Sometimes I see GAMS code like:
SETS
K index of periods of time /1*4/
J index of generators /1*3/
In general I don’t like plain numbers as set elements. I prefer something like:
SETS
K index of periods of time /t1*t4/
J index of generators /gen1*gen3/
This often improves the readability of the output. This is especially the case in the GDX viewer where we can swap rows and columns. Here is a some sample output:
| Numerical | Id+Numerical |
| SETS | SETS |
| ---- 110 VARIABLE p.L output power of generator j at period k
2 3 4
1 150.000 350.000 260.000 2 100.000 3 50.000 140.000
| ---- 110 VARIABLE p.L output power of generator j at period k
t2 t3 t4
gen1 150.000 350.000 260.000 gen2 100.000 gen3 50.000 140.000 |
| | |
For this small example this is not terribly convincing, but for larger, high-dimensional data it surely helps in understanding output quickly.
While this idea helps with report reading, extending it a bit further would help with understanding the model from the GAMS code.
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Period index of periods of time /t1*t4/
Generator index of generators /gen1*gen3/
Then looking at the objective and constraints of the model, what is being indexed is even more clear.
EQUATIONS
...
MeetDemand(Period) .. SUM(Generator,
OrderQuantity(Generator, Period) =E=
Demand(Period);
Instead of
EQUATIONS
...
C1(K) .. SUM(J, Q(K,J) =E= D(K);
Absolutely. I personally like to use short names for heavily used identifiers and vice versa. E.g. for a time index that is used a lot I may decide to use 't' (probably never 'k' like in this fragment). If not used as much I may use 'period'.
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