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Not enough memory error

#1645  Permalink Top

Not enough memory error

Nov-11-11 07:46:05

Hi All,

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

Code:


model circuit

  Modelica.Electrical.Analog.Sources.SineVoltage V (V = 15, freqHz = 795.8);

  Modelica.Electrical.Analog.Lines.OLine 

    T (length = 100.0, r = 4, l = 3e-3, g = 1e-6, c = 0.015e-6, N = 4);

  Modelica.Electrical.Analog.Basic.Ground ground;

equation

  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
#1646  Permalink Top

Re: Not enough memory error

Nov-11-11 11:26:47

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.

#1664  Permalink Top

Re: Not enough memory error

Nov-14-11 06:11:06

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?

#1665  Permalink Top

Re: Not enough memory error

Nov-14-11 08:58:18

Hi,

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.

Cheers,
Adrian Pop/

#1666  Permalink Top

Re: Not enough memory error

Nov-14-11 09:22:32

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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