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  • What about race condition in multithreaded reading?

    - by themoob
    Hi, According to an article on IBM.com, "a race condition is a situation in which two or more threads or processes are reading or writing some shared data, and the final result depends on the timing of how the threads are scheduled. Race conditions can lead to unpredictable results and subtle program bugs." . Although the article concerns Java, I have in general been taught the same definition. As far as I know, simple operation of reading from RAM is composed of setting the states of specific input lines (address, read etc.) and reading the states of output lines. This is an operation that obviously cannot be executed simultaneously by two devices and has to be serialized. Now let's suppose we have a situation when a couple of threads access an object in memory. In theory, this access should be serialized in order to prevent race conditions. But e.g. the readers/writers algorithm assumes that an arbitrary number of readers can use the shared memory at the same time. So, the question is: does one have to implement an exclusive lock for read when using multithreading (in WinAPI e.g.)? If not, why? Where is this control implemented - OS, hardware? Best regards, Kuba

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  • Blackberry Asynchronous HTTP Requests - How?

    - by Kai
    The app I'm working on has a self contained database. The only time I need HTTP request is when the user first loads the app. I do this by calling a class that verifies whether or not a local DB exists and, if not, create one with the following request: HttpRequest data = new HttpRequest("http://www.somedomain.com/xml", "GET", this); data.start(); This xml returns a list of content, all of which have images that I want to fetch AFTER the original request is complete and stored. So something like this won't work: HttpRequest data = new HttpRequest("http://www.somedomain.com/xml", "GET", this); data.start(); HttpRequest images = new HttpRequest("http://www.somedomain.com/xmlImages", "GET", this); images.start(); Since it will not treat this like an asynchronous request. I have not found much information on adding callbacks to httpRequest, or any other method I could use to ensure operation 2 does not execute until operation 1 is complete. Any help would be appreciated. Thanks

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  • smartgwt operationId not working

    - by dubreakkk
    Hello all: How do operationIds work when calling a smartGWT fetch operation? I have the following simple Datasource, and below it the code that calls that datasource. However, the operationId is never acknowledged, and the first fetch operation is always executed... <DataSource ID="cartDS" serverType="sql" tableName="cart"> <fields> <field name="cart_id" type="number"/> <field name="price" type="double"/> <field name="total" type="double" customSQL="true"/> </fields> <dbName></dbName> <operationBindings> <operationBinding operationType="fetch"> <values fieldName="cart_id" value="$session.id"/> </operationBinding> <operationBinding operationType="fetch" operationId="total"> <values fieldName="cart_id" value="$session.id"/> <selectClause>sum(price) AS total </selectClause> </operationBinding> final DynamicForm totalForm = new DynamicForm(); totalForm.setDataSource(cartDS); totalForm.setFetchOperation("total"); totalForm.fetchData();

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  • Parsing multiple files at a time in Perl

    - by sfactor
    I have a large data set (around 90GB) to work with. There are data files (tab delimited) for each hour of each day and I need to perform operations in the entire data set. For example, get the share of OSes which are given in one of the columns. I tried merging all the files into one huge file and performing the simple count operation but it was simply too huge for the server memory. So, I guess I need to perform the operation each file at a time and then add up in the end. I am new to perl and am especially naive about the performance issues. How do I do such operations in a case like this. As an example two columns of the file are. ID OS 1 Windows 2 Linux 3 Windows 4 Windows Lets do something simple, counting the share of the OSes in the data set. So, each .txt file has millions of these lines and there are many such files. What would be the most efficient way to operate on the entire files.

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  • OptimisticLockException in inner transaction ruins outer transaction

    - by Pace
    I have the following code (OLE = OptimisticLockException)... public void outer() { try { middle() } catch (OLE) { updateEntities(); outer(); } } @Transactional public void middle() { try { inner() } catch (OLE) { updateEntities(); middle(); } @Transactional public void inner() { //Do DB operation } inner() is called by other non-transactional methods which is why both middle() and inner() are transactional. As you can see, I deal with OLEs by updating the entities and retrying the operation. The problem I'm having is that when I designed things this way I was assuming that the only time one could get an OLE was when a transaction closed. This is apparently not the case as the call to inner() is throwing an OLE even when the stack is outer()->middle()->inner(). Now, middle() is properly handling the OLE and the retry succeeds but when it comes time to close the transaction it has been marked rollbackOnly by Spring. When the middle() method call finally returns the closing aspect throws an exception because it can't commit a transaction marked rollbackOnly. I'm uncertain what to do here. I can't clear the rollbackOnly state. I don't want to force create a transaction on every call to inner because that kills my performance. Am I missing something or can anyone see a way I can structure this differently? EDIT: To clarify what I'm asking, let me explain my main question. Is it possible to catch and handle OLE if you are inside of an @Transactional method? FYI: The transaction manager is a JpaTransactionManager and the JPA provider is Hibernate.

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  • Any useful suggestions to figure out where memory is being free'd in a Win32 process?

