gams-math - 在 GAMS 软件中计算不可行的解决方案

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。IF语句的条件应该怎么写？

Answer 1

您可以在解决模型后检查模型的 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 Infeasible% 而不仅仅是 %ModelStat.Infeasible%，因此求解后的检查可能变为

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！卢茨