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  • Fixing "Lock wait timeout exceeded; try restarting transaction" for a 'stuck" Mysql table?

    - by Tom
    From a script I sent a query like this thousands of times to my local database: update some_table set some_column = some_value I forgot to add the where part, so the same column was set to the same a value for all the rows in the table and this was done thousands of times and the column was indexed, so the corresponding index was probably updated too lots of times. I noticed something was wrong, because it took too long, so I killed the script. I even rebooted my computer since them, but something stuck in the table, because simple queries take a very long time to run and when I try dropping the relevant index it fails with this message: Lock wait timeout exceeded; try restarting transaction It's an innodb table, so stuck the transaction is probably implicit. How can I fix this table and remove the stuck transaction from it?

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  • Windows Mobile 6.x How to explicitly lock the app in one orientation?

    - by Stuart
    I'm trying to get an app on the WinMo App Store. As part of this, Microsoft App's Store has asked that I need to support landscape as well as portrait. What they've said is OK is: If dynamic switching is implicitly allowed, the app will be tested just as if it supports both portrait and landscape even if only a portrait or landscape resolution is checked. You may explicitly lock the app in one orientation (which means portrait mode if the app does not handle landscape mode functions), provided the default OS orientation is preserved once the app exits. I'd love to do answer 2 - but I can't find any way of doing it - and they won't provide me any other clues - they suggested I ask on the forums... so here I am on Stack Overflow - far better than on the forums :) Anyone got any suggestions?

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  • How do I mimic Windows Explorer multi-select/drag-n-drop behavior in a DataGridView?

    - by bsh152s
    I'm trying to mimic the way Windows Explorer handles multiple selection. In a default DataGridView, you can select multiple items using Ctrl-click. But if you release the Ctrl key and then try and drag/drop the selected items, it clears the selected items and only selects the "hit" row. I found the following solution somewhere online. protected override OnMouseDown(MouseEventArgs e) { int hitRowIndex = HitTest(e.X, e.Y).RowIndex; if(!SelectedRows.Contains(Rows[hitRowIndex])) { base.OnMouseDown(); } } However, this causes other side effects. With the CTRL key pressed and mousing down on a selected item, the item remains selected. This makes sense because the mousedown event is bypassed if the row clicked on is selected. From looking at the behavior of Windows Explorer, it looks like the deselection of an item with the CTRL key held is not handled until the MouseUp event. Has anyone tried to do this?

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  • An image cropper: How to prevent the default drag n' drop action?

    - by David Gore
    I am developing an image cropper and would like to ask you the following question: In order to prevent the default drag n' drop action when you press the left button on an image and keeping it pressed try to move the mouse, wouldn't it be cross-browser if to just use the picture as a background to a div box? Just like so: <div id="theDiv" style="background:url(pic.png) no-repeat;"></div> How do you think? Is it acceptable? Not too ugly? Or should be done with JS?

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  • Anyway to find out the current Windows is in lock mode?

    - by David.Chu.ca
    I have a windows application written in VS 2005. The application makes queries against to sql database in a timer cycle every 2 minutes. If there any data changes, the window will be refreshed with new data. If the user leaves the window, the windows will be automatically locked after a while. There is no sense to keep querying data in ever 2 minutes when the windows is locked; therefore I would like to stop the query when lock is on so that the network data trafic will be reduced and also saves the current windows resources such as memory and CPUs. I am not sure if there is any way to find out the current windows is locked? Not sure if there is any Windows APIs for this purpose if no .Net classes available? My project is in .Net 2.0 and all users are in Windows XP.

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  • Why timed lock doesnt throws a timeout exception in C++0x?

    - by Vicente Botet Escriba
    C++0x allows to lock on a mutex until a given time is reached, and return a boolean stating if the mutex has been locked or not. template <class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time); In some contexts, I consider an exceptional situation that the locking fails because of timeout. In this case an exception should be more appropriated. To make the difference a function lock_until could be used to get a timeout exception when the time is reached before locking. template <class Clock, class Duration> void lock_until(const chrono::time_point<Clock, Duration>& abs_time); Do you think that lock_until should be more adequate in some contexts? if yes, on which ones? If no, why try_lock_until will always be a better choice?

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  • Will lock() statement block all threads in the proccess/appdomain?

    - by MikeJ
    Maybe the question sounds silly, but I don't understand 'something about threads and locking and I would like to get a confirmation (here's why I ask). So, if I have 10 servers and 10 request in the same time come to each server, that's 100 request across the farm. Without locking, thats 100 request to the database. If I do something like this: private static readonly object myLockHolder = new object(); if (Cache[key] == null) { lock(myLockHolder) { if (Cache[key] == null) { Cache[key] = LengthyDatabaseCall(); } } } How many database requests will I do? 10? 100? Or as much as I have threads?

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  • Can I lock rows in a cursor if the cursor only returns a single count(*) row?

    - by RenderIn
    I would like to restrict users from inserting more than 3 records with color = 'Red' in my FOO table. My intentions are to A) retrieve the current count so that I can determine whether another record is allowed and B) prevent any other processes from inserting any Red records while this one is in process, hence the for update of. I'd like to do something like: cursor cur_cnt is select count(*) cnt from foo where foo.color = 'Red' for update of foo.id; Will this satisfy both my requirements or will it not lock only the rows in the count(*) who had foo.color = 'Red'?

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  • How can I lock the cursor to the inside of a window on Linux?

    - by ZorbaTHut
    I'm trying to put together a game for Linux which involves a lot of fast action and flinging around of the mouse cursor. If the user wants to play in windowed mode, I'd quite like to lock the cursor to the inside of the window to avoid accidentally changing programs in the heat of battle (obviously this will cancel itself if the user changes programs or hits escape for the pause menu.) On Windows, this can be accomplished easily with ClipCursor(). I can't find an equivalent on Linux. Is there one? I plan to do this in pure X code, but obviously if anyone knows of a way to do this in any Linux windowing library then I can just read the source code and figure out how to duplicate it in X.

