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  • May the FileInputStream.available foolish me?

    - by Tom Brito
    This FileInputStream.available() javadoc says: Returns an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes. In some cases, a non-blocking read (or skip) may appear to be blocked when it is merely slow, for example when reading large files over slow networks. I'm not sure if in this check: if (new FileInputStream(xmlFile).available() == 0) can I rely that empty files will always return zero?

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  • custom MSSQL driver

    - by hoodoos
    I had a crazy thought about writing my own MSSQL driver to make it work something like non-blocking http client, so it won't be thread thirsty and could handle lots of db queries within one thread. I tried to look over google for some guidelines about implementing MSSQL client protocol, but found none really, where do those guys get information about it when they write own implementations for PHP or python? I need a really low level to be documented so I can implement all phases of working with a connection through sockets. And would be really nice to have a an example in c# langauge. :)

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  • How can I pause a BackgroundWorker? Or something similar...

    - by juan
    I was using a BackgroundWorker to download some web sites by calling WebClient.DownloadString inside a loop. I wanted the option for the user to cancel in the middle of downloading stuff, so I called CancelAsync whenever I found that CancellationPending was on in the middle of the loop. But now I noticed that the function DownloadString kinda freezes sometimes, so I decided to use DownloadStringAsync instead (all this inside the other thread created with BackgroundWorker). An since and don't want to rewrite my whole code by having to exit the loop and the function after calling DownloadStringAsync, I made a while loop right after calling it that does nothing but checks for a variable bool Stop that I turn true either when the DownloadStringCompleted event handler is called or when the user request to cancel the operation. Now, the weird thing is that it works fine on the debug version, but on the release one, the program freezes in the while loop like if it were the main thread.

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  • Console appliction with Multithreading on Single core.

    - by Harsha
    Hello all, I am reposting my question on Multithreading on Single core processor. Original question is: http://stackoverflow.com/questions/2856239/will-multi-threading-increase-the-speed-of-the-calculation-on-single-processor I have been asked a question, At any given time, only one thread is allowed to run on a single core. If so, why people use multithreading in a application. Lets say you are running console application and It is very much possible to write the application to run on the main thread. But still people go for multithreading.

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  • custom php library with pear local installation

    - by andreas
    Hello i wish to be able to deploy a PHP web application along with a local installation of PEAR. To be more specific, i am trying to find a way to do a 'per-application' or local installation of PEAR if this is possible. For example: The application 'MyApplication' is located in: /var/www/applications/myapplication The php library is located in: /var/www/applications/myapplication/library I am looking for a way to do a per-application installation of PEAR since not all applications are managed by me (and i want to control which PEAR packages are installed and when). I found some tutorials for a local PEAR installation (on a shared host) but i don't know if my scenario fits the one for a local PEAR installation. Any thoughts/help appreciated.

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  • Analysis services with non normalized table

    - by Uwe
    I have a table with several million rows. Each row represents a user session. There is a column called user which is not unique. There can be multiple sessions per user. I want to use Analysis services to get me the additional properties per user. Example: How many users (unique!) had a session longer than x minutes. How is that possible without changing the database. Note: there is no lookup-table and I cannot create one. What I am able of at the moment is to ask how many sessions were longer then x minutes.

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  • Why Tokyo Tyrant so slow

    - by Tantra
    I have follow situation tyrant server lunched on freebsd host, like this: ttserver -uas -log /data/tyrant/1.log -sid 1 -thnum 8 -tout 5 /data/tyrant/data/1.tct And i try to communicate this server on windows from python and pyrant-0.3.5: like this: import pyrant; import time; t = pyrant.Tyrant(host="192.168.0.220", port=1978); tbegin = time.time(); for i in xrange(4000000): if i and ((i % 10000) == 0): print time.time() - tbegin; tbegin = time.time(); t[i] = {"text": "ruslan text", "value": i}; and have i think very slow performance about 5-6 per 10,000 records. But if i start this code on the same machine like server(ttserver). Performance are good - about 0.5 sec per 10,000 records What i must do to workaround this problem?

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  • How do I get Java to use my multi-core processor?

