Simulink running on multiple cores (or not) for a given model

Question

I have a huge simulink model that takes about ~1 hour to execute. In my computer (HP Z210), the execution makes the computer use all cpu cores at 100%. What is intriguing me is that the same model running on my colleague computer (Dell precision T3600) uses ~50% of the cpu "power" (some cores at 100% and some cores remain idle).

My questions is:

1. I always thought Simulink runs in a single core. I´m not using parrallel computer toolbox or any other toolbox. I´m only using Matlab and Simulink licenses.
2. Why the execution in my computer is different from my colleague? Does it have anything to do with hyper-threading?

Answer 1

While simulink itself is single threaded in executing a single model, a block itself might be multi threaded. For example a simulink block executing matrix multiplication will use the multi threaded implementation which is also used by matlab.

Answer 2

Simnulink is definitely a single-threaded application. The exception to this is if you are using Rapid Accelerator mode and have multiple cores available, then the standalone executable runs on a separate core. See How Acceleration Modes Work for more details.

If you are running multiple simulations, then you can distribute these across multiple cores with the Parallel Computing Toolbox, or even multiple workers (machines) with the MATLAB Distributed Computing Server. However, this is for multiple simulations of a model (e.g. a Monte-Carlo simulation), not for breaking uo a large model in several chunks (currently not possible as far as I know). see Run Parallel Simulations for more details.

Not sure why the execution would be different from one machine to the other. Are you both using the same release of MATLAB? Same O/S? There are so many things that could be different. With regards to speeding up the execution of model, you could try running the model in accelerated mode, using the Simulink profiler to see where the bottlenecks are, changing some of the solver settings (e.g. variable-step vs fixed-step), etc...

Answer 3

If your model can be built with Simulink Coder, you can use xMOD software (www.xmodsoftware.com) to execute your model in multi-core (subsystem per thread basis, with a dedicated solver and step-size for each subsystem).