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  • Working around MySQL error "Deadlock found when trying to get lock; try restarting transaction"

    - by Anon Guy
    Hi all: I have a MySQL table with about 5,000,000 rows that are being constantly updated in small ways by parallel Perl processes connecting via DBI. The table has about 10 columns and several indexes. One fairly common operation gives rise to the following error sometimes: DBD::mysql::st execute failed: Deadlock found when trying to get lock; try restarting transaction at Db.pm line 276. The SQL statement that triggers the error is something like this: UPDATE file_table SET a_lock = 'process-1234' WHERE param1 = 'X' AND param2 = 'Y' AND param3 = 'Z' LIMIT 47 The error is triggered only sometimes. I'd estimate in 1% of calls or less. However, it never happened with a small table and has become more common as the database has grown. Note that I am using the a_lock field in file_table to ensure that the four near-identical processes I am running do not try and work on the same row. The limit is designed to break their work into small chunks. I haven't done much tuning on MySQL or DBD::mysql. MySQL is a standard Solaris deployment, and the database connection is set up as follows: my $dsn = "DBI:mysql:database=" . $DbConfig::database . ";host=${DbConfig::hostname};port=${DbConfig::port}"; my $dbh = DBI->connect($dsn, $DbConfig::username, $DbConfig::password, { RaiseError => 1, AutoCommit => 1 }) or die $DBI::errstr; I have seen online that several other people have reported similar errors and that this may be a genuine deadlock situation. I have two questions: What exactly about my situation is causing the error above? Is there a simple way to work around it or lessen its frequency? For example, how exactly do I go about "restarting transaction at Db.pm line 276"? Thanks in advance.

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  • how to clone the drag-event using jquery and jquery-ui.

    - by zjm1126
    i want to create a new '.b' div appendTo document.body, and it can dragable like its father, but i can not clone the drag event, how to do this, thanks this is my code : <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta name="viewport" content="width=device-width, user-scalable=no"> </head> <body> <style type="text/css" media="screen"> </style> <div id="map_canvas" style="width: 500px; height: 300px;background:blue;"></div> <div class=b style="width: 20px; height: 20px;background:red;position:absolute;left:700px;top:200px;"></div> <script src="jquery-1.4.2.js" type="text/javascript"></script> <script src="jquery-ui-1.8rc3.custom.min.js" type="text/javascript"></script> <script type="text/javascript" charset="utf-8"> $(".b").draggable({ start: function(event,ui) { //console.log(ui) //$(ui.helper).clone(true).appendTo($(document.body)) $(this).clone(true).appendTo($(document.body))//draggable is not be cloned, } }); $("#map_canvas").droppable({ drop: function(event,ui) { //console.log(ui.offset.left+' '+ui.offset.top) ui.draggable.remove(); } }); </script> </body> </html>

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  • Using C#, can you drag a canvas in WPF?

    - by TERACytE
    Can you drag a canvas in WPF? How do you set the position of the canvas? Here is what I got so far: /// xaml <Window x:Class="TestApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="350" Width="525" WindowStyle="None" ResizeMode="NoResize" AllowsTransparency="True" Background="Transparent" Loaded="MainWindow_Loaded"> <Canvas Name="ParentCanvas" Background="#FF6E798D"> </Canvas> </Window> /// code behind public partial class MainWindow : Window { private Boolean isMouseCapture; public MainWindow() { InitializeComponent(); } void MainWindow_Loaded(object sender, RoutedEventArgs e) { this.ParentCanvas.MouseLeftButtonDown += new MouseButtonEventHandler(_MouseLeftButtonDown); this.ParentCanvas.MouseLeftButtonUp += new MouseButtonEventHandler(_MouseLeftButtonUp); this.ParentCanvas.MouseMove += new MouseEventHandler(_MouseMove); } void _MouseLeftButtonUp(object sender, MouseButtonEventArgs e) { this.ParentCanvas.ReleaseMouseCapture(); isMouseCapture = false; } void _MouseLeftButtonDown(object sender, MouseButtonEventArgs e) { this.ParentCanvas.CaptureMouse(); isMouseCapture = true; } void _MouseMove(object sender, MouseEventArgs e) { if (isMouseCapture) { this.ParentCanvas.X= e.GetPosition(this).X; this.ParentCanvas.Y = e.GetPosition(this).Y; } } } 'X' is not a property of Canvas (i.e."this.ParentCanvas.X"). What do I use to set the position?

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  • we would like the user to be able to pick a file from native file system and drag & drop it to our a

    - by user261740
    We have an existing java desktop application which starts, when user click on our application icon (placed on desktop) OR double click on executable(.exe). It opens the frame which allows user to select the file from native file system and uploads it to the server. Now we would like to facilitate user, that he can pick a file from windows explorer and drag it to the "shortcut / Application icon" & drop it on the "shortcut / Application icon" on the desktop. This would start the uploading of that file on the server. we need to capture the action of "drop" and launch on shortcut.. which may be completely not related to java, it can be very generic to any application. We are using JSmooth to build an executable from jar and NSIS for installer purpose. I would like to know.. How we can launch the application if user drops local file onto the system icon ? How we get the absolute path of file name which has been dropped onto the executable ?

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  • How to find out where a thread lock happend?

