Add support of JuMP variable/constraint names on GAMS level about gams.jl HOT 6 CLOSED

Yeah, there is currently no feature to look up the autogenerated names. I agree that it would be useful to use the JuMP variable names on the GAMS level. I'll look into it. Thanks for the feature request.

from gams.jl.

Looks great! I did not realize there was an issue with naming restrictions when I opened the issue, but this seems like a good solution. I look forward to trying it.

from gams.jl.

I added writing the variable and constraint (only linear and quadratic) names that the user passes to the generated GAMS model with v0.3.0 - along with some other updates. Note however, that GAMS is very restrictive when it comes to variable naming and that something like x[1,2] or β is not allowed in GAMS source. Therefore, forbidden characters are replaced by _. I can then happen that the name is invalid because it will start with _, e.g. if you are using unicode symbols. In that case GAMS.jl should fall back to generic names. I hope this solution is fine for debugging. The generated files were never meant to be beautiful 😉

Version 0.3.0 should be available in a moment.

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Thanks! That should work except for the issue with not just illegal characters, but also case insensitivity of GAMS. Would it be possible to access some mapping (e.g. a dict) between the two? The users can easily do a search and replace of any error message or LST file if needed.

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Right, I forgot about this. I guess I should revert back to the generated names then, because otherwise the possibility of provoking GAMS compilation errors is too high. Instead, I will introduce Attributes in order to get the mapping, e.g.:

MOI.get(model, GAMS.GeneratedVariableName(), x[1,1])
MOI.get(model, GAMS.OriginalVariableName("x1"))

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Okay, done with the latest commit, see https://github.com/GAMS-dev/gams.jl#gams-names-vs-jump-names. Version 0.3.1 will be available soon.

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