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• Would watching a file for changes or redundantly querying that file be more efficient?

  - by badpanda

  I am wondering whether watching a file/directory for changes using the FileSystemWatcher class is extremely memory intensive. I am developing a desktop application in C# that will be running behind the scenes continuously on low-performance computers, and I need some way of checking to see if various files have changed. I can think of a few solutions: Watch the directories using FileSystemWatcher. Run a timed thread on an interval that goes through and manually checks this. Check manually every time the actionhandler thread runs (the program will occasionally do something, on an action). Any suggestions? Thanks! badPanda

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• python file type error

  - by lakshmipathi

  While testing answer from another thread from this site, Im getting open("temp","w").write(''.join(data)) TypeError How to fix this?

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• Wiping a laptop from Bios

  - by joshuahornby10

  I am trying to wipe an old laptops hard drive, it doesn't have a CD drive so have been using a USB to try and wipe the hard drive from the BIOS. I have been using http://www.dban.org/ which I installed as an ISO on the USB Stick. When ever I try to boot into this I get an error saying 'No operating system' Does anyone know of a way to wipe a hard drive? I also tried to boot into safe mode but I just stay on a constant loop. Thanks

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• Issue with RegConnectRegistry connecting to 64 bit machines

  - by RA

  I'm seeing a weird thing when connecting to the performance registry on 64 bit editions of Windows. The whole program stalls and callstacks becomes unreadable. After a long timeout, the connection attempts aborts and everything goes back to normal. The only solution is to make sure that only one thread at the time queries the remote registry, unless the remote machine is a 32 bit Windows XP, 2003, 2000 , then you can use as many threads as you like. Have anyone a technical explanation why this might be happening ? I've spent 2-3 days searching the web without coming up with anything. Here is a test program, run it first with one thread (connecting to a 64 bit Windows), then remove the comment in tmain and run it with 4 threads. Running it with one thread works as expected, running with 4, returns ERROR_BUSY (dwRet == 170) after stalling for a while. Remember to set a remote machine correctly in RegConnectRegistry before running the program. #define TOTALBYTES 8192 #define BYTEINCREMENT 4096 void PerfmonThread(void *pData) { DWORD BufferSize = TOTALBYTES; DWORD cbData; DWORD dwRet; PPERF_DATA_BLOCK PerfData = (PPERF_DATA_BLOCK) malloc( BufferSize ); cbData = BufferSize; printf("\nRetrieving the data..."); HKEY hKey; DWORD dwAccessRet = RegConnectRegistry(L"REMOTE_MACHINE",HKEY_PERFORMANCE_DATA,&hKey); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData, &cbData ); while( dwRet == ERROR_MORE_DATA ) { // Get a buffer that is big enough. BufferSize += BYTEINCREMENT; PerfData = (PPERF_DATA_BLOCK) realloc( PerfData, BufferSize ); cbData = BufferSize; printf("."); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData,&cbData ); } if( dwRet == ERROR_SUCCESS ) printf("\n\nFinal buffer size is %d\n", BufferSize); else printf("\nRegQueryValueEx failed (%d)\n", dwRet); RegCloseKey(hKey); } int _tmain(int argc, _TCHAR* argv[]) { _beginthread(PerfmonThread,0,NULL); /* _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); */ while(1) { Sleep(2000); } }

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• How should I convert a physical drive to a VHD for use with VirtualPC?

