division by zero problem

Page Start Prev 1 Next End

- Subscribe

division by zero problem

#5241 Permalink

division by zero problem

Nov-12-14 22:33:06

Hello,

i just wrote a simple program as follows:

Code:


model tmp

  parameter Real x(fixed = false);

  parameter Real y = 1 / x;

initial equation

  x = 2;

equation

end tmp;

when i run this program i get the following error:
division by zero at time 0, (a=1) / (b=0), where divisor b expression is: x

i slightly modified the above code as follows:

Code:


model tmp

  parameter Real x(fixed = false);

  parameter Real y(fixed=false);

initial equation

  x = 2;

  y = 1 / x;

equation

end tmp;

and the error did not appear anymore.

could you please explain me, why this happens?

Thanks,
Arvin

arvin_ttl: 23 Posts; Thank you [ 0 ]

#5276 Permalink

Re: division by zero problem

Nov-25-14 15:38:04

Hi,

It seems that in the first code, x is unevaluated when the code reaches y=1/x. And perhaps 0 is used as a default value for x.

In the second code, the value 2 is already assigned to x when the code reaches y=1/x.

Gregory

ggtlse: 14 Posts; Thank you [ 1 ]

#5277 Permalink

Re: division by zero problem

Nov-25-14 18:14:06

Thanks for your answer Gregory

So you mean that first equations in the parameter declaration are evaluated and then initial equations are solved?

,Arvin

arvin_ttl: 23 Posts; Thank you [ 0 ]

#5278 Permalink

Re: division by zero problem

Nov-26-14 08:04:49

I suppose it since I just begin with this language.

Also 'parameter' seems to be a keyword reserved for constants.

What do you want to do with this code ?