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XPRSalter (ALTER)

XPRSalter

ALTER

Purpose
Alters or changes matrix elements, right hand sides and constraint senses in the current problem.
Synopsis
int XPRS_CC XPRSalter(XPRSprob prob, const char *filename);
ALTER [filename]
Arguments
prob 
The current problem.
filename 
A string of up to MAXPROBNAMELENGTH characters specifying the file to be read. If omitted, the default problem_name is used with a .alt extension.
Related controls
Integer
EXTRAELEMS 
Number of extra matrix elements to be allowed for.

Double
MATRIXTOL 
Tolerance on matrix elements.

Example 1 (Library)
Since the following call does not specify a filename, the file problem_name .alt is read in, from which commands are taken to alter the current matrix. 
XPRSalter(prob,"");
Example 2 (Console)
The following example reads in the file fred.alt, from which instructions are taken to alter the current matrix: 
ALTER fred
Further information
1. The file filename.alt is read. It is an ASCII file containing matrix revision statements in the format described in Section The Matrix Alteration (.alt) File. The MODIFY format of the MPS REVISE data is also supported.
2. It is not possible to alter a problem that is in a presolved state. Call XPRSpostsolve to bring the problem back to its original state.
3. If the problem was read from an .lp file, the name to use for the right-hand side is the one given by the attribute RHSNAME which by default is set to RHS00001.
Related topics
Section The Matrix Alteration (.alt) File.

Parent Topic Console and Library Functions

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