help for generating random input network

GAMS
1

hi! i am very new to Gams
how can i create a random input network in gams
i mean arc costs will be randomly generated and also number of node
and arcs will be randomly generated
do you have any examples for generating random input

thx

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2

Dear Muhtelif,

I really would like to help, but I don’t really understand what your
question is.

If you want to know how to generate random numbers in GAMS, I can tell
you how I do it, normally. Since I often have to work with randomly
generated instances that follow a certain distribution and are
dependant on a few other parameters, I use Excel to generate my random
numbers and import them using GDX. The nice thing is, if you set
Excel just right, it generates a new number each time GAMS accesses
the file, resulting in random numbers for each run I perform in GAMS.

Maybe that helped, if not, let me (or us) know. :slight_smile:

Regards
Christian

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3

Hi,

I got some contribution for this question. Please find the GAMS model
below. You do not want a generator to select the number of nodes
randomly. You want this at input. Also the density of the arcs in a
network is usually supplied.

Hope this helps,
Michael Bussieck - GAMSWorld Coordinator

  • here are a few hints.

  • 1 check that a random (undirected) network is connected

  • the arcs in the upper/lower triangle of the adjacency

  • matrix cannot have an empty row/column.

set n nodes / n1*n10 /; alias (n,nn);

set a(n,n) adjacancy matrix (symetric);

parameter arcs(n) total arcs entering or leaving node
cnt(n) row or col count;

  • create a random connected network

a(n,n+UniformInt(1,card(n)-ord(n)))$(ord(n) wrote:

hi! i am very new to Gams
how can i create a random input network in gams
i mean arc costs will be randomly generated and also number of node
and arcs will be randomly generated
do you have any examples for generating random input

thx

\