
EplexInstance:eplex_solve(-Cost)

   Explicitly invoke the external solver associated with EplexInstance.

Arguments
   Cost                Value of returned solution

Type
   library(eplex)

Description

   Explicitly triggers the solver associated with the eplex instance 
   EplexInstance. If the solver was set up without any trigger conditions,
   then it needs to be explicitly triggered via a call to this predicate.

   The external solver's LP, QP or MIP solver is applied to the
   problem represented by the eplex instance.  Precisely which method is used
   depends on the options given at set up.  eplex_solve/1 fails if
   there is no solution or succeeds if an optimal solution is found,
   returning the solution's cost in Cost. After a success, various
   solution and status information can be retrieved using eplex_get/2
   and eplex_var_get/3.

   Normally, the external solver is invoked once per call in this
   predicate, but if the problem contain cutpool constraints (see
   lp_add_cutpool_constraints/4), then the external solver may be invoked
   repeatedly to produce a solution which does not violate the cutpool
   constraints. 

   When a solver is triggered repeatedly, each invocation will
   automatically take into account the current variable bounds.  The set of
   constraints considered by the solver is the one given when the solver
   was created plus any new constraints that were posted in the
   meantime.

   The user can define their own handlers (per eplex instance/problem) to
   handle cases where there was some  error condition, or some limits were 
   exceeded during the solving of the problem. If no handler was defined,
   by default an event would be raised. These are:

    suboptimal handler (eplex_suboptimal event)
    	This means that a solution was found but it may be suboptimal.
	The default behaviour is to print a warning and succeed.
    unbounded_handler (eplex_unbounded event)
	This means that the problem is unbounded.  The default
	behaviour is to bind Cost to infinity (positive or negative
	depending on the optimisation direction), print a warning and
	succeed.  CAUTION: No solution values are computed when the
	problem is unbounded, so unless the problem was set up with
	the solution(no) option, an error will occur when trying to
	continue as if the optimisation had succeeded.
    unknown_handler (eplex_unknown event)
    	This means that due to the solution method chosen, it is unknown
	whether the problem is unbounded or infeasible. The default
	behaviour is to print a warning and fail (even though this
	may be logically wrong!).
    abort_handler (eplex_abort event)
    	Some other error condition occurred during optimisation.
	The default behaviour is to print an error and abort.


   Note that the events are raised for the low-level primitive lp_solve/2,
   which is called by eplex_solve/1.


Fail Conditions
   External solver was unable to find a solution.

Exceptions
     5 --- EplexInstance does not a solver setup for it.
   eplex_suboptimal --- Solution was found, but is possibly suboptimal
   eplex_unbounded --- Problem is unbounded, no solution values
   eplex_unknown --- Result is unknown (infeasible or unbounded)
   eplex_abort --- External solver aborted for some reason
    40 --- Solver state had been previously destroyed.

See Also
   eplex_solver_setup / 4, eplex_solver_setup / 1, eplex_var_get / 3, eplex_get / 2, $= / 2, $=< / 2, $>= / 2, =:= / 2, >= / 2, =< / 2, $:: / 2, :: / 2, integers / 1, reals / 1
