# Reversing Differences

Fellow blogger Håkan Kjellerstrand posted an interesting question on OR Stack Exchange recently. Starting from a list of integers, it is trivial to compute the list of all pairwise absolute differences, but what about going in the other direction? Given the pairwise (absolute) differences, with duplicates removed, can you recover the source list (or a …

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# Collections of CPLEX Variables

Recently, someone asked for help online regarding an optimization model they were building using the CPLEX Java API. The underlying problem had some sort of network structure with $$N$$ nodes, and a dynamic aspect (something going on in each of $$T$$ periods, relating to arc flows I think). Forget about solving the problem: the program …

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# Generic Callback Changes in CPLEX 12.10

CPLEX 12.10 is out, and there have been a few changes to the new(ish) generic callbacks. Rather than go into them in detail (and likely screw something up), I’ll just point you to the slides for a presentation by Daniel Junglas of IBM at the 2019 INFORMS Annual Meeting. I’ve written about half a dozen …

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