For key search, the signatures of all entries are compared against
the signature of the key that is being looked up. Since all
signatures are contiguously put in a bucket, they can be compared
with vector instructions (AVX2), achieving higher lookup performance.
This patch adds AVX2 implementation in a separate header file.
Signed-off-by: Yipeng Wang <yipeng1.wang@intel.com>
Reviewed-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Bloom Filter (BF) [1] is a well-known space-efficient
probabilistic data structure that answers set membership queries.
Vector of Bloom Filters (vBF) is an extension to traditional BF
that supports multi-set membership testing. Traditional BF will
return found or not-found for each key. vBF will also return
which set the key belongs to if it is found.
Since each set requires a BF, vBF should be used when set count
is small. vBF's false positive rate could be set appropriately so
that its memory requirement and lookup speed is better in certain
cases comparing to HT based set-summary.
This patch adds the vBF implementation.
[1]B H Bloom, “Space/Time Trade-offs in Hash Coding with Allowable
Errors,” Communications of the ACM, 1970.
Signed-off-by: Yipeng Wang <yipeng1.wang@intel.com>
Reviewed-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
One of the set-summary structures is hash-table based
set-summary (HTSS). One example is cuckoo filter [1].
Comparing to a traditional hash table, HTSS has a much more
compact structure. For each element, only one signature and
its corresponding set ID is stored. No key comparison is required
during lookup. For the table structure, there are multiple entries
in each bucket, and the table is composed of many buckets.
Two modes are supported for HTSS, "cache" and "none-cache" modes.
The non-cache mode is similar to the cuckoo filter [1].
When a bucket is full, one entry will be evicted to its
alternative bucket to make space for the new key. The table could
be full and then no more keys could be inserted. This mode has
false-positive rate but no false-negative. Multiple entries
with same signature could stay in the same bucket.
The "cache" mode does not evict key to its alternative bucket
when a bucket is full, an existing key will be evicted out of
the table like a cache. Thus, the table will never reject keys when
it is full. Another property is in each bucket, there cannot be
multiple entries with same signature. The mode could have both
false-positive and false-negative probability.
This patch adds the implementation of HTSS.
[1] B Fan, D G Andersen and M Kaminsky, “Cuckoo Filter: Practically
Better Than Bloom,” in Conference on emerging Networking
Experiments and Technologies, 2014.
Signed-off-by: Yipeng Wang <yipeng1.wang@intel.com>
Reviewed-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Membership library is an extension and generalization of a traditional
filter (for example Bloom Filter and cuckoo filter) structure.
In general, the Membership library is a data structure that provides a
"set-summary" and responds to set-membership queries of whether a
certain element belongs to a set(s). A membership test for an element
will return the set this element belongs to or not-found if the
element is never inserted into the set-summary.
The results of the membership test are not 100% accurate. Certain
false positive or false negative probability could exist. However,
comparing to a "full-blown" complete list of elements, a "set-summary"
is memory efficient and fast on lookup.
This patch adds the main API definition.
Signed-off-by: Yipeng Wang <yipeng1.wang@intel.com>
Reviewed-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
