# Eli Towle

Gurobi Staff
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## Activity overview

Latest activity by Eli Towle
• Eli Towle commented,

Pyomo does not include any integration to Gurobi's general constraint methods like Model.addGenConstrExp(). If you use Pyomo's persistent Gurobi interface, you can access the underlying gurobipy Mo...

• Eli Towle created an article,

### Why does Gurobi 10.0.0 report an incorrect objective value for my multi-objective problem?

Gurobi 10.0.0 includes a bug that can result in Gurobi printing an incorrect optimal objective value for multi-objective optimization problems in the log file. This issue will be fixed in the next ...

• Eli Towle commented,

I'm not aware of a way to suppress these messages in Pyomo. You can do this using Gurobi's native Python API by following the instructions in the article How do I suppress all console output from G...

• Eli Towle commented,

Since your code uses process-based parallelism (not thread-based parallelism) and you do not directly interact with the Gurobi environment, you shouldn't run into any issues related to thread safety.

• Eli Towle commented,

By default, Python executes the Python code within a process using a single thread (the Gurobi shared library launches additional solver threads during solve time). In order for multiple user threa...

• Eli Towle commented,

What exactly do you mean by interact? Directly or indirectly accessing or manipulating the environment data structure (in Python, the Env object). Can each process that creates an environment ha...

• Eli Towle commented,

Each model is tied to a specific environment. However, environments and models are two very different data structures: The environment defines the configuration and start/end of a Gurobi session. ...

• Eli Towle commented,

You create a separate environment for each model in each parallel process, so the environments are only ever accessed by a single thread. That will work fine. Given that Pyomo doesn't give you dire...

• Eli Towle commented,

The Gurobi environment is created in step a).

• Eli Towle commented,

You can just call $$\texttt{opt.set_instance(model)}$$ to set up the next solve. With this approach, any Gurobi parameters you set on Pyomo's $$\texttt{GurobiPersistent}$$ object (e.g., \(\texttt{o...