    - by LeopardSkinPillBoxHat
    An application I am working with is exhibiting the following behaviour: During a particular high-memory operation, the memory usage of the process under Task Manager (Mem Usage stat) reaches a peak of approximately 2.5GB (Note: A registry key has been set to allow this, as usually there is a maximum of 2GB for a process under 32-bit Windows) After the operation is complete, the process size slowly starts decreasing at a rate of 1MB per second. I am trying to figure out the easiest way to quickly determine who is freeing this memory, and where it is being free'd. I am having trouble attaching a memory profiler to my code, and I don't particularly want to override the new/delete operators to track the allocations/deallocations (IOW, I want to do this without re-compiling my code). Can anyone offer any useful suggestions of how I could do this via the Visual Studio debugger? Update I should also mention that it's a multi-threaded application, so pausing the application and analysing the call stack through the debugger is not the most desirable option. I considered freezing different threads one at a time to see if the memory stops reducing, but I'm fairly certain this will cause the application to crash.

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  • Fast way to manually mod a number

    - by Nikolai Mushegian
    I need to be able to calculate (a^b) % c for very large values of a and b (which individually are pushing limit and which cause overflow errors when you try to calculate a^b). For small enough numbers, using the identity (a^b)%c = (a%c)^b%c works, but if c is too large this doesn't really help. I wrote a loop to do the mod operation manually, one a at a time: private static long no_Overflow_Mod(ulong num_base, ulong num_exponent, ulong mod) { long answer = 1; for (int x = 0; x < num_exponent; x++) { answer = (answer * num_base) % mod; } return answer; } but this takes a very long time. Is there any simple and fast way to do this operation without actually having to take a to the power of b AND without using time-consuming loops? If all else fails, I can make a bool array to represent a huge data type and figure out how to do this with bitwise operators, but there has to be a better way.

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  • Threshold of blurry image - part 2

    - by 1''
    How can I threshold this blurry image to make the digits as clear as possible? In a previous post, I tried adaptively thresholding a blurry image (left), which resulted in distorted and disconnected digits (right): Since then, I've tried using a morphological closing operation as described in this post to make the brightness of the image uniform: If I adaptively threshold this image, I don't get significantly better results. However, because the brightness is approximately uniform, I can now use an ordinary threshold: This is a lot better than before, but I have two problems: I had to manually choose the threshold value. Although the closing operation results in uniform brightness, the level of brightness might be different for other images. Different parts of the image would do better with slight variations in the threshold level. For instance, the 9 and 7 in the top left come out partially faded and should have a lower threshold, while some of the 6s have fused into 8s and should have a higher threshold. I thought that going back to an adaptive threshold, but with a very large block size (1/9th of the image) would solve both problems. Instead, I end up with a weird "halo effect" where the centre of the image is a lot brighter, but the edges are about the same as the normally-thresholded image: Edit: remi suggested morphologically opening the thresholded image at the top right of this post. This doesn't work too well. Using elliptical kernels, only a 3x3 is small enough to avoid obliterating the image entirely, and even then there are significant breakages in the digits:

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  • preload image with jquery

    - by robertdd
    ok, I spent 2 days trying to preloaded images but no succes! i have this function: jQuery.getlastimage = function(id) { $.getjs(); $.post('operations.php', {'operation':'getli', 'id':id,}, function(lastimg){ $("#upimages" + id).html('<a href="uploads/'+ lastimg +'?'+ (new Date()).getTime() +'"><img class="thumbs" id="' + id + '" alt="' + lastimg + '" src="uploads/' + lastimg +'?'+ (new Date()).getTime() + '" /></a>'); }); }; while the image loading i want to appear a gif or a text "Loading...". the function will get something like this: <div class="upimage"> <ul class="thumbs" id="upimagesQueue"> **<li id="#upimagesRIFDIB"> <a href="uploads/0001.jpg?1271800088379"> <img src="uploads/0001.jpg?1271800088379" alt="0001.jpg" id="RIFDIB" class="thumbs"> </a> </li>** <li> .... </li> </ul> </div> i tryed like this: ... $.post('operations.php', {'operation':'getli', 'id':id,}, function(lastimg){ $("#upimages" + id) .html('<a href="uploads/'+ lastimg +'?'+ (new Date()).getTime() +'"><img class="thumbs" id="' + id + '" alt="' + lastimg + '" src="uploads/' + lastimg +'?'+ (new Date()).getTime() + '" /></a>') .hide() .load(function() { $(this).show(); }); ... but all the <li> will hide and after is loading the image appear, i want the <li> to apear with a gif or a text in it and after the image is loaded the link and the image to apear! How to do this? Anyone have an idea? Thanks!

