Merge commit '4ebe6417a5fce5f0994fc0c31bebf732be96a07c' as 'boost'

boost/libs/numeric/odeint/performance/odeint_rk4_array.cpp

@@ -0,0 +1,63 @@
+/*
+ * odeint_rk4_array
+ *
+ * Copyright 2011 Mario Mulansky
+ * Copyright 2012 Karsten Ahnert
+ *
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or
+ * copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include <iostream>
+
+#include <boost/timer.hpp>
+#include <boost/array.hpp>
+
+#include <boost/numeric/odeint/stepper/runge_kutta4_classic.hpp>
+#include <boost/numeric/odeint/stepper/runge_kutta4.hpp>
+#include <boost/numeric/odeint/algebra/array_algebra.hpp>
+
+#include "lorenz.hpp"
+
+typedef boost::timer timer_type;
+
+typedef boost::array< double , 3 > state_type;
+
+using namespace boost::numeric::odeint;
+
+//typedef boost::numeric::odeint::runge_kutta4_classic< state_type > rk4_odeint_type;
+
+// use the never resizer explicitely for optimal performance with gcc, 
+// for the intel compiler this doesnt matter and the above definition
+// gives the same performance
+typedef runge_kutta4_classic< state_type , double , state_type , double ,
+                              array_algebra, default_operations, never_resizer > rk4_odeint_type;
+
+
+const int loops = 21;
+const int num_of_steps = 20000000;
+const double dt = 1E-10;
+
+
+int main()
+{
+    double min_time = 1E6; // something big
+    rk4_odeint_type stepper;
+    std::clog.precision(16);
+    std::cout.precision(16);
+    for( int n=0; n<loops; n++ )
+    {
+        state_type x = {{ 8.5, 3.1, 1.2 }};
+        double t = 0.0;
+        timer_type timer;
+        for( size_t i = 0 ; i < num_of_steps ; ++i )
+        {
+            stepper.do_step( lorenz(), x, t, dt );
+            t += dt;
+        }
+        min_time = std::min( timer.elapsed() , min_time );
+        std::clog << timer.elapsed() << '\t' << x[0] << std::endl;
+    }
+    std::cout << "Minimal Runtime: " << min_time << std::endl;
+}