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MapReduce is a programming model and an associated implementation for processing and generating big data sets with a parallel and distributed algorithm on a cluster. [1] [2] [3]A MapReduce program is composed of a map procedure, which performs filtering and sorting (such as sorting students by first name into queues, one queue for each name), and a reduce method, which performs a summary ...
obj.reduce(func, initial) obj.reduce(func) Where func receives as arguments the result of the previous operation (or the initial value on the first iteration); the current item; the current item's index or key; and a reference to the obj: Clojure (reduce func initval list) (reduce func initval (reverse list)) (reduce func list) (reduce func ...
[2] [3] [4] The reduction of sets of elements is an integral part of programming models such as Map Reduce, where a reduction operator is applied to all elements before they are reduced. Other parallel algorithms use reduction operators as primary operations to solve more complex problems.
Map functions can be and often are defined in terms of a fold such as foldr, which means one can do a map-fold fusion: foldr f z . map g is equivalent to foldr (f . g) z. The implementation of map above on singly linked lists is not tail-recursive, so it may build up a lot of frames on the stack when called with a large list. Many languages ...
In computability theory and computational complexity theory, a many-one reduction (also called mapping reduction [1]) is a reduction that converts instances of one decision problem (whether an instance is in ) to another decision problem (whether an instance is in ) using a computable function.
One of the most common solutions is object-relational mapping (ORM), which helps connect object-oriented programs to relational databases. Examples of ORM tools include Visual FoxPro, Java Data Objects, and Ruby on Rails ActiveRecord. Some databases, called object databases, are designed to work with object-oriented programming. However, they ...
All-reduce can be interpreted as a reduce operation with a subsequent broadcast (§ Broadcast). For long messages a corresponding implementation is suitable, whereas for short messages, the latency can be reduced by using a hypercube ( Hypercube (communication pattern) § All-Gather/ All-Reduce ) topology, if p {\displaystyle p} is a power of two.
Flexible and fast read mapping program (twice as fast as BWA), achieves a mapping sensitivity comparable to Stampy. Internally uses a memory efficient index structure (hash table) to store positions of all 13-mers present in the reference genome. Mapping regions where pairwise alignments are required are dynamically determined for each read.