## 9.10 Solver Behaviour Differences

In general, an MP problem can have more than one optimal solution (i.e.
different sets of assignments to the problem variables that gives the
optimal objective value). Any of these solutions is correct, and the
external solver will return one of them. It is possible for a different
solver (or even a different version of the same solver) to return another
of these solutions. If the user's program uses the solution values, then it
is possible that the detailed behaviour of the program could depend on the
solver being used.

The solution that is returned can also depend on the detailed settings of
the floating point unit of the processor. Thus changing some of these
settings may change the solution that is returned. It is thus possible for
eplex to give different solutions on the same machine and solver if these
settings are changed (e.g. when ECL^{i}PS^{e} is embedded into a Java
application).