XPRSglobal (GLOBAL)

XPRSglobal

GLOBAL

Purpose

Starts the global search for an integer solution after solving the LP relaxation with XPRSmaxim ( MAXIM) or XPRSminim ( MINIM) or continues a global search if it has been interrupted.

This function is deprecated and might be removed in a future release. XPRSmipoptimize should be used instead.

Synopsis

int XPRS_CC XPRSglobal(XPRSprob prob);

GLOBAL

Argument

prob	The current problem.

Related controls

Integer

BACKTRACK	Node selection criterion.
BRANCHCHOICE	Once a global entity has been selected for branching, this control determines whether the branch with the minimum or maximum estimate is followed first.
BREADTHFIRST	Limit for node selection criterion.
COVERCUTS	Number of rounds of lifted cover inequalities at top node.
CPUTIME	1 for CPU time; 0 for elapsed time.
CUTDEPTH	Maximum depth in the tree at which cuts are generated.
CUTFREQ	Frequency at which cuts are generated in the tree search.
CUTSTRATEGY	Specifies the cut strategy.
DEFAULTALG	Algorithm to use with the tree search.
GOMCUTS	Number of rounds of Gomory cuts at the top node.
MAXMIPSOL	Maximum number of MIP solutions to find.
MAXNODE	Maximum number of nodes in Branch and Bound search.
MAXTIME	Maximum time allowed.
MIPLOG	Global print flag.
MIPPRESOLVE	Type of integer preprocessing to be performed.
MIPTHREADS	Number of threads used for parallel MIP search.
NODESELECTION	Node selection control.
REFACTOR	Indicates whether to re-factorize the optimal basis.
SBBEST	Number of infeasible global entities on which to perform strong branching.
SBITERLIMIT	Number of dual iterations to perform strong branching.
SBSELECT	The size of the candidate list of global entities for strong branching.
TREECOVERCUTS	Number of rounds of lifted cover inequalities in the tree.
TREEGOMCUTS	Number of rounds of Gomory cuts in the tree.
VARSELECTION	Node selection degradator estimate control.

Double

MIPABSCUTOFF	Cutoff set after an LP Optimizer command.
MIPABSSTOP	Absolute optimality stopping criterion.
MIPADDCUTOFF	Amount added to objective function to give new cutoff.
MIPRELCUTOFF	Percentage cutoff.
MIPRELSTOP	Relative optimality stopping criterion.
MIPTOL	Integer feasibility tolerance.
PSEUDOCOST	Default pseudo cost in node degradation estimation.

Example 1 (Library)

The following example inputs a problem fred.mat, solves the LP and the global problem before printing the solution to file.

XPRSreadprob(prob,"fred","");
XPRSmaxim(prob,"");
XPRSglobal(prob);
XPRSwriteprtsol(prob);

Example 2 (Console)

The equivalent set of commands for the Console Optimizer are:

READPROB fred
MAXIM
GLOBAL
WRITEPRTSOL

Further information

1. When an optimal LP solution has been found with XPRSmaxim ( MAXIM) or XPRSminim ( MINIM), the search for an integer solution is started using XPRSglobal ( GLOBAL). In many cases XPRSglobal ( GLOBAL) is to be called directly after XPRSmaxim ( MAXIM)/ XPRSminim ( MINIM). In such circumstances this can be achieved slightly more efficiently using the g flag to XPRSmaxim ( MAXIM)/ XPRSminim ( MINIM).

2. If a global search is interrupted and XPRSglobal ( GLOBAL) is subsequently called again, the search will continue where it left off. To restart the search at the top node you need to call either XPRSinitglobal or XPRSpostsolve ( POSTSOLVE).

3. The controls described for XPRSmaxim ( MAXIM) and XPRSminim ( MINIM) can also be used to control the XPRSglobal ( GLOBAL) algorithm.

4. ( Console) The global search may be interrupted by typing CTRL-C as long as the user has not already typed ahead.

5. A summary log of six columns of information is output every n nodes, where -n is the value of MIPLOG (see The Simplex Log).

6. Optimizer library users can check the final status of the global search using the MIPSTATUS problem attribute.

7. The Optimizer may create global files (used for storing parts of the tree when there is insufficient available memory) in excess of 2 GigaBytes. If your filing system does not support files this large, you can instruct the Optimizer to spread the data over multiple files by setting the MAXGLOBALFILESIZE control.

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XPRSglobal (GLOBAL)

XPRSglobal

GLOBAL