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pythonpython-3.xcplexdocplex

how to define an indicator constraint in docplex python API?

I want to model an integer programming example with docplex in python. for an indicator constraint I have this equation (X is a binary variable):

equation

I wrote this code :

for i1,i2,i3 in P:
    mdl.add_indicator_constraints(x[(i,j,k)] for i,j,k in ijk if i==i1 and j==i2 and k==i3)==0

I don't know if I am using the right command for defining this indicator. when I run the program I get this error:

    cpx_indvars.append(logct.binary_var.safe_index)

AttributeError: 'Var' object has no attribute 'binary_var'
Solution

  • Your constraint does not look like and indicator constraint. An indicator constraint looks either like "if x=1 then ..." or "if x=0 then ..." where x is a binary variable. There seems to be no "then" part in your constraint.

    In case you just want to fix the variable to 0 then you don't have to use an indicator constraint. Just add a regular constraint:

    mld.add_linear_constraints(x[(i,j,k)] == 0 for i,j,k in ijk if i==i1 and j==i2 and k==i3)