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• Ruby: would using Fibers increase my DB insert throughput?

  - by Zombies

  Currently I am using Ruby 1.9.1 and the 'ruby-mysql' gem, which unlike the 'mysql' gem is written in ruby only. This is pretty slow actually, as it seems to insert at a rate of almost 1 per second (SLOOOOOWWWWWW). And I have a lot of inserts to make too, its pretty much what this script does ultamitely. I am using just 1 connection (since I am using just one thread). I am hoping to speed things up by creating a fiber that will create a new DB connection insert 1-3 records close the DB connection I would imagine launching 20-50 of these would greatly increase DB throughput. Am I correct to go along this route? I feel that this is the best option, as opposed to refactoring all of my DB code :(

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• Do I need to invoke MessageBox calls?

  - by mafutrct

  To pop-up a message box, I'm using MessageBox.Show(...). I usually wrap this call in an Invoke: BeginInvoke (new Action (() => { MessageBox.Show ()); })); I've got 2 questions: Do I always need to wrap the MessageBox call in an Invoke if I'm calling from a non-GUI thread? If so, should I use BeginInvoke or Invoke? I found not much difference in my tests, BeginInvoke is, as expected (and unlike Invoke), displayed with a slight delay.

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• android java.lang.OutOfMemoryError

  - by xiangdream

  hi, all, when i download large data from website, i got this error information: I/global (20094): Default buffer size used in BufferedInputStream constructor. It would be better to be explicit if an 8k buffer is required. D/dalvikvm(20094): GC freed 6153 objects / 3650840 bytes in 335ms I/dalvikvm-heap(20094): Forcing collection of SoftReferences for 3599051-byte al location D/dalvikvm(20094): GC freed 320 objects / 11400 bytes in 144ms E/dalvikvm-heap(20094): Out of memory on a 3599051-byte allocation. I/dalvikvm(20094): "Thread-9" prio=5 tid=17 RUNNABLE I/dalvikvm(20094): | group="main" sCount=0 dsCount=0 s=0 obj=0x439b9480 I/dalvikvm(20094): | sysTid=25762 nice=0 sched=0/0 handle=4065496 anyone can help me?

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• Have threads run indefinitely in a java application

  - by TP

  I am trying to program a game in which I have a Table class and each person sitting at the table is a separate thread. The game involves the people passing tokens around and then stopping when the party chime sounds. how do i program the run() method so that once I start the person threads, they do not die and are alive until the end of the game One solution that I tried was having a while (true) {} loop in the run() method but that increases my CPU utilization to around 60-70 percent. Is there a better method?

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• Best way to move an image across part of the screen?

  - by rushonerok

  I have a Silverlight WP7 app and an image on my page that I want to appear to slide across the screen. What is the best way of doing this? I wrote this real quick but the UI doesn't update until the entire method is done. private void SpinImg(Image img, double left) { for(int i = 1; i <= 10000; i++) { img.Margin = new Thickness(left, img.Margin.Top + 1, 0, 0); if(img.Margin.Top > 314) { //move it to the top img.Margin = new Thickness(left, -105, 0, 0); } int wait = 1000 / i; Thread.Sleep(wait); } }

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• iPhone app launch times and Core Data migration

  - by sehugg

  I have a Core Data application which I plan to update with a new schema. The lightweight migration seems to work, but it takes time proportional to the amount of data in the database. This occurs in the didFinishLaunchingWithOptions phase of the app. I want to avoid <app> failed to launch in time problems, so I assume I cannot keep the migration in the didFinishLaunchingWithOptions method. I assume the best method would involve performing the migration in a background thread. I assume also that I'd need to defer loading of the main ViewController until the loading completes to avoid using the managedObjectContext until initialization completes. Does this make sense, and is there example code (maybe in Apple sample projects) of this sort of initialization?

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• casting a generic array in java

  - by liloboy

  The implementation is for a linked list in java : public AnyType[] toArr() { AnyType[] arr = (AnyType[]) new Object[size]; int i = 0; Node<AnyType> current = head.next; while (cur != head){ arr[i] = current.data;// fill the array i++; current = current.next; } return arr; } public static void main(String[] args) { System.out.println(ll.toArr().toString()); } The error that I get: Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer; Thanks.

