NOTE: Update (but not solved) Below
In my use case for GAMS I wish to define a collection of static variables in a .gdx file rather than in the main model.gms script. This is not an issue unless I define a column that contains only zero (0) values. When defining a table ("data") like this and choosing "Run with GDX Creation in GAMS studio. I get a .gdx file with a missing column.
Set indexA /ch1*ch5/;
Table data(indexA, *)
A_min A_max B_min B_max
ch1 1 10 0 7
ch2 2 10 0 6
ch3 3 10 0 5
ch4 4 10 0 4
ch5 5 10 0 3;
Copy and pasted .gdx contents:
IndexA * Value
ch1 A_min 1
ch1 A_max 10
ch1 B_max 7
ch2 A_min 2
ch2 A_max 10
ch2 B_max 6
ch3 A_min 3
ch3 A_max 10
ch3 B_max 5
ch4 A_min 4
ch4 A_max 10
ch4 B_max 4
ch5 A_min 5
ch5 A_max 10
ch5 B_max 3
Column 'B_min' is nowhere to be seen. When trying to load this .gdx back into my script it gives me an error where I try to access 'B_min' and says "Label is unknown". If I change the value to be non zero, it is not a problem, but I need it to be zero! I have tried using 0.0 vs 0. No change. Why can't I define something to be zero and have it save in my .gdx?
Edit / Update: I created an ugly work around for this. I set all of my "B_min values to -1 in gams, created my .gdx file with the column, but the wrong values. Loaded the .gdx file into python using the GAMS API, iterated over each entry in 'data' to change the -1 values to 0 and saved it. This new .gdx file now works in my test model. I would still really like to get this zero thing solved for others on my team who are not going to use this work around with the python API.
For efficiency GAMS does not store default values, thus no zeros in parameters. What you probably can do is setting $onEps. This will transform your zeros into eps, which is numerically still zero but makes it into the GDX file.