Iason Liagkas
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Recent activity by Iason Liagkas-
Log file does not show the gap
AnsweredHello guys you can ignore my previous post, the time was for parameter setting. My question is now on this run why don't I get the percentile gap per time on the log? I see the below Is there anyt...
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Variable bound
AnsweredHello guys, I have an optimization model and It is feasible. It has one variable bound though that if I remove it it makes the problem infeasible without making any other change. Does that make sen...
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infeasible model has objective function value
Awaiting user inputI am solving a model sequentially and it is feasible in the first iteration. In the second iteration the model becomes infeasible but I get an objective function value when I run subproblem.objVal....
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model write contains duplicate constraints and variables
AnsweredHello guys, I have a model and when I do model.write() the created file contains the binary variables plenty of times and a constraint 2 times. I do not create the variables or the constraint 2 tim...
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Do Variable Bounds create constraints in the solver?
AnsweredHello guys, I am working on the Benders algorithm. I am wondering if I have a problem with a variable x with an upper bound of 1. Does that create a constraint of x<=1 on the solver? Because if tha...
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extreme rays are all 0
Awaiting user inputHello guys, I have a problem that all its extreme rays are 0. Do you have any idea of what could be the case? Can we check if there are numerical issues with a problem solution that produce this re...
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large matrix coefficient meaning
AnsweredHello guys, What does a large matrix coefficient cause to our problem? can we say that the results will be very sensitive to coefficient values? what would be the consequences of this situation? Ki...
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obtain variable values from a program inside a function
AnsweredHello guys, I have created a function named SP_define and inside I have formed an optimization model named SPmodel = gp.Model('SP'). On the final line of the function, I have written: return SPmode...
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Getting the dual variable values when the model status is 4(INF_OR_UNBD)
AnsweredHello guys, I am running the benders algo, When my subproblem is feasible I am using the following line to get the dual variable value: gp.quicksum(BigM*deltars2kE[r,s,k]*subproblem.getConstrByNam...
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Forming a model inside a function
AnsweredHello Guys, I am trying to code a Python function to build a model inside. The name of the function is SP_define. The function returns the model only. I run the below code. When I print the model I...