Fractions

Answered

Hannah Khizgilov

• September 08, 2019 22:11

If the coefficient of a variable in an LP file is a fraction (like 1/3) or an irrational number (e.g., sqt(2)), how do you correctly write that?  I.e., what syntax is correct?

Is the only option to use decimals? Is there no better way?

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• Official comment

  

  Simranjit Kaur

  Gurobi Staff

  • December 06, 2024 00:54

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• 

  Tobias Achterberg

  Gurobi Staff

  • September 09, 2019 05:37

  For fractions you can of course just multiply the whole constraint by the smallest common multiplier of your denominators. So, instead of writing 1/3x + 2y <= 7 you would write x + 6y <= 21. For roots or other irrational numbers, there is no better way than using floating points.

  In any case, you should always use double precision in your calculations to get the floating point values, and you should not truncate digits. So, please don't write 1.414214x + y <= 5, but instead write 1.414213562373095x + y <= 5.

  Regards,

  Tobias

   

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