    - by SchlaWiener
    One of our company's Windows Forms application had a strange problem for several month. The app worked very reliable for most of our customers but on some PC's (mostly with a wireless lan connection) the app sometimes just didn't respond anymore. (You click on the UI and windows ask you to wait or kill the app). I wasn't able to track down the problem for a long time but now I figured out what happend. The app had this line of code // don't blame me for this. Wasn't my code :D Control.CheckForIllegalCrossThreadCalls = false and used some background threads to modify the controls. No I found a way to reproduce the application stopping responding bug on my dev machine and tracked it down to a line where I actually used Invoke() to run a task in the main thread. Me.Invoke(MyDelegate, arg1, arg2) Obviously there was a thread lock somewhere. After removing the Control.CheckForIllegalCrossThreadCalls = false statement and refactoring the whole programm to use Invoke() if modifying a control from a background thread, the problem is (hopefully) gone. However, I am wondering if there is a way to find such bugs without debugging every line of code (Even if I break into debugger after the app stops responding I can't tell what happend last, because the IDE didn't jump to the Invoke() statement) In other words: If my apps hangs how can I figure out which line of code has been executed last? Maybe even on the customers PC. I know VS2010 offers some backwards debugging feature, maybe that would be a solution, but currently I am using VS2008.

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  • C#, Can I check on a lock without trying to acquire it?

    - by Biff MaGriff
    Hello, I have a lock in my c# web app that prevents users from running the update script once it has started. I was thinking I would put a notification in my master page to let the user know that the data isn't all there yet. Currently I do my locking like so. protected void butRefreshData_Click(object sender, EventArgs e) { Thread t = new Thread(new ParameterizedThreadStart(UpdateDatabase)); t.Start(this); //sleep for a bit to ensure that javascript has a chance to get rendered Thread.Sleep(100); } public static void UpdateDatabase(object con) { if (Monitor.TryEnter(myLock)) { Updater.RepopulateDatabase(); Monitor.Exit(myLock); } else { Common.RegisterStartupScript(con, AlreadyLockedJavaScript); } } And I do not want to do if(Monitor.TryEnter(myLock)) Monitor.Exit(myLock); else //show processing labal As I imagine there is a slight possibility that it might display the notification when it isn't actually running. Is there an alternative I can use? Edit: Hi Everyone, thanks a lot for your suggestions! Unfortunately I couldn't quite get them to work... However I combined the ideas on 2 answers and came up with my own solution.

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  • How should I lock the table in this VB6 / Access application?

    - by Brian Hooper
    I'm working on a VB6 application using an Access database. The application writes messages to a log table from time to time. Several instances of the application may be running simultaneously and to distinguish them they each have their own run number. The run number is deduced from the log table thus... Set record_set = New ADODB.Recordset query_string = "SELECT MAX(RUN_NUMBER) + 1 AS NEW_RUN_NUMBER FROM ERROR_LOG" record_set.CursorLocation = adUseClient record_set.Open query_string, database_connection, adOpenStatic, , adCmdText record_set.MoveLast If IsNull(record_set.Fields("NEW_RUN_NUMBER")) Then run_number = 0 Else run_number = record_set.Fields("NEW_RUN_NUMBER") End If command_string = "INSERT INTO ERROR_LOG (RUN_NUMBER, SEVERITY, MESSAGE) " & _ " VALUES (" & Str$(run_number) & ", " & _ " " & Str$(SEVERITY_INFORMATION) & ", " & _ " 'Run Started'); " database_connection.Execute command_string Obviously there is a small gap between the calculation of the run number and the appearance of the new row in the database, and to prevent another instance getting access between the two operations I'd like to lock the table; something along the lines of SET TRANSACTION READ WRITE RESERVING ERROR_LOG FOR PROTECTED WRITE; How should I go about doing this? Would locking the recordset do any good (the row in the record set doesn't match any particular row in the database)?

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  • jquery-ui drag and drop - how to dropped items?

    - by user246114
    Hi, I'm trying to use jquery-ui. I am using one of the drag and drop examples which is pretty much exactly what I need, except instead of moving items between the two lists, I'd like the items to be cloned: http://jqueryui.com/demos/sortable/#connect-lists $(function() { $("#sortable1, #sortable2").sortable({ connectWith: '.connectedSortable' }).disableSelection(); }); <ul id="sortable1" class="connectedSortable"> <li class="ui-state-default">Item 1</li> <li class="ui-state-default">Item 2</li> <li class="ui-state-default">Item 3</li> </ul> <ul id="sortable2" class="connectedSortable"> <li class="ui-state-default">Item 1</li> <li class="ui-state-default">Item 2</li> <li class="ui-state-default">Item 3</li> </ul> so moving an item from the first list to the second list results in list 1 have 2 items, and list 2 having 4 items. I just want it to make clones of the items on the drop. So in the above example, list 1 would still have 3 items, but list 2 would have 4 items, Thank you

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  • Microbenchmark showing process-switching faster than thread-switching; what's wrong?

