PPT-More Hashing

Hashing Part Two Better Collision Resolution Small parts of this material stolen from File Organization and Access by Austing and Cassel Hash function converts key to file address Collision is when two or more keys hash to the same address. Recently bit minwise hashing has been applied to largescale learning and sublinear time near neighbor search The major drawback of minwise hashing is the expensive pre processing as the method requires applying eg 200 to 500 permutations on the dat Constant Worst-Case Operations with a Succinct Representation. Yuriy. . Arbitman. . Moni. Naor Gil . Segev. Dynamic Dictionary. Data structure representing a set of words . S. From a Universe . Management. 7. . course. Reminder. Disk. . and RAM. RAID . Levels. Disk. . space. management. Buffering. Heap. . files. Page. . formats. Record. . formats. Today. System . catalogue. Hash-based. and. Algorithms. Course slides: Hashing. www.mif.vu.lt. /~. algis. 2. Data Structures for Sets. Many applications deal with sets.. Compilers have symbol tables (set of . vars. , classes). Dictionary is a set of words.. Uri . Zwick. January 2014. Hashing. 2. Dictionaries. D .  . Dictionary() . – Create an empty dictionary. Insert(. D. ,. x. ) . – Insert item . x. into . D. Find(. D. ,. k. ) . – Find an item with key . Yunchao. Gong. UNC Chapel Hill. yunchao@cs.unc.edu. The problem. Large scale image search:. We have a candidate image. Want to search a . large database . to find similar images. Search the . internet. Haim Kaplan . and. Uri . Zwick. January 2013. Hashing. 2. Dictionaries. D .  . Dictionary() . – Create an empty dictionary. Insert(. D. ,. x. ) . – Insert item . x. into . D. Find(. D. ,. k. Hessam. . Zakerzadeh. ISAM. (. Indexed Sequential Access Method. ). Static index structure.. Effective when file is not frequently updated.. Data values reside in leaf nodes.. Leaf pages contain . data entries. Martin Åkerblad. William . bruce. What is . Hashing?. Index. Key. 1. 2. 3. 4. 5. 6. 7. Key. 56. 84. 23. 42. 71. 97. 55. Hash. . function. 56. 42. 71. 23. 84. 55. 97. Value. When to use hashing.. Quick searching in large databases. CST203-2 Database Management Systems. Lecture 7. Disadvantages. on index structure:. We must access an index structure to locate data, or must use binary search, and that results in more I/O operations. Hashing & Partitioning. 1. Peng Sun. Server Load Balancing. Balance load across servers. Normal techniques: . Round-robin? . 2. Limitations of Round Robin. Packets of a single connection spread over several servers. Cyryptocurrency Project Proposal - Spring 2015. SHA Use in Bitcoin. SHA256 used heavily as bitcoin’s underlying cryptographic hashing function. Two examples (of many) are its use in the Merkle tree hash, as well as the proof of work calculation. Plan. I spent the last decade advising on numerous cases where hash tables/functions were used. A few observations on . What data structures I’ve seen implemented and where. What do developers think, were they need help. What is a hashing function?. Fingerprint for a given piece of data. Typically generated by a mathematical algorithm. Produces a fixed length string as its . output. Hashes are sometimes . called a . checksum or message digests.