Can I decouple a time-consuming Simulink function block or Function-call subsystem from Simulink fundamental sample time?

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Yingao Zhang
Yingao Zhang 2021-5-18
编辑： Yingao Zhang 2021-6-20
I have a Simulink model performing fixed-step control algorithm in 0.1 second fundamental sample time. However when the control logic enters a certain mode, I want to carry out a time consuming calculation that will run in 100% cpu time for approximately 2 seconds. If I place this computation under any Simulink time step, it will definitely make the model overrun at that certain time step. But the result from this time consuming computation will first be needed when the normal 0.1 second fixed-step control algorithm executes for 1 minute. Can I place this time consuming computation in a Simulink function block or Function-call subsystem and decouple it from the Simulink solver? Such that the result from this time consuming computation will be placed in a data store whenever it finishes, but reading of that data store by the main algorithm will first occur after one minute? The main algorithm execution of once every 0.1 second will thus not be clogged by this time consuming computation module.
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Jonas
Jonas 2021-5-18
There is no such thing as model overrun in simulation mode. Your computer just calculates what it needs to calculate, if it is computationally heavy it just takes longer.
Or are you talking about code generation? I would think not since you say 'Simulink solver'.
Yingao Zhang
Yingao Zhang 2021-5-18
Exactly, Jonas, I'm using Simulink for embedded algorithm development. And this will be deployed for real-time applications. Additionally, overrun can still be observed if one turns on simulation pacing, Simulink will notify you on the bottom left corner that the target pacing cannot be achieved when that time-consuming computation module activates. :)

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Jonas
Jonas 2021-5-18
You need a background task to put those heavy calculations inside.
Depends heavily on your target if it will be easy or hard to implement the background task with code generation. Some hardware support packages may support it.
I generate code with two real-time tasks in Simulink, and then manually attach each task to either a real-time timer or an infinite background while-loop in code.
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Yingao Zhang
Yingao Zhang 2021-5-18
Thanks, Jonas. I'll tentatively accept your idea. Since I'm working with a model with 10k+ individuals blocks and 10min+ code generation time with 6 parallel cores enabled, refactoring every Simulink scheduled algorithm captured by ModelName.step() under rt_OneStep() is not a light work. Additionally, I have already used export function call subsystems several times in the model, however they are all interfacing with external I/O, instead of with Simulink generated functionalities internally. I believe there should be some mechanism from Simulink internally that enables calling function call subsystem under a different thread or a different task being preemptible by periodical tasks with higher sample rates.
Yingao Zhang
Yingao Zhang 2021-5-25
编辑：Yingao Zhang 2021-6-20
Dear, Jonas, I think your hint "hardware support packages" in your answer helps me solve the problem. I actually discovered these 3 blocks that can achieve the modeling goal with some adaption:
I hope that in the further, the C++ 11 std::thread, std::async ,etc. could be complemented as the fourth to the above three.

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