General Constraint error: Invalid general function options or missing closing brackets

Answered

Tanuj Karia

February 12, 2020 15:49

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• 

Hello,

I am trying to solve the Three-hump camelback problem using general constraints options in Gurobi.

I am writing the model in .lp formt and following the example given on the page:  https://www.gurobi.com/documentation/9.0/refman/lp_format.html

However whenever I try to define a general constraint I end up getting this error saying "Invalid general function options or missing closing brackets" (see the screenshot below):

My lp file follows below:

Minimize
k
Subject to
General constraints
gc1: ( PieceLength=0.001 ) k = POLY ( 12 x ^ 2 - 6.3 x ^ 4 + 1 x ^ 6 - 6 x * y + 6 y ^ 2 )
Bounds
-10 <= x <= 10
-10 <= y <= 10
End

Best wishes,

Tanuj

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 03:18 Edited

  This post is more than three 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 why not try our AI Gurobot?.
• 

  Silke Horn

  • Gurobi Staff

  February 12, 2020 17:32

  Hi Tanuj,

  We don't recommend writing LP files by hand. Why don't you use an API to create the LP file?

  There are multiple issues with your file. E.g.:

  • You can only model univariate polynomials (i.e., you cannot use two variables x and y).
  • You should order the terms in the polynomial decreasingly by degree.
  • The attribute for controlling piece length is called FuncPieceLength. (This might be wrong in the LP format documentation.)
  • Bounds should go before the general constraints.

  I would really recommend building the model using one of our APIs!

  Silke

  1

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