[Boost-commit] svn:boost r57047 - in sandbox/odeint: boost/numeric/odeint libs/numeric/odeint/examples

Subject: [Boost-commit] svn:boost r57047 - in sandbox/odeint: boost/numeric/odeint libs/numeric/odeint/examples
From: mario.mulansky_at_[hidden]
Date: 2009-10-21 14:02:07

Author: mariomulansky
Date: 2009-10-21 14:02:06 EDT (Wed, 21 Oct 2009)
New Revision: 57047
URL: http://svn.boost.org/trac/boost/changeset/57047

Log:
specialized stepper for c-style arrays
Added:
   sandbox/odeint/libs/numeric/odeint/examples/lorenz_carray.cpp   (contents, props changed)
Text files modified: 
   sandbox/odeint/boost/numeric/odeint/euler.hpp |    28 +++++++++++++++++++++++++++-            
   1 files changed, 27 insertions(+), 1 deletions(-)

Modified: sandbox/odeint/boost/numeric/odeint/euler.hpp
==============================================================================
--- sandbox/odeint/boost/numeric/odeint/euler.hpp	(original)
+++ sandbox/odeint/boost/numeric/odeint/euler.hpp	2009-10-21 14:02:06 EDT (Wed, 21 Oct 2009)
@@ -74,12 +74,38 @@
     };
 
 
+    /* Euler stepper implementation that works with c-style arrays T* */
+    template< class T>
+    class ode_step_euler<T*>
+    {
+	T* dxdt;
+	size_t current_size;
+
+    private:
+	void resize( size_t N )
+	{
+	    if( dxdt != NULL ) delete[] dxdt;
+	    dxdt = new T[N];
+	    current_size = N;
+	}
+
+    public:
+	ode_step_euler() :dxdt( NULL ) , current_size( 0 ) {}
+
+	template< class DynamicalSystem , class TimeType>
+	void next_step( DynamicalSystem system , T* x , size_t N , TimeType t , TimeType dt )
+	{
+	    if( current_size != N ) resize(N);
+	    detail::euler_imp( system , x , x+N , dxdt , dt , t );
+	}
+    };
+
 /* ToDo:
    Write stepper for
    * fixed size systems
    * array<T>
    * system( T* , T* , T )
- */
+*/
 
 
 } // namespace odeint

Added: sandbox/odeint/libs/numeric/odeint/examples/lorenz_carray.cpp
==============================================================================
--- (empty file)
+++ sandbox/odeint/libs/numeric/odeint/examples/lorenz_carray.cpp	2009-10-21 14:02:06 EDT (Wed, 21 Oct 2009)
@@ -0,0 +1,66 @@
+/* Boost numeric/odeint/examples/lorenz.cpp
+ 
+ Copyright 2009 Karsten Ahnert
+
+ Shows, the usage of odeint, and integrates the Lorenz equations,
+ a deterministic chaotic system. In this version, the system state
+ is represented by a c-style double[3] array. The Lorenz system is
+ defined as
+
+ dx/dt = sigma * ( x - y)
+ dy/dt = R*x - y - x*z
+ dz/dt = x*y - b*z
+
+ with sigma = 10, r=28, b = 8/3
+
+ 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/numeric/odeint.hpp>
+
+#define tab "\t"
+
+using namespace std;
+using namespace boost::numeric::odeint;
+
+const double sigma = 10.0;
+const double R = 28.0;
+const double b = 8.0 / 3.0;
+
+const double dt = 0.01;
+const size_t olen = 10000;
+
+void lorenz( double* x , double* dxdt , double t )
+{
+    dxdt[0] = sigma * ( x[1] - x[0] );
+    dxdt[1] = R * x[0] - x[1] - x[0] * x[2];
+    dxdt[2] = x[0]*x[1] - b * x[2];
+}
+
+int main( int argc , char **argv )
+{
+    double x[3];
+    x[0] = 1.0;
+    x[1] = 0.0;
+    x[2] = 0.0;
+
+    ode_step_euler< double* > euler;
+
+    double t = 0.0;
+    for( size_t oi=0 ; oi<olen ; ++oi,t+=dt )
+    {
+	cout << t << tab << x[0] << tab << x[1] << tab << x[2] << endl;
+	euler.next_step( lorenz , x , 3, t , dt );
+    }
+
+    return 0;
+}
+
+/*
+  Compile with
+  g++ -Wall -I../../../../ lorenz_carray.cpp
+*/