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, ILOG CPLEX uses the LP file format; you may save the problem in any supported file format that you choose.

The read command of the ILOG CPLEX 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 and perturbed problems saved with the dpe or ppe option are in SAV format. Normally, ILOG CPLEX automatically detects which of these file types it is reading; you may also designate the correct file type if ILOG CPLEX does not detect the type automatically.

When ILOG CPLEX reads LP or MPS files, it automatically allocates enough physical memory (if available) to read the problem. However, for large, repetitively solved problems, you should be sure that the read-size parameters are set slightly higher than the actual problem size. Read-size parameters for the Interactive Optimizer / Callable Library / Concert Technology Library are listed below.

• Read-size parameter for constraints:

READ CONSTRAINTS / CPX_PARAM_ROWREADLIM /

READ CONSTRAINTS / CPX_PARAM_ROWGROWTH / RowGrowth

• Read-size parameter for variables:

READ VARIABLES / CPX_PARAM_COLREADLIM /

READ VARIABLES / CPX_PARAM_COLGROWTH / ColGrowth

• Read-size parameter for nonzeros:

READ NONZEROS / CPX_PARAM_NZREADLIM /

READ NONZEROS / CPX_PARAM_NZGROWTH / NzGrowth

READ QPNONZEROS / CPX_PARAM_QPNZREADLIM /

READ QPNONZEROS / CPX_PARAM_QPNZGROWTH /

The default settings of these parameters suffice for most problems. If the problem size exceeds these limits, ILOG CPLEX begins reading the problem, resets the appropriate limits as needed, and finishes reading. In such a case, ILOG CPLEX reads the problem successfully but may not use memory as efficiently as possible, and consequently performance may degrade slightly.

You can reset those parameters yourself in the Interactive Optimizer with the command set read and its options. If you frequently solve a problem that exceeds the default settings of these parameters, we recommend that you create a parameter specification file to set the limits appropriate to your problem. The CPLEX parameters are described in Appendix A, Parameter Table.

When ILOG 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 ILOG CPLEX to allocate adequate space.