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  • Get 1 array from 2 arrays (using RestKit 0.20)

    - by Reez
    I'm using RestKit and was wondering how to combine two array's into one array. I already have the data being pulled in separately from API1 and API2, but I don't know how to combine them into 1 tableView. Each API is pulling in media, and I want the combined tableView to show the most recent media (like any standard timeline does these days). I will post any extra code or help as necessary, thanks so much! Below shows API1 + API2 being pulled in correctly, but not combined into the tableView. Only data from API1 shows in the tableView. ViewController.m @interface StackOverflowViewController () @property (strong, nonatomic) NSArray *hArray; @property (strong, nonatomic) NSArray *springs; @property (strong, nonatomic) RKObjectManager *eObjectManager; @property (strong, nonatomic) NSArray *iArray; @property (strong, nonatomic) NSArray *imagesArray; @property (strong, nonatomic) RKObjectManager *iObjectManager; // Wain @property (strong, nonatomic) NSMutableArray *tableDataList; // Laarme @property (nonatomic, strong) NSMutableArray *contentArray; @property (nonatomic, strong) NSDateFormatter *dateFormatter1; // Dan @property (nonatomic, strong) NSMutableArray *combinedModel; @end @implementation StackOverflowViewController @synthesize tableView = _tableView; @synthesize spring; @synthesize leaf; @synthesize theme; @synthesize hArray; @synthesize springs; @synthesize eObjectManager; @synthesize iArray; @synthesize imagesArray; @synthesize iObjectManager; // Wain @synthesize tableDataList; // Laarme @synthesize contentArray; @synthesize dateFormatter1; // Dan @synthesize combinedModel; - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view. [self configureRestKit]; [self loadMediaDan]; [self sortCombinedModel]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } - (void)configureRestKit { // API1 // initialize AFNetworking HTTPClient NSURL *baseURLE = [NSURL URLWithString:@"https://api.e.com"]; AFHTTPClient *clientE = [[AFHTTPClient alloc] initWithBaseURL:baseURLE]; // initialize RestKit RKObjectManager *eManager = [[RKObjectManager alloc] initWithHTTPClient:clientE]; self.eObjectManager = eManager; // setup object mappings RKObjectMapping *feedMapping = [RKObjectMapping mappingForClass:[Feed class]]; [feedMapping addAttributeMappingsFromArray:@[@"headline", @"premium", @"published", @"description"]]; RKObjectMapping *linksMapping = [RKObjectMapping mappingForClass:[Links class]]; RKObjectMapping *webMapping = [RKObjectMapping mappingForClass:[Web class]]; [webMapping addAttributeMappingsFromArray:@[@"href"]]; RKObjectMapping *mobileMapping = [RKObjectMapping mappingForClass:[Mobile class]]; [mobileMapping addAttributeMappingsFromArray:@[@"href"]]; RKObjectMapping *imagesMapping = [RKObjectMapping mappingForClass:[Images class]]; [imagesMapping addAttributeMappingsFromArray:@[@"height", @"width", @"url"]]; [feedMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"links" toKeyPath:@"links" withMapping:linksMapping]]; [feedMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"images" toKeyPath:@"images" withMapping:imagesMapping]]; [linksMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"web" toKeyPath:@"web" withMapping:webMapping]]; [linksMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"mobile" toKeyPath:@"mobile" withMapping:mobileMapping]]; // register mappings with the provider using a response descriptor RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:feedMapping method:RKRequestMethodGET pathPattern:nil keyPath:@"feed" statusCodes:[NSIndexSet indexSetWithIndex:200]]; [self.eObjectManager addResponseDescriptor:responseDescriptor]; // API2 // initialize AFNetworking HTTPClient NSURL *baseURLI = [NSURL URLWithString:@"https://api.i.com"]; AFHTTPClient *clientI = [[AFHTTPClient alloc] initWithBaseURL:baseURLI]; // initialize RestKit RKObjectManager *iManager = [[RKObjectManager alloc] initWithHTTPClient:clientI]; self.iObjectManager = iManager; // setup object mappings RKObjectMapping *dataMapping = [RKObjectMapping mappingForClass:[Data class]]; [dataMapping addAttributeMappingsFromArray:@[@"link", @"created_time"]]; RKObjectMapping *imagesMapping = [RKObjectMapping mappingForClass:[ImagesI class]]; [IMapping addAttributeMappingsFromArray:@[@""]]; RKObjectMapping *standardResolutionMapping = [RKObjectMapping mappingForClass:[StandardResolution class]]; [standardResolutionMapping addAttributeMappingsFromArray:@[@"url", @"width", @"height"]]; RKObjectMapping *captionMapping = [RKObjectMapping mappingForClass:[Caption class]]; [captionMapping addAttributeMappingsFromArray:@[@"text", @"created_time"]]; RKObjectMapping *userMapping = [RKObjectMapping mappingForClass:[User class]]; [userMapping addAttributeMappingsFromArray:@[@"username"]]; [dataMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"images" toKeyPath:@"images" withMapping:imagesMapping]]; [imagesMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"standard_resolution" toKeyPath:@"standard_resolution" withMapping:standardResolutionMapping]]; [dataMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"caption" toKeyPath:@"caption" withMapping:captionMapping]]; [dataMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"user" toKeyPath:@"user" withMapping:userMapping]]; // register mappings with the provider using a response descriptor RKResponseDescriptor *responseDescriptor2 = [RKResponseDescriptor responseDescriptorWithMapping:dataMapping method:RKRequestMethodGET pathPattern:nil keyPath:@"data" statusCodes:[NSIndexSet indexSetWithIndex:200]]; [self.iObjectManager addResponseDescriptor:responseDescriptor2]; } - (void)loadMedia { // Laarme contentArray = [[NSMutableArray alloc] init]; [self sortByDates]; // API1 NSString *apikey = @kCLIENTKEY; NSDictionary *queryParams = @{@"apikey" : apikey,}; [self.eObjectManager getObjectsAtPath:[NSString