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 200 characters specifying the file to be read. If omitted, the default problem_name is used with a .alt extension.
|
Related Controls
Integer
|
|
Number of extra matrix elements to be allowed for.
|
Double
|
|
Zero 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.
Example 2 (Console)
The following example reads in the file fred.alt,
from which instructions are taken to alter the current matrix:
Further information
1. The file
filename.alt is read.
It is an ASCII file containing matrix revision statements in the format described in
The Matrix Alteration (.alt) File. The
MODIFY format of the
MPS
REVISE data is also supported.
2. The command
XPRSalter (
ALTER) and the control
EXTRAELEMS work together to enable the
user to change values and constraint senses in the problem held in memory. For maximum efficiency,
it should be set to reserve space for additional matrix elements. Defining the maximum number of
extra elements that can be added, it must be set before
XPRSreadprob
(
READPROB).
3. It is not possible to alter an integer model which has been presolved. If it is
required to alter such a model after optimization, either turn the presolve off by setting
PRESOLVE to
0 prior to
optimization, or reread the model with
XPRSreadprob (
READPROB).
Related topics
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