lagd1.gms : Lag and Lead operations on Dynamic Sets

Description

Lag and lead operations require the reference set to  be ordered and
constant. In some special cases one would want to use those operation on dynamic
and/or unordered sets. A DCO option on/offOrder has been added to locally relax
the default requirements. The use of this option comes with a price, the system
will not be able to diagnose odd and incorrect formulations and data sets.

A small example will be used to illustrate the use of $onOrder and $offOrder. We
would like to have a circular lead on the content of a slice as shown below.


Small Model of Type : GAMS


Category : GAMS Test library


Main file : lagd1.gms

$title 'Lag and Lead operations on Dynamic Sets' (LAGD1,SEG=560)

$onText
Lag and lead operations require the reference set to  be ordered and
constant. In some special cases one would want to use those operation on dynamic
and/or unordered sets. A DCO option on/offOrder has been added to locally relax
the default requirements. The use of this option comes with a price, the system
will not be able to diagnose odd and incorrect formulations and data sets.

A small example will be used to illustrate the use of $onOrder and $offOrder. We
would like to have a circular lead on the content of a slice as shown below.
$offText

set a / a1,a2,a3 /, c /c1*c7 /, ac(a,c) / a1.(c2   ,c3   ,c5),    a3.c3 /
    desiredacc(a,c,c) circular lead     / a1.(c2.c3,c3.c5,c5.c2), a3.c3.c3 /
    acc(a,c,c), wrongacc(a,c,c);

wrongacc(ac(a,c),c++1) = yes; display wrongacc;

* the above assignment will not work because the lead operator is relative to
* the set c. we do need to extract the content of the second index position to
* be used as a reference set and relax the requirement to have a ordered and/or
* dynamic reference sets.

set temp(c);

$offOrder
loop(a,
   temp(c) = ac(a,c);
   acc(ac(a,temp),temp++1) = yes);
$onOrder

* arrange the display in list format
option ac:0:0:1,acc:0:0:1; display ac,acc;