Hm, hashCode7() has exactly the same program logic than hashCode1(), but
by different syntax.
hashCode8() should be worse than hashCode7(), because it loads the count
variable twice.
If you compare the byte code by javah or jclasslib bytecode viewer (very
nice tool), you will see that, am I wrong ?
-Ulf
Am 27.02.2010 18:50, schrieb Jason Mehrens:
Here are two more variants you might want to throw into the benchmark.
public int hashCode6() {
int h = hash;
if (h == 0 && count > 0) {
int off = offset;
char val[] = value;
int len = count;
for (int i = 0; i < len; i++) {
h = 31*h + val[off++];
}
hash = h;
}
return h;
}
public int hashCode7() {
int h = hash;
int len;
if (h == 0 && (len = count) > 0) {
int off = offset;
char val[] = value;
for (int i = 0; i < len; i++) {
h = 31*h + val[off++];
}
hash = h;
}
return h;
}
Jason
------------------------------------------------------------------------
Date: Sat, 27 Feb 2010 17:00:14 +0300
Subject: Re: Need reviewer for forward port of 6815768
(File.getXXXSpace) and 6815768 (String.hashCode)
From: dmitry.nadez...@gmail.com
To: core-libs-dev@openjdk.java.net
Ulf,
I ran Caliper benchmarks on different variants of hashCode().
http://code.google.com/p/caliper/
The results and the Caliper code are below:
-Dima
--------- -d32 -clien
0% Scenario{vm=java -d32 -client, benchmark=HashCodeEmpty} 8,85ns;
σ=0,06ns @ 3 trials
8% Scenario{vm=java -d32 -client, benchmark=HashCode1Empty} 7,20ns;
σ=0,04ns @ 3 trials
17% Scenario{vm=java -d32 -client, benchmark=HashCode2Empty} 7,79ns;
σ=0,32ns @ 10 trials
25% Scenario{vm=java -d32 -client, benchmark=HashCode3Empty} 7,88ns;
σ=0,31ns @ 10 trials
33% Scenario{vm=java -d32 -client, benchmark=HashCode4Empty} 7,92ns;
σ=0,31ns @ 10 trials
42% Scenario{vm=java -d32 -client, benchmark=HashCode5Empty} 7,06ns;
σ=0,27ns @ 10 trials
50% Scenario{vm=java -d32 -client, benchmark=HashCodeLong} 145,22ns;
σ=0,68ns @ 3 trials
58% Scenario{vm=java -d32 -client, benchmark=HashCode1Long} 144,58ns;
σ=0,55ns @ 3 trials
67% Scenario{vm=java -d32 -client, benchmark=HashCode2Long} 167,55ns;
σ=1,58ns @ 6 trials
75% Scenario{vm=java -d32 -client, benchmark=HashCode3Long} 122,87ns;
σ=0,34ns @ 3 trials
83% Scenario{vm=java -d32 -client, benchmark=HashCode4Long} 122,69ns;
σ=0,36ns @ 3 trials
92% Scenario{vm=java -d32 -client, benchmark=HashCode5Long} 126,11ns;
σ=0,77ns @ 3 trials
benchmark ns logarithmic runtime
HashCodeEmpty 9 X|||||||||||
HashCode1Empty 7 X||||||||||
HashCode2Empty 8 X|||||||||||
HashCode3Empty 8 X|||||||||||
HashCode4Empty 8 X|||||||||||
HashCode5Empty 7 X||||||||||
HashCodeLong 145 XXXXXXXXXXXXXXXXXXXXXXXXXX|||
HashCode1Long 145 XXXXXXXXXXXXXXXXXXXXXXXXX||||
HashCode2Long 168 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
HashCode3Long 123 XXXXXXXXXXXXXXXXXXXXXX||||||
HashCode4Long 123 XXXXXXXXXXXXXXXXXXXXX|||||||
HashCode5Long 126 XXXXXXXXXXXXXXXXXXXXXX||||||
vm: java -d32 -client
--------
-------- -d32 -server
0% Scenario{vm=java -d32 -server, benchmark=HashCodeEmpty} 1,69ns;
σ=0,01ns @ 3 trials
8% Scenario{vm=java -d32 -server, benchmark=HashCode1Empty} 2,00ns;
σ=0,07ns @ 10 trials
17% Scenario{vm=java -d32 -server, benchmark=HashCode2Empty} 1,97ns;
σ=0,01ns @ 3 trials
25% Scenario{vm=java -d32 -server, benchmark=HashCode3Empty} 1,55ns;
σ=0,01ns @ 3 trials
33% Scenario{vm=java -d32 -server, benchmark=HashCode4Empty} 1,54ns;
σ=0,01ns @ 3 trials
42% Scenario{vm=java -d32 -server, benchmark=HashCode5Empty} 2,32ns;
σ=0,01ns @ 3 trials
50% Scenario{vm=java -d32 -server, benchmark=HashCodeLong} 113,01ns;
σ=5,69ns @ 10 trials
58% Scenario{vm=java -d32 -server, benchmark=HashCode1Long} 101,49ns;
σ=0,89ns @ 3 trials
