This appendix documents the file formats supported by CPLEX.
LP (Linear Programming) is a CPLEX-specific file formatted for entering problems in an algebraic, row-oriented form. In other words, LP format allows you to enter problems in terms of their constraints. When you enter problems interactively in the base system, you are implicitly using LP format. CPLEX will also read files in LP format. The section"LP File Format" on page 433 describes the conventions and usage of this format.
REW is a format to write a problem in MPS format with disguised row and column names. This format may be useful, for example, for problems that you consider highly proprietary. "REW File Format" on page 430 documents this file format.
SAV is a CPLEX-specific binary format for reading and writing problems and their associated basis information. CPLEX includes the basis in a SAV file only if the problem currently in memory has been optimized and a basis exists. This format offers the advantage of being numerically accurate (to the same degree as your platform) in contrast to text file formats that may lose numerical accuracy. It also has the additional benefit of being efficient with respect to read and write time. However, since a SAV file is binary, you cannot read nor edit it with your favorite text editor.
BAS files are text files governed by MPS conventions (that is, they are not binary) for saving a problem basis. They are documented in "BAS File Format" on page 429.
DUA format, governed by MPS conventions, writes the dual formulation of a problem currently in memory so that the MPS file can later be read back in and the dual formulation can then be optimized explicitly. This file format is largely obsolete now since you can use the command set presolve dual in the Interactive Base System to tell CPLEX to solve the dual formulation of an LP automatically. (You no longer have to tell CPLEX to write the dual formulation to a DUA file and then tell CPLEX to read the file back in and solve it.)
set presolve dual
TXT files are ASCII-text files. CPLEX uses this format when it writes solution files in text.
BIN files are binary files. CPLEX uses this format when it writes solution files containing the binary representation of real numbers.
IIS is the format CPLEX uses to represent irreducibly inconsistent sets of constraints.
PRE is the format CPLEX uses to write a presolved, reduced problem formulation to a binary SAV file. Since a presolved problem has been reduced, it will not correspond to the original problem.
PPE is the format CPLEX uses to write a problem in a binary SAV file after the problem has been perturbed for use with the primal simplex optimizer.
DPE is the format CPLEX uses to write a problem in a binary SAV file after the problem has been perturbed for use with the dual simplex optimizer.
EMB is the format CPLEX uses to save an embedded network it extracts from a problem. EMB files are written in MPS format.
MIN format for representing minimum-cost network-flow problems was introduced by DIMACS in 1991. More information about DIMACS network file formats is available via anonymous ftp from ftp://dimacs.rutgers.edu/pub/netflow/general-info/specs.tex.
ftp://dimacs.rutgers.edu/pub/netflow/general-info/specs.tex
NET is a CPLEX-specific ASCII format for network-flow problems. It is flexible and supports named nodes and arcs.
ORD is a format available only if you are licensed to use the CPLEX MIP optimizer. It is used to enter and to save priority orders for branching. It may contain branching instructions for individual variables. "ORD File Format" on page 431 documents this file format.
MST is a text format CPLEX uses to enter a starting solution for a MIP.
SOS is a format available only if you are licensed to use the CPLEX MIP optimizer. It declares special ordered sets, the set branching order, and weights for each set member. "SOS File Format" on page 432 documents this file format.
TRE is a format available only if you are licensed to use the CPLEX MIP optimizer. It saves information about progress through the branch & bound tree. It is a binary format.
VEC is a format available only if you are licensed to use the CPLEX barrier optimizer. It saves the solution to a pure barrier optimization prior to crossover (that is, a nonbasis solution) that can later be read back in and used to initiate crossover. "VEC File Format" on page 430 documents this file format.
QP is a format available only if you are licensed to use the CPLEX barrier optimizer. It contains the coefficients of nonzero coefficients in the Q matrix of a quadratic programming problem. You must enter the linear part of that quadratic program first (by whichever method you choose). QP files are documented on page 428, after remarks about putting quadratic coefficient information into an MPS file.
