GAMS软件中不可行解的计算

Question

我想在GAMS中运行几个数学模型，并计算不可行解的数量。IF语句的条件应该怎么写？

Answer 1

您可以在解算模型之后检查模型的modelstat属性。下面是一个小示例：

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;

如果你有一个整数问题，你还应该检查%ModelStat.Integer不可行%，而不仅仅是%ModelStat.Infeasible%，所以求解后的检查可能会变成

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

我希望，这会有帮助！Lutz