Add simple euler to odeint test

src/test_boost_odeint.cpp

@@ -3,6 +3,7 @@
 
 #include <boost/numeric/odeint/stepper/controlled_runge_kutta.hpp>
 #include <boost/numeric/odeint/stepper/runge_kutta_cash_karp54.hpp>
+#include <boost/numeric/odeint/stepper/euler.hpp>
 
 /* The type of container used to hold the state vector */
 typedef std::vector< double > state_type;
@@ -29,7 +30,7 @@ int main(int /* argc */ , char** /* argv */ )
     state_type x0 = {1.0, 0.0}; // Starting point
 
     // First integrate, adaptively, until you get as close to the end as you can
-    double t = 0, dt = 0.001, tmax = 100.0;
+    double t = 0, dt = 0.001, tmax = 10.0;
     auto write = [&]() { std::cout << t << " " << x0[0] << "," << x0[1] << std::endl;  };
     for (auto i = 0; t < tmax; ++i){
         if (t + dt > tmax) { break; }
@@ -41,4 +42,23 @@ int main(int /* argc */ , char** /* argv */ )
     double dtfinal = tmax - t;
     auto status = controlled_stepper.try_step(xprime, x0, t, dtfinal);
     write();
+
+    {
+        state_type x0 = { 1.0, 0.0 }; // Starting point
+        euler<state_type> eul;
+
+        double t = 0, dt = 0.01, tmax = 10.0;
+        auto write = [&]() { std::cout << t << " " << x0[0] << "," << x0[1] << std::endl;  };
+        for (auto i = 0; t < tmax; ++i) {
+            if (t + dt > tmax) { break; }
+            write();
+            eul.do_step(xprime, x0, t, dt);
+            t += dt;
+        }
+        write();
+        double dtfinal = tmax - t;
+        eul.do_step(xprime, x0, t, dt);
+        write();
+    }
+
 }
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