Beautiful. I could use this often.
-----Original Message-----
From: Andrew Makhorin [mailto:[email protected]]
Sent: Monday, May 02, 2011 9:15 AM
To: Meketon, Marc
Cc: [email protected]
Subject: RE: [Help-glpk] Parsing large, sparse mathprog model takes a (very)
long time
> This "data " statement seems very useful. Could you please provide a
> couple of paragraphs on how the "data" statement works?
The idea is quite simple. Imagine that you declare a plain set:
set S{i,j,k,l,m};
which is provided with data in the data section. However, actually you need to
have, say, array of sets T{j,m}, where T[j,m] is a set of triplets (l,i,k) from
S. Using the data attribute (not documented!) you can declare T as follows:
set T{j,m}, data S[2,5,4,1,3];
This declaration has the same effect as there were corresponding data provided
for T in the data section. [2,5,4,1,3] is a permutation of component indices:
2nd and 5th components of every 5-tuple in S give pair [j,m] used to index
elements of T, and 4th, 1st, and 3rd components of the 5-tuple are used to
build triplets (l,i,k), which are included in set T[j,m].
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