67% Scenario{vm=java -d32 -server, benchmark=HashCode2Long} 102,93ns;
σ=0,26ns @ 3 trials
75% Scenario{vm=java -d32 -server, benchmark=HashCode3Long} 100,29ns;
σ=0,98ns @ 3 trials
83% Scenario{vm=java -d32 -server, benchmark=HashCode4Long} 100,00ns;
σ=0,94ns @ 5 trials
92% Scenario{vm=java -d32 -server, benchmark=HashCode5Long} 112,29ns;
σ=1,22ns @ 10 trials
benchmark ns logarithmic runtime
HashCodeEmpty 2 |||
HashCode1Empty 2 ||||
HashCode2Empty 2 ||||
HashCode3Empty 2 ||
HashCode4Empty 2 ||
HashCode5Empty 2 |||||
HashCodeLong 113 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
HashCode1Long 101 XXXXXXXXXXXXXXXXXXXXXXXXXX|||
HashCode2Long 103 XXXXXXXXXXXXXXXXXXXXXXXXXXX||
HashCode3Long 100 XXXXXXXXXXXXXXXXXXXXXXXXXX|||
HashCode4Long 100 XXXXXXXXXXXXXXXXXXXXXXXXXX|||
HashCode5Long 112 XXXXXXXXXXXXXXXXXXXXXXXXXXXXX
vm: java -d32 -server
------
------ -d64 -client
0% Scenario{vm=java -d64 -client, benchmark=HashCodeEmpty} 1,63ns;
σ=0,01ns @ 3 trials
8% Scenario{vm=java -d64 -client, benchmark=HashCode1Empty} 1,41ns;
σ=0,01ns @ 3 trials
17% Scenario{vm=java -d64 -client, benchmark=HashCode2Empty} 1,40ns;
σ=0,01ns @ 3 trials
25% Scenario{vm=java -d64 -client, benchmark=HashCode3Empty} 1,42ns;
σ=0,01ns @ 3 trials
33% Scenario{vm=java -d64 -client, benchmark=HashCode4Empty} 1,40ns;
σ=0,00ns @ 3 trials
42% Scenario{vm=java -d64 -client, benchmark=HashCode5Empty} 4,29ns;
σ=0,11ns @ 10 trials
50% Scenario{vm=java -d64 -client, benchmark=HashCodeLong} 101,74ns;
σ=0,12ns @ 3 trials
58% Scenario{vm=java -d64 -client, benchmark=HashCode1Long} 102,66ns;
σ=0,91ns @ 3 trials
67% Scenario{vm=java -d64 -client, benchmark=HashCode2Long} 100,41ns;
σ=0,45ns @ 3 trials
75% Scenario{vm=java -d64 -client, benchmark=HashCode3Long} 97,41ns;
σ=0,57ns @ 3 trials
83% Scenario{vm=java -d64 -client, benchmark=HashCode4Long} 97,92ns;
σ=0,46ns @ 3 trials
92% Scenario{vm=java -d64 -client, benchmark=HashCode5Long} 107,27ns;
σ=0,97ns @ 3 trials
benchmark ns logarithmic runtime
HashCodeEmpty 2 |||
HashCode1Empty 1 ||
HashCode2Empty 1 ||
HashCode3Empty 1 ||
HashCode4Empty 1 ||
HashCode5Empty 4 X||||||||
HashCodeLong 102 XXXXXXXXXXXXXXXXXXXXXXXXXXXX|
HashCode1Long 103 XXXXXXXXXXXXXXXXXXXXXXXXXXXX|
HashCode2Long 100 XXXXXXXXXXXXXXXXXXXXXXXXXXXX|
HashCode3Long 97 XXXXXXXXXXXXXXXXXXXXXXXXXXX||
HashCode4Long 98 XXXXXXXXXXXXXXXXXXXXXXXXXXX||
HashCode5Long 107 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
vm: java -d64 -client
-------
------ -d64 -server
0% Scenario{vm=java -d64 -server, benchmark=HashCodeEmpty} 1,62ns;
σ=0,00ns @ 3 trials
8% Scenario{vm=java -d64 -server, benchmark=HashCode1Empty} 1,42ns;
σ=0,00ns @ 3 trials
17% Scenario{vm=java -d64 -server, benchmark=HashCode2Empty} 1,42ns;
σ=0,01ns @ 3 trials
25% Scenario{vm=java -d64 -server, benchmark=HashCode3Empty} 1,42ns;
σ=0,00ns @ 3 trials
33% Scenario{vm=java -d64 -server, benchmark=HashCode4Empty} 1,41ns;
σ=0,01ns @ 3 trials
42% Scenario{vm=java -d64 -server, benchmark=HashCode5Empty} 4,20ns;
σ=0,03ns @ 3 trials
50% Scenario{vm=java -d64 -server, benchmark=HashCodeLong} 102,05ns;
σ=0,22ns @ 3 trials
58% Scenario{vm=java -d64 -server, benchmark=HashCode1Long} 102,33ns;
σ=0,62ns @ 3 trials
67% Scenario{vm=java -d64 -server, benchmark=HashCode2Long} 100,70ns;
σ=0,43ns @ 3 trials
75% Scenario{vm=java -d64 -server, benchmark=HashCode3Long} 96,92ns;
σ=0,90ns @ 3 trials
83% Scenario{vm=java -d64 -server, benchmark=HashCode4Long} 98,22ns;
σ=0,40ns @ 3 trials
92% Scenario{vm=java -d64 -server, benchmark=HashCode5Long} 108,22ns;
σ=1,45ns @ 10 trials
benchmark ns logarithmic runtime
HashCodeEmpty 2 |||
HashCode1Empty 1 ||
HashCode2Empty 1 ||
HashCode3Empty 1 ||
HashCode4Empty 1 ||
HashCode5Empty 4 X||||||||
HashCodeLong 102 XXXXXXXXXXXXXXXXXXXXXXXXXXXX|
HashCode1Long 102 XXXXXXXXXXXXXXXXXXXXXXXXXXXX|
HashCode2Long 101 XXXXXXXXXXXXXXXXXXXXXXXXXXX||
HashCode3Long 97 XXXXXXXXXXXXXXXXXXXXXXXXXX|||
HashCode4Long 98 XXXXXXXXXXXXXXXXXXXXXXXXXXX||
HashCode5Long 108 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
vm: java -d64 -server
-------------
------------- StringHashCodeBenchmark.java
package examples;
import com.google.caliper.SimpleBenchmark;
import java_lang.String;
public class StringHashCodeBenchmark extends SimpleBenchmark {
private String EMPTY = new String("");
private String LONG = new
String("@ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ");
public int timeHashCodeEmpty(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += EMPTY.hashCode();
}
return dummy;
}
public int timeHashCode1Empty(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += EMPTY.hashCode1();
}
return dummy;
}
public int timeHashCode2Empty(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += EMPTY.hashCode2();
}
return dummy;
}
public int timeHashCode3Empty(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += EMPTY.hashCode3();
}
return dummy;
}
public int timeHashCode4Empty(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += EMPTY.hashCode4();
}
return dummy;
}
public int timeHashCode5Empty(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += EMPTY.hashCode5();
}
return dummy;
}
public int timeHashCodeLong(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += LONG.substring(1).hashCode();
}
return dummy;
}
public int timeHashCode1Long(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += LONG.substring(1).hashCode1();
}
return dummy;
}
public int timeHashCode2Long(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += LONG.substring(1).hashCode2();
}
return dummy;
}
public int timeHashCode3Long(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += LONG.substring(1).hashCode3();
}
return dummy;
}
public int timeHashCode4Long(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += LONG.substring(1).hashCode4();
}
return dummy;
}
public int timeHashCode5Long(int reps) {
int dummy = 0;
for (int i = 0; i < reps; i++) {
dummy += LONG.substring(1).hashCode5();
}
return dummy;
}
}
----------------
On Sat, Feb 27, 2010 at 2:18 AM, Ulf Zibis <ulf.zi...@gmx.de
<mailto:ulf.zi...@gmx.de>> wrote:
Am 26.02.2010 20:32, schrieb Alan Bateman:
Ulf Zibis wrote:
For these other suggestions it would be great to create
micro-benchmarks and try our your changes.
For now though, as I said, I'm just fixing the method to avoid the
store for the empty string case.
Here the benchmark for my different approaches on non-empty strings:
hashCode() warmup = 38,227 ms
hashCode1() warmup = 323,462 ms
hashCode() time = 12,066 ms
hashCode1() time = 11,620 ms
hashCodes sum = 0
hashCode() warmup = 34,928 ms
hashCode1() warmup = 19,010 ms
hashCode2() warmup = 25,938 ms
hashCode3() warmup = 22,428 ms
hashCode4() warmup = 22,966 ms
hashCode5() warmup = 21,372 ms
hashCode() time = 418,962 ms
hashCode1() time = 306,977 ms
hashCode2() time = 296,899 ms
hashCode3() time = 363,364 ms
hashCode4() time = 286,098 ms
hashCode5() time = 269,519 ms
hashCodes sum = -1427881024
See new revision:
https://java-nio-charset-enhanced.dev.java.net/source/browse/java-nio-charset-enhanced/branches/j7_EUC_TW/src/java/lang/String.java?rev=955&view=markup
<https://java-nio-charset-enhanced.dev.java.net/source/browse/java-nio-charset-enhanced/branches/j7_EUC_TW/src/java/lang/String.java?rev=955&view=markup>
-Ulf
------------------------------------------------------------------------
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