    - by Rudiger
    I'm using a GZIPInputStream in my program, and I know that the performance would be helped if I could get Java running my program in parallel. In general, is there a command-line option for the standard VM to run on many cores? It's running on just one as it is. Thanks! Edit I'm running plain ol' Java SE 6 update 17 on Windows XP. Would putting the GZIPInputStream on a separate thread explicitly help? No! Do not put the GZIPInputStream on a separate thread! Do NOT multithread I/O! Edit 2 I suppose I/O is the bottleneck, as I'm reading and writing to the same disk... In general, though, is there a way to make GZIPInputStream faster? Or a replacement for GZIPInputStream that runs parallel? Edit 3 Code snippet I used: GZIPInputStream gzip = new GZIPInputStream(new FileInputStream(INPUT_FILENAME)); DataInputStream in = new DataInputStream(new BufferedInputStream(gzip));

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  • Form gets disposed somehow

    - by mnn
    I have a client-server application, in which I use classic Sockets and threads for receiving/sending data and listening for clients. The application works fine, but after some random time I get the ObjectDisposedException: System.ObjectDisposedException: Cannot access a disposed object. Object name: 'MainForm'. at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous) at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args) at System.Windows.Forms.Control.Invoke(Delegate method) That code is called from client Socket thread and I use Invoke() method to run the code on UI thread. I'm sure that I don't manually dispose the form nor using Close() (form is closed by user clicking Close button), so I don't know what could cause its disposing.

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  • Interrupt an Http Request blocked in read() on Android

    - by twk
    Using the Apache Http stack on Android, I'm trying to force a thread out of a call to read. This is what the stack looks like: OSNetworkSystem.receiveStreamImpl(FileDescriptor, byte[], int, int, int) line: not available [native method] OSNetworkSystem.receiveStream(FileDescriptor, byte[], int, int, int) line: 478 PlainSocketImpl.read(byte[], int, int) line: 565 SocketInputStream.read(byte[], int, int) line: 87 SocketInputBuffer(AbstractSessionInputBuffer).fillBuffer() line: 103 SocketInputBuffer(AbstractSessionInputBuffer).read(byte[], int, int) line: 134 IdentityInputStream.read(byte[], int, int) line: 86 EofSensorInputStream.read(byte[], int, int) line: 159 Fetcher.readStream() line: 89 I've tried InputStream.close(), Thread.Interrupt(), and HttpUriRequest.abort(), without any success. Any ideas? I'm also open to some kind of non-blocking IO, but I don't see any way to do that with the HttpUriRequest object. Thanks!

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  • Crash in Reachability API

    - by Marc
    I'm using the Reachability sample code provided by Apple to check the network connectivity and get notified of changes (Reachability Sample code). I had a look at some crash locks of my app. It seems that some crashes are due to the Reachability/SystemConfiguration Reachablity API stuff (see below). SCNetworkReachabilityGetFlags is only used in the Reachability class provided by Apple. Or am I misinterpreting the crash log? Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x00000000, 0x00000000 Crashed Thread: 0 Thread 0 Crashed: 0 libSystem.B.dylib 0x00000e70 mach_msg_trap + 20 1 libSystem.B.dylib 0x00003354 mach_msg + 60 2 SystemConfiguration 0x0001f480 configopen + 168 3 SystemConfiguration 0x00004d08 SCDynamicStoreCreateWithOptions + 272 4 SystemConfiguration 0x00004e54 SCDynamicStoreCreate + 24 5 SystemConfiguration 0x00015244 updateReachabilityStoreInfo + 152 6 SystemConfiguration 0x00016f04 updateCommCenterStatus + 32 7 SystemConfiguration 0x00017678 checkAddress + 1368 8 SystemConfiguration 0x0001a260 __SCNetworkReachabilityGetFlags + 1992 9 SystemConfiguration 0x0001b00c rlsPerform + 132 10 CoreFoundation 0x00058266 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 8 11 CoreFoundation 0x00028692 __CFRunLoopDoSources0 + 214 12 CoreFoundation 0x00027f62 __CFRunLoopRun + 258 13 CoreFoundation 0x00027d74 CFRunLoopRunSpecific + 220 14 CoreFoundation 0x00027c82 CFRunLoopRunInMode + 54 15 GraphicsServices 0x00004e84 GSEventRunModal + 188 16 UIKit 0x00004f8c -[UIApplication _run] + 564 17 UIKit 0x000024cc UIApplicationMain + 964 18 MyApp 0x0000f80c main (main.m:21) 19 MyApp 0x0000f77c start + 44

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  • python multithread "maximum recursion depth exceed"

    - by user293487
    I use Python multithread to realize Quicksort. Quicksort is implement in a function. It is a recursive function. Each thread calls Quicksort to sort the array it has. Each thread has its own array that stores the numbers needs to be sorted. If the array size is smaller (<10,000). It runs ok. However, if the array size is larger, it shows the "maximum recursion depth exceed". So, I use setrecursionlimit () function to reset the recursion depth to 1500. But the program crash directly...

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  • UdpClient receiving and sending at the same time

    - by SoMoS
    Hello, I am maintaining other's code and its using the class UdpClient. The code declares one instance of UdpClient and receives data continuosly using the UdpClient.Receive(). When data is received it is processed in another thread and the UdpClient calls Receive() again. At the same time when the data is processed the same client is sending a response back. Question: Is this a bug? I think so because UdpClient is not thread safe so you can not call two methods at the same time. Anyways code is working fine but ...

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  • ASP.NET - Display Message While Page Is Loading

    - by Chris
    I have a page that performs a long-running task (10 to 15 seconds) in the page_load method. I have client-side javascript code that will display a decent "page loading" animated gif to the user. I am able to invoke the JavaScript method from the code-behind, to display the "page loading" animated gif, however, the long-running task is hanging up the UI such that the animated gif doesn't actually display until after the long-running task is complete, which is the exact opposite of what I want. To test this out, in my page_load method I make a call to the JavaScript method to display the animated gif. Then, I use Thread.Sleep(10000). What happens is that the animated gif doesn't display until after Thread.Sleep is complete. Obviously I am doing something incorrect. Any advice would be appreciated. Thanks. Chris

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  • Java Future and infinite computation

    - by Chris
    I'm trying to optimize an (infinite) computation algorithm. I have an infinte Sum to calculate ( Summ_{n- infinity} (....) ) My idea was to create several threads using the Future < construct, then combine the intermediate results together. My problem hoewer is that I need a certain precision. So I need to constantly calculate the current result while other threads keep calculating. My question is: Is there some sort of result queue where each finished thread can put its results in, while a main thread can receive those results and then either lets the computation continues or terminate the whole ExecutorService? Any Help would really be appreciated! Thanks!

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  • how to implement a "soft barrier" in multithreaded c++

    - by Jason
    I have some multithreaded c++ code with the following structure: do_thread_specific_work(); update_shared_variables(); //checkpoint A do_thread_specific_work_not_modifying_shared_variables(); //checkpoint B do_thread_specific_work_requiring_all_threads_have_updated_shared_variables(); What follows checkpoint B is work that could have started if all threads have reached only checkpoint A, hence my notion of a "soft barrier". Typically multithreading libraries only provide "hard barriers" in which all threads must reach some point before any can continue. Obviously a hard barrier could be used at checkpoint B. Using a soft barrier can lead to better execution time, especially since the work between checkpoints A and B may not be load-balanced between the threads (i.e. 1 slow thread who has reached checkpoint A but not B could be causing all the others to wait at the barrier just before checkpoint B). I've tried using atomics to synchronize things and I know with 100% certainty that is it NOT guaranteed to work. For example using openmp syntax, before the parallel section start with: shared_thread_counter = num_threads; //known at compile time #pragma omp flush Then at checkpoint A: #pragma omp atomic shared_thread_counter--; Then at checkpoint B (using polling): #pragma omp flush while (shared_thread_counter > 0) { usleep(1); //can be removed, but better to limit memory bandwidth #pragma omp flush } I've designed some experiments in which I use an atomic to indicate that some operation before it is finished. The experiment would work with 2 threads most of the time but consistently fail when I have lots of threads (like 20 or 30). I suspect this is because of the caching structure of modern CPUs. Even if one thread updates some other value before doing the atomic decrement, it is not guaranteed to be read by another thread in that order. Consider the case when the other value is a cache miss and the atomic decrement is a cache hit. So back to my question, how to CORRECTLY implement this "soft barrier"? Is there any built-in feature that guarantees such functionality? I'd prefer openmp but I'm familiar with most of the other common multithreading libraries. As a workaround right now, I'm using a hard barrier at checkpoint B and I've restructured my code to make the work between checkpoint A and B automatically load-balancing between the threads (which has been rather difficult at times). Thanks for any advice/insight :)

