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David Cumin wrote:
>
> Andrew,
>
> Quick question ? the attached cellml file runs perfectly well in COR
> but throws errors in PCEnv. Any idea why?
>
Hi David,

I'm not sure about COR, but PCEnv only allows you to write derivatives
with respect to a single variable, which causes that variable to be
treated globally as 'the variable of integration' which is known at each
time-step. You have an equation:
<apply id="ddummy-eqn">
<eq/>
<apply>
<diff/>
<bvar>
<ci>time</ci>
</bvar>
<ci>dummy</ci>
</apply>
<cn cellml:units="dimensionless">1</cn>
</apply>
(I added the id to help identify the equations as this is displayed in
error messages - it is very useful to have this as it makes it easier to
understand the messages PCEnv writes out).

where time is connected to beattime, but you also have:
<apply id="beattime-eqn">
<eq/>
<ci>beattime</ci>
<apply>
<minus/>
<ci>realtime</ci>
<apply>
<times/>
<apply>
<floor/>
<apply>
<divide/>
<ci>realtime</ci>
<ci>HR</ci>
</apply>
</apply>
<ci>HR</ci>
</apply>
</apply>
</apply>

and you have further equations which take derivatives with respect to
realtime (and HR is a constant). The overconstrained error occurs
because in the above equation, beattime and realtime have been used as a
bvar for a diff operator, and so are treated as known at each time step,
while HR is a constant, and therefore, CCGS treats the above equation as
making the system overconstrained.

Best regards,
Andrew

> Thanks and regards,
>
> David Cumin
>
> PhD Student
>
> Department of Anaesthesiology / Bioengineering
>
> University of Auckland
>
> Ph: +64 9 373 7599 ext 85948
>

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• [cellml-dev] COR works, PCEnv not - I'm so confused, Andrew Miller, 02/26/2008

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