gams:i_know_a_better_solution

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gams:i_know_a_better_solution [2020/05/18 14:52] Michael Bussieck |
gams:i_know_a_better_solution [2020/05/18 14:58] (current) Michael Bussieck |
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- For models with discrete variables or global solvers in general, make sure you have set ''option optCR=0;'' so the solver looks indeed for the global solution. | - For models with discrete variables or global solvers in general, make sure you have set ''option optCR=0;'' so the solver looks indeed for the global solution. | ||

- If you solve with a //local// solver this situation is a possibility for non-convex models. Select a global solver or use a better starting point to overcome this. | - If you solve with a //local// solver this situation is a possibility for non-convex models. Select a global solver or use a better starting point to overcome this. | ||

- | - Your better //solution// is not a solution. You can have the solver or GAMS check your conjecture by either fixing the variables to the proposed solution (e.g. ''x.FX(i,j) = ...;'') or set the variable level (e.g. ''x.L(i,j) = ...;''). In the former case the solver either accepts your //solution// or reports infeasible. In the latter case, the equation listing (see [[https://www.gams.com/latest/docs/UG_GAMSOutput.html#UG_GAMSOutput_TheEquationListing]]) lists some ''INFES'' markers. Make sure to use set limRow ([[https://www.gams.com/latest/docs/UG_GamsCall.html#GAMSAOlimrow]]) to see all equations and tolInfRep ([[https://www.gams.com/latest/docs/UG_GamsCall.html#GAMSAOtolinfrep]]) to filter the small infeasibilities. | + | - Your better //solution// is not a solution. You can have the solver or GAMS check your conjecture by either fixing the variables to the proposed solution (e.g. ''x.FX(i,j) = ...;'') or set the variable level (e.g. ''x.L(i,j) = ...;''). In the former case the solver either accepts your //solution// or reports infeasible. In the latter case, the [[https://www.gams.com/latest/docs/UG_GAMSOutput.html#UG_GAMSOutput_TheEquationListing|equation listing]] has some ''INFES'' markers. Make sure to use set [[https://www.gams.com/latest/docs/UG_GamsCall.html#GAMSAOlimrow|limRow]] to see all equations and [[https://www.gams.com/latest/docs/UG_GamsCall.html#GAMSAOtolinfrep|tolInfRep]] to filter the small infeasibilities. |

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gams/i_know_a_better_solution.txt ยท Last modified: 2020/05/18 14:58 by Michael Bussieck