project - MapReduce ECE 563 Spring 2012 Default Course...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
MapReduce ECE 563 Spring 2012 Default Course Project version 1.0 (1/22/2012) Projects may be performed by teams of two people. If you would like to do another project, let’s talk about it. MapReduce is a programming model that involves two steps. The first, the map step, takes an input set I and groups into N equivalence classes I 0 , I 1 , I 2 , ..., I N-1 . I can be thought of as a set of tuples <key, data> , and the function map maps I into the equivalence classes based on the value of key . In the second reduce step, the equivalence classes are processed, and the set of tuples in an equivalence class I j are reduced into a single value. MapReduce has become very popular in part because of its use by Google, but is an old parallel programming model. It is surprisingly general. To perform a parallel MapReduce, the input is spread across the available processors. Each processor runs one or more instances of map , followed by executing one or more instances of reduce . Each instance of map will potentially form equivalence classes I 0 , I 1 , I 2 , ..., I N-1 . Consider the word counting problem, which can be solved in parallel using MapReduce. Given a list of words, the output should consist of how many times each word appeared in the list (or tex). Viewing the input as tuples, the word is the key , and the data is the constant 1. A naive map function would collect all instances of a word into an equivalence class. Each equivalence class would then be assigned to a processor n , and processor n would determine the cardinality of the equivalence class, which would be the word count. A more intelligent map function would form singleton equivalence classes I word , where the only element is <word, count> . The processor assigned I word to reduce would receive the I word equivalence classes from all of the map functions, and would perform a reduction on the class.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern