Initializing help system before first use

POOLENUMSTRATEGY

Description
Enables extended branch-and-bound search strategies to identify and capture additional solutions into the solution pool. The built-in solution pool will collect solutions encountered during a branch-and-bound search, subject to the limitations imposed by controls such as POOLLIMIT, POOLRELGAP and POOLABSGAP. With the default setting of POOLENUMSTRATEGY=0 the collection will not affect the branch-and-bound search itself. When POOLENUMSTRATEGY > 0, more of the branch-and-bound tree will be explored and additional nodes will be searched based on whether they admit additional solutions that can be added to the solution pool.
Type
Integer
Topic area
Solution Pool
Values
0 
XPRS_POOLENUMSTRATEGY_STANDARD Collect solutions that are found through a standard branch-and-bound search.
1 
XPRS_POOLENUMSTRATEGY_EXTENDED Extend the branch-and-bound search to include solutions reachable through fractional branching.
2 
XPRS_POOLENUMSTRATEGY_FULL Extend the branch-and-bound search to include solutions reachable through both fraction and non-fractional branching on MIP column entities.
Default value
0
Notes
1. Enumeration is only available for MIP column entities. This is either a binary, integer, semi-continuous, semi-integer or partial integer variable. It is not available for continuous variables or non-column MIP entities such as special ordered sets, piece-wise linear functions or general constraints.
2. A typical case when looking for alternative solutions is to find the n-best MIP solutions that differ in the MIP column entities. To do this, set POOLLIMIT = n to collect n solutions and set POOLENUMSTRATEGY=2 to guarantee that all integer solutions are reachable through the branch-and-bound search.
3. In combination with POOLENUMSTRATEGY=1 or 2, it is possible to specify exactly which MIP column entities to include in the enumeration, by passing the corresponding column indices to XPRSloadbranchdirs.
Affects routines
XPRSoptimize, XPRSmipoptimize, XPRSnlpoptimize
See also
POOLLIMIT, POOLSIZE, POOLRELGAP, POOLABSGAP, POOLDUPLICATECHECK
Category
Control

Parent Topic Control Parameters

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