Originally posted by: felycite28

Hi folks  ,

Can anyone tell me a good way for defining the invetory level at t=0?

I[N][0]==0, when I do thi direcly , naturally, I am getting an error ?

Thank you so much in advance

Can you please be more specific? What is the error you get? How is l defined?

Originally posted by: felycite28

I am getting "out of range "I(N)":0

I have N machines in period t , at the beginning of period where t=0, the inventory level must be=0 

this is what I am trying to do

in I(N)(T) the variable itself , N is the numbr of machines, T is the number of periods

Thank you so much in advance

Are your machines/numbered from 1 or numbered from 0? Could you show the code defining l, N, T and the offending constraint?

Originally posted by: felycite28

Hello ,

range m=1..N;//number of the machines , N=5

range t=1..T;//number of the periods , N=3

dvar int I[m][t]; //inventory variable

each period I am working with N machine so at the beginning of each period I will have some inventory from the previous but I have to say to the model , at the beginning where t=0 , there is no inventory . So I am trying to say I[5][0]=0

Thank you

Your range t only ranges from 1 through 5, so there is no index 0 in this range. This is why you get an error when trying to reference l[5][0]. This variable just does not exist. I can see at least the following two ways to fix your problem:

1. Define an additional 'range t0 = 0..T' and then define 'dvar int l[m][t0]', then state your constraint.
2. Everywhere you use l[.][0] in your model use a hard-coded 0 instead. The keyword "if" may be helpful in doing that.

Originally posted by: felycite28

Thank you Daniel , I think it will work but I tried first way , since I have I (m)(t) for the range t=1...T, when I define I(m)(t0) for t0=0...T, it gives me the  I is already defined error . Somehow I have to use "I "for I(N)(0) . How can I fix it ? I guess I could not understand if part you explained exactly

Thank you for your help

You have to replace 'dvar int l[m][t]' by 'dvar int l[m][t0]'.