hi
what is the best way to find fractional variables in the node realxation, and variables already fixed to integer values , in the branch callback.

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srinivas tamvada
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#DecisionOptimization

To start, you can call getUB() or getUBs() and getLB() or getLBs() to get the upper and lower bounds of the integer variables. I believe that variables CPLEX has fixed will have lower bound = upper bound. You can then call getValue() or getValues() to get the values of all remaining integer variables, and check whether their fractional parts are > epsilon and less than 1 - epsilon, where epsilon is the integrality tolerance.

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Paul Rubin
Professor Emeritus
Michigan State University
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hi Prof Rubin
thank you for the note.

method getFeasibilities () seems to be useful for finding variables that are fractional

but to find variables that are fixed to an integer value already, by going thruough all the varaibles and finding their UB and LB seems expensive. Is there a faster way ?

------------------------------
srinivas tamvada
------------------------------

Original Message:
Sent: Sun August 23, 2020 04:25 PM
From: Paul Rubin
Subject: finding fractional variables in the branch callback

To start, you can call getUB() or getUBs() and getLB() or getLBs() to get the upper and lower bounds of the integer variables. I believe that variables CPLEX has fixed will have lower bound = upper bound. You can then call getValue() or getValues() to get the values of all remaining integer variables, and check whether their fractional parts are > epsilon and less than 1 - epsilon, where epsilon is the integrality tolerance.

------------------------------
Paul Rubin
Professor Emeritus
Michigan State University
------------------------------

Yes, you can use node user data to keep track of the unfixed variables and then only check those variables.

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Daniel Junglas
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Original Message:
Sent: Sun August 23, 2020 05:34 PM
From: srinivas tamvada
Subject: finding fractional variables in the branch callback

hi Prof Rubin
thank you for the note.

method getFeasibilities () seems to be useful for finding variables that are fractional

but to find variables that are fixed to an integer value already, by going thruough all the varaibles and finding their UB and LB seems expensive. Is there a faster way ?

------------------------------
srinivas tamvada
------------------------------


Original Message:
Sent: Sun August 23, 2020 04:25 PM
From: Paul Rubin
Subject: finding fractional variables in the branch callback

To start, you can call getUB() or getUBs() and getLB() or getLBs() to get the upper and lower bounds of the integer variables. I believe that variables CPLEX has fixed will have lower bound = upper bound. You can then call getValue() or getValues() to get the values of all remaining integer variables, and check whether their fractional parts are > epsilon and less than 1 - epsilon, where epsilon is the integrality tolerance.

------------------------------
Paul Rubin
Professor Emeritus
Michigan State University