[Help-glpk] Regarding understanding MIP output

[gaurav khanna]

Hi all,

I used glpsol to solve the linear relaxed version of a MIP problem ( all
variables in my problem are 0 or 1) and  output the solution using -o
flag. What I want  is to get all those variables which have been set to
either 0 or 1 as a part of the solution and do not have  a fractional
value. In the output file , I extracted all the column ids having value 0
or 1 and added these as a new set of constraints to the original MIP
problem by fixing the variables as 0 or 1 according to the relaxed
solution.


Thus,  this new MIP problem should surely be feasible right?

I did that but I found the new MIP problem to be infeasible. I dont know
why this is happening. The problem instance is present at
http://www.cse.ohio-state.edu/~khannag/bip_8_20_new.lp.

The solution I get when I run the relaxed version of the problem is
present at http://www.cse.ohio-state.edu/~khannag/solution

In this solution file,  I took the value for column name under the
activity label as their solution value. Based on my
interpretation of the output file, 9409 variables out of 10244 were either
0 or 1 according to the number under the Activity Label in the solution
file. I added these as constraints to the original MIP but it becomes
infeasible.

Could you help me figure out the problem?

Thanks

Regards
Gaurav


Gaurav Khanna
Phd Student
CSE Department,OSU

Phone (office):614-292-7036