Re: [Help-glpk] TRYING TO GET A NON-OPTMIAL SOLUTION OF A MIP MODEL.

[Chris Matrakidis]

The problem is that in this part, it takes about 5h working on analyzing the whole tree, but the strange thing is that it keeps showing the same value every iteration it does until it gets to the end of the tree. The value it shows is the same value that can be seen when it finds the lp solution, does it means that the LP solution was the optimal since the beginning? Am i able to interrupt the execution and take a look at this solution?

What this means is that there are many feasible non-integer solutions with the same value as the integer one. The solver actually finds the solution following the very first branch (the last 0 in the parenthesis indicates that there were no backtracking steps taken) and does this after considering 1213 nodes. which seems quite good given the size of the problem. The issue is that each node takes a lot of time to do so, leading to your next question:

 

Or is there a way to speed it up a little bit?

Cant really say without more information, but the obvious thing to check is the scaling of the problem. Another thing to consider is reformulating the problem. On occasion, even adding redundant constraints helps.

Best Regards,

Chris Matrakidis