From 1343a3fe6bd17a2487f12a0d61be8dc83cd722a0 Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Mon, 15 Oct 2018 22:57:17 -0400
Subject: many changes, including reworking the measurements system

---
 examples/src/models/ising/ising.hpp | 33 +++++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

(limited to 'examples/src/models/ising/ising.hpp')

diff --git a/examples/src/models/ising/ising.hpp b/examples/src/models/ising/ising.hpp
index ae20840..73b06ed 100644
--- a/examples/src/models/ising/ising.hpp
+++ b/examples/src/models/ising/ising.hpp
@@ -5,17 +5,31 @@
 
 #include <wolff/types.h>
 
+// all that is required to use wolff.hpp is a default constructor
 class ising_t {
   public:
     bool x;
 
-    typedef int M_t;
-    typedef double F_t;
-
     ising_t() : x(false) {}
-    ising_t(bool x) : x(x) {}
+
+    // optional constructors for syntactic sugar
+    ising_t(bool x) : x(x) {} 
     ising_t(int x) : x((bool)x) {}
 
+    /* below this comment is code required only for using measure.hpp in the
+     * examples folder, which provides an interface for measuring several
+     * generic features of models. these require
+     *
+     *  - an M_t, representing the magnetization or sum of all spins
+     *  - an F_t, representing a double-weighted version of the magnetization
+     *  - the overloaded operator *, which takes a v_t (unsigned int) and returns an M_t
+     *  - the overloaded operator *, which takes a double and returns an F_t
+     *  - the overloaded operator -, which takes another X_t and returns an M_t
+     */
+
+    typedef int M_t;
+    typedef double F_t;
+
     inline int operator*(v_t a) const {
       if (x) {
         return -(int)a;
@@ -45,6 +59,12 @@ class ising_t {
     }
 };
 
+/* using measure.hpp additionally requires a norm_squared function which takes
+ * an F_t to a double, and a write_magnetization function, which takes an M_t
+ * and a FILE pointer and appropriately records the contents of the former to
+ * the latter.
+ */
+
 double norm_squared(double s) {
   return pow(s, 2);
 }
@@ -53,6 +73,11 @@ void write_magnetization(int M, FILE *outfile) {
   fwrite(&M, sizeof(int), 1, outfile);
 }
 
+/* these definitions allow wolff/finite_states.hpp to be invoked and provide
+ * much faster performance for models whose number of possible spin
+ * configurations is finite.
+ */
+
 #define N_STATES 2
 const ising_t states[2] = {ising_t(0), ising_t(1)};
 q_t state_to_ind(ising_t state) { return (q_t)state.x; }
-- 
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