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[cellml-discussion] how to units make a difference to simulation


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  • From: alan.garny at dpag.ox.ac.uk (Alan Garny)
  • Subject: [cellml-discussion] how to units make a difference to simulation
  • Date: Tue, 7 Aug 2007 02:56:28 +0100
> > Anyway, the view we have now taken in Oxford is that models
> shouldn't have
> > any problem related to units.
> I absolutely agree that models should not have units problems. The
> problem is that many of them do, and, speaking for myself, I do not
> have
> the skills or the knowledge to know how to rearrange someone else's
> model to fix the units. Especially with big models, it can just get
> too
> complex. I'd like to see unit checking in PCEnv, but I wouldn't want a
> model with bad units to not run - I'd just want error messages telling
> me there is a problem.

That's exactly the way COR works. It will just generate a warning wherever
there is a problem related to units. Doing mainly maintenance work on COR, I
haven't gone very far in the warning message COR generates. In other words,
it will just tell the user there is a problem, while it could easily tell
you where exactly the problem is.

> > The idea is, therefore, to have models that have no unit issues *at
> all*. I
> > appreciate that this may seem a bit restrictive, but we have had so
> many
> > issues with units over the years that we believe it will be worth it
> in the
> > long term.
>
> This would be great. I think it needs to start with the model authors
> though, which is where standards such as MIRIAM come in.

Yes and you will realise that some models authors have made mistake
themselves. We came across such a model back in Oxford where units were
simply wrong and there is nothing we could do about that. Pretty bad indeed,
but nothing we can help unfortunately.

> > Alternatively, we could have the software doing units conversion for
> the
> > user... but that's another issue... and I understand that some are
> against
> > that idea.
> Again, this is a feature that it would be useful to be able to turn on
> and off. However I think in most cases the software will not be smart
> enough to figure out what the units should be.

Wrong, it can easily be done. I was about to work on that in COR when Peter
got me to move over to "PCEnv". Check also JSim, it does units conversion
and, as far as I know and can tell, it does a pretty good job at it.

Alan.



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