Reading and entering file formats in the Interactive Optimizer

These file formats are appropriate for the Interactive Optimizer.

By default, the Interactive Optimizer displays data according to the ISO-8859-1 encoding (also known as the Latin-1 code page). Likewise by default, the Interactive Optimizer accepts data entered in that encoding as well. CPLEX offers a parameter, the file encoding switch, to change the encoding or code page in use in the Interactive Optimizer, whether for reading files, writing files, entering data, or displaying data. To access or to change that parameter in an interactive session, enter this command:

set read fileencoding

After you enter that command to access the file encoding switch, the Interactive Optimizer prompts you for a string that is the name of a valid encoding or code page. For a complete list of valid strings, consult the web site of a standards organization such as:

• A brief introduction to code pages

• ICU: International Components for Unicode

• International Components for Unicode at IBM

The Interactive Optimizer accepts problems that you read in from files by means of the read command or that you enter interactively by means of the enter command. When you enter a problem interactively, CPLEX uses the LP file format; you may save the problem in any supported file format that you choose.

The read command of the Interactive Optimizer accepts problem files in LP, MPS, and SAV formats. It also accepts basis files in BAS format. Problems previously saved in DUA, EMB, or REW formats are actually in MPS format. Presolved problems saved with the pre option are in SAV format. Problems in which the objective function has been perturbed and the problem saved with the dpe option are in SAV format. Problems in which the righthand side has been perturbed and the problem saved with the ppe option are in SAV format. Normally, CPLEX automatically detects which of these file types it is reading; you may also designate the correct file type if CPLEX does not detect the type automatically.

When  CPLEX reads LP or MPS files, it automatically allocates enough physical memory (if available) to read the problem.

CPLEX reallocates memory automatically as it is reading from LP and MPS files so usually it is not necessary to set values for the parameters ColReadLim, RowReadLim, and NzReadLim, but you can set these parameters to the problem sizes so no reallocations need be done. When  CPLEX reads a SAV file, it is not necessary for you to reset these parameters. SAV files contain sufficient information about the size of the problem for  CPLEX to allocate adequate space. For more information on the read limit parameters, see variable (column) read limit, constraint (row) read limit, and nonzero element read limit in the CPLEX Parameters Reference Manual.