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  • C++ priority queue structure used ?

    - by John Retallack
    While searching for some functions in C++ STL documentation I read that push and pop for priority queues needs constant time. "Constant (in the priority_queue). Although notice that push_heap operates in logarithmic time." My question is what kind of data structure is used to mantain a priority queue with O(1) for push and pop ?

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  • Well tested C/C++ lock free queue?

    - by uj
    I am looking for a well-tested, publicly available C/C++ implementation of a lock free queue. I need at least multiple-producers/single-consumer functionality. Multiple-consumers is even better, if exists. I'm targetting VC's _Interlocked... intrinsics, though anything which is straight forward to port would be fine. Could anyone give any pointers?

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  • C++ priority queue structure userd ?

    - by John Retallack
    While searching for some functions in C++ STL documentation I read that push and pop for priority queues needs constant time. "Constant (in the priority_queue). Although notice that push_heap operates in logarithmic time." My question is what kind of data structure is used to mantain a priority queue with O(1) for push and pop ?

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  • Why does storage's performance change at various queue depths?

    - by Mxx
    I'm in the market for a storage upgrade for our servers. I'm looking at benchmarks of various PCIe SSD devices and in comparisons I see that IOPS change at various queue depths. How can that be and why is that happening? The way I understand things is: I have a device with maximum (theoretical) of 100k IOPS. If my workload consistently produces 100,001 IOPS, I'll have a queue depth of 1, am I correct? However, from what I see in benchmarks some devices run slower at lower queue depths, then speedup at depth of 4-64 and then slow down again at even larger depths. Isn't queue depths a property of OS(or perhaps storage controller), so why would that affect IOPS?

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  • Why is my mail stuck in the queue with the status "retry" in Exchange 2003?

    - by Mike C
    I have been having a problem recently where some of our mail is not getting to clients. I looked into the Message queue on my SBS2k3 server and noticed that several recipients are showing up in the queue with a state of "Retry". When I highlight the recipient, the additional queue information says "An SMTP protocol error occured". How can I find out more specifically what error occured, and how could I then go about correcting it? Thanks, Mike

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  • Queued Loadtest to remove Concurrency issues using Shared Data Service in OpenScript

