Minimal perfect hash functions provide space-efficient and collision-free hashing on static sets. Existing algorithms and implementations that build such functions have practical limitations on the number of input elements they can process, due to high construction time, RAM or external memory usage. We revisit a simple algorithm and show that it is highly competitive with the state of the art, especially in terms of construction time and memory usage. We provide a parallel C++ implementation called BBhash. It is capable of creating a minimal perfect hash function of 10^{10} elements in less than 7 minutes using 8 threads and 5 GB of memory, and the resulting function uses 3.7 bits/element. To the best of our knowledge, this is also the first implementation that has been successfully tested on an input of cardinality 10^{12}. Source code: https://github.com/rizkg/BBHash
@InProceedings{limasset_et_al:LIPIcs.SEA.2017.25, author = {Limasset, Antoine and Rizk, Guillaume and Chikhi, Rayan and Peterlongo, Pierre}, title = {{Fast and Scalable Minimal Perfect Hashing for Massive Key Sets}}, booktitle = {16th International Symposium on Experimental Algorithms (SEA 2017)}, pages = {25:1--25:16}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-036-1}, ISSN = {1868-8969}, year = {2017}, volume = {75}, editor = {Iliopoulos, Costas S. and Pissis, Solon P. and Puglisi, Simon J. and Raman, Rajeev}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2017.25}, URN = {urn:nbn:de:0030-drops-76196}, doi = {10.4230/LIPIcs.SEA.2017.25}, annote = {Keywords: Minimal Perfect Hash Functions, Algorithms, Data Structures, Big Data} }
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