About priority queue

I tried to use priority queue which I saw on the JavaTM 2 Platform
Standard Ed. 5.0(on the web),but when I tried to create a priority queue for my work(PriorityQueue myQ = new PriorityQueue();)the compiler complaint about that,
"C:\Program Files\Xinox Software\JCreator LE\MyProjects\Trypq\Trypq.java:7: cannot resolve symbol"
and then I found that I can not find this priority queue class in JavaTM 2 Platform Std. Ed. v1.4.2,so what's wrong with this 2 different API,does it mean that I have to create the priority queue class by myself,because my work can only base on JavaTM 2 Platform Std. Ed. v1.4.2???
can you help?
thanks!

The feature was added in the latest release of Java. If you want to use it, you have to have the latest release.
Some of the concurrency features added in 1.5 (J2SE 5.0) were taken from Doug Lea's util.concurrent library, but I don't believe this was one of them. For those that were you have the option of using Doug's excellent library with pre 1.5 code.
You could also write your own, but I wouldn't particularly recommend it if you can upgrade to J2SE 5.0
Dave.

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Java priority queue

Java provides PriorityQueue, and I have gone through its API.
The implementation of PriorityQueue in Java does not provide method for increase or decrease key,
and there must be a reason for it.
But, when i go through books on data strucutre, a lot of them talk about the increase/decrease key function
of the PriorityQueue.
So I am just wondering, why is it that increase/decrease function not provided in PriorityQueue. I cannot come up with a reason for it, but i think there must be. Does anybody have any thought on this. Or is it just
because the designers thought its not needed?
I checked the source for the Priority Queue and the heapify() method was declared private.

lupansansei wrote:
I have used Java's priority queue an I have written my own but I have never come accros the terms "increase or decrease key". Do you mean something like 'upheap' or 'downheap' in relation to a 'heap' implementation meaning move an entry to it correct position if the key changes? If so then one should make the 'key' immutable so that the functions are not needed.
Yes, i mean 'upheap' or 'downheap' by increase or decrease key. Sorry
maybe my choice of words was not correct.
I couldn't get what you mean by 'key' immutable. Can you please explain it. If the key cannot change (i.e. it is immutable) then there is no need to ever change the position of an element.
>
Correct. Since the PriorityQueue does not need to implemented using a 'heap' there is no need for the heapify() method to be exposed. If one implemented using a balanced tree or a skip list the heapify() method would not be applicable.I am using PriorityQueue and i need to update the priority of the elements and i was wondering whether to implement the whole queue
myself or look for a better way of using the PriorityQueue class.
Do you have any suggestions for efficiently updating the priority of element?I have a priority queue implementation where elements know they are in a heap and know where they are in the heap. By doing this I can modify 'keys' and then move a value to it's correct place in the queue in a very short time. The limitations this feature imposes on the elements and the possibility of corrupting the heap means I don't often use this these days. It is far too error prone.
These days in my simulations I normally remove an element from the queue, process the element and then create new elements and insert them back in the queue. This sometimes takes 2 lots of Log(n) operations where my specialized priority queue just takes Log(n) operations. The code is just so much more maintainable and I accept the hit.

Does the priority queue always work?

Hi
I have a 8Mbp of wan link which sometime gets saturated and I have shaped average this to 8Mbps but i am running vocie on this WAN link and have defined priority for voice with 850kbps under voice class. My question is when the link is not fully utilized, Will the packets from priority queue are always dequeued first as compared to packets sent from from other queus or will the QoS will not do anything here since the link utilization is lot less than what is sepecified in shape average. I am asking this to confirm if the priority queue always help to overcome the issue of jitter if either the link is saturated or not?
Thanks

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Posting
You describe PQ and shaping, but the former is usually a part of doing QoS on L2/L3 switches, and the latter on routers. What device(s) and their IOS versions and the WAN media are you working with?
On "routers", interfaces generally have FIFO tx-rings, only when they overflow, are packets placed in CBWFQ queues. Within CBWFQ, LLQ will be dequeued first, but such packets might have already been queued behind other non-LLQ traffic within the interface tx-ring. (NB: for routers, with tx-rings, when supporting VoIP, you may want to minimize the size of the tx-ring.)
Shapers, in my experience, are "interesting". First, I believe many shapers don't account for L2 overhead, but provider CIRs often do. So unless you shape slower than the nomimal CIR rate, you can send faster than the available bandwidth. (Often I've found shaping 10 to 15% slower allows for average L2 overhead.)
Second, shapers work on averages over time intervals. For VoIP, you'll often want to insure the shaper is using a small Tc, otherwise it will allow FIFO bursts. (I've found a Tc of 10ms seems to support VoIP fairly well.)
Third, I suspect some shapers might have their own queues between the interface and the defined policy queues. If they do, unknown what their queuing organization is or their supported queuing depths. If this is the case, makes it difficult to engineer QoS.
Whenever possible, I've found it beneficial to work to avoid using shapers especially for timing sensitive traffic, like VoIP. In your case, I would suggest, if possible, obtaining 10 Mbps of WAN bandwidth and somewhere passing the traffic through a physical 10 Mbps interface, with a QoS policy.
But to more directly answer your question, PQ (or LQ) will dequeue its packets next compared to other "peer" queues. This should always help VoIP for delay and jitter, but there's more involved whether this is necessary and/or whether it's helpful enough when necessary.
You ask about when a link is saturated, but a link is 100% saturated everytime a packet is being transmitted. Often link usage is represented in percentages of usage of possible maximum transmission rate over some time period, but when it comes to QoS, 100% utilization might be just fine while 1% utilization is not. Much, much more information, about your situation, might be needed to offer truly constructive recommendations.

[svn] 3539: Updated RadioButtonGroup to account for recent changes to LayoutManager priority queue .

Revision: 3539
Author: [email protected]
Date: 2008-10-09 10:58:31 -0700 (Thu, 09 Oct 2008)
Log Message:
Updated RadioButtonGroup to account for recent changes to LayoutManager priority queue. The order that a RadioButtonGroup was traversed was always dependent on what order that the radio buttons properties were validated. Since this assumption no longer holds true, we are now very specific about how the group orders the RadioButtons (breadth-first for consistency with Flex 2 and Flex 3).
Check-in Tests: Pass
Mustella Tests: (RadioButton, RadioButtonGroup) Pass
Reviewer: Glenn
QA: Yes
Bugs: SDK-17248
Ticket Links:
http://bugs.adobe.com/jira/browse/SDK-17248
Modified Paths:
flex/sdk/trunk/frameworks/projects/framework/src/mx/controls/RadioButtonGroup.as

Revision: 3539
Author: [email protected]
Date: 2008-10-09 10:58:31 -0700 (Thu, 09 Oct 2008)
Log Message:
Updated RadioButtonGroup to account for recent changes to LayoutManager priority queue. The order that a RadioButtonGroup was traversed was always dependent on what order that the radio buttons properties were validated. Since this assumption no longer holds true, we are now very specific about how the group orders the RadioButtons (breadth-first for consistency with Flex 2 and Flex 3).
Check-in Tests: Pass
Mustella Tests: (RadioButton, RadioButtonGroup) Pass
Reviewer: Glenn
QA: Yes
Bugs: SDK-17248
Ticket Links:
http://bugs.adobe.com/jira/browse/SDK-17248
Modified Paths:
flex/sdk/trunk/frameworks/projects/framework/src/mx/controls/RadioButtonGroup.as

Multiple Priority Queues?

All,
I have read that one may configure up to 4 priority queues, not using the Modular QOS CLI (e.g. "priority-list" command, etc).
For the Modular QOS CLI, PQs are implemented using LLQ ("priority" command), and for this one can only specify a single PQ (though multiple classes may be mapped to this single PQ).
What I would like to do is to have 2 distinct PQs (as should be possible in the non modular cli case) and also use CBWFQ (e.g. "bandwidth" command) for the rest of the clases. Basically I want to have EF in one PQ, another "special" class in the other PQ (lower priority than EF), and AF classes using CBWFQ.
Does anyone know of a way to combine the 2 methods (modular and non modular CLI) of configuring LLQ in order to implement such a configuration? I was encouraged to see that heirarchical policies are supported but so far I have not found a way to specify multiple PQs as well as CBWFQ.
Thanks much!

There has been alot of discussion on this subject. But it seems that while IOS will allow you to configure multiple priority queues, its not really possible for it to deliver multiple priority queues.
Which, if you think about it makes sense. A priority queue is just that, it takes priority over all other queues. If you configue 2 priority queues, how would you then then tell the scheduler that these are both priority, but the 2nd is less of a priority?
One way you can accomplish what you're trying to do:
1. Create a single "priority" queue for your EF traffic
2. Use "bandwidth" to guarantee bandwidth to your special class.
3. Put your AF traffic in class-default and let it "fair-queue".
Something like this:
policy-map foo
class EF
priority 100
class Special
bandwith 50
class class-default
fair-queue
-Geoff

6500 strict priority queue size ???

Hi guys,
Is it possible to adjust the 6500 line cards strict priority queue size? Most cards assign 85% of thebandwdith to the oridinary queues and 15% to the strict priority queue. It seems that it is not possible to adjust the size of the strict priority queue.
I have a customer who has numerous T1's encapsulated into IP and the gross amount of traffic is about 200Meg, all of which is real time. If I were to mark this as DSCP 46 (COS 5) it would saturate the strict priorty queue leading not only to performance problems on the T1's but would also starve the rest of the traffic on the 1Gig WAN link.
Any thoughts guys?
Regards, Steve

Hi Paresh,
Thanks for your reply. I think I didn't explain myself properly. There is a bandwidth allocation of memory for each port. The priority queue gets 15%by default. I have so much priority queue traffic that I want to increase this to 25% because all of it is strict priority (its voice after all). If this canot be done then I will be losing packets of voice since the priorty queue will not be able to accomdate the amount of traffic.
Best regards, Steve

Question: Priority Queue "deleteMin()" trouble

Hello, I am having trouble formulating a delete() method here, which could also be called deleteMin() here.
The priority queue, is suppose to have quick insertion O(1) time, and slow deletion O(N) because it's going to have to search through the unordered array, find the minimum object then delete it once "delete()" is called.
However, I am stuck on trying to come up with the logic for my delete() method....
Here's what I am thinking...
I need to examine all the items and shift half of them, on average, down to fill in the hole once the minimum item is found.
How would I find the minimum item, and once found how would I delete this? Any direction or statements you can show me to clear this up would be appreciated. Please see my code below :) Please excuse my empty javadocs as of right now, I do those last.
Thank you
* This class is to demonstrate.....
* @version 1.0
public class PriorityQ {
     private int maxSize;
     private long[] queArray;
     private int nItems;
      * Javadoc here
     public PriorityQ(int s) // constructor
          maxSize = s;
          queArray = new long[maxSize];
          nItems = 0;
      * Javadoc here
     public void insert(long value) {
          queArray[nItems] = value;
          nItems++;
      * Javadoc here
      public long remove () {
      * Javadoc here
     public long peekMin() {
               return queArray[nItems - 1];
      * Javadoc here
     public boolean isEmpty() {
               return (nItems == 0);
      * Javadoc here
     public boolean isFull() {
               return (nItems == maxSize);
} // end class PriorityQ
class PriorityQApp {
             public static void main(String[] args)
                PriorityQ q1 = new PriorityQ(5);
                q1.insert(30);
                q1.insert(50);
                q1.insert(10);
                q1.insert(40);
                while( !q1.isEmpty() )
                   long item = q1.remove();
                   System.out.print(item + " "); // 10, 20, 30, 40, 50
                   } // end while
                System.out.println("");
     } // end main()
} // end class PriorityQApp
// //////////////////////////////////////////////////////////////Edited by: Cole1988 on Feb 21, 2009 9:03 AM

Sorry no one got to you sooner.
Using your instance variables:
public long remove()
     long minValue = Long.MAX_VALUE;
     int minIndex = 0;
     for(int i = 0; i < nItems; i++) //Here we iterate through all the items to find the smallest one
          if(queArray[i] < minValue) //If this particular value is less than the smallest one found so far,
               minValue = queArray; //This value is now the smallest one found so far
               minIndex = i; //minIndex now contains the index of the smallest one found so far
     /*Now we can remove the smallest term, because after the above iteration, minIndex is the index number of the smallest value and minValue is the smallest value.*/
     for(int i = minIndex + 1; i < nItems; i++) //Starting at the term right AFTER the smallest one
          queArray[i-1]=queArray[i]; //Copy the value into the space right BEFORE it
     nItems--; //The number of items has decreased by one
     return minValue;
}Note: This code does NOT resize your array after you remove an item; depending on how you'll implement it, you'll need to check if you're about to overflow the array by comparing nItems with queArray.length and resize your array accordingly.
It seems like you're a bit confused about loops and iterating through arrays; I'd recommend reviewing a good Java book or online tutorial and practicing with some basic array iterations before you go any farther. You've got the basic grasp of things, it just hasn't "clicked" for you yet. :)
Let me know if you need any more help or if you don't understand anything about what I just said.
Regards,
Alvin

C2960: ingress priority-queue and CoS/DSCP mapping

I have read the C2960 manuals for a few times, but I don't seem to find an answer.
You can enable the priority queue on the ingress interface which has two available input queues for QoS-services.
What seems to be missing from the manuals is that how can I map/direct the traffic (CoS & DSCP values) to the priority queue?
I can map traffic to two other WRR (SRR) queues with command: "mls qos srr-queue input cos-map queue queue-id threshold threshold-id cos1...cos8", but there is nothing about the priority queue.
So is the CoS/DSCP values for the priority queue fixed or how/what traffic is directed to it?
Thanks,
Miska

What seems to be missing from the manuals is that how can I map/direct the traffic (CoS & DSCP values) to the priority queue?
A: By default, the priority queue is queue 2, and 10 percent of the bandwidth is allocated to it.
?For queue-id, the range is 1 to 2.
Map DSCP or CoS values to an ingress queue and to a threshold ID.
By default, DSCP values 0-39 and 48-63 are mapped to queue 1 and threshold 1. DSCP values 40-47 are mapped to queue 2 and threshold 1.
By default, CoS values 0-4, 6, and 7 are mapped to queue 1 and threshold 1. CoS value 5 is mapped to queue 2 and threshold 1.
?For queue-id, the range is 1 to 2.
?For threshold-id, the range is 1 to 3. The drop-threshold percentage for threshold 3 is predefined. It is set to the queue-full state.
?For dscp1...dscp8, enter up to eight values, and separate each value with a space. The range is 0 to 63.
?For cos1...cos8, enter up to eight values, and separate each value with a space. The range is 0 to 7.
What above is saying is queue 2 is priority queue, you can use the CoS/DSCP mapping to queue to move certain CoS?DSCP to either queue 1 or queue 2.
I can map traffic to two other WRR (SRR) queues with command: "mls qos srr-queue input cos-map queue queue-id threshold threshold-id cos1...cos8", but there is nothing about the priority queue.
So is the CoS/DSCP values for the priority queue fixed or how/what traffic is directed to it?
A; See above.
For more info:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat2960/12225see/scg/swqos.htm#wp1161845
Please rate all posts.

Priority Queue Ordering

In the process of using a Priority Queue the question came up about what order elements with equal priority are removed. The two logical orders would be first in, first out, like the standard queue, or first in, last out, like a stack. However, testing the Priority Queue showed that the elements of equal priority were removed in neither order, and moreover, the elements were stored in a neither consistent nor prioritized order. My question is, what causes this situation, is there any way to predict the order in which equally prioritized elements will be removed, and is there any way to force the Priority Queue into removing elements in a first in, first out order without writing my own?

In the process of using a Priority Queue the question came up ...I don' t know why.The Javadoc clearly specifies that 'ties are broken arbitrarily'.
My question is, what causes this situationThe fact that it uses a priority heap algorithm, which is where its O(log(n)) performance comes from.
is there any way to predict the order in which equally prioritized elements will be removedNo.
and is there any way to force the Priority Queue into removing elements in a first in, first out order without writing my own?Encode insertion time as a minor key of the priority.

Custom order of priority queue

I am a novice in Java. I intend to use a priority queue which holds objects. The objects have a string and two integers. I have to order the priority queue based on one of the integer.
I write syntax according to my understanding please correct me.
PriorityQueue<Object> pr = new PriorityQueue<Object>();
comparable(){
sort(Object.int2)// this is the place where I am confused
}

Here's an example:
public class Caller
    public static void main(String[] args)
        Flight f1 = new Flight( "java", 2, 34 );
        Flight f2 = new Flight( "java", 2, 3 );
        Flight f3 = new Flight( "java", 2, 4 );
        Flight f4 = new Flight( "java", 2, 64 );
        Flight f5 = new Flight( "java", 2, 22 );
        Flight f6 = new Flight( "java", 2, 12 );
        PriorityQueue pq = new PriorityQueue();
        pq.add(f1);
        pq.add(f2);
        pq.add(f3);
        pq.add(f4);
        pq.add(f5);
        pq.add(f6);
        System.out.println(pq.poll());
        System.out.println(pq.poll());
        System.out.println(pq.poll());
        System.out.println(pq.poll());
        System.out.println(pq.poll());
        System.out.println(pq.poll());
public class Flight implements Comparable
    private String airlinename;
    private int flightnumber;
    private int number;
    public int compareTo(Object o)
        Flight f = (Flight) o;
        return number - f.getNumber();
    public String toString()
        return airlinename + " - " + number;
    public Flight(String airname, int num1, int num2)
        airlinename = airname;
        flightnumber = num1;
        number = num2;
    public String getAirlinename()
        return airlinename;
    public void setAirlinename(String airlinename)
        this.airlinename = airlinename;
    public int getFlightnumber()
        return flightnumber;
    public void setFlightnumber(int flightnumber)
        this.flightnumber = flightnumber;
    public int getNumber()
        return number;
    public void setNumber(int number)
        this.number = number;
}Got it?

About message queue in message mapping?

Hi SDNer,
I have been read help.sap.com and sdn threads about message queue
I hope this thread should be help for all like me.
thank you
Sha

Hi Shankar,
XI uses Queue's to store messages, If you worked on message mapping you can see the how queue look like,
Every queue having context ,it separate the values,it store the messages in highrarchy manner.
Using Context Handling we resoleve context issues.
Using node functions we aceive Context Handling.
Search in SDN there is some good blogs abt Node Functions, if you understand nodefunction you wil understand the Queue concepts.
Regards,
Raj

Howto get information about available queues?

Any ideas how to get information about available queues on a Weblogic Server to browse them?
          When you have the jndi namespace and the name of the queue it's no problem to browse that queue, but when you don't have the name of the queue is there a way to still be able to browse the queue(s)?
          Any information is warmly welcomed.
          Thanks,
          Chris

A QueueBrowser is currently the only way to view message contents. WebLogic 9.0 (out in beta now), provides comprehensive message management both via console and JMX.
          For 8.1, the following links may help get you started.
          JMS technology page:
          http://dev2dev.bea.com/technologies/jms/index.jsp
          WebLogic public management/monitoring APIs:
          http://edocs.bea.com/wls/docs81/jmx/index.html
          jsp based dest browser (which ultimately uses a QueueBrowser):
          http://dev2dev.bea.com/codelibrary/code/jmsdest.jsp
          JMS statistics dump:
          http://dev2dev.bea.com/codelibrary/code/jms_stats.jsp
          Tom Barnes, BEA

Priority Queues

hi iam a beginner in java, could you please help me with this code. thanks
Implement (provide complete Java code) a priority queue using a singly linked list. You may call this class LinkedPriorityQueue. The use of classes contained in the Java Collections framework in the above implementing is strictly forbidden.
You may need to write a second class, PQNode, which defines the nodes in your linked list. Feel free to implement the PQNode class in anyway that you see fit. However, the LinkedPriorityQueue class should implement all methods and constructors

Here is the search of the forums
http://search.java.sun.com/search/java/index.jsp?qp=&nh=10&qt=%22singly+linked+list%22&col=javaforums&x=23&y=16
Here is a google search
http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=%22singly+linked+list%22+java
Due tomorrow???

Priority Queue problem

Hi Everybody.
Can anyone tell me in which order elements of priority queue are sorted.
I have used following code
class Test{
PriorityQueue <strings> pq=new PriorityQueue <Strings>();
pq.add("silpa");
pq.add("swati");
pq.add("roopa");
pq.add("abc");
System.out.println(pq);
System.out.println(pq.poll());
System.out.println(pq.peak());
The output I got is
[abc silpa swathi roopa]
abc
roopa.
Can anybody explain why the collection elements are not sorted ?
I am getting correct output with peek() n poll().According that methods i should get
[abc roopa silpa swathi ]
Explain the reason?

System.out.println(pq);This line prints out the contents of the queue, by implicitly calling pq.toString(), whose behaviour is inherited from AbstractCollection, which therefore has nothing to do with sorting. So you have no valid reason for expecting any particular ordering.

Low priority and high priority queue

Hi
we have high priority and low priority queue's. Functionality wise i know that time critical messages will be sent through high priority queue's and low priority messages will be sent
through low priority queues. But like to know what technicality makes this separation of
low priority and high priority queue's ? The crus of the question is what technical setting(s)
makes the queue as high priority and what technical setting(s) makes the queue as low priority
queue.
Thanks
kumar

i Michal
I am talking abt queue prioritization on Integration eninge only.
I am good with queue prioritization and am able to successfully implement
the same. We are using only PI7.0.
My question is what is the technical difference between high priority
and low priority queues ? what technical setting makes it a high priority
queue and what technical setting makes a low priority queue ?
Your answer:
how the system reacts to new messages if almost all queues are already blocked
for some types of messages
My comment: what setting makes the system to behave like that ? what property
of that queue makes them to behave like that ?
Thanks
kumar

About priority queue

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