    - by stefan.thieme(at)oracle.com
    Queued Processing to remove Concurrency issues in Loadtest ScriptsSome scripts act on information returned by the server, e.g. act on first item in the returned list of pending tasks/actions. This may lead to concurrency issues if the virtual users simulated in a load test scenario are not synchronized in some way.As the load test cases should be carried out in a comparable and straight forward manner simply cancel a transaction in case a collision occurs is clearly not an option. In case you increase the number of virtual users this approach would lead to a high number of requests for the early steps in your transaction (e.g. login, retrieve list of action points, assign an action point to the virtual user) but later steps would be rarely visited successfully or at all, depending on the application logic.A way to tackle this problem is to enqueue the virtual users in a Shared Data Service queue. Only the first virtual user in this queue will be allowed to carry out the critical steps (retrieve list of action points, assign an action point to the virtual user) in your transaction at any one time.Once a virtual user has passed the critical path it will dequeue himself from the head of the queue and continue with his actions. This does theoretically allow virtual users to run in parallel all steps of the transaction which are not part of the critical path.In practice it has been seen this is rarely the case, though it does not allow adding more than N users to perform a transaction without causing delays due to virtual users waiting in the queue. N being the time of the total transaction divided by the sum of the time of all critical steps in this transaction.While this problem can be circumvented by allowing multiple queues to act on individual segments of the list of actions, e.g. per country filter, ends with 0..9 filter, etc.This would require additional handling of these additional queues of slots for the virtual users at the head of the queue in order to maintain the mutually exclusive access to the first element in the list returned by the server at any one time of the load test. Such an improved handling of multiple queues and/or multiple slots is above the subject of this paper.Shared Data Services Pre-RequisitesStart WebLogic Server to host Shared Data ServicesYou will have to make sure that your WebLogic server is installed and started. Shared Data Services may not work if you installed only the minimal installation package for OpenScript. If however you installed the default package including OLT and OTM, you may follow the instructions below to start and verify WebLogic installation.To start the WebLogic Server deployed underneath of Oracle Load Testing and/or Oracle Test Manager you can go to your Start menu, Oracle Application Testing Suite and select the Restart Oracle Application Testing Suite Application Service entry from the Tools submenu.To verify the service has been started you can run the Microsoft Management Console for Services by Selecting Run from the Start Menu and entering services.msc. Look for the entry that reads Oracle Application Testing Suite Application Service, once it has changed it status from Starting to Started you can proceed to verify the login. Please note that this may take several minutes, I would say up to 10 minutes depending on the strength of your CPU horse-power.Verify WebLogic Server user credentialsYou will have to make sure that your WebLogic Server is installed and started. Next open the Oracle WebLogic Server Adminstration Console on http://localhost:8088/console.It may take a while until the application is deployed and started. It may display the following until the Administration Console has been deployed on the fly.Afterwards you can login using the username oats and the password that you selected during install time for your Application Testing Suite administrative purposes.This will bring up the Home page of you WebLogic Server. You have actually verified that you are able to login with these credentials already. However if you want to check the details, navigate to Security Realms, myrealm, Users and Groups tab.Here you could add users to your WebLogic Server which could be used in the later steps. Details on the Groups required for such a custom user to work are exceeding this quick overview and have to be selected with the WebLogic Server Adminstration Guide in mind.Shared Data Services pre-requisites for Load testingOpenScript Preferences have to be set to enable Encryption and provide a default Shared Data Service Connection for Playback.These are pre-requisites you want to use for load testing with Shared Data Services.Please note that the usage of the Connection Parameters (individual directive in the script) for Shared Data Services did not playback reliably in the current version 9.20.0370 of Oracle Load Testing (OLT) and encryption of credentials still seemed to be mandatory as well.General Encryption settingsSelect OpenScript Preferences from the View menu and navigate to the General, Encryption entry in the tree on the left. Select the Encrypt script data option from the list and enter the same password that you used for securing your WebLogic Server Administration Console.Enable global shared data access credentialsSelect OpenScript Preferences from the View menu and navigate to the Playback, Shared Data entry in the tree on the left. Enable the global shared data access credentials and enter the Address, User name and Password determined for your WebLogic Server to host Shared Data Services.Please note, that you may want to replace the localhost in Address with the hosts realname in case you plan to run load tests with Loadtest Agents running on remote systems.Queued Processing of TransactionsEnable Shared Data Services Module in Script PropertiesThe Shared Data Services Module has to be enabled for each Script that wants to employ the Shared Data Service Queue functionality in OpenScript. It can be enabled under the Script menu selecting Script Properties. On the Script Properties Dialog select the Modules section and check Shared Data to enable Shared Data Service Module for your script. Checking the Shared Data Services option will effectively add a line to your script code that adds the sharedData ScriptService to your script class of IteratingVUserScript.@ScriptService oracle.oats.scripting.modules.sharedData.api.SharedDataService sharedData;Record your scriptRecord your script as usual and then add the following things for Queue handling in the Initialize code block, before the first step and after the last step of your critical path and in the Finalize code block.The java code to be added at individual locations is explained in the following sections in full detail.Create a Shared Data Queue in InitializeTo create a Shared Data Queue go to the Java view of your script and enter the following statements to the initialize() code block.info("Create queueA with life time of 120 minutes");sharedData.createQueue("queueA", 120);This will create an instantiation of the Shared Data Queue object named queueA which is maintained for upto 120 minutes.If you want to use the code for multiple scripts, make sure to use a different queue name for each one here and in the subsequent steps. You may even consider to use a dynamic queueName based on filters of your result list being concurrently accessed.Prepare a unique id for each IterationIn order to keep track of individual virtual users in our queue we need to create a unique identifier from the virtual user id and the used username right after retrieving the next record from our databank file.getDatabank("Usernames").getNextDatabankRecord();getVariables().set("usernameValue1","VU_{{@vuid}}_{{@iterationnum}}_{{db.Usernames.Username}}_{{@timestamp}}_{{@random(10000)}}");String usernameValue = getVariables().get("usernameValue1");info("Now running virtual user " + usernameValue);As you can see from the above code block, we have set the OpenScript variable usernameValue1 to VU_{{@vuid}}_{{@iterationnum}}_{{db.Usernames.Username}}_{{@timestamp}}_{{@random(10000)}} which is a concatenation of the virtual user id and the iterationnumber for general uniqueness; as well as the username from our databank, the timestamp and a random number for making it further unique and ease spotting of errors.Not all of these fields are actually required to make it really unique, but adding the queue name may also be considered to help troubleshoot multiple queues.The value is then retrieved with the getVariables.get() method call and assigned to the usernameValue String used throughout the script.Please note that moving the getDatabank("Usernames").getNextDatabankRecord(); call to the initialize block was later considered to remove concurrency of multiple virtual users running with the same userid and therefor accessing the same "My Inbox" in step 6. This will effectively give each virtual user a userid from the databank file. Make sure you have enough userids to remove this second hurdle.Enqueue and attend Queue before Critical PathTo maintain the right order of virtual users being allowed into the critical path of the transaction the following pseudo step has to be added in front of the first critical step. In the case of this example this is right in front of the step where we retrieve the list of actions from which we select the first to be assigned to us.beginStep("[0] Waiting in the Queue", 0);{info("Enqueued virtual user " + usernameValue + " at the end of queueA");sharedData.offerLast("queueA", usernameValue);info("Wait until the user is the first in queueA");String queueValue1 = null;do {// we wait for at least 0.7 seconds before we check the head of the// queue. This is the time it takes one user to move through the// critical path, i.e. pass steps [5] Enter country and [6] Assign// to meThread.sleep(700);queueValue1 = (String) sharedData.peekFirst("queueA");info("The first user in queueA is currently: '" + queueValue1 + "' " + queueValue1.getClass() + " length " + queueValue1.length() );info("The current user is '"+ usernameValue + "' " + usernameValue.getClass() + " length " + usernameValue.length() + ": indexOf " + usernameValue.indexOf(queueValue1) + " equals " + usernameValue.equals(queueValue1) );} while ( queueValue1.indexOf(usernameValue) < 0 );info("Now the user is the first in queueA");}endStep();This will enqueue the username to the tail of our Queue. It will will wait for at least 700 milliseconds, the time it takes for one user to exit the critical path and then compare the head of our queue with it's username. This last step will be repeated while the two are not equal (indexOf less than zero). If they are equal the indexOf will yield a value of zero or larger and we will perform the critical steps.Dequeue after Critical PathAfter the virtual user has left the critical path and complete its last step the following code block needs to dequeue the virtual user. In the case of our example this is right after the action has been actually assigned to the virtual user. This will allow the next virtual user to retrieve the list of actions still available and in turn let him make his selection/assignment.info("Get and remove the current user from the head of queueA");String pollValue1 = (String) sharedData.pollFirst("queueA");The current user is removed from the head of the queue. The next one will now be able to match his username against the head of the queue.Clear and Destroy Queue for FinishWhen the script has completed, it should clear and destroy the queue. This code block can be put in the finish block of your script and/or in a separate script in order to clear and remove the queue in case you have spotted an error or want to reset the queue for some reason.info("Clear queueA");sharedData.clearQueue("queueA");info("Destroy queueA");sharedData.destroyQueue("queueA");The users waiting in queueA are cleared and the queue is destroyed. If you have scripts still executing they will be caught in a loop.I found it better to maintain a separate Reset Queue script which contained only the following code in the initialize() block. I use to call this script to make sure the queue is cleared in between multiple Loadtest runs. This script could also even be added as the first in a larger scenario, which would execute it only once at very start of the Loadtest and make sure the queues do not contain any stale entries.info("Create queueA with life time of 120 minutes");sharedData.createQueue("queueA", 120);info("Clear queueA");sharedData.clearQueue("queueA");This will create a Shared Data Queue instance of queueA and clear all entries from this queue.Monitoring QueueWhile creating the scripts it was useful to monitor the contents, i.e. the current first user in the Queue. The following code block will make sure the Shared Data Queue is accessible in the initialize() block.info("Create queueA with life time of 120 minutes");sharedData.createQueue("queueA", 120);In the run() block the following code will continuously monitor the first element of the Queue and write an informational message with the current username Value to the Result window.info("Monitor the first users in queueA");String queueValue1 = null;do {queueValue1 = (String) sharedData.peekFirst("queueA");if (queueValue1 != null)info("The first user in queueA is currently: '" + queueValue1 + "' " + queueValue1.getClass() + " length " + queueValue1.length() );} while ( true );This script can be run from OpenScript parallel to a loadtest performed by the Oracle Load Test.However it is not recommend to run this in a production loadtest as the performance impact is unknown. Accessing the Queue's head with the peekFirst() method has been reported with about 2 seconds response time by both OpenScript and OTL. It is advised to log a Service Request to see if this could be lowered in future releases of Application Testing Suite, as the pollFirst() and even offerLast() writing to the tail of the Queue usually returned after an average 0.1 seconds.Debugging QueueWhile debugging the scripts the following was useful to remove single entries from its head, i.e. the current first user in the Queue. The following code block will make sure the Shared Data Queue is accessible in the initialize() block.info("Create queueA with life time of 120 minutes");sharedData.createQueue("queueA", 120);In the run() block the following code will remove the first element of the Queue and write an informational message with the current username Value to the Result window.info("Get and remove the current user from the head of queueA");String pollValue1 = (String) sharedData.pollFirst("queueA");info("The first user in queueA was currently: '" + pollValue1 + "' " + pollValue1.getClass() + " length " + pollValue1.length() );ReferencesOracle Functional Testing OpenScript User's Guide Version 9.20 [E15488-05]Chapter 17 Using the Shared Data Modulehttp://download.oracle.com/otn/nt/apptesting/oats-docs-9.21.0030.zipOracle Fusion Middleware Oracle WebLogic Server Administration Console Online Help 11g Release 1 (10.3.4) [E13952-04]Administration Console Online Help - Manage users and groupshttp://download.oracle.com/docs/cd/E17904_01/apirefs.1111/e13952/taskhelp/security/ManageUsersAndGroups.htm

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  • Using a priority queue in Java

    - by Bharat
    Forgive me if this is a tried question, but I'm having a little difficulty figuring it out. I currently have a class Node, and each 'node' is a square in a maze. I'm trying to implement the A* algorithm, so each of these nodes will have an f-cost (int) data member inside of it. I was wondering if there's a way that I can create a priority queue of these nodes, and set up the f-cost variable as the comparator? I've looked at examples online, but all I can find are String priority queues. Can I implement Comparator for the Node class? Would this allow me to access the data member stored inside it? Many Thanks!

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  • Lock Free Queue -- Single Producer, Multiple Consumers

    - by Shirish
    Hello, I am looking for a method to implement lock-free queue data structure that supports single producer, and multiple consumers. I have looked at the classic method by Maged Michael and Michael Scott (1996) but their version uses linked lists. I would like an implementation that makes use of bounded circular buffer. Something that uses atomic variables? On a side note, I am not sure why these classic methods are designed for linked lists that require a lot of dynamic memory management. In a multi-threaded program, all memory management routines are serialized. Aren't we defeating the benefits of lock-free methods by using them in conjunction with dynamic data structures? I am trying to code this in C/C++ using pthread library on a Intel 64-bit architecture. Thank you, Shirish

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  • jQuery .queue() not working as expected

    - by Andrew
    The page in question is right here: http://s289116086.onlinehome.us/lawjournaltv/index.php I'm 90% of the way there, I'm just assuming there's an error with my syntax. Focus on the blue callout area with "Workers' Compensation" as the title: Basically, I've created a little slideshow there with the controls at the top and when you click on any of them both the callout and the background are to slide. As you can see it's working now, but the problem is that I want the new background to slide in over the old one. I've tried several things including the queue() method, delay(), and adding everything else to the animate() callback with no success (right now the background goes black and then the new image slides in). You guys have never let me down before, so I'm hoping this is an easy fix. Thanks in advance!

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  • How to create a delayed queue in RabbitMQ?

    - by eandersson
    What is the easiest way to create a delay (or parking) queue with Python, Pika and RabbitMQ? I have seen an similar questions, but none for Python. I find this an useful idea when designing applications, as it allows us to throttle messages that needs to be re-queued again. There are always the possibility that you will receive more messages than you can handle, maybe the HTTP server is slow, or the database is under too much stress. I also found it very useful when something went wrong in scenarios where there is a zero tolerance to losing messages, and while re-queuing messages that could not be handled may solve that. It can also cause problems where the message will be queued over and over again. Potentially causing performance issues, and log spam.

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  • C++: A variation of priority queue

    - by Helltone
    I need some kind of priority queue to store pairs <key, value>. Values are unique, but keys aren't. I will be performing the following operations (most common first): random insertion; retrieving (and removing) all elements with the least key. random removal (by value); I can't use std::priority_queue because it only supports removing the head. For now, I'm using an unsorted std::list. Insertion is performed by just pushing new elements to the back (O(1)). Operation 2 sorts the list with std::sort (O(N*logN)), before performing the actual retrieval. Removal, however, is O(n), which is a bit expensive. Any idea of a better data structure?

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  • How to Create a Queue

    - by regex
    Hello All, I have an application built that hits a third party company's web service in order to create an email account after a customer clicks a button. However, sometimes the web service takes longer than 1 minute to respond, which is way to long for my customers to be sitting there waiting for a response. I need to devise a way to set up some sort of queuing service external from the web site. This way I can add the web service action to the queue and advise the customer it may take up to 2 minutes to create the account. I'm curious of the best way to achieve this. My initial thought is to request the actions via a database table which will be checked on a regular basis by a Console app which is run via Windows Scheduled tasks. Any issues with that method? Is there a better method you can think of?

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  • Which data structure(s) to back a Final Fantasy ATB-style queue? (a delay queue)

    - by ZoFreX
    Situation: There are several entities in a simulated environment, which has an artificial notion of time called "ticks", which has no link to real time. Each entity takes it in turns to move, but some are faster than others. This is expressed by a delay, in ticks. So entity A might have a delay of 10, and B 25. In this case the turn order would go: A A B A A I'm wondering what data structure to use. At first I automatically thought "priority queue" but the delays are relative to "current time" which complicates matters. Also, there will be entities with larger delays and it's not unforseeable that the program will run through millions of ticks. It seems silly for an internal counter to be building higher and higher when the delays themselves stay relatively small and don't increase. So how would you solve this?

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  • Using MySQL as a job queue

    - by user237815
    I'd like to use MySQL as a job queue. Multiple machines will be producing and consuming jobs. Jobs need to be scheduled; some may run every hour, some every day, etc. It seems fairly straightforward: for each job, have a "nextFireTime" column, and have worker machines search for the job with the nextFireTime, change the status of the record to "inProcess", and then update the nextFireTime when the job ends. The problem comes in when a worker dies silently. It won't be able to update the nextFireTime or set the status back to "idle". Unfortunately, jobs can be long-running, so a reaper thread that looks for jobs that have been inProcess too long isn't an option. There's no timeout value that would work. Can anyone suggest a design pattern that would properly handle unreliable worker machines?

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  • Tomcat 6 thread safe email queue (javax.mail.*)

    - by Eric V
    Hi I have design/architecture question. I would like to send emails from one of my jsp pages. I have one particular issue that has been a little bit of a problem. there is an instance where one of the pages will need to send around 50 emails at near the same time. I would like the messages sent to a queue where a background thread will actually do the email sending. What is the appropriate way to solve this problem? If you know of a tutorial, example code or tomcat configuration is needed please let me know. Thanks,

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  • Implementing Java Priority Queue

    - by Kay
    public class PriorityQueue<T> { private PriorityNode<T> head, tail; private int numItems; public PriorityQueue(){ numItems = 0; head=null; tail=null; } public void add(int priority, T value){ PriorityNode<T> newNode = new PriorityNode<T>(priority,value); if(numItems == 0){ head = newNode; tail = newNode; } else{ head.setNext(newNode); head = newNode; } } } Where PriorityNode is defined as: public class PriorityNode<T> implements Comparable<T> { private T value; private PriorityNode<T> next; private int priority; public PriorityNode(int priority,T newValue){ value = newValue; next = null; priority = 0; } public PriorityNode(T newValue){ value = newValue; next = null; priority = 0; } public void setPriority(int priority){ this.priority = priority; } public int getPriority(){ return this.priority; } public T getValue(){ return value; } public PriorityNode<T> getNext(){ return next; } public void setNext(PriorityNode<T> nextNode){ this.next = nextNode; } public void setValue(T newValue){ value = newValue; } public int compareTo(int pri) { // TODO Auto-generated method stub if(this.priority<pri){ return -1; } else if(this.priority == pri){ return 0; } else{ return 1; } } } I'm having a lot of difficulty using the Comparator here and implementing a priority queue - please point me in the right direction.

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  • Minimal "Task Queue" with stock Linux tools to leverage Multicore CPU

    - by Manuel
    What is the best/easiest way to build a minimal task queue system for Linux using bash and common tools? I have a file with 9'000 lines, each line has a bash command line, the commands are completely independent. command 1 > Logs/1.log command 2 > Logs/2.log command 3 > Logs/3.log ... My box has more than one core and I want to execute X tasks at the same time. I searched the web for a good way to do this. Apparently, a lot of people have this problem but nobody has a good solution so far. It would be nice if the solution had the following features: can interpret more than one command (e.g. command; command) can interpret stream redirects on the lines (e.g. ls > /tmp/ls.txt) only uses common Linux tools Bonus points if it works on other Unix-clones without too exotic requirements.

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  • Task Queue stopped working

    - by pocoa
    I was playing with Goole App Engine Task Queue API to learn how to use it. But I couldn't make it trigger locally. My application is working like a charm when I upload to Google servers. But it doesn't trigger locally. All I see from the admin is the list of the tasks. But when their ETA comes, they just pass it. It's like they runs but they fails and waiting for the retries. But I can't see these events on command line. When I try to click "Run" on admin panel, it runs successfuly and I can see these requests from the command line. I'm using App Engine SDK 1.3.4 on Linux with google-app-engine-django. I'm trying to find the problem from 3 hours now and I couldn't find it. It's also very hard to debug GAE applications. Because debug messages do not appear on console screen. Thanks.

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  • mysterical error

    - by Görkem Buzcu
    i get "customer_service_simulator.exe stopped" error, but i dont know why? this is my c programming project and i have limited time left before deadline. the code is: #include <stdio.h> #include <stdlib.h> #include<time.h> #define FALSE 0 #define TRUE 1 /*A Node declaration to store a value, pointer to the next node and a priority value*/ struct Node { int priority; //arrival time int val; //type int wait_time; int departure_time; struct Node *next; }; Queue Record that will store the following: size: total number of elements stored in the list front: it shows the front node of the queue (front of the queue) rear: it shows the rare node of the queue (rear of the queue) availability: availabity of the teller struct QueueRecord { struct Node *front; struct Node *rear; int size; int availability; }; typedef struct Node *niyazi; typedef struct QueueRecord *Queue; Queue CreateQueue(int); void MakeEmptyQueue(Queue); void enqueue(Queue, int, int); int QueueSize(Queue); int FrontOfQueue(Queue); int RearOfQueue(Queue); niyazi dequeue(Queue); int IsFullQueue(Queue); int IsEmptyQueue(Queue); void DisplayQueue(Queue); void sorteddequeue(Queue); void sortedenqueue(Queue, int, int); void tellerzfunctionz(Queue *, Queue, int, int); int main() { int system_clock=0; Queue waitqueue; int exit, val, priority, customers, tellers, avg_serv_time, sim_time,counter; char command; waitqueue = CreateQueue(0); srand(time(NULL)); fflush(stdin); printf("Enter number of customers, number of tellers, average service time, simulation time\n:"); scanf("%d%c %d%c %d%c %d",&customers, &command,&tellers,&command,&avg_serv_time,&command,&sim_time); fflush(stdin); Queue tellerarray[tellers]; for(counter=0;counter<tellers;counter++){ tellerarray[counter]=CreateQueue(0); //burada teller sayisi kadar queue yaratiyorum } for(counter=0;counter<customers;counter++){ priority=1+(int)rand()%sim_time; //this will generate the arrival time sortedenqueue(waitqueue,1,priority); //here i put the customers in the waiting queue } tellerzfunctionz(tellerarray,waitqueue,tellers,customers); DisplayQueue(waitqueue); DisplayQueue(tellerarray[0]); DisplayQueue(tellerarray[1]); // waitqueue-> printf("\n\n"); system("PAUSE"); return 0; } /*This function initialises the queue*/ Queue CreateQueue(int maxElements) { Queue q; q = (struct QueueRecord *) malloc(sizeof(struct QueueRecord)); if (q == NULL) printf("Out of memory space\n"); else MakeEmptyQueue(q); return q; } /*This function sets the queue size to 0, and creates a dummy element and sets the front and rear point to this dummy element*/ void MakeEmptyQueue(Queue q) { q->size = 0; q->availability=0; q->front = (struct Node *) malloc(sizeof(struct Node)); if (q->front == NULL) printf("Out of memory space\n"); else{ q->front->next = NULL; q->rear = q->front; } } /*Shows if the queue is empty*/ int IsEmptyQueue(Queue q) { return (q->size == 0); } /*Returns the queue size*/ int QueueSize(Queue q) { return (q->size); } /*Shows the queue is full or not*/ int IsFullQueue(Queue q) { return FALSE; } /*Returns the value stored in the front of the queue*/ int FrontOfQueue(Queue q) { if (!IsEmptyQueue(q)) return q->front->next->val; else { printf("The queue is empty\n"); return -1; } } /*Returns the value stored in the rear of the queue*/ int RearOfQueue(Queue q) { if (!IsEmptyQueue(q)) return q->rear->val; else { printf("The queue is empty\n"); return -1; } } /*Displays the content of the queue*/ void DisplayQueue(Queue q) { struct Node *pos; pos=q->front->next; printf("Queue content:\n"); printf("-->Priority Value\n"); while (pos != NULL) { printf("--> %d\t %d\n", pos->priority, pos->val); pos = pos->next; } } void enqueue(Queue q, int element, int priority){ if(IsFullQueue(q)){ printf("Error queue is full"); } else{ q->rear->next=(struct Node *)malloc(sizeof(struct Node)); q->rear=q->rear->next; q->rear->next=NULL; q->rear->val=element; q->rear->priority=priority; q->size++; } } void sortedenqueue(Queue q, int val, int priority) { struct Node *insert,*temp; insert=(struct Node *)malloc(sizeof(struct Node)); insert->val=val; insert->priority=priority; temp=q->front; if(q->size==0){ enqueue(q, val, priority); } else{ while(temp->next!=NULL && temp->next->priority<insert->priority){ temp=temp->next; } //printf("%d",temp->priority); insert->next=temp->next; temp->next=insert; q->size++; if(insert->next==NULL){ q->rear=insert; } } } niyazi dequeue(Queue q) { niyazi del; niyazi deli; del=(niyazi)malloc(sizeof(struct Node)); deli=(niyazi)malloc(sizeof(struct Node)); if(IsEmptyQueue(q)){ printf("Queue is empty!"); return NULL; } else { del=q->front->next; q->front->next=del->next; deli->val=del->val; deli->priority=del->priority; free(del); q->size--; return deli; } } void sorteddequeue(Queue q) { struct Node *temp; struct Node *min; temp=q->front->next; min=q->front; int i; for(i=1;i<q->size;i++) { if(temp->next->priority<min->next->priority) { min=temp; } temp=temp->next; } temp=min->next; min->next=min->next->next; free(temp); if(min->next==NULL){ q->rear=min; } q->size--; } void tellerzfunctionz(Queue *a, Queue b, int c, int d){ int i; int value=0; int priority; niyazi temp; temp=(niyazi)malloc(sizeof(struct Node)); if(c==1){ for(i=0;i<d;i++){ temp=dequeue(b); sortedenqueue((*(a)),temp->val,temp->priority); } } else{ for(i=0;i<d;i++){ while(b->front->next->val==1){ if((*(a+value))->availability==1){ temp=dequeue(b); sortedenqueue((*(a+value)),temp->val,temp->priority); (*(a+value))->rear->val=2; } else{ value++; } } } } } //end of the program

