# Poor linear relaxation

**URL:** <https://discourse.julialang.org/t/poor-linear-relaxation/53170>\
**Category:** Optimization (Mathematical)\
**Created:** [January 11, 2021, 5:31pm UTC](https://discourse.julialang.org/t/poor-linear-relaxation/53170 "2021-01-11T17:31:18Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![angeloaliano1](https://avatars.discourse-cdn.com/v4/letter/a/7ea924/32.png) [@angeloaliano1](https://discourse.julialang.org/u/angeloaliano1)\
**Post date:** [January 11, 2021, 5:31pm UTC](https://discourse.julialang.org/t/poor-linear-relaxation/53170/1 "2021-01-11T17:31:18Z")

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Dear users,  
I have a MIP problem whose linear relaxation is very poor. Observe the report of CPLEX below:

 ![relatorio_cplex](https://global.discourse-cdn.com/julialang/original/3X/8/3/83f7d4787a4cfe39a006c1ec1af804beef07e4f0.png)  
(Gap greater to 999.99%, then the symbol “–”).  
Does have any parameter in CPLEX to set to improve these performance?  
Many thanks.

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [January 11, 2021, 8:12pm UTC](https://discourse.julialang.org/t/poor-linear-relaxation/53170/2 "2021-01-11T20:12:20Z")

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This question is better suited for a forum like [https://or.stackexchange.com](https://or.stackexchange.com).

You’re more likely to get help if you provide more information, such as the formulation of your problem.

By the looks of it, I’m guessing you may have some big-M type constraints. Read [https://www.gurobi.com/documentation/9.0/refman/num\_dealing\_with\_big\_m\_con.html](https://www.gurobi.com/documentation/9.0/refman/num_dealing_with_big_m_con.html) You will probably get better performance by improving the formulation of your model, rather than searching for different solver parameters.