  - by RBerteig

  I have the hard disks from a PC that was happily running Windows Me until is it suffered an unknown hardware failure. The drives are intact, and can be mounted and read on other PCs. We have data backups, but there is licensed software installed that may not be possible to migrate to newer versions running on a more modern platform making the idea of just booting a virtual image attractive. Is it possible to make VHDs from the drives such that I can boot them in VirtualPC? If not VirtualPC, would it be possible in any other virtualization tool? Edit: Some more details.... The system was running Windows Me, but upgraded from Windows 95 (or possibly 98). It can't have been more than a Pentium II, but I will have to look at the motherboard to confirm that. There were no "exotic" devices installed, and nothing beyond the usual legacy stuff that would need to survive into a virtual machine. The licensed software did not have a dongle, so I won't need to worry about virtualizing a physical dongle of some kind. Licenses were probably died to the disk serial number. There were two HDs, both IDE. The boot disk is about 6GB, and the spare data disk is 12GB, but nearly empty. I have a small bias in favor of VirtualPC just because its free and I've used it successfully in the past. But this is a good excuse to revisit the state of the art. I do know from direct experience that it is possible to install and boot DOS 5.0 and Win95 in VirtualPC, but the VM extensions weren't available so the experience isn't as seamless as I would have liked. A very old DirectX game that failed miserably under XP SP2 runs really nicely on that VM, and actually plays better in a lot of ways than it did on period hardware, so that gives me hope that this is possible. Edit 2: Well, I'm closer than I was when I asked... so thanks to all for helpful suggestions and hints to what I should be trying. I used WinImage to copy the disks, and VirtualPC 2007 to attempt to boot. So far, I have it booting in safe mode, but hanging with a black screen otherwise. I strongly suspect that the copy of Artisoft Lantastic 8.0 (anyone else remember them?) that is still installed for networking with even older PCs that mostly don't exist any more is the culprit there. In my infinite free time, I will try to resolve the differences between a Safe Mode boot and a normal boot, and feel that it is likely to yield to pressure. I'd accept more than one answer if I could... this isn't as black and white a question as the one accepted answer convention assumes.

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• launching java test bycommand line

  - by lamisse

  I created runner.bat to launch one java test it contains : path to java,classpath org.junit.runner.JUnitCore package.class when I launch it : FAILURES Tests run: 1, Failures: 1 Exception in thread "Thread-0" java.lang.IllegalStateException: Shutdown in progress at java.lang.ApplicationShutdownHooks.add(Unknown Source) at java.lang.Runtime.addShutdownHook(Unknown Source) at com.sun.imageio.stream.StreamCloser$2.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at com.sun.imageio.stream.StreamCloser.addToQueue(Unknown Source) at javax.imageio.stream.FileCacheImageInputStream.<init>(Unknown Source) at com.sun.imageio.spi.InputStreamImageInputStreamSpi.createInputStreamInstance(Unknown Source) at javax.imageio.ImageIO.createImageInputStream(Unknown Source) at javax.imageio.ImageIO.read(Unknown Source) at com.polyspace.util.guicomponent.CompositePanel.setBufferedImage(Unknown Source) at com.polyspace.util.guicomponent.CompositePanel.<init>(Unknown Source)

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• synchronized block in JSP tag class

  - by Sudhakar

  Hi, I am trying to find answer for the following ,for the past couple of days ,but couldnt find comprehensive answer Problem Statement I have a custom JSP tag class which handles a web form submission ,captures data and write it to same file in the filesystem. As all web applications,this can be triggeredsimultaneosly ,and i fear that multiple threads would be in action handling each of the submission (we all know thats how Servlet works.) CODE synchronized (this){ final String reportFileName = "testReport.csv"; File reportDir = new File( rootCsDirectory, "reports" ); if(!reportDir.isDirectory())reportDir.mkdir(); File reportFile = new File (reportDir, reportFileName); logReport(reportFile,reportContent.toString()); } ISSUE: - A File object can be opened by one thread for writing and at same time another thread might try to access and fail and throw an exception So i thought of synchronizing (on the object ) should solve the issue , but read some where that jsp engine would have pool of jsp tag objects, so i am afraid that synchronized (this) wont work and it should be changed to synchronized (this.getClass())

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• disable using of desktop.ini file

  - by osgx

  Hello How can i disable explorer in winXP from using desktop.ini /folder.ini files? some viruses are on the flash card, and they can be in that files. I want make explorer safe from opening such flashes. Autorun is disabled. Yes, there are another file managers, but it is comp of my girlfriend.

