GAMS/PATH User Guide Version 4.3

loss function can be positive since we are not producing in the jth sector.
If yj is strictly between its bounds, then the loss function must be zero by
complementarity; this is the competitive assumption. However, if yj is at
its upper bound, then the loss function can be negative. Of course, if the
market does not allow free entry, some firms may operate at a profit (negative
loss). For more examples of problems, the interested reader is referred to
[10, 19, 20].
1.3 Solution
We will assume that a file named transmcp.gms has been created using
the GAMS syntax which defines an MCP model transport as developed in
Section 1.1. The modeler has a choice of the complementarity solver to use.
We are going to further assume that the modeler wants to use PATH.
There are two ways to ensure that PATH is used as opposed to any other
GAMS/MCP solver. These are as follows:
1. Add the following line to the transmcp.gms file prior to the solve
statement
option mcp = path;
PATH will then be used instead of the default solver provided.
2. Rerun the gamsinst program from the GAMS system directory and
choose PATH as the default solver for MCP.
To solve the problem, the modeler executes the command:
gams transmcp
where transmcp can be replaced by any filename containing a GAMS model.
Many other command line options for GAMS exist; the reader is referred to
[4] for further details.
At this stage, control is handed over to the solver which creates a log
providing information on what the solver is doing as time elapses. See Chapter
2 for details about the log file. After the solver terminates, a listing file
is generated containing the solution to the problem. We now describe the
output in the listing file specifically related to complementarity problems.
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