1. What is Spark?

1. What is Spark?#

A unified compute engine and a set of libraries for parallel data processing on computer clusters.
Click the JupyterHub link

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Unified: Spark supports a wide range of data analytic tasks over the same computing engine and a consistent set of APIs.
Computing engine: Spark handles loading data from storage systems and perform computation on the data (in memory) rather than on permanent storage. To adhere to the data locality principle, Spark relies on APIs to provide a transparent common interface with different storage systems for all applications.
Libraries: Via its APIs, Spark supports a wide array of internal and external libraries for complex data analytic tasks.

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Research project at UC Berkeley AMP Lab in 2009 to address drawbacks of Hadoop MapReduce.
Paper published in 2010: Spark: Cluster Computing with Working Sets
Source code is contributed to Apache in 2013. The project had more than 100 contributors from more than 30 organizations outside UC Berkeley.
Version 1.0 was released in 2014.
Currently, Spark is being used extensively in academic and industry (NASA, CERN, Uber, Netflix …).

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What is map? A function/procedure that is applied to every individual elements of a collection/list/array/…

int square(x) { return x*x;}
map square [1,2,3,4] -> [1,4,9,16]

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What is “reduce”? A function/procedure that performs an operation on a list. This operation will “fold/reduce” this list into a single value (or a smaller subset).

reduce ([1,2,3,4]) using sum -> 10
reduce ([1,2,3,4]) using multiply -> 24

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Programmers implement:
- Map function: Take in the input data and return a key,value pair.
- Reduce function: Receive the key,value pairs from the mapper and provide a final output as a reduction operation on the pairs.
MapReduce Framework handles everything else.
Spark implements a MapReduce framework.

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