Problem

[akram mirahmadi]

Hi there,

I have difficulty to define a decision variable in Ampl. I have x[p,t,n], which p, t and n are parameter. However, n can gets amount from 1 to t each time. it means if for example in one constraint I have x[p,t,n] which p=1,2, t=1,2,3 each time I want n to get amount till t. for example: p=2, t=3, n=1,2,3. How can I define this?

Regards,

Akram

[Robert Fourer]

You can write

param P;
param T;
var x {p in 1..P, t in 1..T, n in 1..t};

Note that n only runs from 1 to t in this indexing expression (not from 1 to T).

Bob Fourer
am...@googlegroups.com

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[aki]

Thanks Bob for your response, 
I have another question as well. I am not sure if I can put an amount of a parameter as the ending number of a loop.
for example: can I have this:

subject to waiting_time {p in 1..Patient}:

sum{t in 1..time, n in 1..waiting[p]} amount[p,t,n]>=0.9*sum{t in 1..time} demand[1,t];
which waiting[p] is a parameter itself.

Thanks.

[Robert Fourer]

This is fine. In general, the operands to .. can be any expressions involving sets and params that evaluate to numbers.

Bob Fourer
am...@googlegroups.com

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