XPRSreadprob (READPROB)
Purpose
Topic areas
Synopsis
int XPRS_CC XPRSreadprob(XPRSprob prob, const char *filename, const char *flags);
READPROB [-flags] [filename]
Arguments
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prob
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The current problem.
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filename
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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.
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flags
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Flags to be passed:
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Related controls
Integer
Double
String
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Number of extra columns to be allowed for.
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Number of extra matrix elements to be allowed for.
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Number of extra MIP entities to be allowed for.
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Number of extra rows to be allowed for.
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Status for nonbinding rows.
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Whether MPS comments are to be echoed.
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Specifies format of MPS files.
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Type of scaling.
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Double
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Tolerance on matrix elements.
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Minimum gap between reference row entries.
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String
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The active bound name.
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Name of objective function row.
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Name of range.
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Name of right hand side.
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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.
See also examples
addmipsol.c, fixbv.c, globjpar.c, glrhspar.c, knapsack.c, mipsolenum.c, mipsolpool.c, mostviolated.c, repair.c, roundint.c, savesol.c, tableau.c, trimloss.c.
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 the function fails and the error is anything but "Xpress has not been initialized" or "out of memory" then the problem will be reset to empty and the objective sense will be reset to "minimize". If the function returns with "out of memory" then the only safe thing to do with the problem is to call
XPRSdestroyprob().
2. If no flags are given, file types are searched for in the order:
.mps,
.mat,
.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. Files with compressed extensions are also searched for, e.g.,
.mps.gz.
3. The Optimizer can read matrix files that have been compressed using one of the following formats, as long as the command-line tool necessary to decompress the file can be located in the path:
bzip2,
xz,
lzma,
Z,
zip,
tar,
tgz. The Optimizer has built-in support for the
gz format: no external tools are necessary to read gzipped matrix files.
4. If
filename has been specified, the problem name is changed to
filename, ignoring any extension.
5.
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.
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.
6. 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.
7. 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.
8. If the problem is not to be scaled automatically, set the parameter
SCALING to
0 before issuing the
XPRSreadprob (
READPROB) command.
Related topics
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