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  • How to remove animation glitch ?

    - by hib
    Hi all , I am downloading and then parsing some data on separate thread and then updating my ui on main thread with the following code but in this scenario I am getting animation "glitch" . I have read this word somewhere . - (void)didFinishParsing2:(NSArray *)appList { [self performSelectorOnMainThread:@selector(handleLoadedApps2:) withObject:appList waitUntilDone:NO]; self.queue = nil; // we are finished with the queue and our ParseOperation } - (void)handleLoadedApps2:(NSArray *)loadedApps{ [activityLabel removeFromSuperview]; self.controller.MyArray = (MyClass *)[arrMyArray objectAtIndex:0]; [[MySharedClass sharedSource].detailSource setObject:self.controller.MyArray forKey:someObject]; self.controller.hidesBottomBarWhenPushed = YES; isPushed = YES; [[self navigationController] pushViewController:self.controller animated:YES]; } Can anyone tell me what I am doing wrong so that I can remove the animation glitch .

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  • SELECT TOP N With Two Variables

    - by Ricardo Deano
    Hello all. It's Tuesday morning and I am being thick as (I'm blaming my daughter waking up early this morning!) I have the following example in a SQL table Cust Group Sales A 1 15 A 1 10 A 1 5 A 2 15 A 2 10 A 2 5 B 1 15 B 1 10 B 1 5 B 2 15 B 2 10 B 2 5 What I would like to show is the top 2 products per customer, per group sorted descending by Sales i.e. Cust Group Sales A 1 15 A 1 10 A 2 15 A 2 10 B 1 15 B 1 10 B 2 15 B 2 10 I'm assuming I need to declare two variables, Cust and Group, I'm just not sure how to complete this in one fell swoop. Apologies for the thick question...no excuse. Thanks for any help.

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  • Call to C++ COM interface from C# being blocked

    - by dauphic
    I have a C++ DLL that exposes a COM interface. A C# application uses the COM interface. I've recently run into a problem where some calls to the COM interface are taking 500-5000 ms to return, though they should return almost instantly (no longer than 10 ms). Profiling the application shows that all of the delay is being caused by the 'thread being blocked;' no other information is available. There are no locks, etc. in my code, so the blocking has to be occurring internally in the COM/interop code. Only one thread interfaces with the COM DLL. Any ideas what could be causing this, and how I would fix it? EDIT: Further investigation shows that the block is occuring when the C++ returns to the C#.

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  • Cancel UDP recvfrom in C on Unix

    - by hora
    I'm just starting to learn how network programming in C works, and I've written a small program that sends messages to and from a UNIX terminal. I'm using pthreads in my program, one of which essentially just waits on recvfrom() to receive a message. However, I want to be able to close all threads properly if the users chooses to quit the program. The way I have it set up right now, a different thread just cancels the thread waiting on recvfrom, but I'm worried this might not be a good idea since I'm leaving sockets unclosed and I'm not freeing all the memory I allocated. Is there a way to cancel a recvfrom() call, or some way to run a certain routine upon cancelling a pthread? Thanks.

