CSC352 Homework 4

This homework is due 4/20/10, at midnight.

Problem #1

Below is the timeline of the WordCount program running on 4 xml files of 180 MB each on a cluster of 6 single-core Linux servers. (data available here). The files are in the HDFS on our cluster, in wikipages/block.

Question

Explain the camel back of the time line, in particular the dip in the middle of the Map tasks. Note that this is not an artifact of unsynchronized clocks. The server clocks had been synchronized before the experiment.

Submission

Submit your answer as a pdf from your 352b beowulf account, please.

    submit hw4 hw4a.pdf

Problem #2

Write a Map/Reduce program that reports the number of unique categories and the number of times they appear in wikipages/00/00 on the HDFS. wikipages/00/00 contains 591 individual wikipages in xml.

Same question for the categories in wikipages/block/all_00.xml, which contains all the wikipages with the Ids of the form x...x00xx. all_00.xml contains 117,617 individual wiki pages.

You are free to write in Java or use streaming and program in Python or some other language of your choice.

Question 1

Report the execution time of your two versions in the header of your program(s).

Question 2

There could be a problem with the exactness of the result when a MapReduce program processes the file all_00.xml. Why? Report the answer in the header of your program(s).

Note: all the 5 million wikipedia files are available on the local disk of hadoop6, which, unlike the other servers in our cluster contains only one OS, Ubuntu, which takes over the whole local disk, and offers us the server with the biggest local storage.

Submission

Submit your program(s) as above:

  submit hw4  yourprogram
  submit hw4  yourotherprogram

Problem #3

Write a Map/Reduce program that reports the five most frequent words in each page, and the number of times they occur in all the pages processed. They should not include stop-words.