The easiest way to call a predicate if you are only interested in the
first solution is to call the function SP_query(). It will
create a goal from the predicate definition and the arguments, call
it, and commit to the first solution found, if any.
If you are only interested in the side effects of a
predicate, then you can call SP_query_cut_fail(). It will try to
prove the predicate, cut away the rest of the solutions, and
finally fail. This will reclaim any memory used after the call, and
throw away any solution found.