en	Statistics

en	:idprefix: stats_

en	Open-addressing and concurrent containers can be configured to keep running statistics of some internal operations affected by the quality of the supplied hash function.

en	Synopsis

en	__stats-summary-type__

en	Provides the average value, variance and standard deviation of a sequence of numerical values.

en	__insertion-stats-type__

en	Provides the number of insertion operations performed by a container and statistics on the associated __probe length__ (number of xref:structures.adoc#structures_open_addressing_containers[bucket groups] accessed per operation).

en	__lookup-stats-type__

en	For successful (element found) or unsuccessful (not found) lookup, provides the number of operations performed by a container and statistics on the associated __probe length__ (number of xref:structures.adoc#structures_open_addressing_containers[bucket groups] accessed) and number of element comparisons per operation.

en	__stats-type__

en	Provides statistics on insertion, successful and unsuccessful lookups performed by a container. If the supplied hash function has good quality, then:

en	Average probe lenghts should be close to 1.0.

en	For successful lookups, the average number of element comparisons should be close to 1.0.

en	For unsuccessful lookups, the average number of element comparisons should be close to 0.0.

en	These statistics can be used to determine if a given hash function can be marked as link:../../../../../container_hash/doc/html/hash.html#ref_hash_is_avalanchinghash[__avalanching__].

en	---