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  • Job queue manager with RPC interface

    - by admr
    I need a job queue manager that I can control over the Internet. It should be able to execute and stop processes, check on their status (ideally notice and execute some code when a process exits), respond to commands and also be able to report back to a server. Background: I have a GWT application that allows to create jobs to execute on a cloud instance (currently EC2). I want to push a "job packet" (data for a process to operate on etc) to S3, start a Linux EC2 instance (or use one that's already running), and tell a job manager on the instance to execute that job (possibly parallel to other jobs). It should then pull the "job packet" from S3, run a process that operates on that data and report back to the server that is running the server part of my GWT application with some information (e.g. exit code, stdout, stderr). If I have to write e.g. stdour/err to a file from the process and read that file, that's OK too. I would really like the manager to be "close" to the processes it runs, meaning I want to avoid using something like Runtime.exec from the JDK. It seems like I would have to do that if I used Quartz for example. I'm fine with the calls in both directions being asynchronous. I'm fine with any reasonable technology for the calls as long as I can easily build an interface for that in my GWT server side (e.g. HTTP requests to a servlet over SSL would be nice and trivial). The job manager does not need to have a very sophisticated queueing system. Running several processes either sequentially or in parallel should be fine. Determining how much compute time a process received during its lifetime would be nice (AFAIK, this might be challenging). I did not yet find any existing software that does this, including http://java-source.net/open-source/job-schedulers. I suspect I might have to build an RPC interface (with authentication etc, of course) around a job manager; maybe use something like Apache Commons Exec. In that case, I would prefer Java or Python for the job manager part. I would be happy to hear suggestions for either the former or latter scenario!

