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Questions tagged [pyomo]

For questions related to the Python optimization modeling package Pyomo.

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9
votes
2answers
133 views

Reading an LP/MPS file using Pyomo software

I would like to know is it possible to read an LP/MPS file into the Pyomo software and solve the problem? If so, how can I do that?
7
votes
1answer
160 views

Understanding why this MINLP formulation is infeasible

Algebraic Formulation - Note: All parameter values are subject to change, I have just used the numbers you see here as place holders for the time being. Additionally, there are a few other equations ...
6
votes
1answer
77 views

Pyomo: Looping Over A Variable Method

I am trying to extract my variable values into unique lists so that I can pass them to a panadas dataframe and eventually export the dataframe to Excel after I solve my model. The idea is to have the ...
7
votes
2answers
81 views

Pyomo: Building Up A Constraint Over An Index

I am trying to create a constraint for model.z that builds up as a summation during a new time index. I tried to use the += but this does not work with Constraints ...
5
votes
0answers
60 views

Pyomo: Is this triple summation objective function formatted correctly?

I am writing a Pyomo model and trying to code the following mathematical constraint: $$ \sum_{i=1}^I\sum_{j=1}^J\sum_{t=1}^T 5I_{ijt} + 10L_{ijt}I_{ijt} $$ where $L_{ijt}$ is binary. However, I am ...
6
votes
2answers
88 views

What Exactly Is A Warm Start? [duplicate]

I am fairly new to optimization modelling but I am encountering a situation in which I supply initial values to my problem and then after I run my optimization those initial values change. This seems ...
9
votes
2answers
105 views

Integer Decision Variables Always Forced to Zero in Minimization Problem (MINLP)

I am trying to write out a MINLP problem of optimal control for an invasive species and the code that I have for my PYOMO model is below. Some of the initialization values take from an Excel ...
12
votes
3answers
1k views

What is the purpose of libraries like Pyomo and Google OR tools?

I'm new to the OR world, and trying to learn the various tools available. I originally thought that Pyomo and Google OR tools were open source alternatives to commercial solvers like Gurobi or CPLEX. ...
8
votes
1answer
55 views

Understanding the AMPL Solver LIbrary within Pyomo

For anyone familiar with the Pyomo book, it occasionally makes reference to the AMPL Solver Library, and to my understanding, if you can manage to hook up to the solver library then you are able to ...
6
votes
1answer
67 views

Problems Installing APOPT in Pyomo

I am trying to install the solver "APOPT" in Pyomo by following the guidelines laid out below: *Instructions for usage: Place apopt.py in an appropriate folder in the system path (e.g. Linux, /usr/...
8
votes
1answer
124 views

Formulating a MINLP for CPLEX in PYOMO

I am trying to do my first MINLP problem using PYOMO and CPLEX - although I am not committed to using CPLEX, but it was recommended to me. To my understanding you need to formulate your problem in ...
8
votes
1answer
67 views

How to get solver time from CPLEX when using the NEOS server through Pyomo?

I've been using CPLEX on the NEOS server, via Pyomo, to solve a binary program I'm working on. NEOS is amazing, but the documentation is somewhat lacking on the Pyomo side, so I haven't been able to ...
10
votes
2answers
113 views

How to get GAMS's solvers to work from Pyomo?

I want to run a model written in Pyomo language with CPLEX solver of GAMS. However I get the following error: ...
14
votes
4answers
488 views

NLP solvers in pyomo other than ipopt?

I am solving a highly constrained (large number of constraints and large number of variables, but small degree of freedom) NLP problem, and for start, I was using Matlab's ...
7
votes
1answer
94 views

How to set a maximum time to improve a solution with Pyomo and CBC

In relation to using CBC via Pyomo: I was wondering if anyone knew if it was possible to set a maximum allowed time to improve a solution, rather than a maximum total time. This way, if you've been ...
1
vote
0answers
129 views

Optimal value exceeds actual value for a minimization problem [closed]

I am solving a nonlinear numerical optimization problem in Pyomo using Scip as a solver. The goal is to minimize a certain objective function. For certain input conditions, I notice that the solver ...
10
votes
1answer
79 views

Termination Criteria of Solver in Pyomo

I am solving a nonlinear optimization problem using Pyomo with Ipopt as solver. The solver exits with the status: EXIT: Optimal Solution Found. This I can cross ...
4
votes
2answers
188 views

Installing COIN-OR solvers in Ubuntu (Azure)

For a side project, I'm looking to install COIN-OR project solvers on a Microsoft Azure Ubuntu VM. (I will be running Pyomo optimization models on this VM as well; using NEOS isn't cutting it.) ...
9
votes
1answer
117 views

pyomo - pass time limit to NEOS

I am sending a pretty complex Pyomo MINLP to NEOS using Couenne. I'm getting an error message that the solve time is too long (sorry, I don't have it still in my Python console). Is there a way to set ...