Simulink algebraic loop error when using parsim

I have a model that runs fine in MATLAB R2020b with parsim, and with sim in 2021b. But when using parsim, I get the following error in R2021b:

simOut(1).ErrorMessage

ans =

'Error due to multiple causes.

Caused by:

'.../Engine_Actuators/Function' or the model referenced by it contains blocks that updates persistent or state variables while computing outputs and is not supported in an algebraic loop. The parent subsystem '.../Engine_Actuators' is in an algebraic loop with the following blocks.

'.../Engine_MARS_Core/Function' or the model referenced by it contains blocks that updates persistent or state variables while computing outputs and is not supported in an algebraic loop. The parent subsystem '.../Engine_MARS_Core' is in an algebraic loop with the following blocks.

'.../Engine_Sensors/Function' or the model referenced by it contains blocks that updates persistent or state variables while computing outputs and is not supported in an algebraic loop. The parent subsystem '.../Engine_Sensors' is in an algebraic loop with the following blocks.

Input ports (5) of '.../Engine_Actuators' are involved in the loop.

Input ports (3) of '.../Engine_MARS_Core' are involved in the loop.

Input ports (1) of '.../Engine_Sensors' are involved in the loop.

Input ports (1) of '.../Sensor_Latency' are involved in the loop.'

It's complaining about this part of the model. The 'Sensor Latency' contains unit delays for all signals. So not sure why the error is appearing, and why only when using parsim in R2021b

Answer 1

[Swaraj]

Hi Afzal,

Model References might have affected the execution order in this case. Model references act as nonvirtual blocks. The below link discusses how to display and control the execution order in a model:

https://in.mathworks.com/help/releases/R2021b/simulink/ug/controlling-and-displaying-the-sorted-order.html

To remove the algebraic loop, the below link is very helpful:

https://in.mathworks.com/help/releases/R2021b/simulink/ug/remove-algebraic-loops.html

Hope it helps!