Hi all,
I made some tests in org.apache.log4j.performance.ListVsVector.
(Whose purpose is "Compares the performance of looping through a list
versus a Vector.")
You said there that "Chain looping is *20* times faster than vector
access on JDK 1.1.7B on NT".
I made the same test with jdk1.4.1_01 on Windows 2000 ; it seems that
Vector are "only" little more than 3 times slower.
However, the tests are not really "fair" for me cause Vector are
synchronized while Chains are not.
I added some tests : I compared both initialization time and loop time
for : Chain, Vector, ArrayList and LinkedList. Here are the results I
got (on a PII 350):
Initialization time : similars
Chain looping : 0.2654
Vector looping : 0.8733
ArrayList looping : 0.721
LinkedList looping : 0.0961
These results show that linked list looping is 2.71 times faster than
chain looping.
I would therefore suggest you to use linked list instead of Chains. (I
attached the modified file so you can make your own tests)
What do you think about it ?
NB: FYI, I go through the list via a java.util.ListIterator
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software
* License version 1.1, a copy of which has been included with this
* distribution in the LICENSE.txt file. */
//package org.apache.log4j.performance;
import java.util.Vector;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.ListIterator;
/**
Compares the performance of looping through a list versus a Vector.
Chain looping is *20* times faster than vector access on JDK 1.1.7B on NT
*/
public class ListVsVector {
static int RUN_LENGTH = 10000000;
static Vector v = new Vector();
static ArrayList al = new ArrayList();
static LinkedList ll, ll2, ll3, head3;
static ListIterator litcc, llhead;
static Chain head;
static String tmp;
static
public
void main(String[] args) {
double t;
long before;
before = System.currentTimeMillis();
v.addElement("aaa");
v.addElement("bbb");
v.addElement("ccc");
v.addElement("ddd");
v.addElement("eee");
t=(System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
System.out.println("Initializing the vector took "+t);
before = System.currentTimeMillis();
al.add("aaa");
al.add("bbb");
al.add("ccc");
al.add("ddd");
al.add("eee");
t=(System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
System.out.println("Initializing the array list took "+t);
before = System.currentTimeMillis();
ll = new LinkedList();
litcc = ll.listIterator(0);
llhead = litcc;
litcc.add("aaa");
litcc.add("bbb");
litcc.add("ccc");
litcc.add("ddd");
litcc.add("eee");
t=(System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
System.out.println("Initializing the linked list took "+t);
ll2 = new LinkedList();
ll2.add("aaa");
ll2.add("bbb");
ll2.add("ccc");
ll2.add("ddd");
ll2.add("eee");
ll3 = (LinkedList) ll2.clone();
head3 = ll3;
before = System.currentTimeMillis();
Chain c = new Chain("aaa");
head = c;
c.next = new Chain("bbb"); c = c.next;
c.next = new Chain("ccc"); c = c.next;
c.next = new Chain("ddd"); c = c.next;
c.next = new Chain("eee");
t=(System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
System.out.println("Initializing the chain took "+t);
t = loopChain();
System.out.println("Looping through the chain took " + t);
t = loopVector();
System.out.println("Looping through the vector took " + t);
t = loopArrayList();
System.out.println("Looping through the arraylist took " + t);
t = loopLinkedList();
System.out.println("Looping through the linked list took " + t);
}
static
double loopChain() {
long before = System.currentTimeMillis();
Chain c;
for(int i = 0; i < RUN_LENGTH; i++) {
c = head;
while(c != null) {
tmp = c.s;
c = c.next;
}
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
static
double loopLinkedList() {
long before = System.currentTimeMillis();
ListIterator litcc;
for(int i = 0; i < RUN_LENGTH; i++) {
litcc = llhead;
while(litcc.hasNext()) {
tmp = (String) litcc.next();
}
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
static
double loopLinkedList2() {
long before = System.currentTimeMillis();
for(int i = 0; i < RUN_LENGTH; i++) {
int len = ll2.size();
for (int k=0; k<len; k++)
{
tmp = (String) ll2.get(k);
}
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
static
double loopLinkedList3() {
long before = System.currentTimeMillis();
LinkedList ll3;
for(int i = 0; i < RUN_LENGTH; i++) {
ll3 = head3;
ListIterator li3 = ll3.listIterator(0);
while (li3.hasNext())
{
tmp = (String) li3.next();
}
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
static
double loopVector() {
long before = System.currentTimeMillis();
int size = v.size();
for(int i = 0; i < RUN_LENGTH; i++) {
for(int j = 0; j < size; j++)
tmp = (String) v.elementAt(j);
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
static
double loopArrayList() {
long before = System.currentTimeMillis();
int size = al.size();
for(int i = 0; i < RUN_LENGTH; i++) {
for(int j = 0; j < size; j++)
tmp = (String) al.get(j);
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
static class Chain {
public String s;
public Chain next;
Chain(String s) {
this.s = s;
}
void setNext(Chain c) {
next = c;
}
}
}
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
