Brief Descriptions of File Formats

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Brief Descriptions of File Formats

INDEX

BAS files are text files governed by Mathematical Programming System (MPS) conventions (that is, they are not binary) for saving a problem basis. They are documented in BAS File Format: Advanced Basis.
BZ2 is not a file format specific to ILOG CPLEX. Rather, this file extension indicates that a file (possibly in one of the formats that ILOG CPLEX reads) has been compressed by BZIP2. On most platforms, ILOG CPLEX can automatically uncompress such a file and then read data from the file in one of the formats briefly described here
CLP is the format ILOG CPLEX uses to represent the conflicting constraints and bounds (a subset of an infeasible model) that were found by the conflict refiner.
CSV files contain comma-separated values. Concert Technology offers facilities in ILOG CPLEX for reading and writing such files. See the Concert Technology Reference Manual for details, especially the classes IloCsvReader, IloCsvLine, and IloCsvReader::Iterator.
DPE is the format ILOG CPLEX uses to write a problem in a binary SAV file after the objective function of the problem has been perturbed.
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 Optimizer to tell ILOG CPLEX to solve the dual formulation of an LP automatically. (You no longer have to tell ILOG CPLEX to write the dual formulation to a DUA file and then tell ILOG CPLEX to read the file back in and solve it.)
EMB is the format ILOG CPLEX uses to save an embedded network it extracts from a problem. EMB files are written in MPS format.
FLT is the format ILOG CPLEX uses to save filters for solution pools.
GZ is not a file format specific to ILOG CPLEX. Rather, this file extension indicates that a file (possibly in one of the formats that ILOG CPLEX reads) has been compressed by gzip, the GNU zip program. On most platforms, ILOG CPLEX can automatically uncompress a gzipped file and then read data from a file in one of the formats briefly described here.
LP (Linear Programming) is a ILOG 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 Interactive Optimizer, you are implicitly using LP format. ILOG CPLEX also reads files in LP format. The section LP File Format: Matrix Models describes the conventions and use of this 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
MPS is an industry-standard, ASCII-text file format for mathematical programming problems. This file format is documented in MPS File Format: Industry Standard. Besides the industry conventions, ILOG CPLEX also supports extensions to this format for ILOG CPLEX-specific cases, such as names of more than eight characters, blank space as delimiters between columns, etc. The extensions are documented in ILOG CPLEX Extensions to MPS Format and in Special Records in MPS Files: ILOG CPLEX Extensions.
MST is an XML format available with the ILOG CPLEX MIP optimizer. It is a text format ILOG CPLEX uses to enter a starting solution for a MIP. MST File Format: MIP Starts documents this file format.
NET is a ILOG CPLEX-specific ASCII format for network-flow problems. It supports named nodes and arcs. NET File Format: Network Flow Models offers a fuller description of this file format.
ORD is a format available with the ILOG 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: Priorities and Branching Orders documents this file format.
PPE is the format ILOG CPLEX uses to write a problem in a binary SAV file after the righthand side has been perturbed.
PRE is the format ILOG CPLEX uses to write a presolved, reduced problem formulation to a binary SAV file. Since a presolved problem has been reduced, it does not correspond to the original problem.
PRM is the format ILOG CPLEX uses to read and write non-default values of parameters in a file. PRM File Format: Parameter Settings documents the format and conventions for reading and writing such files through the Callable Library.
REW is a format to write a problem in MPS format with disguised row and column names. This format is simply an MPS file format with all variable (column) and constraint (row) names converted to generic names. Variables are relabeled x1 through xn, and rows are renamed c1 through cm. This format may be useful, for example, for problems that you consider highly proprietary.
RLP is the LP format using generic names in the Interactive Optimizer.
SAV is a ILOG CPLEX-specific binary format for reading and writing problems and their associated basis information. ILOG 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.
SOL files are XML formatted files that contain solution information; they may also provide an advanced start for an optimization.
XML as a file format is available to C++ users of Concert Technology to serialize models and solutions (that is, instances of IloModel and IloSolution). XML File Format: Serialized Models and Solutions explains more about this serialization API.

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