class RooNormSetCache

Class RooNormSet cache manage the bookkeeping of multiple instances of sets of integration and normalization observables that effectively have the same definition. In complex function expression many RooArgSets with the same contents may be passed to an object that caches intermediate results dependent on the normalization/integration set To avoid unnecessary cache faulting, This class tracks all instances with the same contents and reports to the owner if the present nset/iset is truely different from the current reference. Class RooNormSet only evaluates each RooArgSet pointer once, it therefore assumes that RooArgSets with normalization and/or integration sets are not changes during their lifetime.