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• Using device variable by multiple threads on CUDA

  - by ashagi

  I am playing around with cuda. At the moment I have a problem. I am testing a large array for particular responses, and when I get the response, I have to copy the data onto another array. For example, my test array of 5 elements looks like this: [ ][ ][v1][ ][ ][v2] Result must look like this: [v1][v2] The problem is how do I calculate the address of the second array to store the result? All elements of the first array are checked in parallel. I am thinking to declare a device variable int addr = 0. Every time I find a response, I will increment the addr. But I am not sure about that because it means that addr may be accessed by multiple threads at the same time. Will that cause problems? Or will the thread wait until another thread finishes using that variable?

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• log4j performance

  - by Bob

  Hi, I'm developing a web app, and I'd like to log some information to help me improve and observe the app. (I'm using Tomcat6) First I thought I would use StringBuilders, append the logs to them and a task would persist them into the database like every 2 minutes. Because I was worried about the out-of-the-box logging system's performance. Then I made some test. Especially with log4j. Here is my code: Main.java public static void main(String[] args) { Thread[] threads = new Thread[LoggerThread.threadsNumber]; for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i] = new Thread(new LoggerThread("name - " + i)); } LoggerThread.startTimestamp = System.currentTimeMillis(); for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i].start(); } LoggerThread.java public class LoggerThread implements Runnable{ public static int threadsNumber = 10; public static long startTimestamp; private static int counter = 0; private String name; public LoggerThread(String name) { this.name = name; } private Logger log = Logger.getLogger(this.getClass()); @Override public void run() { for(int i=0; i<10000; ++i){ log.info(name + ": " + i); if(i == 9999){ int c = increaseCounter(); if(c == threadsNumber){ System.out.println("Elapsed time: " + (System.currentTimeMillis() - startTimestamp)); } } } } private synchronized int increaseCounter(){ return ++counter; } } } log4j.properties log4j.logger.main.LoggerThread=debug, f log4j.appender.f=org.apache.log4j.RollingFileAppender log4j.appender.f.layout=org.apache.log4j.PatternLayout log4j.appender.f.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.appender.f.File=c:/logs/logging.log log4j.appender.f.MaxFileSize=15000KB log4j.appender.f.MaxBackupIndex=50 I think this is a very common configuration for log4j. First I used log4j 1.2.14 then I realized there was a newer version, so I switched to 1.2.16 Here are the figures (all in millisec) LoggerThread.threadsNumber = 10 1.2.14: 4235, 4267, 4328, 4282 1.2.16: 2780, 2781, 2797, 2781 LoggerThread.threadsNumber = 100 1.2.14: 41312, 41014, 42251 1.2.16: 25606, 25729, 25922 I think this is very fast. Don't forget that: in every cycle the run method not just log into the file, it has to concatenate strings (name + ": " + i), and check an if test (i == 9999). When threadsNumber is 10, there are 100.000 loggings and if tests and concatenations. When it is 100, there are 1.000.000 loggings and if tests and concatenations. (I've read somewhere JVM uses StringBuilder's append for concatenation, not simple concatenation). Did I missed something? Am I doing something wrong? Did I forget any factor that could decrease the performance? If these figures are correct I think, I don't have to worry about log4j's performance even if I heavily log, do I?

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• What happens to an ActiveX control (COleControl) after the call to OnDestroy() ?

  - by richj

  I have an ActiveX control written in C++ that runs in Internet Explorer 8. Most of the time (approx 90%) when the tab or browser containing the control is closed, there is an access violation like this: The thread 'Win32 Thread' (0x1bf0) has exited with code 0 (0x0). Unhandled exception at 0x77b3b9fd in iexplore.exe: 0xC0000005: Access violation reading location 0x65007408. The access violation occurs after the call to OnDestroy() but before the call to the control's destructor. The debug output says: No symbols are loaded for any call stack frame. The source code cannot be displayed. None of my code is present in the stacktrace, although perhaps the heap was corrupted at some earlier point during execution. What lifecycle events does an ActiveX control receive between the call to OnDestroy() and the control's destructor?

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• How to free virtual memory ?

  - by Mehdi Amrollahi

  I have a crawler application (with C#) that downloads pages from web . The application take more virtual memory , even i dispose every object and even use GC.Collect() . This , have 10 thread and each thread has a socket that downloads pages . I use dispose method and even use GC.Collect() in my application , but in 3 hour my application take 500 MB on virtual memory (500 MB on private bytes in Process explorer) . Then my system will be hang and i should restart my pc . Is there any way that i use to free vitual memory ? Thanks .

