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  • Pthread Queue System

    - by Wallace
    Hi. I'm working on my assignment on pthreads. I'm new and never touched on pthreads before. Is there any sample codes or resources out there that anyone of you have, that might aid me in my assignment? Here are my assignment details. A pthread program about queue system: Write a C/C++ Pthread program for a Dental clinic’s queuing system that declares an array of integers of size N, where N is the maximum number of queue for the day. The pthread program uses two threads. Whenever there is a new dental appointment, the first thread (the creator) puts the queue numbers in the array, one after the other. The second thread (the remover) removes the queue numbers from the array whenever the dentist has seen the patient. This is done in a FIFO fashion (First In First Out). The algorithm of the creator is as follows: • If the array is not full then put a new number in it (the numbers start at 1 and are incremented by one each time, so the creator create queue number 1, 2, 3 etc.) • sleep for 1 to 10 seconds, randomly • repeat The algorithm of the remover is as follows: • If the array is not empty then remove its smallest queue number • sleep for 1 to 10 seconds, randomly • repeat You should use mutex locks to protect things that must be protected. Each thread should print on the screen what it is doing (eg: "number 13 is added into the queue", "number 7 is removed from the queue", etc.). The program should run forever. Any help will be appreciated. Thanks.

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  • Lazy Sequences that "Look Ahead" for Project Euler Problem 14

    - by ivar
    I'm trying to solve Project Euler Problem 14 in a lazy way. Unfortunately, I may be trying to do the impossible: create a lazy sequence that is both lazy, yet also somehow 'looks ahead' for values it hasn't computed yet. The non-lazy version I wrote to test correctness was: (defn chain-length [num] (loop [len 1 n num] (cond (= n 1) len (odd? n) (recur (inc len) (+ 1 (* 3 n))) true (recur (inc len) (/ n 2))))) Which works, but is really slow. Of course I could memoize that: (def memoized-chain (memoize (fn [n] (cond (= n 1) 1 (odd? n) (+ 1 (memoized-chain (+ 1 (* 3 n)))) true (+ 1 (memoized-chain (/ n 2))))))) However, what I really wanted to do was scratch my itch for understanding the limits of lazy sequences, and write a function like this: (def lazy-chain (letfn [(chain [n] (lazy-seq (cons (if (odd? n) (+ 1 (nth lazy-chain (dec (+ 1 (* 3 n))))) (+ 1 (nth lazy-chain (dec (/ n 2))))) (chain (+ n 1)))))] (chain 1))) Pulling elements from this will cause a stack overflow for n2, which is understandable if you think about why it needs to look 'into the future' at n=3 to know the value of the tenth element in the lazy list because (+ 1 (* 3 n)) = 10. Since lazy lists have much less overhead than memoization, I would like to know if this kind of thing is possible somehow via even more delayed evaluation or queuing?

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  • How OpenStack Swift handles concurrent restful API request?

    - by Chen Xie
    I installed a swift service and was trying to know the capability of handling concurrent request. So I created massive amount of threads in Java, and sent it via the RestFUL API Not surprisingly, when the number of requests climb up, the program started to throw out exceptions. Caused by: java.net.ConnectException: Connection timed out: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:69) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:157) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391) at java.net.Socket.connect(Socket.java:579) at java.net.Socket.connect(Socket.java:528) at sun.net.NetworkClient.doConnect(NetworkClient.java:180) at sun.net.www.http.HttpClient.openServer(HttpClient.java:378) at sun.net.www.http.HttpClient.openServer(HttpClient.java:473) at sun.net.www.http.HttpClient.(HttpClient.java:203) But can anyone tell me how that time outhappened? I am curious of how SWIFT handles those requests. Is that by queuing the requests and because there are too many requests in the queue and wait for too long time and it's just get kicked out from the queue? If this holds, does it mean that it's an asynchronized mechanism to handle requests? Thanks.

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  • Injecting correct object graph using StructureMap in Queue of different Objects

    - by davy
    I have a queuing service that has to inject a different dependency graph depending on the type of object in the queue. I'm using Structure Map. So, if the object in the queue is TypeA the concrete classes for TypeA are used and if it's TypeB, the concrete classes for TypeB are used. I'd like to avoid code in the queue like: if (typeA) { // setup TypeA graph } else if (typeB) { // setup TypeB graph } Within the graph, I also have a generic classes such as an IReader(ISomething, ISpomethingElse) where IReader is generic but needs to inject the correct ISomething and ISomethingElse for the type. ISomething will also have dependencies and so on. Currently I create a TypeA or TypeB object and inject a generic Processor class using StructureMap into it and then pass a factory manually inject a TypeA or TypeB factory into a method like: Processor.Process(new TypeAFactory) // perhaps I should have an abstract factory... However, because the factory then creates the generic IReader mentioned above, I end up manually injecting all the TypeA or TypeB classes fro there on. I hope enough of this makes sense. I am new to StructureMap and was hoping somebody could point me in the right direction here for a flexible and elegant solution. Thanks

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  • How to hold a queue of messages and have a group of working threads without polling?

