Question

Hello优化人员！

我遇到以下约束的一些问题：

#The supply at node i equals what was present at the last time period + any new supply and      subtracted by what has been extracted from the node.    
subject to Constraint1 {i in I, t in T, c in C}:
    l[i,t-1,c] + splus[i,t] - sum{j in J, v in V, a in A} x[i,j,v,t,c,a]= l[i,t,c];

自然导致此约束在第一次循环时提供错误，因为未定义t-1（对我来说，l [i，0，c]未定义。其中

  var l{I,T,C} >= 0;    # Supply at supply node I in time period T for company C.
  param splus{I,T};     # Additional supply at i.
  var x{N,N,V,T,C,A} integer >= 0;  #Flow from some origin within N to a destination within N using vehicle V, in time T, for company C and product A.

并设置T; （在.mod中）是一个定义为：

的集合

 set T := 1 2 3 4 5 6 7; in the .dat file

我试过：

subject to Constraint1 {i in I, t in T: t >= 2, c in C}:
all else same

这给我一个语法错误。我还试图为所有可能的组合包含“let l [1,0,1]：= 0”，这让我错误

  error processing var l[...]:
  no data for set I

我也试过

subject to Constraint1 {i in I, t in T, p in TT: p>t, c in C}:
   l[i,t,c] + splus[i,p] - sum{j in J, v in V, a in A} x[i,j,v,p,c,a]= l[i,p,c];

其中

set TT := 2 3 4 5 6;

<。>在.dat文件中（并且仅设置TT;在.mod中）也会出错。有人知道怎么做吗？

Answer 1

解决此问题的一种方法是在索引表达式的末尾指定条件t >= 2：

subject to Constraint1 {i in I, t in T, c in C: t >= 2}:
  ...

有关索引表达式语法的更多详细信息，另请参阅Section A.3 Indexing expressions and subscripts。

AMPL：下标超出范围

1 个答案: