Generate-Test-Aggregate is a library for systematic parallel programming of MapReduce. This slides is made for my presentation on PPoPP - PMAM 2013.

1. A Generate-Test-Aggregate
Parallel Programming Library
Yu Liu1, Kento Emoto2, Zhenjiang Hu3
1The Graduate University for Advanced Studies
2The University of Tokyo
3National Institute of Informatics
PPoPP PMAM 2013
Systematic Parallel Programming for MapReduce

2. Outline
Introduction to GTA
The GTA library
 Implementation strategy
 Programming interface
 Automatic parallelization and optimization
Applications and evaluations
Conclusions

3. Outline
Introduction to GTA
The GTA library
 Implementation strategy
 Programming interface
 Automatic parallelization and optimization
Applications and evaluations
Conclusions

4. The GTA Programming Methodology
 Simple programming pattern
1. Generate all possible solution candidates;
2. Test and filter candidates;
3. Aggregate the valid candidates.
 Expressive and code efficient
 Covers a large class of problems
 Automatic optimization and parallelization
~ Kento Emoto, et.al., [ESOP’12]

5. An Example: The Knapsack Problem
Writing a parallel (MapReduce) program for the
knapsack problem is not easy.
Picture from Wikipedia

6. input: [ (1 $, 2 Kg), (2 $, 6 Kg), (3 $, 10 Kg) ]
weight limitation =15
generate:
[ [ ], [ (1$, 2 Kg) ], [ (2$, 6 Kg) ], [ (3 $, 10 Kg) ], [(1$, 2 Kg) , (2$,
6 Kg) ], [1$, 2 Kg) , (3 $, 10 Kg) ], [(2$, 6 Kg) , (3 $, 10 Kg) ],
[(1$, 2 Kg) , (2$, 6 Kg) , (3 $, 10 Kg) ] ]
test: [true, true, true, true, true, false, false]
filter: [ [ ], [ (1$, 2 Kg) ], [ (2$, 6 Kg) ], [ (3 $, 10 Kg) ],
[(1$, 2 Kg) , (2$, 6 Kg) ], [1$, 2 Kg) , (3 $, 10 Kg) ] ]
aggregate: 0$, 1$, 2 $, 3$, 3$, 4$

7. Naively implementing Knapsack is inefficient (O(2n)).
Input (length) Time (ms)
8 30
12 86
16 97
20 2829
24
java.lang.OutOfMemoryError: Java heap
space
performance of the naïve Knapsack program
The GTA fusion theorem is introduced for resolve
efficiency problem

8. GTA Fusion
mapReduce
able
predicates
generator
aggregator
map ( mapReduceable.f ) .
reduce ( mapReduceable.combine )
MapReduce

9. Definitions of G,T,A
Class Name Algebraic Structure
Generator polymorphic semiring
generator
Predicate almost list
homomorphism
Aggregator semiring homomorphism
Ref: K.Emoto [ESOP’12]

10. Main Contributions
The implementation of a GTA library
 A simple and statically typed GTA-DSL is
implemented
 Algebraic structures and
computations/transformations of them are
implemented
Evaluation of GTA methodology

11. Outline
GTA programming methodology
The GTA library
 Implementation strategy
 Programming interface
 Automatic parallelization and optimization
Applications and evaluations
Conclusions

12. Object-oriented Functional Style
We defined the basic
algebraic structures.
Relations/transformations
of the algebras are well
typed

13. Examples

14. Outline
GTA programming methodology
The GTA library
 Implementation strategy
 Programming interface
 Automatic parallelization and optimization
Applications and evaluations
Conclusions

15. The users write GTA expressions like:
generate(g:GEN) filter(t:Predicate)* aggregate(a:Aggregator)
G‧T‧A Programming DSL
GEN, Aggregator, Predicate are Scala traits defined in the GTA library

16. Outline
GTA programming methodology
The GTA library
 Implementation strategy
 Programming interface
 Automatic parallelization and optimization
Applications and evaluations
Conclusions

17. GTA-fusion
G+A+T 𝑀𝑎𝑝𝑅𝑒𝑑𝑢𝑐𝑒𝑎𝑏𝑙𝑒[𝑓,⊕]
Input x1, x2, x3, … , xn
MAP
REDUCE
table1 tablen
f f f f
…
table1 tablentable2 ⊕ ⊕⊕ …
[EuroPar’11]

18. Implementation of GTA
Fusion/Optimization
The main difficulties:
How to define a polymorphic generator
How to define a predicate for test
How to define intermediate data structures
and other algebraic structures

19. Outline
GTA programming methodology
The GTA library
 Implementation strategy
 Programming interface
 Automatic parallelization and optimization
Applications and evaluations
Conclusions

20. More Examples
More examples in the paper and source package:
 Extended Knapsack problems
 The maximum-segments-sum problem
 Finding the most possible sequence (viterbi algorithm)
More information on: https://bitbucket.org/inii/gtalib

21. G‧T‧A Building Blocks
Our library provides commonly used G·T·A building
blocks and users can also implement their own G,T,As.

22. Performance Evaluations
Evaluations on EdubaseCluster (Cloud)
– Up to 32 VM nodes, each has 3GB RAM, 1 single
core CPU
– Executed on Spark – an in-memory MR cluster

23. Execution Time (Knapsack)
203.63
92.83 64.64 47.76 37.06 29.78 25.17 23.25
1727.973
679.305
637.33
471.2
362.36
287.08
234.25 223.44
0
200
400
600
800
1000
1200
1400
1600
1800
4 8 12 16 20 24 28 32
Time(second)
Number of VM nodes
1.00E+07 items
1.00E+08 items

24. Linear Speedup
0
1
2
3
4
5
6
7
8
9
4 8 12 16 20 24 28 32
speedup
number of VM
Knapsack
ViterbiAlg
MSS

25. Outline
GTA programming methodology
The GTA library
 Implementation strategy
 Programming interface
 Automatic parallelization and optimization
Applications and evaluations
Conclusions

26. Conclusions
We show GTA can be efficiently implemented
GTA-DSL can simplify parallel programming
 Simple programming model
 Good code efficiency
GTA-DSL is architecture independent

27. Future Works
Enrich the library by more building blocks in
terms of G, T, A
GTA-DSL can be extended to processing more
complex data structures such as tree/graph

28. Q&A
Thank you very much!