
+ * double norm_squared(F_t x);
+ * void write_magnetization(M_t M, FILE *outfile);
+ *
+ */
+
 class ising_t {
   public:
     bool x;
@@ -33,8 +51,15 @@ ising_t copy(ising_t s) {
   return s;
 }
 
-template <class T>
-void add(T *s1, T a, ising_t s2) {
+void add(int *s1, int a, ising_t s2) {
+  if (s2.x) {
+    *s1 -= a;
+  } else {
+    *s1 += a;
+  }
+}
+
+void add(double *s1, double a, ising_t s2) {
   if (s2.x) {
     *s1 -= a;
   } else {
@@ -50,31 +75,11 @@ int scalar_multiple(int factor, ising_t s) {
   }
 }
 
-
 double norm_squared(double s) {
   return pow(s, 2);
 }
 
-template <class T>
-void write_magnetization(T M, FILE *outfile) {
-  fwrite(&M, sizeof(T), 1, outfile);
-}
-
-// below this line is unnecessary, but convenient
-
-double ising_dot(ising_t s1, ising_t s2) {
-  if (s1.x == s2.x) {
-    return 1.0;
-  } else {
-    return -1.0;
-  }
-}
-
-double scalar_field(ising_t s, double H) {
-  if (s.x) {
-    return -H;
-  } else {
-    return H;
-  }
+void write_magnetization(int M, FILE *outfile) {
+  fwrite(&M, sizeof(int), 1, outfile);
 }
 
diff --git a/lib/z2.h b/lib/z2.h
index 599a6a5..dae1eb7 100644
--- a/lib/z2.h
+++ b/lib/z2.h
@@ -1,10 +1,21 @@
 
 #pragma once
 
-#include <gsl/gsl_rng.h>
 #include "types.h"
 #include "ising.h"
-#include "state.h"
+
+/* The minimum definition for a group type R_t to act on a spin type X_t is
+ * given by the following.
+ *
+ * void init(R_t *p);
+ * void free_spin(R_t r);
+ * R_t copy(R_t r);
+ * X_t act(R_t r, X_t x);
+ * R_t act(R_t r, R_t r);
+ * X_t act_inverse(R_t r, X_t x);
+ * R_t act_inverse(R_t r, R_t r);
+ *
+ */
 
 struct z2_t { bool x; };
 
@@ -52,13 +63,3 @@ z2_t act_inverse(z2_t r1, z2_t r2) {
   return act(r1, r2);
 }
 
-// these are all functions necessary for wolff.h
-
-z2_t generate_ising_rotation(gsl_rng *r, const state_t <z2_t, ising_t> *s) {
-  z2_t rot;
-  rot.x = true;
-  return rot;
-}
-
-
-
diff --git a/src/wolff_ising.cpp b/src/wolff_ising.cpp
index fd2f0bb..e9d0185 100644
--- a/src/wolff_ising.cpp
+++ b/src/wolff_ising.cpp
@@ -45,24 +45,50 @@ int main(int argc, char *argv[]) {
   gsl_rng *r = gsl_rng_alloc(gsl_rng_mt19937);
   gsl_rng_set(r, rand_seed());
 
-  state_t <z2_t, ising_t> s(D, L, T, ising_dot, std::bind(scalar_field, std::placeholders::_1, H));
+  // define spin-spin coupling
+  std::function <double(ising_t, ising_t)> Z = [] (ising_t s1, ising_t s2) -> double {
+    if (s1.x == s2.x) {
+      return 1.0;
+    } else {
+      return -1.0;
+    }
+  };
 
-  std::function <z2_t(gsl_rng *, const state_t <z2_t, ising_t> *)> gen_R = generate_ising_rotation;
+  // define spin-field coupling
+  std::function <double(ising_t)> B = [=] (ising_t s) -> double {
+    if (s.x) {
+      return -H;
+    } else {
+      return H;
+    }
+  };
 
-  double average_M = 0;
+  // initialize state object
+  state_t <z2_t, ising_t> s(D, L, T, Z, B);
 
-  typedef std::function <void(const state_t <z2_t, ising_t> *)> meas_func;
+  // define function that generates self-inverse rotations
+  std::function <z2_t(gsl_rng *, const state_t <z2_t, ising_t> *)> gen_R = [] (gsl_rng *, const state_t <z2_t, ising_t> *) -> z2_t {
+    z2_t rot;
+    rot.x = true;
+    return rot;
+  };
 
-  meas_func measurement = [&] (const state_t <z2_t, ising_t> *s) {
+  // define function that updates any number of measurements
+  double average_M = 0;
+  std::function <void(const state_t <z2_t, ising_t> *)> measurement = [&] (const state_t <z2_t, ising_t> *s) {
     average_M += (double)s->M / (double)N / (double)s->nv;
   };
 
+  // run wolff for N cluster flips
   wolff(N, &s, gen_R, measurement, r, silent);
 
+  // tell us what we found!
   printf("%" PRIcount " Ising runs completed. D = %" PRID ", L = %" PRIL ", T = %g, H = %g, <M> = %g\n", N, D, L, T, H, average_M);
 
+  // free the random number generator
   gsl_rng_free(r);
 
   return 0;
+
 }
 
-- 
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