[AMPL 24629] integer infeasible

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1

Hi everyone, thanks for your help,

I am just been introduced to AMPL programming and I don’t know what is the problem of a constraint that gives a which is in the iis of the problem I am trying to solve.

The constraint is the following:

subject to EACH_RESOURCE {k in K}:
1 = sum{j in J} x[k,j];

It is used to restric each resource to be placed just in one area

Definitions are as follows:
set K;
#resources availables

set J;
#centers for resource placement

var x {k in K, j in J} binary;
#resource k is placed at j

The result of cplex solver is the follwing:
option iis_table ’
0 non not in the iis
1 low at lower bound
2 fix fixed
3 upp at upper bound
4 mem member
5 pmem possible member
6 plow possibly at lower bound
7 pupp possibly at upper bound
8 bug
';
ampl: display EACH_RESOURCE.iis;
EACH_RESOURCE.iis [*] :=
K1 non
K3 mem
K4 non
;

And on the .dat file:

set K:= K1 K2 K3 K4;

set J:= J1 J2 J3 J4;

I know that my knowledge is not the best, since I am a student at a phinal project, but I am really stuck with the modeling and I would appreciate some help.

2

For the variables, constraints, and data that you give, there are feasible solutions. For example, you could set x[“K1”,“J1”] = x[“K2”,“J1”] = x[“K3”,“J1”] = x[“K4”,“J1”] = 1 and all the variables = 0. But an IIS only exists for an problem that has no feasible solution. Are you showing only part of your model? To get help, post the complete model and data.