How can I set branch priority into a variable?

[zuhal kartal]

Hi,

I wanna set the branch priority attribute one of my binary variables.

I tried to use this:

m.getVars()[h].BranchPriority = 9

However, I got this error message:

 
m.getVars()[h].BranchPriority = 9
TypeError: list indices must be integers, not list.

So, if anyone can help me, how can I set branch priority on a variable?

Thank you so much,
Zuhal

[Sonja Mars]

Hi,

What is "h"? The error message indicates that it is a list. It needs to be an integer, if you want to use it as an index for a list.

Additionally, if you are only interested in one variable, it might me more efficient to use the method getVarByName():
http://www.gurobi.com/documentation/6.5/refman/py_model_getvarbyname.html

Best regards,
Sonja


----
Dr. Sonja Mars
Gurobi Optimization - Technical Support

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[zuhal kartal]

Hi Sonja,

Firstly, thanks for the reply.

"h" is a binary variable. I defined "h" in the formulation:

h = []
for i in N:
    h.append(m.addVar(vtype=GRB.BINARY, name="h%s"))

And I want to give branch priority on my "h" variable which can be done in CPLEX like: 

m.setPriorityOrder(h,1,"UP")

Is there any way that I can make the same thing in GUROBI as well?

Regards,

Zuhal

[Sonja Mars]

Hi Zuhal,

So "h" is a list of Gurobi Variable objects. This cannot be used as index of a list.

There are a few ways to do exactly what you want in Gurobi. I give two examples:

First:

for h_var in h:
h_var.BranchPriority = 9



Second:

m.setAttr("BranchPriority", h, [9]*len(h))

assuming your want to set the Branch Priority to 9 for all h variables. Also see here for more details on setAttr: http://www.gurobi.com/documentation/6.5/refman/py_model_setattr.html

[zuhal kartal]

Thanks Sonja,

It is working right now:)

Zuhal.