RE: [AMPL 13879] infeasible, no Basis, no primary variables returned

[Robert Fourer]

The important message is "Gurobi 7.0.0: infeasible" which tells you that there are no feasible solutions to your constraints. You can ignore "No basis" and "No primal variables returned" which are just side-effects of the no feasible solution condition. (Since Gurobi determined that no feasible solution was possible, it couldn't return any basis statuses or primal variable values.)

AMPL also reports an error with one of your constraints:

=======
ampl: model anke.mod;

../anke.mod, line 64 (offset 2893):
d is undefined
context: subject to TageszentrumKundeVerknuepfung{b in B}: sum{i in B} >>> V[i,b,d] <<< = sum{q in Qb[b]} Omega[d,q]* H[b,q,Phi[d]];

../anke.mod, line 64 (offset 2919):
d is undefined
context: subject to TageszentrumKundeVerknuepfung{b in B}: sum{i in B} V[i,b,d]= sum{q in Qb[b]} >>> Omega[d,q] <<< * H[b,q,Phi[d]];

../anke.mod, line 64 (offset 2931):
d is not defined
context: subject to TageszentrumKundeVerknuepfung{b in B}: sum{i in B} V[i,b,d]= sum{q in Qb[b]} Omega[d,q]* >>> H[b,q,Phi[d] <<< ];
=======

You use the "d" in this constraint but it is not defined in the scope of the constraint; maybe you meant to index the constraint over {b in B, d in D}. Due to this error, these constraints were not included in the problem sent to the solver.

Bob Fourer
am...@googlegroups.com

=======

From: am...@googlegroups.com [mailto:am...@googlegroups.com] On Behalf Of Anke
Sent: Wednesday, April 19, 2017 3:51 AM
To: AMPL Modeling Language
Subject: [AMPL 13879] infeasible, no Basis, no primary variables returned

may i kindly ask you to help me with this complex model?
AMPL(Gurobi) is telling me after solving that this is infeasible as there is no basis and no primary variables returned.

What does that mean? Does this simply mean that because of my data the Serviceplan i am trying to create is infeasible?

If not what could be wrong with the variables?

[Robert Fourer]

If there is not any error in the data, the infeasibility may be due to an error in formulating the constraints. To track down the error it may help to look at an Irreducible Infeasible Subset of the constraints and variable bounds, as explained in

https://groups.google.com/d/msg/ampl/o8aNfwpoBAc/D46d6cfICQAJ

Bob Fourer
am...@googlegroups.com

=======

From: am...@googlegroups.com [mailto:am...@googlegroups.com] On Behalf Of Anke
Sent: Monday, April 24, 2017 3:02 PM
To: AMPL Modeling Language

Subject: RE: [AMPL 13927] infeasible, no Basis, no primary variables returned

Thank you a lot Bob.
But by the way...any idea why it ist infeasible? I cannot find something in the data

[Robert Fourer]

There is an IIS option for Gurobi, too. See iisfind and iismethod in the Parameter Reference section of the AMPL-Gurobi Guide: http://www.gurobi.com/documentation/7.0/ampl-gurobi/parameters.html.

Bob Fourer
am...@googlegroups.com

=======

From: am...@googlegroups.com [mailto:am...@googlegroups.com] On Behalf Of Anke
Sent: Wednesday, April 26, 2017 4:09 AM
To: AMPL Modeling Language

Subject: [AMPL 13931] Re: infeasible, no Basis, no primary variables returned

Ok i need to check this, but actually i used Gurobi to solve the model as student version of cplex is only covering 300 variables. which is too less for the model.
Are there any options in gurobi?

[Robert Fourer]

To get more help with this problem, post the complete text of the messages that you received from the Gurobi solver.

Bob Fourer
am...@googlegroups.com

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From: am...@googlegroups.com [mailto:am...@googlegroups.com] On Behalf Of Anke
Sent: Wednesday, April 26, 2017 5:53 PM
To: AMPL Modeling Language

Subject: [AMPL 13939] Re: infeasible, no Basis, no primary variables returned

inbetween i found the coinstants which made it unfeasible. I hab to change the Parameter Tauday and Tauweek to 1 as they were too low.
Now the Problem is feasible but there is still no basis and no primary variables returned. Still not what i want. What else could be wrong?

[Robert Fourer]

This is also explained in

https://groups.google.com/d/msg/ampl/o8aNfwpoBAc/D46d6cfICQAJ

right at the end of the message.

Bob Fourer
am...@googlegroups.com

=======

From: am...@googlegroups.com [mailto:am...@googlegroups.com] On Behalf Of Anke
Sent: Wednesday, April 26, 2017 6:13 PM
To: AMPL Modeling Language

Subject: [AMPL 13940] Re: infeasible, no Basis, no primary variables returned

and by the way is there an pption to Show the iis constraints explicit?.
How is the command?

[Robert Fourer]

Since your problem is infeasible, you can ignore the "no basis" and "no variables" messages -- they do not indicate that anything is wrong.

Except for specifying gurobi_options instead of cplex_options, you should use exactly the instructions given in the link previously posted. They work just as well for Gurobi as for CPLEX. In particular to see the names of all the variables and constraints in the IIS, use the commands

display {i in 1.._ncons: _con[i].iis <> 'non'} (_conname[i],_con[i].iis);
display {j in 1.._nvars: _var[j].iis <> 'non'} (_varname[j],_var[j].iis);

To see explicitly each of the constraints in the IIS, use the command

for {i in 1.._ncons: _con[i].iis <> 'non'} expand _con[i];

The IIS gives you a relatively small subset of constraints and variable bounds that already have no feasible solution. This information may help you to locate the cause of the infeasibility. However, since you are the expert on your model, it is up to you to study the model and the IIS and to figure out *why* your constraints have no feasible solution.

Bob Fourer
am...@googlegroups.com

=======

From: am...@googlegroups.com [mailto:am...@googlegroups.com] On Behalf Of Anke

Sent: Friday, April 28, 2017 2:37 AM
To: AMPL Modeling Language

Cc: 4...@ampl.com
Subject: Re: [AMPL 13952] Re: infeasible, no Basis, no primary variables returned

This is the full message
Gurobi 7.0.0 infeasible
returning an IIS on 107 contraints
no basis
no Primary variabled retruned
Suffix IIS symbolic out
Option iss table `\
0 non
1 low
2 fix
3 up
4 nem
5 pnem
6 plow
7 pupp
8 bug
;

as i am not using cplex the explanations in the other link doesn`t help me that much..
Can you tell me which 107 constraints cannot work? and due to that which of my data cannot work? How do I need to change the data that the the model is feasible?