You cannot have an expression on the left hand side in algorithm sections! Only:

// component reference on the left hand side is fine

a := some_expression;

// this is not allowed by the grammar:

a + b := c:

In you case in while you have:

x ^ 2 + y ^ 2 := L ^ 2;

which is not allowed, you can write that as:

x := sqrt(L ^ 2 -  y ^ 2);

You can use any algorithm section in a function with no issues, including loops.

Hello Adrpo,
Thank you so much for your help.

Now, the model looks like the one attached below.
By the way, I still get the following error message:

[1] 11:11:43 Translation Error
Internal error BackendDAE.adjacencyRowEnhanced failed for eqn:
algorithm
  while F < 20.0 loop
    x := sqrt(L ^ 2.0 - y ^ 2.0);
    vx := (-y) * vy / sqrt(L ^ 2.0 - y ^ 2.0);
  end while;

[2] 11:11:43 Translation Error
Internal error BackendDAEUtil.getAdjacencyMatrixEnhancedScalar failed

[3] 11:11:43 Translation Error
Internal error - IndexReduction.dynamicStateSelectionWork failed!

I think my problem is due to the fact that the model is formed by DAEs.
If I include this in a function, am I still able to simulate it? Can I insert DAEs inside a function?

I am new in OpenModelica and I am sure my questions may seem silly so thank you so much for your help!

Gabry


model Pendulum
  parameter Real m = 1, g = 9.81, L = 0.5;
  Real F;
  Real x(start = 0.5, fixed = true), y(start = 0, fixed = true);
  Real vx, vy;

equation
  m * der(vx) = -x / L * F;
  m * der(vy) = (-y / L * F) - m * g;
  der(x) = vx;
  der(y) = vy;


algorithm
while F<20 loop

x := sqrt(L ^ 2 -  y ^ 2); 
   
end while;
 
end Pendulum;

Hi Ardpo,

basically what I want to implement in my code is the following logic:

when a variable reaches a determined value, then stop the simulation.
In the case in the example is when F=20 then stop the simulation.

So, I thought to model this concept using a while loop. While the F is below 20, then calculate x.

This is the way I model the problem in Matlab.

By the way, maybe in Modelica there is another way to do this without using a loop. Do you know if there is another way?

Thank you so much!

Gabry

Hi Adrpo,

First of all, sorry for all the messages I sent!
In the meantime, I made some progress and I managed to solve my issue using as follows:

equation
  m * der(vx) = -x / L * F;
  m * der(vy) = (-y / L * F) - m * g;
  der(x) = vx;
  der(y) = vy;
  x ^ 2 + y ^ 2 = L ^ 2;
  algorithm
  when F>20 then
  terminate("end");
  end when;

Using this algorithm inside my model I am able to stop the simulation when the condition is reached.

I just have one last question: Do you know if there is a way to calculate the time (wall-clock time) of the simulation? I need something similar to the function tic/toc in Matlab. By the way, something more general could be useful too. In fact, I need to know the tot time of the simulation starting from the first line of the model to the last one (I don't need the time of a particular part of the code).

Thank you so much again, Gabry

See:
https://www.openmodelica.org/doc/OpenMo … filer.html

Gabri wrote:

basically what I want to implement in my code is the following logic:

when a variable reaches a determined value, then stop the simulation.
In the case in the example is when F=20 then stop the simulation.

model M

  Real F = ...;

equation

  when F < 20 then

    terminate("F successfully reached <20");

  end when;

end M;

https://build.openmodelica.org/Documentation/ModelicaReference.Operators.%27terminate()%27.html

Hi Adrpo,

Thanks for the link. With this, now I am able to measure the simulation time but I am not able to measure the time required for the initialization of the variables in my DAE system.
Do you know if there is a way to do this?
Thank you so much!
Gabry

There is a simulation flag (https://openmodelica.org/doc/OpenModeli … lags.html) for that:

$ ./M -lv LOG_STATS

LOG_SUCCESS       | info    | The initialization finished successfully without homotopy method.

LOG_STATS         | info    | ### STATISTICS ###

|                 | |       | | timer

|                 | |       | | |  0.000294868s          reading init.xml

|                 | |       | | |   4.1369e-05s          reading info.xml

|                 | |       | | |  0.000147484s [  3.6%] pre-initialization

|                 | |       | | |   7.5327e-05s [  1.8%] initialization

|                 | |       | | |    5.107e-06s [  0.1%] steps

|                 | |       | | |    2.627e-05s [  0.6%] solver (excl. callbacks)

|                 | |       | | |  0.000536842s [ 13.1%] creating output-file

|                 | |       | | |            0s [  0.0%] event-handling

|                 | |       | | |  0.000217657s [  5.3%] overhead

|                 | |       | | |   0.00303205s [ 73.8%] simulation

|                 | |       | | |   0.00417501s [100.0%] total

|                 | |       | | events

|                 | |       | | |     0 state events

|                 | |       | | |     0 time events

|                 | |       | | solver: euler

|                 | |       | | |   500 steps taken

|                 | |       | | |   500 calls of functionODE

|                 | |       | | |     0 evaluations of jacobian

|                 | |       | | |     0 error test failures

|                 | |       | | |     0 convergence test failures

|                 | |       | | | 0s time of jacobian evaluation

LOG_SUCCESS       | info    | The simulation finished successfully.

Thank you so much sjoelund.se,
I have already tried to use this flag but the time I get back is a way smaller than the real one (clock-wall).

In fact, using an external timer I found that my total time (starting when I press the "simulate" button to the end of the simulation) is, more or less, 4 mins and the time I obtain bt the function is 5.86 seconds.

Do you know why I have this huge difference?

Thank you again, Gabry