    - by Yang
    I have two simple microbenchmarks trying to measure thread- and process-switching overheads, but the process-switching overhead. The code is living here, and r1667 is pasted below: https://assorted.svn.sourceforge.net/svnroot/assorted/sandbox/trunk/src/c/process_switch_bench.c // on zs, ~2.1-2.4us/switch #include <stdlib.h> #include <fcntl.h> #include <stdint.h> #include <stdio.h> #include <semaphore.h> #include <unistd.h> #include <sys/wait.h> #include <sys/types.h> #include <sys/time.h> #include <pthread.h> uint32_t COUNTER; pthread_mutex_t LOCK; pthread_mutex_t START; sem_t *s0, *s1, *s2; void * threads ( void * unused ) { // Wait till we may fire away sem_wait(s2); for (;;) { pthread_mutex_lock(&LOCK); pthread_mutex_unlock(&LOCK); COUNTER++; sem_post(s0); sem_wait(s1); } return 0; } int64_t timeInMS () { struct timeval t; gettimeofday(&t, NULL); return ( (int64_t)t.tv_sec * 1000 + (int64_t)t.tv_usec / 1000 ); } int main ( int argc, char ** argv ) { int64_t start; pthread_t t1; pthread_mutex_init(&LOCK, NULL); COUNTER = 0; s0 = sem_open("/s0", O_CREAT, 0022, 0); if (s0 == 0) { perror("sem_open"); exit(1); } s1 = sem_open("/s1", O_CREAT, 0022, 0); if (s1 == 0) { perror("sem_open"); exit(1); } s2 = sem_open("/s2", O_CREAT, 0022, 0); if (s2 == 0) { perror("sem_open"); exit(1); } int x, y, z; sem_getvalue(s0, &x); sem_getvalue(s1, &y); sem_getvalue(s2, &z); printf("%d %d %d\n", x, y, z); pid_t pid = fork(); if (pid) { pthread_create(&t1, NULL, threads, NULL); pthread_detach(t1); // Get start time and fire away start = timeInMS(); sem_post(s2); sem_post(s2); // Wait for about a second sleep(1); // Stop thread pthread_mutex_lock(&LOCK); // Find out how much time has really passed. sleep won't guarantee me that // I sleep exactly one second, I might sleep longer since even after being // woken up, it can take some time before I gain back CPU time. Further // some more time might have passed before I obtained the lock! int64_t time = timeInMS() - start; // Correct the number of thread switches accordingly COUNTER = (uint32_t)(((uint64_t)COUNTER * 2 * 1000) / time); printf("Number of process switches in about one second was %u\n", COUNTER); printf("roughly %f microseconds per switch\n", 1000000.0 / COUNTER); // clean up kill(pid, 9); wait(0); sem_close(s0); sem_close(s1); sem_unlink("/s0"); sem_unlink("/s1"); sem_unlink("/s2"); } else { if (1) { sem_t *t = s0; s0 = s1; s1 = t; } threads(0); // never return } return 0; } https://assorted.svn.sourceforge.net/svnroot/assorted/sandbox/trunk/src/c/thread_switch_bench.c // From <http://stackoverflow.com/questions/304752/how-to-estimate-the-thread-context-switching-overhead> // on zs, ~4-5us/switch; tried making COUNTER updated only by one thread, but no difference #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <pthread.h> #include <unistd.h> #include <sys/time.h> uint32_t COUNTER; pthread_mutex_t LOCK; pthread_mutex_t START; pthread_cond_t CONDITION; void * threads ( void * unused ) { // Wait till we may fire away pthread_mutex_lock(&START); pthread_mutex_unlock(&START); int first=1; pthread_mutex_lock(&LOCK); // If I'm not the first thread, the other thread is already waiting on // the condition, thus Ihave to wake it up first, otherwise we'll deadlock if (COUNTER > 0) { pthread_cond_signal(&CONDITION); first=0; } for (;;) { if (first) COUNTER++; pthread_cond_wait(&CONDITION, &LOCK); // Always wake up the other thread before processing. The other // thread will not be able to do anything as long as I don't go // back to sleep first. pthread_cond_signal(&CONDITION); } pthread_mutex_unlock(&LOCK); return 0; } int64_t timeInMS () { struct timeval t; gettimeofday(&t, NULL); return ( (int64_t)t.tv_sec * 1000 + (int64_t)t.tv_usec / 1000 ); } int main ( int argc, char ** argv ) { int64_t start; pthread_t t1; pthread_t t2; pthread_mutex_init(&LOCK, NULL); pthread_mutex_init(&START, NULL); pthread_cond_init(&CONDITION, NULL); pthread_mutex_lock(&START); COUNTER = 0; pthread_create(&t1, NULL, threads, NULL); pthread_create(&t2, NULL, threads, NULL); pthread_detach(t1); pthread_detach(t2); // Get start time and fire away start = timeInMS(); pthread_mutex_unlock(&START); // Wait for about a second sleep(1); // Stop both threads pthread_mutex_lock(&LOCK); // Find out how much time has really passed. sleep won't guarantee me that // I sleep exactly one second, I might sleep longer since even after being // woken up, it can take some time before I gain back CPU time. Further // some more time might have passed before I obtained the lock! int64_t time = timeInMS() - start; // Correct the number of thread switches accordingly COUNTER = (uint32_t)(((uint64_t)COUNTER * 2 * 1000) / time); printf("Number of thread switches in about one second was %u\n", COUNTER); printf("roughly %f microseconds per switch\n", 1000000.0 / COUNTER); return 0; }

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  • Parallelism in .NET – Part 4, Imperative Data Parallelism: Aggregation

