Question

我想在GAMS中运行几个数学模型并计算不可行解决方案的数量。我该如何写IF语句的条件？

Answer 1

解决后，您可以检查模型的modelstat属性。这是一个小例子：

equation obj;
variable z;
positive variable x;

obj.. z =e= 1;

equation feasible;
feasible..    x =g= 1;

equation infeasible1;
infeasible1.. x =l= -1;

equation infeasible2;
infeasible2.. x =l= -2;

model m1 /obj, feasible   /;
model m2 /obj, infeasible1/;
model m3 /obj, infeasible2/;

scalar infCount Number of infeasible models /0/;

solve m1 min z use lp;
if(m1.modelstat = %ModelStat.Infeasible%, infCount = infCount+1;)

solve m2 min z use lp;
if(m2.modelstat = %ModelStat.Infeasible%, infCount = infCount+1;)

solve m3 min z use lp;
if(m3.modelstat = %ModelStat.Infeasible%, infCount = infCount+1;)

display infCount;

如果您有整数问题，您还应该检查％ModelStat.Integer不可行％，而不仅仅是％ModelStat.Infeasible％，因此解决后的检查可能会变为

solve m3 min z use mip;
if(m3.modelstat = %ModelStat.Infeasible% or m3.modelstat = %ModelStat.Integer Infeasible%,
  infCount = infCount+1;
)

我希望，这有帮助！鲁兹

在GAMS软件中计算不可行的解决方案

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