Ask HN: Do you use an optimization solver? Which one? Do you like it?

* MiniZinc is my favourite tool for prototyping models. Looking into the feasibility of using it in a roduction environment as well. Typically models are small to medium sized. Also using it for recreational problem solving (e.g., Advent of Code).

* Gecode is my go-to solver for writing applications where I need more control over the solving process or I want to write a custom propagator or heuristic. Used it for scheduling, planning, and configuration.

* When in the JVM ecosystem, I've used Choco.

* I've used OR-tools some, but would like to be better at it. Mainly because OR-tools has a nice set-up with a lazy clause generation solver, good automatic heuristics, and a nice portfolio solver for parallel work.

* Quite often, a custom optimization heuristic is also the right tool for the job.

I've tried to use Gurobi sometimes, but for the problems I've tried, it has either been to hard to model effectively or was not a good fit. The licensing cost is a limiting factor as well.

I have a niggling feeling somewhere that JSON is the wrong language for this. Something like cue lang may be the right thing. (https://www.sobyte.net/post/2022-04/cue/)

Initially, CPLEX and Xpress were founded in the eighties. In the nineties, CPLEX was acquired by ILOG (a French CP company), which in turn was purchased by IBM around 2009. Around the same time, the original technical co-founder of CPLEX, along with the two latest head developers, left CPLEX to found Gurobi. Since then, there has been a slow trickle of developers leaving CPLEX for Gurobi... until 2020, when CPLEX suddenly lost its 7 remaining devs over 6 months (because of catastrophic mismanagement at IBM, from what I heard). Unsurprisingly, those devs ended up mostly at Gurobi, resulting in the CPLEX team from 20 years ago being essentially Gurobi now. Other CPLEX devs also ended up at XPRESS, which had been purchased around 2008 by FICO (the credit rating company).

Meanwhile, there is also a smaller Danish company, Mosek, that does its own thing (they have a MIP solver, but their focus seems to be on their amazing conic optimization code). And SAS (the analytics giant) has a small MIP team too.

Then over the last 2 years, three new solvers appeared out of China: COPT (by Cardinal Operations, a startup by Stanford graduates), MindOpt (Alibaba Research) and OptVerse (Huawei). They mostly have LP solvers for now, but for newcomers, the performance is extremely impressive. This is only partially out of nowhere, though: COPT in particular has hired several devs from the incumbents.

On the academic side, ZIB (a PhD-granting research institute in Berlin) maintains a source-available family of solvers, and has been a steady provider of talent for commercial solvers. The dev behind SoPlex (LP solver) went to CPLEX after his PhD and now Gurobi. The main dev behind SCIP did the same, and is now VP of R&D at Gurobi. Many more XPRESS and Gurobi people did their PhDs at ZIB.

The Coin-OR open-source codes for LP (clp) and MIP (cbc) were written decades ago by a founding father of computational optimization, John Forrest, now retired from IBM research. Their source code is difficult to read, and Coin-OR aims to eventually replace them with a new code, HiGHS. The dev who wrote the simplex code of HiGHS as his PhD thesis went on to XPRESS and now COPT. The dev who writes the MIP code of HiGHS comes from ZIB.

As you can see, everyone is very inter-connected. Hence the throwaway :-).