    - by Reed
    In the article on simple data parallelism, I described how to perform an operation on an entire collection of elements in parallel.  Often, this is not adequate, as the parallel operation is going to be performing some form of aggregation. Simple examples of this might include taking the sum of the results of processing a function on each element in the collection, or finding the minimum of the collection given some criteria.  This can be done using the techniques described in simple data parallelism, however, special care needs to be taken into account to synchronize the shared data appropriately.  The Task Parallel Library has tools to assist in this synchronization. The main issue with aggregation when parallelizing a routine is that you need to handle synchronization of data.  Since multiple threads will need to write to a shared portion of data.  Suppose, for example, that we wanted to parallelize a simple loop that looked for the minimum value within a dataset: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This seems like a good candidate for parallelization, but there is a problem here.  If we just wrap this into a call to Parallel.ForEach, we’ll introduce a critical race condition, and get the wrong answer.  Let’s look at what happens here: // Buggy code! Do not use! double min = double.MaxValue; Parallel.ForEach(collection, item => { double value = item.PerformComputation(); min = System.Math.Min(min, value); }); This code has a fatal flaw: min will be checked, then set, by multiple threads simultaneously.  Two threads may perform the check at the same time, and set the wrong value for min.  Say we get a value of 1 in thread 1, and a value of 2 in thread 2, and these two elements are the first two to run.  If both hit the min check line at the same time, both will determine that min should change, to 1 and 2 respectively.  If element 1 happens to set the variable first, then element 2 sets the min variable, we’ll detect a min value of 2 instead of 1.  This can lead to wrong answers. Unfortunately, fixing this, with the Parallel.ForEach call we’re using, would require adding locking.  We would need to rewrite this like: // Safe, but slow double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach(collection, item => { double value = item.PerformComputation(); lock(syncObject) min = System.Math.Min(min, value); }); This will potentially add a huge amount of overhead to our calculation.  Since we can potentially block while waiting on the lock for every single iteration, we will most likely slow this down to where it is actually quite a bit slower than our serial implementation.  The problem is the lock statement – any time you use lock(object), you’re almost assuring reduced performance in a parallel situation.  This leads to two observations I’ll make: When parallelizing a routine, try to avoid locks. That being said: Always add any and all required synchronization to avoid race conditions. These two observations tend to be opposing forces – we often need to synchronize our algorithms, but we also want to avoid the synchronization when possible.  Looking at our routine, there is no way to directly avoid this lock, since each element is potentially being run on a separate thread, and this lock is necessary in order for our routine to function correctly every time. However, this isn’t the only way to design this routine to implement this algorithm.  Realize that, although our collection may have thousands or even millions of elements, we have a limited number of Processing Elements (PE).  Processing Element is the standard term for a hardware element which can process and execute instructions.  This typically is a core in your processor, but many modern systems have multiple hardware execution threads per core.  The Task Parallel Library will not execute the work for each item in the collection as a separate work item. Instead, when Parallel.ForEach executes, it will partition the collection into larger “chunks” which get processed on different threads via the ThreadPool.  This helps reduce the threading overhead, and help the overall speed.  In general, the Parallel class will only use one thread per PE in the system. Given the fact that there are typically fewer threads than work items, we can rethink our algorithm design.  We can parallelize our algorithm more effectively by approaching it differently.  Because the basic aggregation we are doing here (Min) is communitive, we do not need to perform this in a given order.  We knew this to be true already – otherwise, we wouldn’t have been able to parallelize this routine in the first place.  With this in mind, we can treat each thread’s work independently, allowing each thread to serially process many elements with no locking, then, after all the threads are complete, “merge” together the results. This can be accomplished via a different set of overloads in the Parallel class: Parallel.ForEach<TSource,TLocal>.  The idea behind these overloads is to allow each thread to begin by initializing some local state (TLocal).  The thread will then process an entire set of items in the source collection, providing that state to the delegate which processes an individual item.  Finally, at the end, a separate delegate is run which allows you to handle merging that local state into your final results. To rewriting our routine using Parallel.ForEach<TSource,TLocal>, we need to provide three delegates instead of one.  The most basic version of this function is declared as: public static ParallelLoopResult ForEach<TSource, TLocal>( IEnumerable<TSource> source, Func<TLocal> localInit, Func<TSource, ParallelLoopState, TLocal, TLocal> body, Action<TLocal> localFinally ) The first delegate (the localInit argument) is defined as Func<TLocal>.  This delegate initializes our local state.  It should return some object we can use to track the results of a single thread’s operations. The second delegate (the body argument) is where our main processing occurs, although now, instead of being an Action<T>, we actually provide a Func<TSource, ParallelLoopState, TLocal, TLocal> delegate.  This delegate will receive three arguments: our original element from the collection (TSource), a ParallelLoopState which we can use for early termination, and the instance of our local state we created (TLocal).  It should do whatever processing you wish to occur per element, then return the value of the local state after processing is completed. The third delegate (the localFinally argument) is defined as Action<TLocal>.  This delegate is passed our local state after it’s been processed by all of the elements this thread will handle.  This is where you can merge your final results together.  This may require synchronization, but now, instead of synchronizing once per element (potentially millions of times), you’ll only have to synchronize once per thread, which is an ideal situation. Now that I’ve explained how this works, lets look at the code: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Although this is a bit more complicated than the previous version, it is now both thread-safe, and has minimal locking.  This same approach can be used by Parallel.For, although now, it’s Parallel.For<TLocal>.  When working with Parallel.For<TLocal>, you use the same triplet of delegates, with the same purpose and results. Also, many times, you can completely avoid locking by using a method of the Interlocked class to perform the final aggregation in an atomic operation.  The MSDN example demonstrating this same technique using Parallel.For uses the Interlocked class instead of a lock, since they are doing a sum operation on a long variable, which is possible via Interlocked.Add. By taking advantage of local state, we can use the Parallel class methods to parallelize algorithms such as aggregation, which, at first, may seem like poor candidates for parallelization.  Doing so requires careful consideration, and often requires a slight redesign of the algorithm, but the performance gains can be significant if handled in a way to avoid excessive synchronization.

