Difference: SetsInAMPL (10 vs. 11)

Revision 112008-04-06 - MichaelOSullivan

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META TOPICPARENT	name="AMPLSyntax"

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

Sets in AMPL

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Declaring a Set

Changed:

<
<

Sets are declared using the set keyword followed by a label, possibly some attributes and either a set literal or set expression. The most common attribute is set by the within keyword. This specifies that the set will only contain elements from the following set definition:

set ARCS within NODES cross NODES; # Elements of ARCS must have both elements in NODES

If you need a multi-dimensional set, but don't have the 1-dimensional sets to construct it yet you can use the dimen keyword:

set ROUTES dimen 2;

There are some other set attributes, but we will not use them.

>
>

set ARCS within NODES cross NODES;
# Elements of ARCS must have both elements in NODES

If you need a multi-dimensional set, but don't have the 1-dimensional sets to construct it yet you can use the dimen keyword:

set ROUTES dimen 2;

There are some other set attributes, but we will not use them here.

Set literals can be defined as a list of elements:

Changed:

<
<

{'HOST', 'DEVICE', 'SWITCH', 'HUB', 'LINK', 'SUPERLINK'}

or a sequence of numbers:

param start; param end > start; param step;  set NUMBERS := start .. end by step;

If the by step is missing, the step is assumed to be 1

set NUMBERS := 1..5; # NUMBERS = {1, 2, 3, 4, 5}

Note Automatic set generation can only be done in the model environment, in the data environment you must define the set explicitly:

set NUMBERS := 1 2 3 4 5; # NUMBERS = {1, 2, 3, 4 5}

>
>

{'HOST', 'DEVICE', 'SWITCH', 'HUB', 'LINK', 'SUPERLINK'}

or a sequence of numbers:

param start;
param end > start;
param step;
set NUMBERS := start .. end by step;

If the by step is missing, the step is assumed to be 1:

set NUMBERS := 1..5; # NUMBERS = {1, 2, 3, 4, 5}

Note Automatic set generation can only be done in the model environment, in the data environment you must define the set explicitly:

set NUMBERS := 1 2 3 4 5; # NUMBERS = {1, 2, 3, 4 5}

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# The set of time-staged arcs

Changed:

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< set TIME_ARCS within TIME_NODES cross TIME_NODES := { (m, t) in TIME_NODES, (n, u) in TIME_NODES : ( ( (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

>
> set TIME_ARCS within TIME_NODES cross TIME_NODES := { (m, t) in TIME_NODES, (n, u) in TIME_NODES : ( ( (m, n) in ARCS) and (t = u) ) or # The transportation arcs ( (m = n) and (ord(t, MONTHS) + 1 = ord(u, MONTHS)) )}; # The storage arcs

There are many concepts within this one statement, let's look at them one at a time.

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