Gurobi OverflowError error

[Amogu Ukairo]

When I run the following code, Gurobi reports an OverflowError: value too large to convert to char message.

I resolved this by removing the arrow in the lanes items. Is this a 'normal' behavior and where can I learn more about it?

m = Model()

lanes = ['A→B', 'B→C', 'C→A', 'C→B']

carriers = ['hier', 'cony']

flows = m.addVars(l, c, vtype=GRB.CONTINUOUS, name = 'flow')

[Daniel Espinoza]

Hi Amogu

The issue is that all variable and constraint names are internally represented as regular chars; unfortunately the arrow is an extended character, and not representable as a regular char, thus the overflow.

In your case, m.addVars will create variables named 'flow[a,b]' where a is the string version if lanes, and b a string version of carriers, but the string version of lanes has that extended character in the middle.

If you use 

lanes = ['A->B', 'B->C', 'C->A', 'C->B']

instead, everything will work as expected.

Let me know if this is helpful.

Best

Daniel