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  • Working with PivotTables in Excel

    - by Mark Virtue
    PivotTables are one of the most powerful features of Microsoft Excel.  They allow large amounts of data to be analyzed and summarized in just a few mouse clicks. In this article, we explore PivotTables, understand what they are, and learn how to create and customize them. Note:  This article is written using Excel 2010 (Beta).  The concept of a PivotTable has changed little over the years, but the method of creating one has changed in nearly every iteration of Excel.  If you are using a version of Excel that is not 2010, expect different screens from the ones you see in this article. A Little History In the early days of spreadsheet programs, Lotus 1-2-3 ruled the roost.  Its dominance was so complete that people thought it was a waste of time for Microsoft to bother developing their own spreadsheet software (Excel) to compete with Lotus.  Flash-forward to 2010, and Excel’s dominance of the spreadsheet market is greater than Lotus’s ever was, while the number of users still running Lotus 1-2-3 is approaching zero.  How did this happen?  What caused such a dramatic reversal of fortunes? Industry analysts put it down to two factors:  Firstly, Lotus decided that this fancy new GUI platform called “Windows” was a passing fad that would never take off.  They declined to create a Windows version of Lotus 1-2-3 (for a few years, anyway), predicting that their DOS version of the software was all anyone would ever need.  Microsoft, naturally, developed Excel exclusively for Windows.  Secondly, Microsoft developed a feature for Excel that Lotus didn’t provide in 1-2-3, namely PivotTables.  The PivotTables feature, exclusive to Excel, was deemed so staggeringly useful that people were willing to learn an entire new software package (Excel) rather than stick with a program (1-2-3) that didn’t have it.  This one feature, along with the misjudgment of the success of Windows, was the death-knell for Lotus 1-2-3, and the beginning of the success of Microsoft Excel. Understanding PivotTables So what is a PivotTable, exactly? Put simply, a PivotTable is a summary of some data, created to allow easy analysis of said data.  But unlike a manually created summary, Excel PivotTables are interactive.  Once you have created one, you can easily change it if it doesn’t offer the exact insights into your data that you were hoping for.  In a couple of clicks the summary can be “pivoted” – rotated in such a way that the column headings become row headings, and vice versa.  There’s a lot more that can be done, too.  Rather than try to describe all the features of PivotTables, we’ll simply demonstrate them… The data that you analyze using a PivotTable can’t be just any data – it has to be raw data, previously unprocessed (unsummarized) – typically a list of some sort.  An example of this might be the list of sales transactions in a company for the past six months. Examine the data shown below: Notice that this is not raw data.  In fact, it is already a summary of some sort.  In cell B3 we can see $30,000, which apparently is the total of James Cook’s sales for the month of January.  So where is the raw data?  How did we arrive at the figure of $30,000?  Where is the original list of sales transactions that this figure was generated from?  It’s clear that somewhere, someone must have gone to the trouble of collating all of the sales transactions for the past six months into the summary we see above.  How long do you suppose this took?  An hour?  Ten?  Probably. If we were to track down the original list of sales transactions, it might look something like this: You may be surprised to learn that, using the PivotTable feature of Excel, we can create a monthly sales summary similar to the one above in a few seconds, with only a few mouse clicks.  We can do this – and a lot more too! How to Create a PivotTable First, ensure that you have some raw data in a worksheet in Excel.  A list of financial transactions is typical, but it can be a list of just about anything:  Employee contact details, your CD collection, or fuel consumption figures for your company’s fleet of cars. So we start Excel… …and we load such a list… Once we have the list open in Excel, we’re ready to start creating the PivotTable. Click on any one single cell within the list: Then, from the Insert tab, click the PivotTable icon: The Create PivotTable box appears, asking you two questions:  What data should your new PivotTable be based on, and where should it be created?  Because we already clicked on a cell within the list (in the step above), the entire list surrounding that cell is already selected for us ($A$1:$G$88 on the Payments sheet, in this example).  Note that we could select a list in any other region of any other worksheet, or even some external data source, such as an Access database table, or even a MS-SQL Server database table.  We also need to select whether we want our new PivotTable to be created on a new worksheet, or on an existing one.  In this example we will select a new one: The new worksheet is created for us, and a blank PivotTable is created on that worksheet: Another box also appears:  The PivotTable Field List.  This field list will be shown whenever we click on any cell within the PivotTable (above): The list of fields in the top part of the box is actually the collection of column headings from the original raw data worksheet.  The four blank boxes in the lower part of the screen allow us to choose the way we would like our PivotTable to summarize the raw data.  So far, there is nothing in those boxes, so the PivotTable is blank.  All we need to do is drag fields down from the list above and drop them in the lower boxes.  A PivotTable is then automatically created to match our instructions.  If we get it wrong, we only need to drag the fields back to where they came from and/or drag new fields down to replace them. The Values box is arguably the most important of the four.  The field that is dragged into this box represents the data that needs to be summarized in some way (by summing, averaging, finding the maximum, minimum, etc).  It is almost always numerical data.  A perfect candidate for this box in our sample data is the “Amount” field/column.  Let’s drag that field into the Values box: Notice that (a) the “Amount” field in the list of fields is now ticked, and “Sum of Amount” has been added to the Values box, indicating that the amount column has been summed. If we examine the PivotTable itself, we indeed find the sum of all the “Amount” values from the raw data worksheet: We’ve created our first PivotTable!  Handy, but not particularly impressive.  It’s likely that we need a little more insight into our data than that. Referring to our sample data, we need to identify one or more column headings that we could conceivably use to split this total.  For example, we may decide that we would like to see a summary of our data where we have a row heading for each of the different salespersons in our company, and a total for each.  