LinkedList and ArrayList Iterator speeds
Is an ArrayList Iterator hugely faster than a LinkedList Iterator?
I have swapped, for storing my 8000 dataObjects, from using an ArrayList to a LinkedList and all seems fine except that the Iterator I get is much slower (by more than 10 times slower)
I have scoured my code but I have come to the conclusion that a LinkedList is just slow
Id just like one of you to comfirm my beliefs
How odd.
According to Bruce Eckel's Thinking in Java [p.505]
(downloadable for free at
http://www.mindview.net/Books/TIJ/ ), LinkedList
should be faster than ArrayList for iteration,
insertion, and removal; and only slower for getting by
index.
I haven't done any tests of my own on it, but it makes
sense. I don't know why your LinkedList iterators
would be slower.Yes, LinkedList will be faster at inserts/deletes and slower at indexed lookups. Keep in mind that when you say myLinkedList.get(7000) the iterator has to go through 6999 objects to retrieve the 7000th object. When you do the same thing on an ArrayList it just goes directly to that index and returns it.
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I have seen some websites discussing about the performance of ArrayLists, LinkedLists, and Hashmaps:
http://forum.java.sun.com/thread.jspa?threadID=442985
http://java.sun.com/developer/JDCTechTips/2002/tt0910.html
http://www.javaspecialists.co.za/archive/Issue111.html
http://joust.kano.net/weblog/archives/000066.html
If I understand it right an ArrayList in general is faster for accessing a particular element in the collection and I can't find some pro's of using a LinkedList.
My question is: If I only use a large collection with more than 1 million elements for iterating from begin to end (i.e. for loop), is it faster to use a linked list or a custom linked list instead of an arraylist (or hashmap)? Since you can iterate "directly" through a (custom) linked list, which is not possible with a arraylist?
Edited by: 9squared on Nov 23, 2007 1:48 PMThanks for the help, I wrote some code and tested it
import java.util.ArrayList;
import java.util.List;
import java.util.LinkedList;
public class TestTemp {
public static void main(String[] args) {
List<Node> a = new ArrayList<Node>();
Node b = new Node("a");
String[] c = new String[10000000];
Node temp = b;
for (int i = 0; i < 10000000; i++)
a.add(new Node("a"));
temp.next = new Node("b");
temp = temp.next;
c[i] = "c";
long tstart;
tstart = System.currentTimeMillis();
for (int i = 0; i < 10000000; i++)
c[i] = "cc";
if (i%200000 == 0)
System.out.println("Array " + i + ": " + (System.currentTimeMillis()-tstart));
tstart = System.currentTimeMillis();
temp = b;
for (int i = 0; i < 10000000; i++)
temp.next.text = "bb";
temp = temp.next;
if (i%200000 == 0)
System.out.println("LinkedList " + i + ": " + (System.currentTimeMillis()-tstart));
tstart = System.currentTimeMillis();
for (int i = 0; i < 10000000; i++)
a.get(i).text = "aa";
if (i%200000 == 0)
System.out.println("ArrayList " + i + ": " + (System.currentTimeMillis()-tstart));
public class Node {
public String text;
public Node next;
public Node(String text)
this.text = text;
}Here are some results in milliseconds, and indeed just iterating doesn't take very long
Elements Linked Arraylist Array
200000 0 0 1
400000 5 13 5
600000 9 22 9
800000 14 32 12
1000000 20 42 16
1200000 25 52 19
1400000 31 63 23
1600000 37 72 26
1800000 42 82 30
2000000 47 92 33
2200000 51 101 37
2400000 56 112 40
2600000 60 123 44
2800000 65 134 47
3000000 69 143 51
3200000 73 152 55
3400000 78 162 59
3600000 84 175 63
3800000 103 185 67
4000000 108 195 70
4200000 113 207 74
4400000 117 216 78
4600000 122 225 81
4800000 127 237 85
5000000 131 247 88
5200000 136 256 92
5400000 142 266 97
5600000 147 275 101
5800000 153 286 107
6000000 159 298 113
6200000 162 307 117
6400000 167 317 121
6600000 171 326 125
6800000 175 335 128
7000000 180 346 132
7200000 184 358 136
7400000 188 368 139
7600000 193 377 143
7800000 197 388 147
8000000 201 397 150
8200000 207 410 154
8400000 212 423 157
8600000 217 432 162
8800000 222 442 167
9000000 227 452 171
9200000 231 462 175
9400000 236 473 178
9600000 242 483 182
9800000 249 495 185
10000000 257 505 189 -
LinkedList class and ArrayList class
Hi everyone,
What is difference between LinkedList class and ArrayList class ??Hi samue!
If you had typed that question you would have got many answers.anyway
difference between Linked List and ArrayList
1.In linked list each element is stored as an object but not in arraylist
2.Linked list need iterator to go through its contents but not arraylist
3.reading element from each takes same time but if you want to add or remove element from the arraylist it takes considerable amount of time depending on the index number. in Linkedlist case it takes constant amount of time to add/remove at any index.
this should be enough guess to know the difference but if u need try goooogle -
Iteration Speed issue when Indexing 3D array wried to a while-loop
Brief Description of my Program:
I am working on the real-time signal generation by using LabView and DAQmx (PCI-6110 card). My vi reads the big data file (typically 8MB txt file containing about 400,000 samples (complex double precision). Then, the signal is pre-processed and I end up with a huge 3D array to feed while-loop (typically 3D array dimension is N x 7 x M where N & M >> 7). Inside the loop, that 3D array is indexed and processed before the results are written to the DAQmx outputs. I have a speed issue when indexing the large 3D array (i.e, 3D array having a large sub-array size). My while-loop could not run fast enough to top-up the DAQmx AO buffer (at the output rate of 96kHz). It could run faster only if I use smaller 3D array (i.e, smaller-sized sub-arrays). I do not quite understand why the size of 3D sub-array affects the rate of looping although I am indexing same sub-array size at each iteration. I really appreciate your comments, advices and helps.
I include my 3D array format as a picture below.
Question on LabView:
How does indexing an 3D array which wires to the while-loop affect the speed of the loop iteration? I found that large dimension of sub-arrays in the 3D array slows down the iteration speed by comparing to indexing the same size of sub-array from smaller-sized sub-arrays of the 3D array to perform signal processing inside the while-loop. Why? Is there any other way of designing LabView Program to improve speed of iteration?
attachment:Thank you all for your prompt replies and your interests. I am sorry about my attachment. But, I have now attached a jpg format image file as you suggested.
I had read the few papers on large data handling such as "LabVIEW Performance and Memory Management". Thus, I had already tried to avoid making unnecessary copies of data and growing arrays in my while-loop. I am not an expert on LabView, so I am not sure if the issues I have are just LabView fundamental limitations or there are any other ways to improve the iteration speed without reducing the input file size and DAQ output rate.
As you request, I also attach my top-level vi showing essential sections such as while-loop and its indexing. The attached file is as an image jpg format because the actual vi including Sub-VIs are as big as 3MB in total. I hope my attachment would be useful for anyone who would like to reply my question. If anyone would like to see my whole vi & llb files, I would be interesting to send it to you by an e-mail privately and thus please provide your e-mail address.
The dimension of my 3D array is N x 7 x M (Page x Row x Column), where N represents number of pages in 3D array, and M represents the size of 1D array. The file I am currently using forms 3D array of N = 28, & M = 10,731. Refering to the top-level vi picture I attached, my while-loop indexes each page per iteration and wrap-around. The sub-VI called "channel" inside the while-loop will further index its input (2D array) into seven of 1D arrays for other signal processsing. The output from that "channel" sub-VI is the superposition of those seven arrays. I hope my explaination is clear.
Attachement: 3Darray.jpg and MyVi.jpg
Kind Regards,
Shein
Attachments:
3Darray.jpg 30 KB
MyVI.jpg 87 KB -
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hello,
i have a linkedlist of objects of size 1000. Every object(every node of linked list is an instance of a class) in linkedlist contains of 20 variables. Now i want to take objects from this linkedlist and put it into array list.???
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LinkedList<String> ll = new LinkedList<String>();
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ArrayList<String> al = new ArrayList<String>(ll);
System.out.println(al.get(0));
} -
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http://csc-studentweb.lr.edu/swp/Berg/articles/NW2009/NW2009_20_technical_tips_tricks_speed_SAP_BI_performance.ppt
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Hi,
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www.xlr8yourmac.com does have readers reports in a database and write-ups.
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helo
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pleasr help me for that , i can not buy any thing inside the game .
i wating , thank you
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Life | 1967 Plus Radio | 1000 Classical Hits | Kafka's World
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