stringWithFormat:@"v1/n/?limit=4&leafs=%@&themes=%@", leafAbbreviation, themeID] // Changed limit to 4 for the time being parameters:queryParams success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) { hArray = mappingResult.array; [self.tableView reloadData]; } failure:^(RKObjectRequestOperation *operation, NSError *error) { NSLog(@"No?: %@", error); }]; // API2 [self.iObjectManager getObjectsAtPath:[NSString stringWithFormat:@"v1/u/2/m/recent/?client_id=e999"] parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) { iArray = mappingResult.array; [self.tableView reloadData]; } failure:^(RKObjectRequestOperation *operation, NSError *error) { NSLog(@"No: %@", error); }]; } // Laarme - (void)sortByDates { NSDateFormatter *dateFormatter2 = [[NSDateFormatter alloc] init]; //Do the dateFormatter settings, you may have to use 2 NSDateFormatters if the format is different for Data & Feed //The initialization of the dateFormatter is done before the block, because its alloc/init take some time, and you may have to declare it with "__block" //Since in your edit you do that and it seems it's the same format, just do @property (nonatomic, strong) NSDateFormatter dateFormatter; NSArray *sortedArray = [contentArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) { // Added Curly Braces around if else statements and used feedObject NSDate *aDate, *bDate; Feed *feedObject = (Feed *)a; Data *dataObject = (Data *)b; if ([a isKindOfClass:[Feed class]]) { //Feed *feedObject = (Feed *)a; aDate = [dateFormatter1 dateFromString:feedObject.published];} else { //if ([a isKindOfClass:[Data class]]) aDate = [dateFormatter2 dateFromString:dataObject.created_time];} if ([b isKindOfClass:[Feed class]]) { bDate = [dateFormatter1 dateFromString:feedObject.published];} else {//if ([b isKindOfClass:[Data class]]) bDate = [dateFormatter2 dateFromString:dataObject.created_time];} return [aDate compare:bDate]; }]; } #pragma mark - Table View - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // API1 //return hArray.count; // API2 //return iArray.count; // API1 + API2 return hArray.count + iArray.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell; if(indexPath.row < hArray.count) { // Date Change NSDateFormatter *df = [[NSDateFormatter alloc] init]; [df setDateFormat:@"MMMM d, yyyy h:mma"]; // API 1 TableViewCell *api1Cell = [tableView dequeueReusableCellWithIdentifier:@"YourAPI1Cell"]; // Do everything you need to do with the api1Cell // Use the index in 'indexPath.row' to get the object from you array // API1 Feed *feedLocal = [hArray objectAtIndex:indexPath.row]; // API1 NSString *dateString = [self timeSincePublished:feedLocal.published]; NSString *headlineText = [NSString stringWithFormat:@"%@", feedLocal.headline]; NSString *descriptionText = [NSString stringWithFormat:@"%@", feedLocal.description]; NSString *premiumText = [NSString stringWithFormat:@"%@", feedLocal.premium]; api1Cell.labelHeadline.text = [NSString stringWithFormat:@"%@", headlineText]; api1Cell.labelPublished.text = dateString; api1Cell.labelDescription.text = descriptionText; // SDWebImage API1 if ([feedLocal.images count] == 0) { // Not sure anything needed here } else { Images *imageLocal = [feedLocal.images objectAtIndex:0]; NSString *imageURL = [NSString stringWithFormat:@"%@", imageLocal.url]; NSString *imageWith = [NSString stringWithFormat:@"%@", imageLocal.width]; NSString *imageHeight = [NSString stringWithFormat:@"%@", imageLocal.height]; __weak UITableViewCell *wcell = cell; [cell.imageView setImageWithURL:[NSURL URLWithString:imageURL] placeholderImage:[UIImage imageNamed:@"X"] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) { // Something }]; } cell = api1Cell; } else { // Date Change NSDateFormatter *df = [[NSDateFormatter alloc] init]; [df setDateFormat:@"MMMM d, yyyy h:mma"]; // API 2 MRWebListTableViewCellTwo *api2Cell = [tableView dequeueReusableCellWithIdentifier:@"YourAPI2Cell"]; // Do everything you need to do with the api2Cell // Remember to use 'indexPath.row - hArray.count' as the index for getting an object for your second array // API 2 Data *dataLocal = [iArray objectAtIndex:indexPath.row - hArray.count]; // API 2 NSString *dateStringI = [self timeSincePublished:dataLocal.created_time]; NSString *captionTextI = [NSString stringWithFormat:@"%@", dataLocal.caption.text]; NSString *usernameI = [NSString stringWithFormat:@"%@", dataLocal.user.username]; api2Cell.labelHeadline.text = usernameI; api2Cell.labelDescription.text = captionTextI; api2Cell.labelPublished.text = dateStringI; // SDWebImage API 2 if ([dataLocal.images count] == 0) { NSLog(@"Images Count: %lu", (unsigned long)dataLocal.images.count); // Not sure anything needed here } else { ImagesI *imageLocalI = [dataLocal.images objectAtIndex:0]; StandardResolutionI *standardResolutionLocal = [imageLocalI.standard_resolution objectAtIndex:0]; NSString *imageURLI = [NSString stringWithFormat:@"%@", standardResolutionLocal.url]; NSString *imageWithI = [NSString stringWithFormat:@"%@", standardResolutionLocal.width]; NSString *imageHeightI = [NSString stringWithFormat:@"%@", standardResolutionLocal.height]; // 11.2 __weak UITableViewCell *wcell = cell; [cell.imageView setImageWithURL:[NSURL URLWithString:imageURLI] placeholderImage:[UIImage imageNamed:@"X"] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) { // Something }]; } cell = api2Cell; } return cell; } Feed.h @property (nonatomic, strong) Links *links; @property (nonatomic, strong) NSString *headline; @property (nonatomic, strong) NSString *source; @property (nonatomic, strong) NSDate *published; @property (nonatomic, strong) NSString *description; @property (nonatomic, strong) NSString *premium; @property (nonatomic, strong) NSArray *images; Data.h @property (nonatomic, strong) NSString *link; @property (nonatomic, strong) NSDate *created_time; @property (nonatomic, strong) UserI *user; @property (nonatomic, strong) NSArray *images; @property (nonatomic, strong) CaptionI *caption;

