Effectiveness and code optimization in Java

Effectiveness and code optimization
in Java
Sergey Morenets, sergey.morenets@gmail.com
December, 4 2015

About author
• Works in IT since 2000
• 12 year of Java SE/EE experience
• Regular speaker at Java conferences
• Author of “Development of Java applications” and “Main
errors in Java programming ”books
• Founder of http://it-simulator.com

Agenda
• What is effectiveness?
• Code optimization
• JVM optimization
• Code samples
• Measurements

Ideal code
Concise Readable
Self-describing Reusable
Testable Modern
Flexible Scalable
Effective

Effectiveness
• Hard to determine on code/design review stages or in
unit-tests
• Is relevant for the specific project configuration
• Cannot be defined in development environment
• Depends on the application environment
• Premature optimization is evil
• Hardware-specific
• The only aspect of the ideal code that affects users

Effectiveness
CPU
utilization
Memory
utilization
Network I/O
utilization
Disk I/O
utilization

Effectiveness
• Can be measured
• Can be static or dynamic
• Can be tuned

Tuning
• JVM options
• Metaspace/heap/stack size
• Garbage collector options
• http://blog.sokolenko.me/2014/11/javavm-options-
production.html
• http://www.javaspecialists.eu/

Code optimization
Java compiler
JIT compiler
JVM

Code optimization
public int execute();
Code:
0: iconst_2
1: istore_1
2: iinc 1, 1
5: iconst_1
6: ireturn

Code optimization
Code:
0: iconst_2
1: istore_1
2: iconst_1
3: ireturn

Code optimization
public void execute();
Code:
0: return

Code optimization
public static boolean get();
Code:
0: iconst_1
1: ireturn

Code optimization
Code:
0: iconst_2
1: istore_1
2: iconst_4
3: istore_2
4: iload_1
5: iload_2
6: iadd
7: ireturn

Code optimization
Code:
0: bipush 6
2: ireturn

Code optimization
Code:
0: bipush 12
2: ireturn

Javacompiler
Dead code elimination
Constant folding
Fixed expression calculation

Measurements
• JMH is micro benchmarking framework
• Developed by Oracle engineers
• First release in 2013
• Requires build tool(Maven, Gradle)
• Can measure throughput or average time
• Includes warm-up period

Environment
• JMH 1.11.1
• Maven 3.3.3
• JDK 1.8.0.65
• Intel Core i7, 4 cores, 16 GB

Measurements
Type Time(ns)
Multiply 4 2,025
Shift 2,024

Measurements
Type Time(ns)
Multiply 17 2,04
Shift 2,04

Measurements
Type Time(ns)
Field 1,945
Method 1,933

Measurements
Type Time(ns)
Static 2,17
Instance 2,30

Measurements
Type Time(ns)
Addiction 2,06
Incrementation 2,06

Measurements
Type Time(ns)
Standard 2,10
Addiction 2,08
XOR 2,04

Measurements
Type Time(ns)
Ternary operation 2,05
If operator 2,03

Measurements
Type Time(ns)
Long usage(small numbers) 3
Long usage(average numbers) 19
Long usage(big numbers) 33
Long usage (not a number) 849
Regexp (small numbers) 58
Regexp (average numbers) 75
Regexp (big numbers) 82
Regexp (not a number) 47

Measurements
Type Time(ns)
Loop(1000 elements) 52,6
arrayCopy(1000 elements) 45,6
Loop(100 000 elements) 21666
arrayCopy(100 000 elements) 21707
Loop(10 000 000 elements) 6432557
arrayCopy(10 000 000 elements) 6616976

Measurements
Type Time(ns)
Rows(10 elements) 37
Columns(10 elements) 67
Rows(5000 elements) 9,6(ms)
Columns(5000 elements) 387(ms)

Measurements
Type Time(ns)
+ 7,62
Concat 13,4
StringBuffer 7,32
StringBuilder 7,24

Measurements
Type Time(ns)
Entries (10 pairs) 30
Keys/Values(10 pairs) 70
Entries (1000 pairs) 2793
Keys/Values(1000 pairs) 8798
Entries (200 000 pairs) 237652
Keys/Values(200 000 pairs) 350821

Measurements
Type Time(ns)
For (10 elements) 4,9
For-each (10 elements) 5,1
For (1000 elements) 260
For (50000 elements) 12957
For-each (50000 elements) 12958

Measurements
Type Time(ns)
For optimized(10 elements) 5,07

Measurements
Type Time(ns)
Sequential (10 elements) 5
Parallel (10 elements) 6230

Measurements
Type Time(ns)
Sequential (5 000 000 elements) 1 765 206
Parallel (5 000 000 elements) 2 668 564
Sequential (500 000 000) 183 ms
Parallel (500 000 000) 174 ms

Measurements
Type Time(ns)
If 2,40
Exceptions 2,47

Measurements
Type Time(ns)
Parse(1000 tokens) 12239
Parse with intern(1000 tokens) 72814

Measurements
Type Time(ns)
Fill array (1000 elements) 148
Fill bit set(1000 elements) 1520
Fill array (50 000 elements) 4669
Fill bit set(50 000 elements) 71395

Measurements
Type Time(ns)
Fill array (1000 elements) 148
Fill bit set(1000 elements) 261
Fill array (50 000 elements) 4669
Fill bit set(50 000 elements) 12758

Measurements
Type Time(ns)
New ArrayList() 3,6
emptyList() 2,4

Measurements
Type Time(ns)
Array(100 elements) 58
List(100 elements) 390
Array(10 000 elements) 4776
List(10 000 elements) 48449

LIFO
Stack
LinkedList
ArrayDeque

Measurements
Type Time(ns)
Stack(1000 elements) 5729
LinkedList(1000 elements) 7928
ArrayDeque(1000 elements) 4366
Stack(100 000 elements) 588770
LinkedList(100 000 elements) 773684
ArrayDeque(100 000 elements) 484280

Collections
Type Time(ns)
Fill HashMap(1000 elements) 16000
Fill TreeMap(1000 elements) 40115
Fill HashMap(100 000 elements) 2 027 116
Fill TreeMap(100 000 elements) 11 195 422
Iteration HashMap(1000 elements) 3086
Iteration TreeMap(1000 elements) 5038

Reflection
Type Time(ns)
instanceof 2,266
isAssignableFrom 2,146
== 2,401

Measurements
Type Time(ns)
New object 3,0
Reflection 5,4

Measurements
Type Time(ns)
Method call 0,3
Reflection 232

Measurements
Type Time(ns)
Method call 0,3
Reflection (cached) 3,1

Measurements
Type Time(ns)
Clone 6,5
Direct copying 3,8

Measurements
Type Time(ns)
ArrayList (1000 elements) 4766
ArrayList (100 000 elements) 381707
LinkedList (1000 elements) 5504
LinkedList (100 000 elements) 504231

JIT optimization
• Inline methods
• Eliminate locks
• Replace interface with direct method calls
• Join synchronized blocks
• Eliminate dead code
• Drop memory write for non-volatile variables

Q&A
• Sergey Morenets, sergey.morenets@gmail.com

Effectiveness and code optimization in Java

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