lib(branch_and_bound)


	This is a solver-independent library implementing branch-and-bound
	primitives. It can be used with any nondeterministic search routine
	that instantiates a cost variable when a solution is found. The cost
	variable can be an arbitrary numerical domain variable or even a
	simple domain-less variable.
	
	The main predicates are bb_min/3, bb_min/6 and, as a shorthand,
	minimize/2.
	
	Note on the treatment of bounded reals: The library allows the cost
	to be instantiated to a number of type breal. This is useful e.g.
	when using lib(ic) to solve problems with continuous variables.
	When the variable domains have been narrowed sufficiently, the
	problem variables (in particular the cost variable) should be
	instantiated to a bounded real, e.g. using the following idiom:
	
		X is breal_from_bounds(get_min(X),get_max(X))
	
	Bounded reals contain some uncertainty about their true value. If
	this uncertainty is too large, the branch-and-bound procedure may
	not be able to compare the quality of two solutions. In this case,
	a warning is issued and the search terminated prematurely.  The
	problem can be solved by increasing the delta-parameter, or by
	locating the cost value more precisely.
	