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• Mock Assertions on objects inside Parallel ForEach's???

  - by jacko

  Any idea how we can assert a mock object was called when it is being accessed inside Parallel.ForEach via a closure? I assume that because each invocation is on a different thread that Rhino Mocks loses track of the object? Pseudocode: var someStub = MockRepository.GenerateStub() Parallel.Foreach(collectionOfInts, anInt => someStub.DoSomething(anInt)) someStub.AssertWasCalled(s => s.DoSomething, Repeat.Five.Times) This test will return an expectation violation, expecting the stub to be called 5 times but being actually called 0 times. Any ideas how we can tell the lambdas to keep track of the thread-local stub object?

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• All users of a group can edit each others files (Linux)

  - by Xeoncross

  I want anyone in group www-data to have write access to /var/www. For example, if 'a' and 'b' are in group www-data and 'a' creates a file in /var/www - then 'b' will be able to edit it. The problem is that I create files that PHP and Apache can't edit - and they create files I can't edit without sudo. I changed the umask setting /etc/profile from umask 022 to umask 002. Is this a safe and proper way to handle this?

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• two threads acting on the same runnable

  - by Eslam

  Given: public class Thread1 { int x = 0; public class Runner implements Runnable { public void run() { int current = 0; for (int i = 0; i < 4; i++) { current = x; System.out.print(current + " "); x = current + 2; } } } public void go() { Runnable r1 = new Runner(); new Thread(r1).start(); new Thread(r1).start(); } public static void main(String[] args) { new Thread1().go(); } } Which two are possible results? (Choose two) A. 0, 2, 4, 4, 6, 8, 10, 6, B. 0, 2, 4, 6, 8, 10, 2, 4, C. 0, 2, 4, 6, 8, 10, 12, 14, D. 0, 0, 2, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, 14, 14, E. 0, 2, 4, 6, 8, 10, 12, 14, 0, 2, 4, 6, 8, 10, 12, 14, i chosed A,B but i'm not certain is those is the true or not.

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• Group Policy fault - Students force

  - by Richard 'Bean' Williams

  Work at a school and we've got a scenario. We block F8 on all computers so students cannot access Safe Mode to bypass Group Policy... But students are logging into their accounts using AD, and they are turning them off half way through. Then they are claiming that when they login next time, they have Local Administrator accounts. Is this right, but we have blocked F8 and Startup repair, so wondering how they actually did it. Cheers Richard

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• Java multi-threading - what is the best way to monitor the activity of a number of threads?

  - by MalcomTucker

  I have a number of threads that are performing a long runing task. These threads themselves have child threads that do further subdivisions of work. What is the best way for me to track the following: How many total threads my process has created What the state of each thread currently is What part of my process each thread has currently got to I want to do it in as efficient a way as possible and once threads finish, I don't want any references to them hanging around becasuse I need to be freeing up memory as early as possible. Any advice?

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• Php fetch rows from multiple MySQL tables

  - by Jon McIntosh

  Right now I am fetching all of the rows from one of my tables: query = "SELECT * FROM thread WHERE threadid = 2 ORDER BY threadid DESC"; $result = mysql_query($query); $num_rows = mysql_num_rows($result); if((!is_bool($result) || $result) && $num_rows) { while($row = mysql_fetch_array($result)) { $thread = $row['title']; $threadID = $row['threadid']; $poster = $row['postusername']; } What I want to do is go to another table on my database: "post_display", and get the row 'text' where the threadid = 2.

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• Unhandled exceptions in BackgroundWorker

  - by edg

  My WinForms app uses a number of BackgroundWorker objects to retrieve information from a database. I'm using BackgroundWorker because it allows the UI to remain unblocked during long-running database queries and it simplifies the threading model for me. I'm getting occasional DatabaseExceptions in some of these background threads, and I have witnessed at least one of these exceptions in a worker thread while debugging. I'm fairly confident these exceptions are timeouts which I suppose its reasonable to expect from time to time. My question is about what happens when an unhandled exception occurs in one of these background worker threads. I don't think I can catch an exception in another thread, but can I expect my WorkerCompleted method to be executed? Is there any property or method of the BackgroundWorker I can interrogate for exceptions?

