eo/src/eoNormal.h

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+// -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-
+
+//-----------------------------------------------------------------------------
+// eoNormal.h
+// (c) GeNeura Team, 1998
+//-----------------------------------------------------------------------------
+
+#ifndef _EONORMAL_H
+#define _EONORMAL_H
+
+//-----------------------------------------------------------------------------
+
+#include <time.h>
+#include <stdlib.h> 
+
+#include <math.h>
+
+#include <eoRnd.h> // for base class
+
+//-----------------------------------------------------------------------------
+// Class eoNormal
+//-----------------------------------------------------------------------------
+
+/// Generates random number using a normal distribution
+template<class T>
+class eoNormal: public eoRnd<T>
+{
+ public:
+  /**
+   * Default constructor.
+   * @param _mean  Dsitribution mean
+   * @param _sd    Standard Deviation
+   */
+  eoNormal(T _mean, T _sd)
+    : eoRnd<T>(), mean(_mean), sd(_sd), phase(false) {}
+
+  /**
+   * Copy constructor.
+   * @param _rnd the other one
+   */
+  eoNormal( const eoNormal& _rnd )
+    : eoRnd<T>( _rnd), mean(_rnd.mean), sd(_rnd.sd), phase(false) {}
+  
+  /** Returns an uniform random number over the interval [min, max).
+      @return an uniform random number over the interval [min, max).
+   */
+  virtual T operator()() {
+    if (phase) { // Already have one stored up.
+      phase = false;
+      return T ( (sqRatio * q * sd) + mean );
+    }
+
+    double p, v;
+    do {
+      p = ((double)rand() / RAND_MAX)*2-1;
+      q = ((double)rand() / RAND_MAX)*2-1;
+      v = p*p + q*q;
+    } while(v > 1.0 || v <0.25);
+
+    sqRatio = sqrt(-2*log((double)rand() / RAND_MAX) / v);
+    phase = true;
+    return T( (sqRatio * p * sd) + mean );
+  };
+
+ private:
+  T mean;
+  T sd;
+  bool phase;
+  double sqRatio, q;
+};
+
+//-----------------------------------------------------------------------------
+
+#endif