What are the .L items

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In the nonlinear equation system chemical engineering GAMS formulation a line was introduced which is

 

ba.l=1; so4.l=1; baoh.l=1; oh.l=1; hso4.l=1; h.l=1;(nonlinsys.gms)

 

This line provides a starting point for the variables in the model.  In particular the notation variablename.l=value is the way one introduces a starting value for a variable in GAMS as discussed in the chapter on NLP and MCP Model Types.  Such a practice can be quite important in achieving success and avoiding numerical problems in model solution (as discussed in the Fixing Execution Errors chapter).

Notes:

•One may also need to introduce lower (variablename.lo=value) and upper (variablename.up=value) bounds on the variables as also discussed in the Fixing Execution Errors chapter.
•The .l, .lo and .up appendages on the variable names are illustrations of variable attributes as discussed in the Variables, Equations, Models and Solves chapter.
•The = statements setting the variable attributes to numbers are the first example we have encountered of a GAMS assignment statement as extensively discussed in the Calculating Items chapter.