Evaluation of recursive functions during instantiation

[Christoph Höger]

Hi all,

this model:

model Fak

  function f 
    input Real x;
    output Real y = if x < 1.0 then 1.0 else x * f(x-1);
  end f;

  Real x;
  Real y = 24;
  equation
  
  f(x) = y;

end Fak;

crashes during instantiation with a stackoverflow. Just two thoughts:

• It seems like a bad idea in general to evaluate (recursive) functions at that time
• At least omc should catch the stackoverflow and discard the attempted optimization IMO.

[Christoph Höger]

Stacktrace

[Martin Sjölund]

It is not trying to do any optimisation as far as I know. It for sure did not try to evaluate the function.
It is just some weird dependency analysis gone haywire if the output binding of the function is recursive. The following works fine:

model Fak

  function f 
    input Real x;
    output Real y;
  algorithm
    y := if x < 1.0 then 1.0 else x * f(x-1);
  end f;

  Real x;
  Real y = 24;
  equation
  
  f(x) = y;

end Fak;

[Martin Sjölund]

Postponed until 1.9.1

[Martin Sjölund]

This ticket was not closed for 1.9.1, which has now been released. It was batch modified for milestone 1.9.2 (but maybe an empty milestone was more appropriate; feel free to change it).

[Martin Sjölund]

Milestone changed to 1.9.3 since 1.9.2 was released.

[Martin Sjölund]

Moved to new milestone 1.9.4

[Martin Sjölund]

Milestone pushed to 1.9.5

[Martin Sjölund]

Milestone renamed

[Martin Sjölund]

Ticket retargeted after milestone closed

[Martin Sjölund]

Milestone moved to 1.12.0 due to 1.11.0 already being released.

[Francesco Casella]

The milestone of this ticket has been reassigned to "Future".

If you think the issue is still valid and relevant for you, please select milestone 1.13.0 for back-end, code generation and run-time issues, or 2.0.0 for front-end issues.

If you are aware that the problem is no longer present, please select the milestone corresponding to the version of OMC you used to check that, and set the status to "worksforme".

In both cases, a short informative comment would be welcome.

[Per Östlund]

Works fine with the new frontend.