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  • Atomic operations on several transactionless external systems

    - by simendsjo
    Say you have an application connecting 3 different external systems. You need to update something in all 3. In case of a failure, you need to roll back the operations. This is not a hard thing to implement, but say operation 3 fails, and when rolling back, the rollback for operation 1 fails! Now the first external system is in an invalid state... I'm thinking a possible solution is to shut down the application and forcing a manual fix of the external system, but then again... It might already have used this information (and perhaps that's why it failed), or we might not have sufficient access. Or it might not even be a good way to rollback the action! Are there some good ways of handling such cases? EDIT: Some application details.. It's a multi user web application. Most of the work is done with scheduled jobs (through Quartz.Net), so most operations is run in it's own thread. Some user actions should trigger jobs that update several systems though. The external systems are somewhat unstable. I Was thinking of changing the application to use the Command and Unit Of Work pattern

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  • java.lang.IllegalArgumentException: View not attached to window manager

    - by alex2k8
    I have an activity that starts AsyncTask and shows progress dialog for the duration of operation. The activity is declared NOT be recreated by rotation or keyboard slide. <activity android:name=".MyActivity" android:label="@string/app_name" android:configChanges="keyboardHidden|orientation" > <intent-filter> </intent-filter> </activity> Once task completed, I dissmiss dialog, but on some phones (framework: 1.5, 1.6) such error is thrown: java.lang.IllegalArgumentException: View not attached to window manager at android.view.WindowManagerImpl.findViewLocked(WindowManagerImpl.java:356) at android.view.WindowManagerImpl.removeView(WindowManagerImpl.java:201) at android.view.Window$LocalWindowManager.removeView(Window.java:400) at android.app.Dialog.dismissDialog(Dialog.java:268) at android.app.Dialog.access$000(Dialog.java:69) at android.app.Dialog$1.run(Dialog.java:103) at android.app.Dialog.dismiss(Dialog.java:252) at xxx.onPostExecute(xxx$1.java:xxx) My code is: final Dialog dialog = new AlertDialog.Builder(context) .setTitle("Processing...") .setCancelable(true) .create(); final AsyncTask<MyParams, Object, MyResult> task = new AsyncTask<MyParams, Object, MyResult>() { @Override protected MyResult doInBackground(MyParams... params) { // Long operation goes here } @Override protected void onPostExecute(MyResult result) { dialog.dismiss(); onCompletion(result); } }; task.execute(...); dialog.setOnCancelListener(new OnCancelListener() { @Override public void onCancel(DialogInterface arg0) { task.cancel(false); } }); dialog.show(); From what I have read (http://bend-ing.blogspot.com/2008/11/properly-handle-progress-dialog-in.html) and seen in Android sources, it looks like the only possible situation to get that exception is when activity was destroyed. But as I have mentioned, I forbid activity recreation for basic events. So any suggestions are very appreciated.

