Right hand side expression of a constraint

[程颖毅]

I have put a decision variable w[x,y,t] on the right hand side of a constraint and it is reported that i and j are undefined. In the AMPL book, it uses avail[s] on the right hand side of a formula.

param r {(x,y) in stope};

var w {(x,y) in stope, t in 1..T} binary;

subject to rate {t in 1..T}:

sum {(x,y) in block}r[x,y]*w[x,y,t]<=r[x,y];

r[x,y] was defined previously as 

2 1 200000

2 2 200000

2 3 200000

2 4 200000

2 5 200000

2 6 200000

.       .                  .

.       .                  .

7      7      200000;

Could anyone give me some advice? Thank you.

[Robert Fourer]

In the statement of the constraint in your question, the decision variable r[x,y] is on the *left* side of the constraint. In the parameter expression r[x,y] on the right side, x and y are undefined because the scope of {(x,y) in block} on the left goes only as far as r[x,y]*w[x,y,t] -- that is, to the end of the term being summed. Probably you meant to write r[t] (and to index param r over 1..T).

Bob Fourer
am...@googlegroups.com

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