AMPL 循环和省略变量

Question

最近开始使用 ampl，运行在迭代和索引方面陷入困境。

我有以下模型脚本：

set NUTR;
set FOOD;

param Cost {FOOD} > 0; #Costs pr. gramm

param f_min {FOOD} >=0;
param f_max {j in FOOD} >= f_min[j];

param n_min {NUTR} >=0;
param n_max {i in NUTR} >= n_min[i];

param amount {NUTR,FOOD} >= 0; #amount nutrients pr. gramm

var Purchase {j in FOOD} >= f_min[j], <= f_max[j];

minimize Total_cost: sum{j in FOOD} Cost[j] * Purchase[j];
s.t. Intake {i in NUTR}: n_min[i] <= sum {j in FOOD} amount[i,j] *  
Purchase[j] <= n_max[i]; 

data;

set NUTR := PRT CRB FAT KCAL;
set FOOD := CD VL HM SLM TN MCR EGG BN PS FSL PEN RC ORG PT ON AVC CLF CBG ALM TMT OLV MLK ;

模型运行适合数据集，但我的问题是：是否可以创建一个给出最佳解决方案的循环，一次从 FOOD 集合中省略一种产品？

Answer 1

您可以在 .运行中相当轻松地执行此操作，方法是循环 FOOD，然后使用集合差分运算符定义集合 "everything from FOOD except this one element"。这应该给你大致的想法：

model;
set FOOD;
data; 
set FOOD := CD VL HM SLM TN MCR EGG BN PS FSL PEN RC ORG PT ON AVC CLF CBG ALM TMT OLV MLK ;

for{f in FOOD}{
    printf "\nThe set Food minus %s is:", f;
    display (FOOD diff {f});
    # replace with your model and solve commands, indexing over "FOOD diff {f}". 
}

AMPL 循环和省略变量

AMPL loops and omitting variables

iteration

syntax

ampl