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  • problem with implementing a simple work queue

    - by John Deerikio
    Hi all, I am having troubles with implementing a simple work queue. Doing some analysis, I am facing a subtle problem. The work queue is backed by a regular linked list. The code looks like this (simplified): 0. while (true) 1. while (enabled == true) 2. acquire lock on the list and get the next action to be executed (blocking operation) (store it in a local variable) 3. execute the action (outside the lock on the list on previous line) 4. get lock on this work queue 5. wait until this work queue has been notified (triggered when setEnabled(true) has been callled) The setEnabled(e) operation looks like this (simplified): enabled = e if (enabled == true) acquire lock on this work queue and do notify() Although this works, there is a condition in which a deadlock occurs. It happens in the following rare situation: while an action is being executed, setEnabled(false) is called just before step (4) is entered, setEnabled(true) is called now step (5) keeps waiting forever, because this work queue has already been notified How do I solve this? I have been looking at this for some time, but I cannot come up with a solution. Please note I am fairly new to thread synchronization. Thanks a lot.

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  • Multithreaded linked list traversal

    - by Rob Bryce
    Given a (doubly) linked list of objects (C++), I have an operation that I would like multithread, to perform on each object. The cost of the operation is not uniform for each object. The linked list is the preferred storage for this set of objects for a variety of reasons. The 1st element in each object is the pointer to the next object; the 2nd element is the previous object in the list. I have solved the problem by building an array of nodes, and applying OpenMP. This gave decent performance. I then switched to my own threading routines (based off Windows primitives) and by using InterlockedIncrement() (acting on the index into the array), I can achieve higher overall CPU utilization and faster through-put. Essentially, the threads work by "leap-frog'ing" along the elements. My next approach to optimization is to try to eliminate creating/reusing the array of elements in my linked list. However, I'd like to continue with this "leap-frog" approach and somehow use some nonexistent routine that could be called "InterlockedCompareDereference" - to atomically compare against NULL (end of list) and conditionally dereference & store, returning the dereferenced value. I don't think InterlockedCompareExchangePointer() will work since I cannot atomically dereference the pointer and call this Interlocked() method. I've done some reading and others are suggesting critical sections or spin-locks. Critical sections seem heavy-weight here. I'm tempted to try spin-locks but I thought I'd first pose the question here and ask what other people are doing. I'm not convinced that the InterlockedCompareExchangePointer() method itself could be used like a spin-lock. Then one also has to consider acquire/release/fence semantics... Ideas? Thanks!

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  • "Too many indexes on table" error when creating relationships in Microsoft Access 2010.

    - by avianattackarmada
    I have tblUsers which has a primary key of UserID. UserID is used as a foreign key in many tables. Within a table, it is used as a foreign key for multiple fields (e.g. ObserverID, RecorderID, CheckerID). I have successfully added relationships (with in the the MS Access 'Relationship' view), where I have table aliases to do the multiple relationships per table: *tblUser.UserID - 1 to many - tblResight.ObserverID *tblUser_1.UserID - 1 to many - tblResight.CheckerID After creating about 25 relationships with enforcement of referential integrity, when I try to add an additional one, I get the following error: "The operation failed. There are too many indexes on table 'tblUsers.' Delete some of the indexes on the table and try the operation again." I ran the code I found here and it returned that I have 6 indexes on tblUsers. I know there is a limit of 32 indexes per table. Am I using the relationship GUI wrong? Does access create an index for the enforcement of referential integrity any time I create a relationship (especially indexes that wouldn't turn up when I ran the script)? I'm kind of baffled, any help would be appreciated.

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  • Problems with Threading in Python 2.5, KeyError: 51, Help debugging?

    - by vignesh-k
    I have a python script which runs a particular script large number of times (for monte carlo purpose) and the way I have scripted it is that, I queue up the script the desired number of times it should be run then I spawn threads and each thread runs the script once and again when its done. Once the script in a particular thread is finished, the output is written to a file by accessing a lock (so my guess was that only one thread accesses the lock at a given time). Once the lock is released by one thread, the next thread accesses it and adds its output to the previously written file and rewrites it. I am not facing a problem when the number of iterations is small like 10 or 20 but when its large like 50 or 150, python returns a KeyError: 51 telling me element doesn't exist and the error it points out to is within the lock which puzzles me since only one thread should access the lock at once and I do not expect an error. This is the class I use: class errorclass(threading.Thread): def __init__(self, queue): self.__queue=queue threading.Thread.__init__(self) def run(self): while 1: item = self.__queue.get() if item is None: break result = myfunction() lock = threading.RLock() lock.acquire() ADD entries from current thread to entries in file and REWRITE FILE lock.release() queue = Queue.Queue() for i in range(threads): errorclass(queue).start() for i in range(desired iterations): queue.put(i) for i in range(threads): queue.put(None) Python returns with KeyError: 51 for large number of desired iterations during the adding/write file operation after lock access, I am wondering if this is the correct way to use the lock since every thread has a lock operation rather than every thread accessing a shared lock? What would be the way to rectify this?

