In addition to other file formats, the read command is also used to read basis files. These files contain information for ILOG CPLEX that tells the simplex method where to begin the next optimization. Basis files usually correspond to the result of some previous optimization and help to speed re-optimization. They are particularly helpful when you are dealing with very large problems if small changes are made to the problem data.
Writing Basis Files on page 50 showed you how to save a basis file for the example after it was optimized. For this tutorial, first read the example.lp file. Then read this basis file by typing the following command:
The message of confirmation:
Basis 'example.bas' read.
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indicates that the basis file was successfully read. If the advanced basis indicator is on, this basis will be used as a starting point for the next optimization, and any new basis created during the session will be used for future optimizations. If the basis changes during a session, you can save it by using the write command.
The general syntax for the read command is:
or
where file_extension corresponds to one of the allowed file formats.
