Lukas Barth

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Activity overview

Latest activity by Lukas Barth

  • Lukas Barth commented,

    1. Community
    2. Modeling
    3. Suspected bug in LP parser: Constraint without variables introduces new variables

    Hi Matthias, Thanks for your reply. I missed the part about the left-hand side not being allowed to contain any constants, so Gurobi is right here! While these "constraints" are certainly nonsense,...

  • Lukas Barth created a post,

    Suspected bug in LP parser: Constraint without variables introduces new variables

    Answered
    1. Community
    2. Modeling

    I think I found a bug in Gurobi 9.0.3. Take this example.lp file: Maximize xSubject To test: 10 >= 5Bounds 0 <= x <= 5Generals xEnd If I run from gurobipy import readm = read('example.lp')print...

    • Lukas Barth
    • Edited
    • 4 followers
    • 4 comments
    • 0 votes

  • Lukas Barth commented,

    1. Community
    2. Other
    3. What are postponed nodes?

    Hi Jaromlł, Thanks. The variables for which bounds were inferred were indeed variables of my model. Putting some reasonable upper bounds on them solved the problem with the huge bounds after presol...

  • Lukas Barth commented,

    1. Community
    2. Other
    3. What are postponed nodes?

    Thanks again! Indeed, presolving seems to introduce some large variable bounds: gurobi> m = read("gurobi.mps")Read MPS format model from file gurobi.mpsReading time = 1.51 seconds: 663497 rows, 331...

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    • Lukas Barth
    • Edited
    • 0 votes

  • Lukas Barth commented,

    1. Community
    2. Other
    3. What are postponed nodes?

    Hi Jaromił, This is the size of my model: Optimize a model with 663497 rows, 331973 columns and 2427819 nonzerosModel fingerprint: 0xb4fd3671Model has 296 SOS constraintsVariable types: 111748 cont...

  • Lukas Barth created a post,

    What are postponed nodes?

    Answered
    1. Community
    2. Other

    I'm currently optimizing a MIP model, and this is how my MIP log looks like: Nodes | Current Node | Objective Bounds | WorkExpl Unexpl | Obj Depth IntInf | Incumbent BestBd Gap | It/Node Time0 0 73...

    • Lukas Barth
    • 4 followers
    • 8 comments
    • 1 vote

  • Lukas Barth commented,

    1. Community
    2. Modeling
    3. Tell Gurobi about optimal variable value depending on a set of other variables

    Thanks Jaromił. The main reason I was hoping to get around coding a callback is the issue referenced here: https://support.gurobi.com/hc/en-us/community/posts/360067079431-Callback-Setsolution-from...

  • Lukas Barth commented,

    1. Community
    2. Modeling
    3. Tell Gurobi about optimal variable value depending on a set of other variables

    Hi Jaromił, Thanks for your reply. I'm sorry, I think I did not describe my situation correctly. I do not know any variable assignments before optimization (otherwise I could just make them constan...

  • Lukas Barth created a post,

    Tell Gurobi about optimal variable value depending on a set of other variables

    Ongoing
    1. Community
    2. Modeling

    I'm modelling a scheduling problem (see below for a concrete example). In this problem, I have a set of (integral) variables modelling the start times assigned to jobs. I have a second set of binar...

    • Lukas Barth
    • 3 followers
    • 6 comments
    • 0 votes

  • Lukas Barth created a post,

    Analyzing the conditioning of a MIP

    Answered
    1. Community
    2. Programming

    Hello everyone, I have several different MIP formulations for the same problem, which I am currently benchmarking against each other. One thing I would like to look at is the conditioning of the re...

    • Lukas Barth
    • 2 followers
    • 2 comments
    • 0 votes