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  • Go - Using a container/heap to implement a priority queue

    - by Seth Hoenig
    In the big picture, I'm trying to implement Dijkstra's algorithm using a priority queue. According to members of golang-nuts, the idiomatic way to do this in Go is to use the heap interface with a custom underlying data structure. So I have created Node.go and PQueue.go like so: //Node.go package pqueue type Node struct { row int col int myVal int sumVal int } func (n *Node) Init(r, c, mv, sv int) { n.row = r n.col = c n.myVal = mv n.sumVal = sv } func (n *Node) Equals(o *Node) bool { return n.row == o.row && n.col == o.col } And PQueue.go: // PQueue.go package pqueue import "container/vector" import "container/heap" type PQueue struct { data vector.Vector size int } func (pq *PQueue) Init() { heap.Init(pq) } func (pq *PQueue) IsEmpty() bool { return pq.size == 0 } func (pq *PQueue) Push(i interface{}) { heap.Push(pq, i) pq.size++ } func (pq *PQueue) Pop() interface{} { pq.size-- return heap.Pop(pq) } func (pq *PQueue) Len() int { return pq.size } func (pq *PQueue) Less(i, j int) bool { I := pq.data.At(i).(Node) J := pq.data.At(j).(Node) return (I.sumVal + I.myVal) < (J.sumVal + J.myVal) } func (pq *PQueue) Swap(i, j int) { temp := pq.data.At(i).(Node) pq.data.Set(i, pq.data.At(j).(Node)) pq.data.Set(j, temp) } And main.go: (the action is in SolveMatrix) // Euler 81 package main import "fmt" import "io/ioutil" import "strings" import "strconv" import "./pqueue" const MATSIZE = 5 const MATNAME = "matrix_small.txt" func main() { var matrix [MATSIZE][MATSIZE]int contents, err := ioutil.ReadFile(MATNAME) if err != nil { panic("FILE IO ERROR!") } inFileStr := string(contents) byrows := strings.Split(inFileStr, "\n", -1) for row := 0; row < MATSIZE; row++ { byrows[row] = (byrows[row])[0 : len(byrows[row])-1] bycols := strings.Split(byrows[row], ",", -1) for col := 0; col < MATSIZE; col++ { matrix[row][col], _ = strconv.Atoi(bycols[col]) } } PrintMatrix(matrix) sum, len := SolveMatrix(matrix) fmt.Printf("len: %d, sum: %d\n", len, sum) } func PrintMatrix(mat [MATSIZE][MATSIZE]int) { for r := 0; r < MATSIZE; r++ { for c := 0; c < MATSIZE; c++ { fmt.Printf("%d ", mat[r][c]) } fmt.Print("\n") } } func SolveMatrix(mat [MATSIZE][MATSIZE]int) (int, int) { var PQ pqueue.PQueue var firstNode pqueue.Node var endNode pqueue.Node msm1 := MATSIZE - 1 firstNode.Init(0, 0, mat[0][0], 0) endNode.Init(msm1, msm1, mat[msm1][msm1], 0) if PQ.IsEmpty() { // make compiler stfu about unused variable fmt.Print("empty") } PQ.Push(firstNode) // problem return 0, 0 } The problem is, upon compiling i get the error message: [~/Code/Euler/81] $ make 6g -o pqueue.6 Node.go PQueue.go 6g main.go main.go:58: implicit assignment of unexported field 'row' of pqueue.Node in function argument make: *** [all] Error 1 And commenting out the line PQ.Push(firstNode) does satisfy the compiler. But I don't understand why I'm getting the error message in the first place. Push doesn't modify the argument in any way.

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  • Altq limits not being applied to UDP transfers

    - by overkordbaever
    I have a OpenBSD server acting as a router/firewall with yhr packet filter ruleset shown below, a linux server, and a linux client. When transferring files (using netcat) by TCP, the limits are applied (for example the 100mbit limit in the example), though when transferring data by UDP, the limits aren't applied; the file always takes the same amount of time no matter the queue bandwidth limit I set (I can even turn off the queues completely, and will still get the same result). Why aren't the queuing rules applied to UDP packages? The rules used: #queue rules altq on { $int_if, $ext_if } cbq bandwidth 100Mb queue { def, low } queue def bandwidth 0Mb cbq(default) queue low bandwidth 100Mb cbq #Passrules test pass out quick from $int_if to $ext_if queue low pass in quick from $ext_if to $int_if queue low pass out quick from $ext_if to $int_if queue low pass in quick from $int_if to $ext_if queue low I suppose this may be related a question I've previously asked, though since it's more of a separate question, I suppose a separate question should be used for this

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  • Testing a Non-blocking Queue