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• set map in google maps with TimerTask

  - by Chad White

  I would like to change the Position of the map in google maps v2 But Ive done it in a TimerTask ... target, zoom, bearing and so on and it says "IllegalStateException - not on the main thread What should I do? Any help? class Task extends TimerTask { @Override public void run() { CameraPosition cameraPosition = new CameraPosition.Builder() .target(Zt) // Sets the center of the map to Mountain View .zoom(12) // Sets the zoom .bearing(180) // Sets the orientation of the camera to east .tilt(30) // Sets the tilt of the camera to 30 degrees .build(); // Creates a CameraPosition from the builder mMap.moveCamera(CameraUpdateFactory.newCameraPosition(cameraPosition)); } } Timer timer = new Timer(); timer.scheduleAtFixedRate(new Task(), 0, 20000);

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• android phone's scroll ball, D-Pad not working

  - by user270811

  hi, i have a Cliq and a MyTouch phone. i am writing a game that requires a fire button. on the cliq, it's the center of the D-Pad, and on the MyTouch, the scroll ball. i am handling the onKeyDown events via a separate thread. it all works until i press the button too many times, meaning the key down event is no longer fired off. if i press the D-Pad down or scroll the ball down, then the fire button works again. i can only guess that maybe the message queue within the OS is full, therefore the fire button temporarily malfuntions. can someone help me? thanks.

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• How to solve the "Growing If Statement" problem?

  - by Achilles

  I've been doing some reading about design patterns and wanted some perspective. Consider the following: Dim objGruntWorker as IGruntWorker if SomeCriteria then objGruntWorker = new GoFor() else if SomeOtherCriteria then objGruntWorker = new Newb() else if SomeCriteriaAndTheKitchenSink then objGruntWorker = new CubeRat() end if objGruntWorker.GetBreakfast() system.threading.thread.sleep(GetMilliSecondsFromHours(4)) objGruntWorker.GetLunch() The above code grows each time a new Criteria arises. I've seen code like this all over the place and in ignorance wrote some of it myself. How should this be solved? Does this kind of anti-pattern have a more "formal" name? Thanks for your help!

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• limit of connections with database and number of java threads in an application

  - by Jyoti

  Hi, I am working to develop a JMS application(stand alone multithreaded java application) which can receive 100 messages at a time , they need to be processed and database procedures need to be called for inserting/updating data. Procedures are very heavy as validations are also performed in them. Each procedure is taking about 30 to 50 seconds of time to execute and they are capable to run concurrently. My concern is to execute 100 procedures for all 100 messages and also send reply within time limit of 90 seconds by jms application. No application server to be used(requirement) and database is Teradata (RDBMS) I am using connection pool and thread pool in java code and testing code with 90 connections. Question is : (1) What should be the limit on number of connections with database at a time? (2) How many threads at a time are recommended? Thanks, Jyoti

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• Ref to map vs. map to refs vs. multiple refs

  - by mikera

  I'm working on a GUI application in Swing+Clojure that requires various mutable pieces of data (e.g. scroll position, user data, filename, selected tool options etc.). I can see at least three different ways of handling this set of data: Create a ref to a map of all the data: (def data (ref { :filename "filename.xml" :scroll [0 0] })) Create a map of refs to the individual data elements: (def datamap { :filename (ref "filename.xml") :scroll (ref [0 0]) })) Create a separate ref for each in the namespace: (def scroll (ref [0 0])) (def filename (ref "filename.xml")) Note: This data will be accessed concurrently, e.g. by background processing threads or the Swing event handling thread. However there probably isn't a need for consistent transactional updates of multiple elements. What would be your recommended approach and why?

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• Java - converting String in array to double

  - by cc0

  I'm stuck with this pretty silly thing; I got a textfile like this; Hello::140.0::Bye I split it into a string array using; LS = line.split("::"); Then I try to convert the array values containing the number to a double, like this; Double number = Double.parseDouble(LS[1]); But I get the following error message; Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1 Does anyone have any idea why this doesn't work?

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• Low overhead Java Web Services container?

  - by trojanfoe

  I want to provide a Java-based Web Service, but I don't require the features of a full-blown J2EE Application Server. I would like it to start as quickly as possible, though that's not a hard requirement. The Web Service will handle multiple connections and require access to an Oracle database so it will at least require a thread pool and database connection pool. I may want to put a JSP interface onto it later to provide an internal maintainence interface. I have looked at Jetty with an Apache CXF stack, but it looks like I'll have to do a fair amount configuration before even coding the web service - Will it be worth it? Will it even work? Should I forget about the complexity and simply go with JBoss/Weblogic/etc and put up with the bloat and extra start-up time?

