Few clever algorithms for fast power x^N

src/algo.hpp

@@ -0,0 +1,59 @@
+#ifndef __COSMOTOOL_ALGO_HPP
+#define __COSMOTOOL_ALGO_HPP
+
+#include "config.hpp"
+
+namespace  CosmoTool
+{
+
+  template<typename T>
+  T cube(T a)
+  {
+    return a*a*a;
+  }
+
+  template<typename T>
+  T square(T a)
+  {
+    return a*a;
+  }
+
+  template<int N>
+  class SPowerBase
+  {
+  public:
+    template<typename T>
+    static T spower(T a)
+    {
+      if ((N%2)==0)
+	{
+	  T b = SPowerBase<N/2>::spower(a);
+	  return b*b;
+	}
+      T b = SPowerBase<(N-1)/2>::spower(a);
+      return a*b*b;
+    }
+  };
+
+  template<>
+  class SPowerBase<0>
+  {
+  public:
+    template<typename T>
+    static T spower(T a)
+    {
+      return T(1);
+    }
+  };
+
+  template<int N, typename T>
+  T spower(T a)
+  {
+    return SPowerBase<N>::spower(a);
+  }
+
+
+
+};
+
+#endif