Double summation

[Feras Matar]

Hi,

Please how can I write the following in AMPL

 

I tried several times but always there is an error

[victor.z...@gmail.com]

If this is a constraint then something like

s.t. c{k in K, s in S}: sum{i in 1..n, j in F[i]} q[i, s] * a[j, k] * x[i, j] >= R[k, s];

provided that all the entities are declared accordingly and F(i) can be represented as an indexing set.

HTH,

Victor

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[Feras Matar]

Thank you; it is working

But as you can seen in the formula that summation over j comes before i. and you stated i before j

will this make a difference in model or not ?

Thanks

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[victor.z...@gmail.com]

I'd say it's a sloppy use of mathematical notation, because a symbol should be introduced before it's used. AMPL being a programming language is more strict in this respect. Otherwise summation order makes no difference.

HTH,

Victor

[Feras Matar]

Thank you to much

since the the x variables have (i*j) variables (here i = 25,j = 411), when I solve the model only a part of the utput appeared in the AMPL window)

How to export the output to an excel file or text file ? (please give me the command for that; I did not understand what is written in AMPL manual)

So, it will be better if you give me the command directly instead of giving me the reference for that

[victor.z...@gmail.com]

This have already been answered here: https://groups.google.com/d/msg/ampl/0FV5GJBkyDI/fODmqeigAQAJ

- Victor

[Ruonan Zhao]

Hi all, 

Can anyone please kindly help below. I need to do double summation but index l should not equal to k. Below is what I write but seems wrong.  Do you have any suggestions? Thanks!

sum {k in K,l in K diff {k}} y[k,l]

Best,

Ruonan

[AMPL Google Group]

I did a little test where I set K equal to {1,2,3,4,5} and assigned some random numbers to y. Your sum was evaluated without any errors:

ampl: set K := 1..5; 
ampl: var y {K,K} := Uniform01(); 

ampl: display sum {k in K, l in K diff {k}} y[k,l]; 
sum{k in K, l in K diff {k}} y[k,l] = 9.30924 

However, some other error in your model might be causing an error when you use this expression. To get more help, reply with a complete example that we can run to reproduce the error message.

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{#HS:2203350787-115715#}

On Mon, Apr 3, 2023 at 10:02 PM UTC, AMPL Modeling Language <am...@googlegroups.com> wrote:

Hi all,

Can anyone please kindly help below. I need to do double summation but index l should not equal to k. Below is what I write but seems wrong. Do you have any suggestions? Thanks!

sum {k in K,l in K diff {k}} y[k,l]

Best,

Ruonan

On Tuesday, 20 October 2015 at 14:42:22 UTC-5 Feras Matar wrote:

Hi,

Please how can I write the following in AMPL

I tried several times but always there is an error

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