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  • SQL bottleneck, how to fix

    - by masfenix
    This is related to my previous thread: http://stackoverflow.com/questions/3069806/sql-query-takes-about-10-20-minutes However, I kinda figured out the problem. The problem (as described in the previous thread) is not the insert (while its still slow), the problem is looping through the data itself Consider the following code: Dim rs As DAO.Recordset Dim sngStart As Single, sngEnd As Single Dim sngElapsed As Single Set rs = CurrentDb().QueryDefs("select-all").OpenRecordset MsgBox "All records retreived" sngStart = Timer Do While Not rs.EOF rs.MoveNext Loop sngEnd = Timer sngElapsed = Format(sngEnd - sngStart, "Fixed") ' Elapsed time. MsgBox ("The query took " & sngElapsed _ & " seconds to run.") As you can see, this loop does NOTHING. You'd expect it to finish in seconds, however it takes about 857 seconds to run (or 15 minutes). I dont know why it is so slow. Maybe the lotusnotes sql driver? any other ideas? (java based solution, any other solution) What my goal is: To get all the data from remote server and insert into local access table

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  • Android: simple webview code. ERR: Unable to start Activity

    - by vnshetty
    I have following code: public class reader extends Activity { WebView mWebView; String mFilename; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mWebView = (WebView) findViewById(R.id.webView1); setContentView(R.layout.webview); mWebView.loadUrl("http://www.google.com"); } } When I run this, the emulator shows "Sorry:.. mireader Stopped unexpectedly" error.. Why ? DDMS log dump: 03-02 12:25:26.430: INFO/AndroidRuntime(2837): NOTE: attach of thread 'Binder Thread #3' failed 03-02 12:25:26.729: INFO/ActivityManager(72): Start proc com.mireader for activity com.mireader/.reader: pid=2846 uid=10032 gids={3003, 1015} 03-02 12:25:29.621: DEBUG/AndroidRuntime(2846): Shutting down VM 03-02 12:25:29.621: WARN/dalvikvm(2846): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): FATAL EXCEPTION: main 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mireader/com.mireader.reader}: java.lang.NullPointerException 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.os.Handler.dispatchMessage(Handler.java:99) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.os.Looper.loop(Looper.java:123) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.app.ActivityThread.main(ActivityThread.java:4627) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at java.lang.reflect.Method.invokeNative(Native Method) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at java.lang.reflect.Method.invoke(Method.java:521) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at dalvik.system.NativeStart.main(Native Method) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): Caused by: java.lang.NullPointerException 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at com.mireader.reader.onCreate(reader.java:36) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 03-02 12:25:29.660: ERROR/AndroidRuntime(2846): ... 11 more 03-02 12:25:29.699: WARN/ActivityManager(72): Force finishing activity com.mireader/.reader 03-02 12:25:30.550: WARN/ActivityManager(72): Activity pause timeout for HistoryRecord{44f98868 com.mireader/.reader} 03-02 12:25:33.230: DEBUG/dalvikvm(200): GC_EXPLICIT freed 164 objects / 11312 bytes in 7516ms 03-02 12:25:35.020: INFO/Process(2846): Sending signal. PID: 2846 SIG: 9 03-02 12:25:35.080: WARN/InputManagerService(72): Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@44fc35e0 03-02 12:25:35.809: INFO/ActivityManager(72): Process com.mireader (pid 2846) has died. 03-02 12:25:37.960: DEBUG/dalvikvm(320): GC_EXPLICIT freed 83 objects / 4000 bytes in 78ms 03-02 12:25:42.674: WARN/ActivityManager(72): Activity destroy timeout for HistoryRecord{44f98868 com.mireader/.reader}

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  • Installing PHP APC in Fedora - Unable to initialize module ?

    - by sri
    I have been trying to install APC on my Fedora Apache Server for showing progress bar while uploading files. But I am getting the following PHP Warning while starting XAMPP. Starting XAMPP for Linux 1.7.1... PHP Warning: PHP Startup: apc: Unable to initialize module Module compiled with module API=20090626, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to matchin Unknown on line 0 XAMPP: Starting Apache with SSL (and PHP5)... XAMPP: Starting MySQL... XAMPP: Another FTP daemon is already running. XAMPP for Linux started. My Server Details : OS : Fedora-12 XAMPP version : 1.7.1 PHP Version : 5.2.9 APC Version : 3.1.9 I have tried the process as is mentioned in here : 1)http://2bits.com/articles/installing-php-apc-gnulinux-centos-5.html 2)http://stevejenkins.com/blog/2011/08/how-to-install-apc-alternative-php-cache-on-centos-5-6/

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