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• How to run a jar file in hadoop

  - by Arihant

  I have created a jar file using the java file from this blog using following statements javac -classpath /usr/local/hadoop/hadoop-core-1.0.3.jar -d /home/hduser/dir Dictionary.java /usr/lib/jvm/jdk1.7.0_07/bin/jar cf Dictionary.jar /home/hduser/dir Now i have tried running this jar in hadoop by hit and trial of various commands 1hduser@ubuntu:~$ /usr/local/hadoop/bin/hadoop jar Dictionary.jar Output: Warning: $HADOOP_HOME is deprecated. RunJar jarFile [mainClass] args... 2.hduser@ubuntu:~$ /usr/local/hadoop/bin/hadoop jar Dictionary.jar Dictionary Output: Warning: $HADOOP_HOME is deprecated. Exception in thread "main" java.lang.ClassNotFoundException: Dictionary at java.net.URLClassLoader$1.run(URLClassLoader.java:366) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:423) at java.lang.ClassLoader.loadClass(ClassLoader.java:356) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:264) at org.apache.hadoop.util.RunJar.main(RunJar.java:149) How can i run the jar in hadoop? I have the right DFS Locations as per needed by my program.

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• Can't load AMD 64-bit .dll on a IA 32-bit platform

  - by Guihua

  I download the Gurobi package for linear programming. I import the corresponding gurobi.jar package. Then run the example program. Then it appears the following errors: Exception in thread "main" java.lang.UnsatisfiedLinkError: C:\gurobi460\win64\win64\bin\GurobiJni46.dll: Can't load AMD 64-bit .dll on a IA 32-bit platform Then I downloaded the window 64 bit Jre, and use the "window--preference--Installed JRE" to install this new JRE. However, it still appeared this error. Could you help me? Thank you !

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• ContextSwitchDeadlock Was Detected error in C#

  - by assassin

  Hi, I am running a C# application, and during run-time I get the following error: The CLR has been unable to transition from COM context 0x20e480 to COM context 0x20e5f0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Can anyone please help me out with the problem here? Thanks a lot.

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• Python: Huge file reading by using linecache Vs normal file access open()

  - by user335223

  Hi, I am in a situation where multiple threads reading the same huge file with mutliple file pointers to same file. The file will have atleast 1 million lines. Eachline's length varies from 500 characters to 1500 characters. There won't "write" operations on the file. Each thread will start reading the same file from different lines. Which is the efficient way..? Using the Python's linecache or normal readline() or is there anyother effient way?

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• Multi-Threaded Application - Help with some pseudo code!!

  - by HonorGod

  I am working on a multi-threaded application and need help with some pseudo-code. To make it simpler for implementation I will try to explain that in simple terms / test case. Here is the scenario - I have an array list of strings (say 100 strings) I have a Reader Class that reads the strings and passes them to a Writer Class that prints the strings to the console. Right now this runs in a Single Thread Model. I wanted to make this multi-threaded but with the following features - Ability to set MAX_READERS Ability to set MAX_WRITERS Ability to set BATCH_SIZE So basically the code should instantiate those many Readers and Writers and do the work in parallel. Any pseudo code will really be helpful to keep me going!

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• Why does setting a form's enabled property crash the application?

  - by Ruirize

  private void launchbutton_Click(object sender, EventArgs e) { launchbutton.Enabled = false; Process proc = new Process(); proc.EnableRaisingEvents = true; proc.StartInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden; //The arguments/filename is set here, just removed for privacy. proc.Exited += new EventHandler(procExit); proc.Start(); } private void procExit(object sender, EventArgs e) { MessageBox.Show("YAY","WOOT"); Thread.Sleep(2000); launchbutton.Enabled = true; } 2 Seconds after I quit the created process, my program crashes. Why?

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• Optimizing Dijkstra for dense graph?

  - by Jason

  Is there another way to calculate the shortest path for a near complete graph other than Dijkstra? I have about 8,000 nodes and about 18 million edges. I've gone through the thread "a to b on map" and decided to use Dijkstra. I wrote my script in Perl using the Boost::Graph library. But the result isn't what I expected. It took about 10+ minutes to calculate one shortest path using the call $graph-dijkstra_shortest_path($start_node,$end_node); I understand there are a lot of edges and it may be the reason behind the slow running time. Am I dead in the water? Is there any other way to speed this up?

