Choosing “Big M” Values

I seem to bring up “big M” models a lot, so apologies if I end up repeating myself in places here. Not long ago, someone passed along highlights of a “big M” type model to me and asked if he could somehow reformulate to get rid of $$M$$. I did not see any good way …

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A question posed on OR-Exchange in 2017 asked the following: Given a tour of nodes, how does one best add two new nodes while respecting the ordering of the original tour. Specifically, the author began with a tour 0 – 1 – 2 – 4 – 6 – 0 (where node 0 is a depot) …

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NP Confusion

I just finished reading a somewhat provocative article on the CIO website, titled “10 reasons to ignore computer science degrees” (when hiring programmers). While I’m not in the business of hiring coders (although I recent was hired as a “student programmer” on a grant — the Universe has a sense of humor), I find myself …

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Callback Cuts That Repeat

The following post is specific to the CPLEX integer programming solver. I have no idea whether it applies to other solvers, or even which other solver have cut callbacks. Every so often, a user will discover that a callback routine they wrote has “rediscovered” a cut it previously generated. This can be a bit concerning …

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