Difference: SetsInAMPL (9 vs. 10)

Revision 102008-04-06 - MichaelOSullivan

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META TOPICPARENT	name="AMPLSyntax"

<-- Ready to Review - done - Lauren-->

Sets in AMPL

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Sets are usually defined in a data file:

Changed:

<
< set NODES := Youngstown Pittsburgh Cincinnati 'Kansas City' Chicago Albany Houston Tempe Gary ;

>
> set NODES := Youngstown Pittsburgh Cincinnati 'Kansas City' Chicago Albany Houston Tempe Gary ;

although they may be defined during declaration using either an explicit set literal or using a set expression:

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# The set of time-staged arcs set TIME_ARCS within TIME_NODES cross TIME_NODES := { (m, t) in TIME_NODES, (n, u) in TIME_NODES :

Changed:

<
< ( ( (m, n) in ARCS) and (t = u) ) or # The arcs used for transportation ( (m = n) and (ord(t, MONTHS) + 1 = ord(u, MONTHS)) )}; # The arcs used for storage

>
> ( ( (m, n) in ARCS) and (t = u) ) or # The transportation arcs ( (m = n) and (ord(t, MONTHS) + 1 = ord(u, MONTHS)) )}; # The storage arcs

to create TIME_ARCS you could use these statements

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set STORAGE_ARCS := union {t in MONTHS, (m, n) in ARCS : t <> last(MONTHS)} {(m, t, n, next(t, MONTHS)};

Changed:

<
< set TIME_ARCS within TIME_NODES cross TIME_NODES := TRANSPORT_ARCS union STORAGE_ARCS;

>
> set TIME_ARCS within TIME_NODES cross TIME_NODES := TRANSPORT_ARCS union STORAGE_ARCS;

Rather than looping over all possibilities and only keeping those that are appropriate, the new statement only loops over smaller sets that can be used to build up the TIME_NODES set efficiently.

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