To achieve this, all we need to do is to drag the “Salesperson” field into the Row Labels box: Now, finally, things start to get interesting!  Our PivotTable starts to take shape….   With a couple of clicks we have created a table that would have taken a long time to do manually. So what else can we do?  Well, in one sense our PivotTable is complete.  We’ve created a useful summary of our source data.  The important stuff is already learned!  For the rest of the article, we will examine some ways that more complex PivotTables can be created, and ways that those PivotTables can be customized. First, we can create a two-dimensional table.  Let’s do that by using “Payment Method” as a column heading.  Simply drag the “Payment Method” heading to the Column Labels box: Which looks like this: Starting to get very cool! Let’s make it a three-dimensional table.  What could such a table possibly look like?  Well, let’s see… Drag the “Package” column/heading to the Report Filter box: Notice where it ends up…. This allows us to filter our report based on which “holiday package” was being purchased.  For example, we can see the breakdown of salesperson vs payment method for all packages, or, with a couple of clicks, change it to show the same breakdown for the “Sunseekers” package: And so, if you think about it the right way, our PivotTable is now three-dimensional.  Let’s keep customizing… If it turns out, say, that we only want to see cheque and credit card transactions (i.e. no cash transactions), then we can deselect the “Cash” item from the column headings.  Click the drop-down arrow next to Column Labels, and untick “Cash”: Let’s see what that looks like…As you can see, “Cash” is gone. Formatting This is obviously a very powerful system, but so far the results look very plain and boring.  For a start, the numbers that we’re summing do not look like dollar amounts – just plain old numbers.  Let’s rectify that. A temptation might be to do what we’re used to doing in such circumstances and simply select the whole table (or the whole worksheet) and use the standard number formatting buttons on the toolbar to complete the formatting.  The problem with that approach is that if you ever change the structure of the PivotTable in the future (which is 99% likely), then those number formats will be lost.  We need a way that will make them (semi-)permanent. First, we locate the “Sum of Amount” entry in the Values box, and click on it.  A menu appears.  We select Value Field Settings… from the menu: The Value Field Settings box appears. Click the Number Format button, and the standard Format Cells box appears: From the Category list, select (say) Accounting, and drop the number of decimal places to 0.  Click OK a few times to get back to the PivotTable… As you can see, the numbers have been correctly formatted as dollar amounts. While we’re on the subject of formatting, let’s format the entire PivotTable.  There are a few ways to do this.  Let’s use a simple one… Click the PivotTable Tools/Design tab: Then drop down the arrow in the bottom-right of the PivotTable Styles list to see a vast collection of built-in styles: Choose any one that appeals, and look at the result in your PivotTable:   Other Options We can work with dates as well.  Now usually, there are many, many dates in a transaction list such as the one we started with.  But Excel provides the option to group data items together by day, week, month, year, etc.  Let’s see how this is done. First, let’s remove the “Payment Method” column from the Column Labels box (simply drag it back up to the field list), and replace it with the “Date Booked” column: As you can see, this makes our PivotTable instantly useless, giving us one column for each date that a transaction occurred on – a very wide table! To fix this, right-click on any date and select Group… from the context-menu: The grouping box appears.  We select Months and click OK: Voila!  A much more useful table: (Incidentally, this table is virtually identical to the one shown at the beginning of this article – the original sales summary that was created manually.) Another cool thing to be aware of is that you can have more than one set of row headings (or column headings): …which looks like this…. You can do a similar thing with column headings (or even report filters). Keeping things simple again, let’s see how to plot averaged values, rather than summed values. First, click on “Sum of Amount”, and select Value Field Settings… from the context-menu that appears: In the Summarize value field by list in the Value Field Settings box, select Average: While we’re here, let’s change the Custom Name, from “Average of Amount” to something a little more concise.  Type in something like “Avg”: Click OK, and see what it looks like.  Notice that all the values change from summed totals to averages, and the table title (top-left cell) has changed to “Avg”: If we like, we can even have sums, averages and counts (counts = how many sales there were) all on the same PivotTable! Here are the steps to get something like that in place (starting from a blank PivotTable): Drag “Salesperson” into the Column Labels Drag “Amount” field down into the Values box three times For the first “Amount” field, change its custom name to “Total” and it’s number format to Accounting (0 decimal places) For the second “Amount” field, change its custom name to “Average”, its function to Average and it’s number format to Accounting (0 decimal places) For the third “Amount” field, change its name to “Count” and its function to Count Drag the automatically created field from Column Labels to Row Labels Here’s what we end up with: Total, average and count on the same PivotTable! Conclusion There are many, many more features and options for PivotTables created by Microsoft Excel – far too many to list in an article like this.  To fully cover the potential of PivotTables, a small book (or a large website) would be required.  Brave and/or geeky readers can explore PivotTables further quite easily:  Simply right-click on just about everything, and see what options become available to you.  There are also the two ribbon-tabs: PivotTable Tools/Options and Design.  It doesn’t matter if you make a mistake – it’s easy to delete the PivotTable and start again – a possibility old DOS users of Lotus 1-2-3 never had. We’ve included an Excel that should work with most versions of Excel, so you can download to practice your PivotTable skills. Download Our Practice Excel File Similar Articles Productive Geek Tips Magnify Selected Cells In Excel 2007Share Access Data with Excel in Office 2010Make Excel 2007 Print Gridlines In Workbook FileMake Excel 2007 Always Save in Excel 2003 FormatConvert Older Excel Documents to Excel 2007 Format TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Ben & Jerry’s Free Cone Day, 3/23/10 New Stinger from McAfee Helps Remove ‘FakeAlert’ Threats Google Apps Marketplace: Tools & Services For Google Apps Users Get News Quick and Precise With Newser Scan for Viruses in Ubuntu using ClamAV Replace Your Windows Task Manager With System Explorer