    - by Mark
    I have a workflow that I want to looks something like this: / Worker 1 \ =Request Channel= - [Holding Queue|||] - Worker 2 - =Response Channel= \ Worker 3 / That is: Requests come in and they enter a FIFO queue Identical workers then pick up tasks from the queue At any given time any worker may work only one task When a worker is free and the holding queue is non-empty the worker should immediately pick up another task When tasks are complete, a worker places the result on the Response Channel I know there are QueueChannels in Spring Integration, but these channels require polling (which seems suboptimal). In particular, if a worker can be busy, I'd like the worker to be busy. Also, I've considered avoiding the queue altogether and simply letting tasks round-robin to all workers, but it's preferable to have a single waiting line as some tasks may be accomplished faster than others. Furthermore, I'd like insight into how many jobs are remaining (which I can get from the queue) and the ability to cancel all or particular jobs. How can I implement this message queuing/work distribution pattern while avoiding a polling? Edit: It appears I'm looking for the Message Dispatcher pattern -- how can I implement this using Spring/Spring Integration?

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  • Wicket application + Apache + mod_jk - AJP queues are filling up!

    - by nojyarg
    Dear community, We are having a Wicket-based Java application deployed in a production server cluster using Apache (2.2.3) with mod_jk (1.2.30) as load balancing component w/ sticky session and Jboss 5 as application container for the Java application. We are inconsistently seeing an issue in our production environment where our AJP queues between Apache and Jboss as shown in the JMX console fill up with requests to the point where the application server is no longer taking on any new requests. When looking at all involved system components (overall traffic, load db, process list db, load of all clustered application server nodes) nothing points towards a capacity issue which would explain why the calls are being stalled in the AJP queue. Instead all systems appear sufficiently idle. So far, our only remedy to this issue is to restart the appservers and the load balancer which only occasionally clears the AJP queues. We are trying to figure out why the queues are filling up to the point that no calls get returned to the end user although the system is not under a high load. Has anyone else experienced similar problems? Are there any other system metrics we should monitor that could explain the queuing behavior? Is this potentially a mod_jk issue? If so, is it advisable to swap mod_jk with mod_cluster to resolve the issue? Any advice is highly appreciated. If I can provide additional information for the sake of troubleshooting I would be more than willing to do so. /Ben

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  • Many users, many cpus, no delays. Good for cloud?

    - by Eric
    I wish to set up a CPU-intensive time-important query service for users on the internet. A usage scenario is described below. Is cloud computing the right way to go for such an implementation? If so, what cloud vendor(s) cater to this type of application? I ask specifically, in terms of: 1) pricing 2) latency resulting from: - slow CPUs, instance creations, JIT compiles, etc.. - internal management and communication of processes inside the cloud (e.g. a queuing process and a calculation process) - communication between cloud and end user 3) ease of deployment A usage scenario I am expecting is: - A typical user sends a query (XML of size around 1K) once every 30 seconds on average. - Each query requires a numerical computation of average time 0.2 sec and max time 1 sec on a 1 GHz Pentium. The computation requires no data other than the query itself and is performed by the same piece of code each time. - The delay a user experiences between sending a query and receiving a response should be on average no more than 2 seconds and in general no more than 5 seconds. - A background save to a DB of the response should occur (not time critical) - There can be up to 30000 simultaneous users - i.e., on average 1000 queries a second, each requiring an average 0.2 sec calculation, so that would necessitate around 200 CPUs. Currently I'm look at GAE Java (for quicker deployment and less IT hassle) and EC2 (Speed and price optimization) as options. Where can I learn more about the right way to set ups such a system? past threads, different blogs, books, etc.. BTW, if my terminology is wrong or confusing, please let me know. I'd greatly appreciate any help.

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  • XAML and WPF - Passing Variables to XAML Windows

    - by Erika
    Hi, I'm pretty new to WPF and i'm trying to load a XAML window and pass a variable to this XAML in its constructor or so, because i need it to load some items from this passed variable. Could anyone point me to the direction of how to go about this please? How does one start up a XAML window and give it a variable please? Thanks in advanced.. Erika

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  • Joomla Admin module in "New Article" form?

    - by Honus Wagner
    In Joomla 1.5, I am interested in developing a fairly simple module that I was hoping would live on the right side of the create new article page. I've created a handful of modules before, one on the admin page at the dashboard that is on the right side that you click to expand/collapse. So, can I create a module that I could attach to any new article form on the right side, somewhere under "advanced settings" or something? Thanks.

