XPRSreadprob (READPROB)

XPRSreadprob

READPROB

Purpose

Reads an (X)MPS or LP format matrix from file.

Synopsis

int XPRS_CC XPRSreadprob(XPRSprob prob, const char *probname, const char *flags);

READPROB [-flags] [probname]

Arguments

prob

The current problem.

probname

The path and file name from which the problem is to be read. Limited to MAXPROBNAMELENGTH characters. If omitted (console users only), the default problem_name is used with various extensions - see below.

flags

Flags to be passed:

l	only probname.lp is searched for;
z	read input file in gzip format from a .gz file [ Console only ]

Related controls

Integer

EXTRACOLS	Number of extra columns to be allowed for.
EXTRAELEMS	Number of extra matrix elements to be allowed for.
EXTRAMIPENTS	Number of extra global entities to be allowed for.
EXTRAPRESOLVE	Number of extra elements to allow for in presolve.
EXTRAROWS	Number of extra rows to be allowed for.
KEEPNROWS	Status for nonbinding rows.
MPSECHO	Whether MPS comments are to be echoed.
MPSFORMAT	Specifies format of MPS files.
SCALING	Type of scaling.

Double

MATRIXTOL	Tolerance on matrix elements.
SOSREFTOL	Minimum gap between reference row entries.

String

MPSBOUNDNAME	The active bound name.
MPSOBJNAME	Name of objective function row.
MPSRANGENAME	Name of range.
MPSRHSNAME	Name of right hand side.

Example 1 (Library)

XPRSreadprob(prob,"myprob","");

This instructs the Optimizer to read an MPS format matrix from the first file found out of myprob.mat, myprob.mps or (in LP format) myprob.lp.

Example 2 (Console)

READPROB -l

This instructs the Optimizer to read an LP format matrix from the file problem_name .lp.

Further information

1. If no flags are given, file types are searched for in the order: .mat, .mps, .lp. Matrix files are assumed to be in XMPS or MPS format unless their file extension is .lp in which case they must be LP files.

2. If probname has been specified, the problem name is changed to probname, ignoring any extension.

3. XPRSreadprob ( READPROB) will take as the objective function the first N type row in the matrix, unless the string parameter MPSOBJNAME has been set, in which case the objective row sought will be the one named by MPSOBJNAME. Similarly, if non-blank, the string parameters MPSRHSNAME, MPSBOUNDNAME and MPSRANGENAME specify the right hand side, bound and range sets to be taken. For example:
MPSOBJNAME="Cost"
MPSRHSNAME="RHS 1"
READPROB
The treatment of N type rows other than the objective function depends on the KEEPNROWS control. If KEEPNROWS is 1 the rows and their elements are kept in memory; if it is 0 the rows are retained, but their elements are removed; and if it is -1 the rows are deleted entirely. The performance impact of retaining such N type rows will be small unless the presolve has been disabled by setting PRESOLVE to 0 prior to optimization.

4. The Optimizer checks that the matrix file is in a legal format and displays error messages if it detects errors. When the Optimizer has read and verified the problem, it will display summary problem statistics.

5. By default, the MPSFORMAT control is set to -1 and XPRSreadprob ( READPROB) determines automatically whether the MPS files are in free or fixed format. If MPSFORMAT is set to 0, fixed format is assumed and if it is set to 1, free format is assumed. Fields in free format MPS files are delimited by one or more blank characters. The keywords NAME, ROWS, COLUMNS, QUADOBJ / QMATRIX, QCMATRIX, DELAYEDROWS, MODELCUTS, SETS, RHS, RANGES, BOUNDS and ENDATAmust start in column one and no vector name may contain blanks. If a special ordered set is specified with a reference row, its name may not be the same as that of a column. Note that numeric values which contain embedded spaces (for example after unary minus sign) will not be read correctly unless MPSFORMAT is set to 0.

6. If the problem is not to be scaled automatically, set the parameter SCALING to 0 before issuing the XPRSreadprob ( READPROB) command.

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XPRSreadprob (READPROB)

XPRSreadprob

READPROB