parallel modeling #4613

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1. sschnug commented on Mar 31, 2025

   

   sschnug

   on Mar 31, 2025

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   Personal opinions (no ortools dev):

   • (Fine-grained) Parallel modelling APIs are probably very dev-costly, but seldomly offer "more"
     • (Coarse-grained) is maybe a DIY topic: just wrap every ortools-touching types/data behind a mutex/lock
   • Apart from corner-cases like:
     • type CCA: heavy custom preprocessing/presolving
     • type CCB: native solver language is bad intermediate language
       -> this only happens to interpreted/slow modelling-languages (e.g. Python)
       -> Argument is simple: if C++ solver is able to work with "some model" in X time, you should be easily able to produce "some model"< X time using the same tools (C++)
     • Drop Python; use C++: often this solves the issue at hand
   • CCB is maybe a real problem, but does not happen that often in would claim
     • Sometimes a different model helps (e.g. compact vs. non-compact models)
       • e.g. don't produce all "n over 3" conflict-clauses a-priori
   • CCA should be handled without any need to change ortools
     • Do the preprocessing on your own types/data; do it in parallel; merge results (less work than "compute") into ortools types/data
       • No need for thread-safety (or more) in ortools at all
   • Even if ortools modelling-layer would be thread-safe
     • The how to exploit this in Python is probably not that simple as:
       • Multithreading as is won't help
       • Multithreading without GIL might be a bit too modern / moving target (i'm a bit out of touch with current development-state)
       • Multiprocessing is of very very coarse granularity
         • If that works, the approach of handling CCA should also help

   Or to phrase it differently: If your modelling-time dominates solving-time, there are tons of (better!) options NOT related to solver-provided parallel-modelling tooling. (Maybe you want to share your use-case in ortools' github discussions for further opinions)
2. google

   locked and limited conversation to collaborators on Mar 31, 2025
3. lperron

   converted this issue into a discussion #4614 on Mar 31, 2025
4. Mizux

   assigned

   sschnug

   and

   lperron

   and unassigned

   lperron

   on Mar 31, 2025
5. Mizux

   added

   Help NeededModeling/Usage problemModeling/Usage problem

   Lang: PythonPython wrapper issuePython wrapper issue

   Solver: CP-SAT SolverRelates to the CP-SAT solverRelates to the CP-SAT solver

   on Mar 31, 2025
6. Mizux

   added this to the v9.13 milestone on Mar 31, 2025
7. Mizux

   assigned

   lperron

   on Mar 31, 2025