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• Can Somebody Explain this java code

  - by dubbeat

  Hi, I'm just starting out on android and my java is verry rusty. I can't remember ever seeing a function nested in another function like this before. Could somebody explain to me exactly what final does and explain why you would nest a function in another like this? private final Handler handler = new Handler() { @Override public void handleMessage(final Message msg) { Log.v(Constants.LOGTAG, " " + ReviewList.CLASSTAG + " worker thread done, setup ReviewAdapter"); progressDialog.dismiss(); if ((reviews == null) || (reviews.size() == 0)) { empty.setText("No Data"); } else { reviewAdapter = new ReviewAdapter(ReviewList.this, reviews); setListAdapter(reviewAdapter); } } };

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• iPhone - making the crash information more specific

  - by Digital Robot

  I have an app that is crashing at some point. Even with NSZombieEnabled turned on, the only thing I see is this message on the console: : * -[CFRunLoopTimer release]: message sent to deallocated instance 0x4cb34e0 but as the app is crashed, there's no way to know what object is this and the thread overview is not helping that much. #0 0x34a80466 in objc_msgSend #1 0x357e53c8 in CFRelease #2 0x357f3976 in __CFTypeCollectionRelease #3 0x3580c0b6 in __CFSetReleaseValue #4 0x357e6a5c in __CFBasicHashDrain #5 0x357e6900 in __CFSetDeallocate #6 0x357e54b6 in _CFRelease #7 0x357e53dc in CFRelease #8 0x3580c098 in -[__NSCFSet release] #9 0x3570f3be in -[_NSFaultingMutableSet dealloc] #10 0x3570f260 in -[_NSFaultingMutableSet release] #11 0x35702480 in -[NSManagedObject(_NSInternalMethods) _clearRawPropertiesWithHint:] #12 0x357022a8 in -[NSFaultHandler turnObject:intoFaultWithContext:] #13 0x35703dc0 in -[NSManagedObject dealloc] #14 0x356eab34 in -[_PFManagedObjectReferenceQueue _processReferenceQueue:] #15 0x357127d6 in _performRunLoopAction #16 0x3580ac58 in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ #17 0x3580aacc in __CFRunLoopDoObservers #18 0x358020ca in __CFRunLoopRun #19 0x35801c86 in CFRunLoopRunSpecific #20 0x35801b8e in CFRunLoopRunInMode #21 0x320c84aa in GSEventRunModal #22 0x320c8556 in GSEventRun #23 0x341dc328 in -[UIApplication _run] #24 0x341d9e92 in UIApplicationMain #25 0x00002e02 in main at main.m:14 it appears to be something related to core data, but knowing that doesn't help that much, because the app is all core data based and it crashes when I am not doing anything related to core data. is there a way to make the debugger more specific? thanks

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• How to properly reserve identity values for usage in a database?

  - by esac

  We have some code in which we need to maintain our own identity (PK) column in SQL. We have a table in which we bulk insert data, but we add data to related tables before the bulk insert is done, thus we can not use an IDENTITY column and find out the value up front. The current code is selecting the MAX value of the field and incrementing it by 1. Although there is a highly unlikely chance that two instances of our application will be running at the same time, it is still not thread-safe (not to mention that it goes to the database everytime). I am using the ADO.net entity model. How would I go about 'reserving' a range of id's to use, and when that range runs out, grab a new block to use, and guarantee that the same range will not be used.

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• Handling Messages in Console Apps/DLLs in C++ Win32

  - by vsimon

  I would like to have the ability to process Win32 messages in a console app and/or inside a standalone DLL. I have been able to do it in .NET with the following article and it works great in C# inside a console app and standalone DLL http://msdn.microsoft.com/en-us/magazine/cc163417.aspx Is there a way to do the equivalent with C/C++ Win32 APIs? I have tried doing RegisterClassEx(...) and CreateWindow(...) even passing in HWND_MESSAGE to hWndParent but the trouble is that after the "invisible" window is created messages are not being processed probably due to the lack of a message pump. Where would the message pump go if you had a DLL entry point? I have tried creating another thread in a DLL and put while(GetMesage(..)) there but that did not work either. Any ideas?

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