Performance Problem in Simulink (why is it slower than matlab?)

I have compared Solutions to the same ODE in matlab and simulink. Simulink took 7.6 sec. while ode15s in matlab took 1.4 sec. to solve. What is the reason for this time difference? FYI: I used the same number of time steps in both cases. And simulink model was run from matlab, using 'sim' function.

[Akbar]

Matlab code:

      for i = 1:100
      [t{ind},X{ind}] = ode15s(func,0:.1:10,X0);
      end

Simulink code:

for i = 1:100
  simOut = sim(model_file,'SimulationMode','normal');
  outputs = simOut.get('yout');

    outI = outputs.get('X');
    t{ind} = outI.Values.Time;
    X{ind} = outI.Values.Data;
end

Answer 1

[Steven Lord]

Which solver did you use when you simulated your system? Did you leave the selection up to Simulink?

The ode15s solver in MATLAB is a stiff solver while ode45 is not. So if your simulation used ode45, to compare apples and apples you'd want to compare that with solving the system in MATLAB using ode45 (or switch both to use a stiff solver.)

[Akbar]

In simulink I used: "VariableStepAuto". I have just tried ode15s on both (with the same stepsize: 0.1) and still got a significant difference in time. Apart from that, simulink and ode45 have failed to solve the System correctly, it deviated from the true solution.

ode15s: 0.8488
ode45: 0.088538
simulink (normal): 13.2582