added ising example to cpp collection

1 files changed, 80 insertions, 0 deletions

diff --git a/lib/ising.h b/lib/ising.h
new file mode 100644
index 0000000..4e5164b
--- /dev/null
+++ b/lib/ising.h
@@ -0,0 +1,80 @@
+#pragma once
+
+#include <cmath>
+#include <stdlib.h>
+
+#include "types.h"
+
+class ising_t {
+  public:
+    bool x;
+
+    typedef int M_t;
+    typedef double F_t;
+};
+
+void init(ising_t *p) {
+  p->x = false;
+}
+
+void free_spin(ising_t s) {
+  // do nothing!
+}
+
+void free_spin(int s) {
+  // do nothing
+}
+
+void free_spin(double s) {
+  // do nothing
+}
+
+ising_t copy(ising_t s) {
+  return s;
+}
+
+template <class T>
+void add(T *s1, T a, ising_t s2) {
+  if (s2.x) {
+    *s1 -= a;
+  } else {
+    *s1 += a;
+  }
+}
+
+int scalar_multiple(int factor, ising_t s) {
+  if (s.x) {
+    return -factor;
+  } else {
+    return factor;
+  }
+}
+
+
+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;
+  }
+}
+