For the root node of the optimization the constraint and
variable sets can be initialized explicitly. As in many applications
the initial variable and constraint sets are in a one-to-one correspondence
with the items of the initial variable and constraint pools,
we provide this default initialization
mechanism. By default, the first linear program is solved with the barrier
method followed by a crossover to a basic solution,
but we provide a flexible mechanism for the selection of the LP-method
(see Section 
).