Gecode::Search::Options Class Reference
[Search engines]

Search engine options More...

#include <search.hh>

Public Member Functions
	Options (void)
	Initialize with default values.
Options	expand (void) const
	Expand with real number of threads.
Public Attributes
bool	clone
	Whether engines create a clone when being initialized.
double	threads
	Number of threads to use.
unsigned int	c_d
	Create a clone after every c_d commits (commit distance).
unsigned int	a_d
	Create a clone during recomputation if distance is greater than a_d (adaptive distance).
Stop *	stop
	Stop object for stopping search.
Static Public Attributes
static const Options	def
	Default options.

Detailed Description

Search engine options

Defines options for search engines. Not all search engines might honor all option values.

c_d as minimal recomputation distance: this guarantees that a path between two nodes in the search tree for which copies are stored has at least length c_d. That is, in order to recompute a node in the search tree, c_d recomputation steps are needed. The minimal recomputation distance yields a guarantee on saving memory compared to full copying: it stores c_d times less nodes than full copying.
a_d as adaptive recomputation distance: when a node needs to be recomputed and the path is longer than a_d, an intermediate copy is created (approximately in the middle of the path) to speed up future recomputation. Note that small values of a_d can increase the memory consumption considerably.

Full copying corresponds to a maximal recomputation distance c_d of 1.

All recomputation performed is based on batch recomputation: batch recomputation performs propagation only once for an entire path used in recomputation.

The number of threads to be used is controlled by a double $n$ (assume that $m$ is the number of processing units available). If $1 \leq n$ , $n$ threads are chosen (of course with rounding). If $n \leq -1$ , then $m + n$ threads are chosen (all but $-n$ processing units get a thread). If $n$ is zero, $m$ threads are chosen. If $0<n<1$ , $n \times m$ threads are chosen. If $-1 <n<0$ , $(1+n)\times m$ threads are chosen.