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  • php array split

    - by Rahul Mehta
    I am passing the space separated value to in input and split this in operation and make an array. givecard 442 ashutosh2 Y But i want to pass the message in this string and want to split as complete message in operation or output. givecard 442 ashutosh2 Y hi how are you if i split this line than i get the result is Array ( [0] => givecard [1] => 442 [2] => ashutosh2 [3] => Y [4] => hi [5] => how [6] => are [7] => you ) But i want like this Array ( [0] => givecard [1] => 442 [2] => ashutosh2 [3] => Y [4] => hi how are you ) as here hi how are you i want to extract as complete one message in a variable . How can i achieve this

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  • NHibernate: What are child sessions and why and when should I use them?

    - by stefando
    In the comments for the ayende's blog about the auditing in NHibernate there is a mention about the need to use a child session:session.GetSession(EntityMode.Poco). As far as I understand it, it has something to do with the order of the SQL operation which session.Flush will emit. (For example: If I wanted to perform some delete operation in the pre-insert event but the session was already done with deleting operations, I would need some way to inject them in.) However I did not find documentation about this feature and behavior. Questions: Is my understanding of child sessions correct? How and in which scenarios should I use them? Are they documented somewhere? Could they be used for session "scoping"? (For example: I open the master session which will hold some data and then I create 2 child-sessions from the master one. I'd expect that the two child-scopes will be separated but the will share objects from the master session cache. Is this the case?) Are they first class citizens in NHibernate or are they just hack to support some edge-case scenarios? Thanks in advance for any info.

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  • Matlab GUI: How to Save the Results of Functions (states of application)

    - by niko
    Hi, I would like to create an animation which enables the user to go backward and forward through the steps of simulation. An animation has to simulate the iterative process of channel decoding (a receiver receives a block of bits, performs an operation and then checks if the block corresponds to parity rules. If the block doesn't correspond the operation is performed again and the process finally ends when the code corresponds to a given rules). I have written the functions which perform the decoding process and return a m x n x i matrix where m x n is the block of data and i is the iteration index. So if it takes 3 iterations to decode the data the function returns a m x n x 3 matrix with each step is stired. In the GUI (.fig file) I put a "decode" button which runs the method for decoding and there are buttons "back" and "forward" which have to enable the user to switch between the data of recorded steps. I have stored the "decodedData" matrix and currentStep value as a global variable so by clicking "forward" and "next" buttons the indices have to change and point to appropriate step states. When I tried to debug the application the method returned the decoded data but when I tried to click "back" and "next" the decoded data appeared not to be declared. Does anyone know how is it possible to access (or store) the results of the functions in order to enable the described logic which I want to implement in Matlab GUI?

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  • Are background threads a bad idea? Why?

    - by Matt Grande
    So I've been told what I'm doing here is wrong, but I'm not sure why. I have a webpage that imports a CSV file with document numbers to perform an expensive operation on. I've put the expensive operation into a background thread to prevent it from blocking the application. Here's what I have in a nutshell. protected void ButtonUpload_Click(object sender, EventArgs e) { if (FileUploadCSV.HasFile) { string fileText; using (var sr = new StreamReader(FileUploadCSV.FileContent)) { fileText = sr.ReadToEnd(); } var documentNumbers = fileText.Split(new[] {',', '\n', '\r'}, StringSplitOptions.RemoveEmptyEntries); ThreadStart threadStart = () => AnotherClass.ExpensiveOperation(documentNumbers); var thread = new Thread(threadStart) {IsBackground = true}; thread.Start(); } } (obviously with some error checking & messages for users thrown in) So my three-fold question is: a) Is this a bad idea? b) Why is this a bad idea? c) What would you do instead?

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  • Is it legal to take sealed .NET framework class source and extend it?

    - by Giedrius
    To be short, I'm giving very specific example, but I'm interested in general situation. There is a FtpWebRequest class in .NET framework and it is missing some of new FTP operations, like MFCT. It is ok in a sense that this operation is still in draft mode, but it is not ok in a sense, that FtpWebRequest is sealed and there's no other way (at least I don't see it) to extend it with this new operation. Easiest way to do it would be take FtpWebRequest class source from .NET reference sources and extend it, in such way will be kept all the consistence in naming, implementation, etc. Question is how much legal it is? I won't sell this class as a product, I can publish my changes on web - nothing to hide here. If it is not legal, can I take this class source from mono and include in native .net project? Did you had similar case and how you solved it? Update: as long as extension method is offered, I'm pasting source from .NET framework which should show that extension methods are not the solution. So there's a property Method, where you can pass FTP command: public override string Method { get { return m_MethodInfo.Method; } set { if (String.IsNullOrEmpty(value)) { throw new ArgumentException(SR.GetString(SR.net_ftp_invalid_method_name), "value"); } if (InUse) { throw new InvalidOperationException(SR.GetString(SR.net_reqsubmitted)); } try { m_MethodInfo = FtpMethodInfo.GetMethodInfo(value); } catch (ArgumentException) { throw new ArgumentException(SR.GetString(SR.net_ftp_unsupported_method), "value"); } } } As you can see there FtpMethodInfo.GetMethodInfo(value) call in setter, which basically validates value against internal enum static array. Update 2: Checked mono implementation and it is not exact replica of native code + it does not implement some of the things.

