brief introduction on Map Reduce (google white papers) and its work flow for 5 mins presentation

2.  A simple programming model
 Functional model
 For large-scale data processing
 Exploits large set of commodity computers
 Executes process in distributed manner
 Offers high availability

3.  Lots of demands for very large scale data
processing
 A certain common themes for these demands
 Lots of machines needed (scaling)
 Two basic operations on the input
▪ Map
▪ Reduce

4.  Map:
 Accepts input key/value
pair
 Emits intermediate
key/value pair
 Reduce :
 Accepts intermediate
key/value* pair
 Emits output key/value
pair
Very
big
data
Result
M
A
P
R
E
D
U
C
E
Partitioning
Function

5. Very
big
data
Split data
Split data
Split data
Split data
grep
grep
grep
grep
matches
matches
matches
matches
cat
All
matches

8.  Map
 Process a key/value pair to generate intermediate
key/value pairs
 Reduce
 Merge all intermediate values associated with the
same key
 Partition
 By default : hash(key) mod R
 Well balanced

9.  No reduce can begin until map is complete
 Master must communicate locations of
intermediate files
 Tasks scheduled based on location of data
 If map worker fails any time before reduce
finishes, task must be completely rerun
 MapReduce library does most of the hard work
for us!

10.  User to do list:
 indicate:
▪ Input/output files
▪ M: number of map tasks
▪ R: number of reduce tasks
▪ W: number of machines
 Write map and reduce functions
 Submit the job

11.  String Match, such as Grep
 Reverse index
 Count URL access frequency
 Lots of examples in data mining

13.  Provide a general-purpose model to simplify
large-scale computation
 Allow users to focus on the problem without
worrying about details

14.  Original paper
(http://labs.google.com/papers/mapreduce.h
tml)
 On wikipedia
(http://en.wikipedia.org/wiki/MapReduce)
 Hadoop – MapReduce in Java
(http://lucene.apache.org/hadoop/)
 http://code.google.com/edu/parallel/mapred
uce-tutorial.html