infeasibility vector

GAMS
1

Hello,

I am trying to solve a model using cns and am getting the message

“Infeasible solution to square system. Convergence too slow”.

Is there a way to access the vector of error estimations for the model (either at the input point or at the last iteration) ? It could be helpful in order to understand which equations are problematic and why convergence does not occur.


Thank you in advance,

Joachim

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2

Joachim:



GAMS has a very convenient extension, namely .infeas. So you can use “display .infeas;”. The extension is described in the release notes http://www.gams.com/docs/release/release.htm.



Arne


\

Arne Stolbjerg Drud

ARKI Consulting & Development A/S

Bagsvaerdvej 246A, DK-2880 Bagsvaerd, Denmark

Phone: (+45) 44 49 03 23, Fax: (+45) 44 49 03 33, email: adrud@arki.dk



From: gamsworld@googlegroups.com [mailto:gamsworld@googlegroups.com] On Behalf Of joachim jarreau
Sent: Tuesday, November 12, 2013 7:24 PM
To: gamsworld@googlegroups.com
Subject: infeasibility vector



Hello,

I am trying to solve a model using cns and am getting the message

“Infeasible solution to square system. Convergence too slow”.

Is there a way to access the vector of error estimations for the model (either at the input point or at the last iteration) ? It could be helpful in order to understand which equations are problematic and why convergence does not occur.


Thank you in advance,

Joachim

–
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3

Reply-to: gamsworld@googlegroups.com

thanks very much Arne.

so .infeas returns the value of (right hand side - left hand side)?
not sure how the formula

x.infeas = - min(x.l-x.lo,x.lu-x.l,0);


applies when x is an equation.

I understand that there is no way to apply this to all equations of a model, except for writing the command for each equation?

best,

Joachim

On Wednesday, November 13, 2013 2:08:32 PM UTC+1, Arne Stolbjerg Drud wrote:

Joachim:



GAMS has a very convenient extension, namely .infeas. So you can use “display .infeas;”. The extension is described in the release notes http://www.gams.com/docs/release/release.htm.



Arne


\

Arne Stolbjerg Drud

ARKI Consulting & Development A/S

Bagsvaerdvej 246A, DK-2880 Bagsvaerd, Denmark

Phone: (+45) 44 49 03 23, Fax: (+45) 44 49 03 33, email: ad…@arki.dk



From: gams...@googlegroups.com [mailto:gams...@googlegroups.com] On Behalf Of joachim jarreau
Sent: Tuesday, November 12, 2013 7:24 PM
To: gams...@googlegroups.com
Subject: infeasibility vector



Hello,

I am trying to solve a model using cns and am getting the message

“Infeasible solution to square system. Convergence too slow”.

Is there a way to access the vector of error estimations for the model (either at the input point or at the last iteration) ? It could be helpful in order to understand which equations are problematic and why convergence does not occur.


Thank you in advance,

Joachim

–
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