    - by jsw
    I've ported the non-blocking queue psuedocode here to C#. The code below is meant as a near verbatim copy of the paper. What approach would you take to test the implementation? Note: I'm running in VS2010 so I don't have CHESS support yet. using System.Threading; #pragma warning disable 0420 namespace ConcurrentCollections { class QueueNodePointer<T> { internal QueueNode<T> ptr; internal QueueNodePointer() : this(null) { } internal QueueNodePointer(QueueNode<T> ptr) { this.ptr = ptr; } } class QueueNode<T> { internal T value; internal QueueNodePointer<T> next; internal QueueNode() : this(default(T)) { } internal QueueNode(T value) { this.value = value; this.next = new QueueNodePointer<T>(); } } public class ConcurrentQueue<T> { private volatile int count = 0; private QueueNodePointer<T> qhead = new QueueNodePointer<T>(); private QueueNodePointer<T> qtail = new QueueNodePointer<T>(); public ConcurrentQueue() { var node = new QueueNode<T>(); node.next.ptr = null; this.qhead.ptr = this.qtail.ptr = node; } public int Count { get { return this.count; } } public void Enqueue(T value) { var node = new QueueNode<T>(value); node.next.ptr = null; QueueNodePointer<T> tail; QueueNodePointer<T> next; while (true) { tail = this.qtail; next = tail.ptr.next; if (tail == this.qtail) { if (next.ptr == null) { var newtail = new QueueNodePointer<T>(node); if (Interlocked.CompareExchange(ref tail.ptr.next, newtail, next) == next) { Interlocked.Increment(ref this.count); break; } else { Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(next.ptr), tail); } } } } Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(node), tail); } public T Dequeue() { T value; while (true) { var head = this.qhead; var tail = this.qtail; var next = head.ptr.next; if (head == this.qhead) { if (head.ptr == tail.ptr) { if (next.ptr == null) { return default(T); } Interlocked.CompareExchange(ref this.qtail, new QueueNodePointer<T>(next.ptr), tail); } else { value = next.ptr.value; var newhead = new QueueNodePointer<T>(next.ptr); if (Interlocked.CompareExchange(ref this.qhead, newhead, head) == head) { Interlocked.Decrement(ref this.count); break; } } } } return value; } } } #pragma warning restore 0420

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  • Lockless queue implementation ends up having a loop under stress

    - by Fozi
    I have lockless queues written in C in form of a linked list that contains requests from several threads posted to and handled in a single thread. After a few hours of stress I end up having the last request's next pointer pointing to itself, which creates an endless loop and locks up the handling thread. The application runs (and fails) on both Linux and Windows. I'm debugging on Windows, where my COMPARE_EXCHANGE_PTR maps to InterlockedCompareExchangePointer. This is the code that pushes a request to the head of the list, and is called from several threads: void push_request(struct request * volatile * root, struct request * request) { assert(request); do { request->next = *root; } while(COMPARE_EXCHANGE_PTR(root, request, request->next) != request->next); } This is the code that gets a request from the end of the list, and is only called by a single thread that is handling them: struct request * pop_request(struct request * volatile * root) { struct request * volatile * p; struct request * request; do { p = root; while(*p && (*p)->next) p = &(*p)->next; // <- loops here request = *p; } while(COMPARE_EXCHANGE_PTR(p, NULL, request) != request); assert(request->next == NULL); return request; } Note that I'm not using a tail pointer because I wanted to avoid the complication of having to deal with the tail pointer in push_request. However I suspect that the problem might be in the way I find the end of the list. There are several places that push a request into the queue, but they all look generaly like this: // device->requests is defined as struct request * volatile requests; struct request * request = malloc(sizeof(struct request)); if(request) { // fill out request fields push_request(&device->requests, request); sem_post(device->request_sem); } The code that handles the request is doing more than that, but in essence does this in a loop: if(sem_wait_timeout(device->request_sem, timeout) == sem_success) { struct request * request = pop_request(&device->requests); // handle request free(request); } I also just added a function that is checking the list for duplicates before and after each operation, but I'm afraid that this check will change the timing so that I will never encounter the point where it fails. (I'm waiting for it to break as I'm writing this.) When I break the hanging program the handler thread loops in pop_request at the marked position. I have a valid list of one or more requests and the last one's next pointer points to itself. The request queues are usually short, I've never seen more then 10, and only 1 and 3 the two times I could take a look at this failure in the debugger. I thought this through as much as I could and I came to the conclusion that I should never be able to end up with a loop in my list unless I push the same request twice. I'm quite sure that this never happens. I'm also fairly sure (although not completely) that it's not the ABA problem. I know that I might pop more than one request at the same time, but I believe this is irrelevant here, and I've never seen it happening. (I'll fix this as well) I thought long and hard about how I can break my function, but I don't see a way to end up with a loop. So the question is: Can someone see a way how this can break? Can someone prove that this can not? Eventually I will solve this (maybe by using a tail pointer or some other solution - locking would be a problem because the threads that post should not be locked, I do have a RW lock at hand though) but I would like to make sure that changing the list actually solves my problem (as opposed to makes it just less likely because of different timing).

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  • Cash Application Work Queue in Oracle Receivables Release 12.1.1

    - by Robert Story
    Upcoming WebcastTitle: Cash Application Work Queue in Oracle Receivables Release 12.1.1Date: March 24, 2010Time: 10:00 am EDT, 7:00 am PDT, 14:00 GMT Product Family: E-Business Suite Receivables 12.1.1 Receipts Summary Understand the setups and processes for the Cash Application Work Queue in Release 12.1.1 and learn how to diagnose basic functional issues. This one-hour session is recommended for technical and functional users. We will be covering topics related to processing receipts efficiently, managing the work load of cash application owners and diagnosing issues. Topics will include: Description of Cash Application Work Queue Setup and Work Queue Process Dependencies and Interactions Basic Troubleshooting Steps A short, live demonstration (only if applicable) and question and answer period will be included. Click here to register for this session....... ....... ....... ....... ....... ....... .......The above webcast is a service of the E-Business Suite Communities in My Oracle Support.For more information on other webcasts, please reference the Oracle Advisor Webcast Schedule.Click here to visit the E-Business Communities in My Oracle Support Note that all links require access to My Oracle Support.

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