Describes Map Reduce as a programming model for distributed processing.

1. MCS 7101: Cloud Technologies and Architectures
A. Simon Alex
MapReduce
A. Simon Alex MCS 7101 September 30, 2019 1 / 8

2. Overview
1 MapReduce
What is MapReduce?
MapReduce Programming Model
How MapReduce Works?
MapReduce Example
A. Simon Alex MCS 7101 September 30, 2019 2 / 8

3. MapReduce What is MapReduce?
What is MapReduce?
Programming model and implementation developed at Google for pro-
cessing and generating large datasets across a cluster of computers.
MapReduce is used in Nutch (open source web search) and Apache
Hadoop (developed to index rich textual and structural information).
A. Simon Alex MCS 7101 September 30, 2019 3 / 8

4. MapReduce MapReduce Programming Model
MapReduce Programming Model
This programming model is inspired∗ by the map and reduce primitives
of functional programming languages such as Lisp.
map: takes as input a procedure and a sequence of values and applies
the procedure to each value in the sequence.
reduce: takes as input a sequence of values and combines all values
using binary operator.
∗
but not equivalent!
A. Simon Alex MCS 7101 September 30, 2019 4 / 8

5. MapReduce How MapReduce Works?
How MapReduce Works?
MapReduce works by breaking the processing into two phases: the map
phase and the reduce phase.
Each phase has key-value pairs as input and output, the types of which
may be chosen by the programmer.The programmer also specifies two
functions: the map function and the reduce function.
A. Simon Alex MCS 7101 September 30, 2019 5 / 8

6. MapReduce MapReduce Example
MapReduce Example
Challenge
What’s the highest ever recorded Makerere’s CGPA for each year in
their dataset?
A. Simon Alex MCS 7101 September 30, 2019 6 / 8

7. MapReduce MapReduce Example
MapReduce Example
Figure: MapReduce logical data flow
A. Simon Alex MCS 7101 September 30, 2019 7 / 8

8. MapReduce Conclusion
Questions?
A. Simon Alex MCS 7101 September 30, 2019 8 / 8