Assume we have a multiset (a set which each item can have multiplicity $> 1$) of elements from a universe of infinite size. The number of elements in the multiset is finite and we define the cardinality of the multiset to be the number of distinct elements in it.

Because the multiset is large, it is not feasible to count the cardinality by reducing a multiset into a set and find its cardinality instead. The paper proposed a probabilitic algorithm that use $O(\log\log n)$ amount of memory to find the cardinality with certain error probability.

Bibliographic data

   title = "Loglog Counting of Large Cardinalities",
   author = "Marianne Durand and Philippe Flajolet",
   booktitle = "Algorithms ESA 2003",
   pages = "605--617",
   publisher = "Springer",
   series = "LNCS 2832",
   howpublished = "ESA'03",
   year = "2003",