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Not enough memory error

Not enough memory error

Hi All,

I've been trying to do a very simple model of a transmission line, see below.


model circuit
  Modelica.Electrical.Analog.Sources.SineVoltage V (V = 15, freqHz = 795.8);
    T (length = 100.0, r = 4, l = 3e-3, g = 1e-6, c = 0.015e-6, N = 4);
  Modelica.Electrical.Analog.Basic.Ground ground;
  connect (ground.p, V.n);
  connect (V.p, T.p1);
  connect (T.p3, ground.p);
end circuit;

When I increase N to a number greater than 13, omc (1.8.0, r10397) fails and gives the following error:
returning NULL (not enough memory) from rml_major_collection!
returning NULL (not enough memory) from rml_older_alloc!
rml_prim_gcalloc failed to get 805306368 words
returning NULL (not enough memory) from rml_prim_gcalloc!
Segmentation fault

It also gobbles up all 16GB of memory before crashing. Has anyone seen a similar error before?

Edited by: aido - Nov-11-11 07:48:43

Re: Not enough memory error

Hi aido,

Thank you for reporting this, it turned out to be a small mistake in the compiler that caused it to allocate huge amounts of memory in some cases. I have fixed this in revision 10424.

Re: Not enough memory error

Hi perost,

I've tried it on r10484 this morning and it's working now. Thanks for fixing it so quickly!

I've noticed that omc doesn't scale well on this model and others. Here are the times taken to run the above model with different values of N:

N    Time (s)
16    6
32    11
64    37
128    302
256    4079

Do you know how to improve omc performance on large problems?

Re: Not enough memory error


Improving performance is always tricky as we have a lot of legacy code in the compiler.
Of course one of our goals is to improve performance, but it will take a while as the
priority now is on fully supporting Modelica Standard LIbrary (MSL) 3.1.

Adrian Pop/

Re: Not enough memory error

Hi Adrian,

Thanks for the info.

We are currently considering scaling up some of our lumped element models, so the performance issue will probably become a blocker for us.

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