Streaming of log to buffer (instead of going through a file)

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Christoph Hofer-Temmel

2024年02月05日 10:19

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We wrap Gurobi in our models and deliver these in library form to internal downstream applications and their teams. There is not necessary a a file system present during execution (think kind of serverless), nor do our modelling dlls control any aspect of the execution environment. We would like to access solver logs - but can not choose any file system location, as this is an operational aspect.

Preferrably I would like to register a streaming callback in the API (some kind of StringWriter) and let the solver stream the log into a buffer under modelling library control. 

A secondary option would be to buffer the whole log internally (with a flag like LogToConsole - Gurobi Optimization) ... LogToBuffer or extending LogToConsole with a third option, and retrieve the buffered log contents. This would be less realtime, but sufficient for batch processing. 

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  Simranjit Kaur

  • Gurobi Staff

  2026年11月13日 01:30

  This post is more than two years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
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  Elisabeth Rodríguez Heck

  • Gurobi Staff

  2024年02月05日 11:45

  Hi Christoph,

  Maybe you could use a MESSAGE callback to retrieve the log lines programmatically and then log this into a buffer from your code. 

  If you are using Gurobi Instant Cloud, you could also use the REST API to query the log of an active job.  

  Does one of these options work for you?

  Best regards,

  Elisabeth

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  Christoph Hofer-Temmel

  2024年02月06日 06:57

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  The callback way seems doable. I knew about callbacks, but only ever associated them with the solution process (not logging ...). Thanks, I will try this out.

  For  posteriority, here is the .NET version:

  * Register a callback in the model (prior to solve): https://www.gurobi.com/documentation/current/refman/cs_model_setcb_.html#dotnetmethod:GRBModel.SetCallback

  * Create a concrete subclass of https://www.gurobi.com/documentation/current/refman/cs_cb_.html

  * Follow the example code in https://www.gurobi.com/documentation/current/examples/cb_cs_cs.html

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  Elisabeth Rodríguez Heck

  • Gurobi Staff

  2024年02月06日 07:16

  Great to read that the callbacks may work. Thanks for posting the .NET references!

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  Gwyneth Butera

  • Gurobi Staff

  2024年02月06日 14:19

  We have a Knowledge Base article that could be of interest here : How do I use Gurobi logging with Microsoft.Extensions.Logging?

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