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• Best practice for error handling in an Android Service

  - by Omar Kohl

  I have an Android Service that does some background processing on an image using a separate Thread. If an error occurs in this Service or even worse in the thread, what is the best practice to inform the launching Activity of the problem and allow the application to recover to a stable state (i.e. the state it was in before launching the service). From within the Service I could post a Toast or a Notification, but that doesn't help me. I would like to inform the user about the problem but at the same time recover the application to a stable state.

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• SerialPort not taking input. It throws it back at me!

  - by Mashew

  When I try to write an AT command to my GSM modem, it does not seem to take the command. I have used PuTTY to check that the command words, it does. I have checked to see if the port is opening, it does. What could I possibly be doing wrong? NOTE: The "lol" part is for debugging purposes. ;3 SerialPort sp = new SerialPort("COM3"); sp.BaudRate = 9600; sp.DataBits = 8; sp.StopBits = StopBits.One; sp.Parity = Parity.None; sp.Open(); if (sp.IsOpen == false) { sp.Open(); } Thread.Sleep(1000); sp.WriteLine("AT+CMGF=1"); Thread.Sleep(1000); string lol = sp.ReadExisting(); sp.Close(); return lol;

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• Change Keyboard Layout for Other Process

  - by SLaks

  I'm writing a program in C# that runs in the background and allows users to use a htokey to switch keyboard layouts in the active window. (Windows only supports CTRL+SHIFT & ALT+SHIFT) I'm using RegisterHotKey to catch the hotkey, & it's working fine. The problem is that I can't find any API to change the keyboard layout for the focused window. ActivateKeyboardLayout and LoadKeyboardLayout can only change the keyboard layout for the calling thread. Does anyone know how to change the keyboard layout for a different thread (the way the Language Bar does)?

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• question about c# asp.net

  - by daddyCool

  in order to use the FolderBrowserDialog control in asp.net, i had to add a reference to System.Windows.Forms in my project. i wrote this code: FolderBrowserDialog f = new FolderBrowserDialog(); f.ShowDialog(); but this error occured: Current thread must be set to single thread apartment (STA) mode before OLE calls can be made. Ensure that your Main function has STAThreadAttribute marked on it. This exception is only raised if a debugger is attached to the process. any help?

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• What is design principle behind Servlets being Singleton

  - by Sandeep Jindal

  A servlet container "generally" create one instance of a servlet and different threads of the same instance to serve multiple requests. (I know this can be changed using deprecated SingleThreadModel and other features, but this is the usual way). I thought, the simple reason behind this is performance gain, as creating threads is better than creating instances. But it seems this is not the reason. On the other hand, creating instances have little advantage that developers never have to worry about thread safety. I am trying to understand the reason for this decision over the trade-off of thread-safety.

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• BlackBerry - Exception with null message when sending sms using Connector

  - by vikram deshpande

  I used code given but I am getting "IOCancelledException" and "IOException". And IOCancelledException.getMessage() / IOException.getMessage() giving null string, it does not give error message. Please help me understaing reason. class SMSThread extends Thread { Thread myThread; MessageConnection msgConn; String message; String mobilenumber; public SMSThread(String textMsg, String mobileNumber) { message = textMsg; mobilenumber = mobileNumber; } public void run() { try { msgConn = (MessageConnection) Connector.open("sms://+" + mobilenumber); TextMessage text = (TextMessage) msgConn .newMessage(MessageConnection.TEXT_MESSAGE); text.setPayloadText(message); msgConn.send(text); msgConn.close(); } catch (IOCancelledException ioce) { System.out .println("IOCancelledException: " + ioce.getMessage()); } catch (IOException ioe) { System.out.println("IOException: " + ioe.getMessage()); } catch (Exception e) { System.out.println("Exception: " + e); } } }

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