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  • Creating simple calculator with bison & flex in C++ (not C)

    - by ak91
    Hey, I would like to create simple C++ calculator using bison and flex. Please note I'm new to the creating parsers. I already found few examples in bison/flex but they were all written in C. My goal is to create C++ code, where classes would contain nodes of values, operations, funcs - to create AST (evaluation would be done just after creating whole AST - starting from the root and going forward). For example: my_var = sqrt(9 ** 2 - 32) + 4 - 20 / 5 my_var * 3 Would be parsed as: = / \ my_var + / \ sqrt - | / \ - 4 / / \ / \ ** 32 20 5 / \ 9 2 and the second AST would look like: * / \ my_var 3 Then following pseudocode reflects AST: ast_root = create_node('=', new_variable("my_var"), exp) where exp is: exp = create_node(OPERATOR, val1, val2) but NOT like this: $$ = $1 OPERATOR $3 because this way I directly get value of operation instead of creation the Node. I believe the Node should contain type (of operation), val1 (Node), val2 (Node). In some cases val2 would be NULL, like above mentioned sqrt which takes in the end one argument. Right? It will be nice if you can propose me C++ skeleton (without evaluation) for above described problem (including *.y file creating AST) to help me understand the way of creating/holding Nodes in AST. Code can be snipped, just to let me get the idea. I'll also be grateful if you point me to an existing (possibly simple) example if you know any. Thank you all for your time and assistance!

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  • PHP Form multiple buttons

    - by Ken
    I have a form with 2 buttons, that depending on which is selected will either be deleted or edited from the database. Those are each individual pages using SQL statements (questionedit and questiondelete). However, when i press a button, nothing happens...Any Ideas Here is my javascript <script type="text/javascript"> function SelectedButton(button) { if(button == 'edit') { document.testedit_questionform.action ="testedit_questionedit.php"; } else if(button == 'delete') { document.testedit_questionform.action ="testedit_questiondelete.php"; } document.forms[].testedit_questionform.submit(); } </script> Here is my form (being echoed from a loop) <form name=\"testedit_questionform\" action=\"SelectedButton\" method=\"POST\"> <span class=\"grid_11 prefix_1\" id=\"\" > Question:<input type=\"text\" name=\"QuestionText\" style=\"width:588px; margin-left:10px;\" value=\"$row[0]\"/> <input type=\"button\" value=\"Edit\" name=\"Operation\"onclick=\"submitForm(\'edit\')\" /> <input type=\"button\" value=\"Delete\" name=\"Operation\"onclick=\"submitForm(\'delete\')\" /> <input type=\"hidden\" name=\"QId\" value=\"$row[3]\" /><br />"); </form>

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  • Pointers into elements in a container

    - by Pillsy
    Say I have an object: struct Foo { int bar_; Foo(int bar) bar_(bar) {} }; and I have an STL container that contains Foos, perhaps a vector, and I take // Elsewhere... vector<Foo> vec; vec.push_back(Foo(4)); int *p = &(vec[0].bar_) This is a terrible idea, right? The reason is that vector is going to be storing its elements in a dynamically allocated array somewhere, and eventually, if you add enough elements, it will have to allocate another array, copy over all the elements of the original array, and delete the old array. After that happens, p points to garbage. This is why many operations on a vector will invalidate iterators. It seems like it would be reasonable to assume that an operation that would invalidate iterators from a container will also invalidate pointers to data members of container elements, and that if an operation doesn't invalidate iterators, those pointers will still be safe. However, many reasonable assumptions are false. Is this one of them?

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  • why i change the alpha value of UIImageView but no effect?

    - by chancy
    I am working on a reader app. when you read one magazine, it will display first five pages and download the rest pages one by one. there is a scrollview to view the thumbnail image of pages. At the beginning, if the page needs downloading, the corresponding thumbnail view's alpha value is set to 0.5. when the page is downloaded, i will update the thumbnail view's value to 1.0. I use one operation to download the page, and when one is downloaded i use delegate to set thumbnail view's alpha. But when i update thumbnail view's alpha value, it still the same as the beginning. it seems the alpha has no effect. I wonder is there anything wrong with my code? some snippets are as follows: In the PageViewController.m - (void)downloadPages { DownloadOperation *op = [[DownloadOperation alloc] initWithMagazine:magazine]; op.delegate = self; [[(AppDelegate *)[[UIApplication sharedApplication] delegate] sharedOperationQueue] addOperation:op]; } - (void)downloadOperation:(DownloadOperation *)operation finishedAtIndex:(NSUInteger)index { if (thumbScrollView){ [thumbScrollView viewWithTag:THUMBVIEW_OFFSET+index].alpha = 1.0; } } In DownloadOperation.m - (void)main { // ... NSUInteger index = 0; for (Page *page in mMagazine.pages) { if (/*page doesn't exist*/){ // download the page; if ([delegate respondsToSelector:@selector(downloadOperation:finishedAtIndex:)]) { [delegate downloadOperation:self finishedAtIndex:index]; } } index++; } }

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