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  • How can I back up my ubuntu system?

    - by Eloff
    I'm sure there's a lot of questions on here similar to this, and I've been reading them, but I still feel this warrants a new question. I want nightly, incremental backups (full disk images would waste a lot of space - unless compressed somehow.) Preferably rotating or deleting old backups when running out of space or after a fixed number of backups. I want to be able to quickly and painlessly restore my system from these backups. This is my first time running ubuntu as my main development machine and I know from my experience with it as a server and in virtual machines that I regularly manage to make it unbootable or damage it to the point of being unable to rescue it. So how would you recommend I do this? There are so many options out there I really don't know where to start. There seems to be a vocal school of thought that it's sufficient to backup your home directory and the list of installed packages from the package manager. I've already installed lots of things from source, or outside of the package manager (development tools, ides, compilers, graphics drivers, etc.) So at the very least, if I do not back up the operating system itself I need to grab all config files, all program binaries, all created but required files, etc. I'd rather backup too much than too little - an ubuntu install is tiny anyway. Also this drastically reduces the restore time, which would cost me more in my time than the extra storage space. I tried using Deja Dup to backup the root partition, excluding some things like /mnt /media /dev /proc etc. Although many websites assured me you can backup a running linux system this way - that seems to be false as it complained that it could not backup the following files: /boot/System.map-3.0.0-17-generic /boot/System.map-3.2.0-22-generic /boot/vmcoreinfo-3.0.0-17-generic /boot/vmlinuz-3.0.0-17-generic /boot/vmlinuz-3.2.0-22-generic /etc/.pwd.lock /etc/NetworkManager/system-connections/LAN Connection /etc/apparmor.d/cache/lightdm-guest-session /etc/apparmor.d/cache/sbin.dhclient /etc/apparmor.d/cache/usr.bin.evince /etc/apparmor.d/cache/usr.lib.telepathy /etc/apparmor.d/cache/usr.sbin.cupsd /etc/apparmor.d/cache/usr.sbin.tcpdump /etc/apt/trustdb.gpg /etc/at.deny /etc/ati/inst_path_default /etc/ati/inst_path_override /etc/chatscripts /etc/cups/ssl /etc/cups/subscriptions.conf /etc/cups/subscriptions.conf.O /etc/default/cacerts /etc/fuse.conf /etc/group- /etc/gshadow /etc/gshadow- /etc/mtab.fuselock /etc/passwd- /etc/ppp/chap-secrets /etc/ppp/pap-secrets /etc/ppp/peers /etc/security/opasswd /etc/shadow /etc/shadow- /etc/ssl/private /etc/sudoers /etc/sudoers.d/README /etc/ufw/after.rules /etc/ufw/after6.rules /etc/ufw/before.rules /etc/ufw/before6.rules /lib/ufw/user.rules /lib/ufw/user6.rules /lost+found /root /run/crond.reboot /run/cups/certs /run/lightdm /run/lock/whoopsie/lock /run/udisks /var/backups/group.bak /var/backups/gshadow.bak /var/backups/passwd.bak /var/backups/shadow.bak /var/cache/apt/archives/lock /var/cache/cups/job.cache /var/cache/cups/job.cache.O /var/cache/cups/ppds.dat /var/cache/debconf/passwords.dat /var/cache/ldconfig /var/cache/lightdm/dmrc /var/crash/_usr_lib_x86_64-linux-gnu_colord_colord.102.crash /var/lib/apt/lists/lock /var/lib/dpkg/lock /var/lib/dpkg/triggers/Lock /var/lib/lightdm /var/lib/mlocate/mlocate.db /var/lib/polkit-1 /var/lib/sudo /var/lib/urandom/random-seed /var/lib/ureadahead/pack /var/lib/ureadahead/run.pack /var/log/btmp /var/log/installer/casper.log /var/log/installer/debug /var/log/installer/partman /var/log/installer/syslog /var/log/installer/version /var/log/lightdm/lightdm.log /var/log/lightdm/x-0-greeter.log /var/log/lightdm/x-0.log /var/log/speech-dispatcher /var/log/upstart/alsa-restore.log /var/log/upstart/alsa-restore.log.1.gz /var/log/upstart/console-setup.log /var/log/upstart/console-setup.log.1.gz /var/log/upstart/container-detect.log /var/log/upstart/container-detect.log.1.gz /var/log/upstart/hybrid-gfx.log /var/log/upstart/hybrid-gfx.log.1.gz /var/log/upstart/modemmanager.log /var/log/upstart/modemmanager.log.1.gz /var/log/upstart/module-init-tools.log /var/log/upstart/module-init-tools.log.1.gz /var/log/upstart/procps-static-network-up.log /var/log/upstart/procps-static-network-up.log.1.gz /var/log/upstart/procps-virtual-filesystems.log /var/log/upstart/procps-virtual-filesystems.log.1.gz /var/log/upstart/rsyslog.log /var/log/upstart/rsyslog.log.1.gz /var/log/upstart/ureadahead.log /var/log/upstart/ureadahead.log.1.gz /var/spool/anacron/cron.daily /var/spool/anacron/cron.monthly /var/spool/anacron/cron.weekly /var/spool/cron/atjobs /var/spool/cron/atspool /var/spool/cron/crontabs /var/spool/cups

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  • how to run conky from terminal?

    - by Esmail0022
    http://www.unixmen.com/configure-con...t-howto-conky/ in this link there are 11 steps to get conky , i did all of them but the terminal show this message: The program 'conky' can be found in the following packages: * conky-cli * conky-std Try: sudo apt-get install and i try type this but saw this message: ismail@ismail-ASUS:~$ sudo apt-get install conky [sudo] password for ismail: E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it? Can you help me?

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  • Is it possible to make the Numpad 5 button work as the Numpad Down button while Num Lock is on?

    - by Eddy
    I hope someone can help me out with this; I use a laptop and I like to play games a lot that are arrow key dependent. So after a while of using my laptop, I accidentally broke the Down Arrow key. So I decided to try and find out how to make the Numpad5 button work as the Numpad Down button while Numlock is on. I was trying to use AutoHotkey, but so far I've had no luck. Can anyone help me out with this? So far the scripts I used that didn't work were Numpad5::NumpadDown or Numpad5::Down. Am I doing something wrong here?

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