Alfredo Kalaitzis R The gptk package implements a general-purpose toolkit for Gaussian process regression with an RBF covariance function. Other software that way be useful for implementing Gaussian process models: See Tom Minka 's page on accelerating matlab and his lightspeed toolbox.
A B-tree is kept balanced by requiring that all leaf nodes be at the same depth. This depth will increase slowly as elements are added to the tree, but an increase in the overall depth is infrequent, and results in all leaf nodes being one more node farther away from the root.
B-trees have substantial advantages over alternative implementations when the time to access the data of a node greatly exceeds the time spent processing that data, because then the cost of accessing the node may be amortized over multiple operations within the node.
This usually occurs when the node data are in secondary storage such as disk drives. By maximizing the number of keys within each internal nodethe height of the tree decreases and the number of expensive node accesses is reduced.
In addition, rebalancing of the tree occurs less often. The maximum number of child nodes depends on the information that must be stored for each child node and the size of a full disk block or an analogous size in secondary storage. While B-trees are easier to explain, practical B-trees using secondary storage need a large number of child nodes to improve performance.
Variants[ edit ] The term B-tree may refer to a specific design or it may refer to a general class of designs. In the narrow sense, a B-tree stores keys in its internal nodes but need not store those keys in the records at the leaves.
This spill operation is less costly to do than split, because it requires only shifting the keys between existing nodes, not allocating memory for a new one. B-trees can be turned into order statistic trees to allow rapid searches for the Nth record in key order, or counting the number of records between any two records, and various other related operations.
If the table had 1, records, then a specific record could be located with at most 20 comparisons: Large databases have historically been kept on disk drives. The time to read a record on a disk drive far exceeds the time needed to compare keys once the record is available. The time to read a record from a disk drive involves a seek time and a rotational delay.
The seek time may be 0 to 20 or more milliseconds, and the rotational delay averages about half the rotation period. For a RPM drive, the rotation period is 8. Naively, then, the time to locate one record out of a million would take 20 disk reads times 10 milliseconds per disk read, which is 0.
A disk block might be 16 kilobytes. If each record is bytes, then records could be stored in each block. The disk read time above was actually for an entire block. Once the disk head is in position, one or more disk blocks can be read with little delay. To speed the search further, the first 13 to 14 comparisons which each required a disk access must be sped up.
An index speeds the search[ edit ] A significant improvement can be made with an index. In the example above, initial disk reads narrowed the search range by a factor of two. That can be improved substantially by creating an auxiliary index that contains the first record in each disk block sometimes called a sparse index.
Finding an entry in the auxiliary index would tell us which block to search in the main database; after searching the auxiliary index, we would have to search only that one block of the main database—at a cost of one more disk read.
The index would hold 10, entries, so it would take at most 14 comparisons. Like the main database, the last 6 or so comparisons in the aux index would be on the same disk block. The index could be searched in about 8 disk reads, and the desired record could be accessed in 9 disk reads.DEF CON The Panel.
Mike Petruzzi (wiseacre), Senior Cyber Security Penetration Tester Nikita Kronenberg Not a Security Researcher, DEF CON PushPin Plug Russ Rogers Chief of Operations, DEF CON.
DEF CON has changed for the better since the days at the Alexis Park. Best Paper Awards in Computer Science (since ) By Conference: AAAI ACL CHI CIKM CVPR FOCS FSE ICCV ICML ICSE IJCAI INFOCOM KDD MOBICOM NSDI OSDI PLDI PODS S&P SIGCOMM SIGIR SIGMETRICS SIGMOD SODA SOSP STOC UIST VLDB WWW Institutions with the most Best Papers.
Much of this data was entered by . Course Listings INSTITUTE FOR CLINICAL RESEARCH EDUCATION (ICRE) COURSE DESCRIPTIONS. Clinical Research (CLRES) Medical Education (MEDEDU) Descriptions of Courses Offered Through Other University Departments. 1 Information Extraction. Information comes in many shapes and sizes.
One important form is structured data, where there is a regular and predictable organization of entities and timberdesignmag.com example, we might be interested in the relation between companies and locations. Contents Awards Printed Proceedings Online Proceedings Cross-conference papers Awards In honor of its 25th anniversary, the Machine Learning Journal is sponsoring the awards for the student authors of the best and distinguished papers.
Best Paper Awards in Computer Science (since ) By Conference: AAAI ACL CHI CIKM CVPR FOCS FSE ICCV ICML ICSE IJCAI INFOCOM KDD MOBICOM NSDI OSDI PLDI PODS S&P SIGCOMM SIGIR SIGMETRICS SIGMOD SODA SOSP STOC UIST VLDB WWW Institutions with the most Best Papers. Much of this data was entered by hand (obtained by contacting past conference organizers, .