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  • Good Delphi Blogs?

    - by Andreas Rejbrand
    I just saw http://pages.cs.wisc.edu/~rkennedy/ which appears to be a very interesting in-depth blog about the Delphi programming language, compiler, and IDE. At the more basic level we also have the About site, and DelphiBasics. You can also have fun for a few minutes at http://www.scalabium.com/faq/dc_tips.htm. What are the most interesting blogs and sites devoted to Delphi? I am in particular interested in content at the advanced level.

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  • MS cash drawer with epson TM-IV88 Status API

    - by Xience
    Does anyone know how to monitor cash drawer's open/close state using Advanced Printer Driver's Status API for Epson TM-88IV thermal printer. I wish i could use OPOS for ADK .Net, but haven't had luck setting it up on windows 7. Does anyone know how to be a part of epson developer network. I have gone through the information available at www.epson-pos.com but there is no information available on POS/ESC codes. Please help...........

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  • Error handling in VS/C# build events.

    - by ProfK
    I have just written a small utility to be used in a pre-build event. The utilty works fine when run as standalone, but does nothing when used in the build event. Is there a standard way of noticing and dealing with error conditions in build events, or is that the domain of more advanced build control?

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  • Math for core animation?

    - by jasonbogd
    What is a good level of math required for, like, advanced core animation? Take this for example: http://cocoadex.com/2008/01/lemur-math.html And what's a good book/resource to learn it? -Jason

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  • How to convert long timestamp to UTC timestamp on Objective C

    - by David
    Hey I had a iphone app, the code has a method to retrieve current time stamp from iphone and upload to server. Here is my code: long long timestampMillis = (long long)([[NSDate date] timeIntervalSince1970] * 1000); However, one of customer use the app in Japan sent data shown on server is tomorrow time. How can I retrieve UTC timestamp? Thanks advanced

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  • Javascript Certification

    - by Livingston Samuel
    Is there any proper Certification for Javascript, that covers all the advanced topics of Javascript including the DOM (Document Object Model), BOM (Browser Object Model) and CSS Object Model, that can really evaluate the skills? I've no idea how to scale myself on my JS skills, so any suggestions would be beneficial.

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  • What groupware/collaboration system to choose?

    - by Ivan
    I am looking for a good (stable enough, intuitive enough, and the more technologically modern and advanced - the better) free PHP-based online groupware/collaboration system. 100% UTF-8 is a requirement. OOP-style code is an advantage. And collaborative mindmapping would be a cool feature to have. The team is of ~20 people. Any suggestions?

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  • Software tools to automatically decrypt a file, whose encryption algorithm (and/or encryption keys)

    - by Andrew
    I have an idea for encryption that I could program fairly easily to encrypt some local text file. Given that my approach is novel, and does not use any of the industry standard encryption techniques, would I be able to test the strength of my encryption using 'cracker' apps or suchlike? Or do all those tools rely on advanced knowledge of the encryption process (or intercepted 'keys'), meaning I'd have to build my own cracker for testing?

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  • How to wordWrap the text in a column using ObjectListView

    - by Tiago
    For example I have a big sentence: "I like to eat pie and have fun around the house all day long!" And I want it to appear like this: "I like to eat pie and have fun around the house all day long!" In this post: http://stackoverflow.com/questions/1673963/multi-line-list-items-on-winforms-listview-control Grammarian said that you only need to have WordWrap on but I cannot find that option. Thanks for the help in advanced

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  • Understanding Rails core source code?

    - by jasonbogd
    Hi, I would like to start making code patches to Rails. Are there any good books on 'advanced' Ruby that I should read to understand the rails source code? Are there any other tips on getting started? Rails seems like a large beast and I don't know where to start! Thanks, Jason.

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  • How should I map multidimensional to jagged arrays?

    - by mafutrct
    I'd like to map Foo[,] to Foo[][] and back. There are simple solutions using loops, but isn't there something more elegant? In my specific case, this is required in this scenario: [DataContract] class A { // can't serialize this thingy private readonly Foo[,] _Foo; [DataMember] private Foo[][] SerializableFoo { get { // map here } set { // map here } } } I'm aware there are advanced solutions using IDataContractSurrogate but this seems to be overkill in my case.

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  • Using ExtJS in ASP.NET

    - by Mike
    I don’t have advanced knowledge in JavaScript, and I am trying to learn how to use ExtJS framework in ASP.NET (C# or VB.NET) environment. I’ve got couple of samples, but was unable get the project working. Can anyone point in the right direction such as website or book so I can go a read up about the ExtJS in more details and how I can include this into my website?

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