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  • The right approach to loading dynamic content into a UITableView in iOS

    - by OS.
    ok, I've read tons of bits and pieces on the subject of loading dynamic content (from the web) into a UITableView and the problem with calculating cell height upfront. I've tried different simple implementations but the problem persists... Assuming I need to read a JSON file from the web, parse it into 'item' objects, each with variable size image and various text labels, here is what I believe would be the right approach to avoid long hang time of the app while everything is loading: on app load read JSON file and parse into items array provide only small part of the items array to the tableview (about 10 items) - since I need to load the images associated with each item to calculate cell height - I don't want the view to go through the whole items list and load all images - this hangs the app until every image is loaded display the tableview with the available cells (assuming I load a few 'spare' ones, user can even scroll to more items) in the background using Grand Central Dispatch download images for all/some of the remaining items and then reload the tableview with the new data (repeat step 4 if item list is very long) Step 2 above is necessary since I have no way to calculate the cell height without loading the images first, and since tableview first calculates height of all cells it may take a very long time to download all images for all items. Would you say this is the right approach? am I missing something?

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  • Modifying an ObservableCollection using move() ?

    - by user1202434
    I have a question relating to modifying the individual items in an ObservableCollection that is bound to a ListBox in the UI. The user in the UI can multiselect items and then drop them at a particular index to re-order them. So, if I have items {0,1,2,3,4,5,6,7,8,9} the user can choose items 2, 5, 7 (in that order) and choose to drop them at index 3, so that the collection now becomes, {0,1,3, 2, 5, 7, 4, 8,9} The way I have it working now, is like this inside of ondrop() method on my control, I do something like: foreach (Item item in draggedItems) { int oldIndex = collection.IndexOf(item.DataContext as MyItemType); int newIndex = toDropIndex; if (newIndex == collection.Count) { newIndex--; } if (oldIndex != newIndex) { collection.Move(oldIndex, newIndex); } } But the problem is, if I drop the items before the index where i start dragging my first item, the order becomes reversed...so the collection becomes, {0,1,3, 7, 5, 2, 4, 8,9} It works fine if I drop after index 3, but if i drop it before 3 then the order becomes reversed. Now, I can do a simple remove and then insert all items at the index I want to, but "move" for me has the advantage of keeping the selection in the ui (remove basically de-selects the items in the list..)....so I will need to make use of the move method, what is wrong with my method above and how to fix it? Thanks!

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  • Is there a performance difference between Windows 7 on SSD installed from scratch versus it using a recent ghost/clone drive image from a harddisk?

    - by therobyouknow
    I'm planning to upgrade a notebook PC to a Solid-State Flash Drive (SSD) soon. I want to use the notebook before that and am considering installing Windows 7 on the hard disk (spinning variety, 5400rpm) before I get the SSD. To save time I am wondering if I can ghost/clone the installation of Windows 7 from the hard drive and put on the SSD. Would the performance of this clone from the harddisk onto the SSD be different from starting again and reinstalling Windows 7 from scratch on the SSD? (Windows 7 32bit professional)

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  • Android - HorizontalScrollView within ScrollView Touch Handling

    - by Joel
    Hi, I have a ScrollView that surrounds my entire layout so that the entire screen is scrollable. The first element I have in this ScrollView is a HorizontalScrollView block that has features that can be scrolled through horizontally. I've added an ontouchlistener to the horizontalscrollview to handle touch events and force the view to "snap" to the closest image on the ACTION_UP event. So the effect I'm going for is like the stock android homescreen where you can scroll from one to the other and it snaps to one screen when you lift your finger. This all works great except for one problem: I need to swipe left to right almost perfectly horizontally for an ACTION_UP to ever register. If I swipe vertically in the very least (which I think many people tend to do on their phones when swiping side to side), I will receive an ACTION_CANCEL instead of an ACTION_UP. My theory is that this is because the horizontalscrollview is within a scrollview, and the scrollview is hijacking the vertical touch to allow for vertical scrolling. How can I disable the touch events for the scrollview from just within my horizontal scrollview, but still allow for normal vertical scrolling elsewhere in the scrollview? Here's a sample of my code: public class HomeFeatureLayout extends HorizontalScrollView { private ArrayList<ListItem> items = null; private GestureDetector gestureDetector; View.OnTouchListener gestureListener; private static final int SWIPE_MIN_DISTANCE = 5; private static final int SWIPE_THRESHOLD_VELOCITY = 300; private int activeFeature = 0; public HomeFeatureLayout(Context context, ArrayList<ListItem> items){ super(context); setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT)); setFadingEdgeLength(0); this.setHorizontalScrollBarEnabled(false); this.setVerticalScrollBarEnabled(false); LinearLayout internalWrapper = new LinearLayout(context); internalWrapper.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT)); internalWrapper.setOrientation(LinearLayout.HORIZONTAL); addView(internalWrapper); this.items = items; for(int i = 0; i< items.size();i++){ LinearLayout featureLayout = (LinearLayout) View.inflate(this.getContext(),R.layout.homefeature,null); TextView header = (TextView) featureLayout.findViewById(R.id.featureheader); ImageView image = (ImageView) featureLayout.findViewById(R.id.featureimage); TextView title = (TextView) featureLayout.findViewById(R.id.featuretitle); title.setTag(items.get(i).GetLinkURL()); TextView date = (TextView) featureLayout.findViewById(R.id.featuredate); header.setText("FEATURED"); Image cachedImage = new Image(this.getContext(), items.get(i).GetImageURL()); image.setImageDrawable(cachedImage.getImage()); title.setText(items.get(i).GetTitle()); date.setText(items.get(i).GetDate()); internalWrapper.addView(featureLayout); } gestureDetector = new GestureDetector(new MyGestureDetector()); setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { if (gestureDetector.onTouchEvent(event)) { return true; } else if(event.getAction() == MotionEvent.ACTION_UP || event.getAction() == MotionEvent.ACTION_CANCEL ){ int scrollX = getScrollX(); int featureWidth = getMeasuredWidth(); activeFeature = ((scrollX + (featureWidth/2))/featureWidth); int scrollTo = activeFeature*featureWidth; smoothScrollTo(scrollTo, 0); return true; } else{ return false; } } }); } class MyGestureDetector extends SimpleOnGestureListener { @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { try { //right to left if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { activeFeature = (activeFeature < (items.size() - 1))? activeFeature + 1:items.size() -1; smoothScrollTo(activeFeature*getMeasuredWidth(), 0); return true; } //left to right else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { activeFeature = (activeFeature > 0)? activeFeature - 1:0; smoothScrollTo(activeFeature*getMeasuredWidth(), 0); return true; } } catch (Exception e) { // nothing } return false; } } }

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  • SL3/SL4 - Ado.Net Data Services Error during new DataServiceCollection<T>(queryResponse)

    - by Soulhuntre
    Hey all, I have two functions in a SL project (VS2010) that do almost exactly the same thing, yet one throws an error and the other does not. It seems to be related to the projections, but I am unsure about the best way to resolve. The function that works is... public void LoadAllChunksExpandAll(DataHelperReturnHandler handler, string orderby) { DataServiceCollection<CmsChunk> data = null; DataServiceQuery<CmsChunk> theQuery = _dataservice .CmsChunks .Expand("CmsItemState") .AddQueryOption("$orderby", orderby); theQuery.BeginExecute( delegate(IAsyncResult asyncResult) { _callback_dispatcher.BeginInvoke( () => { try { DataServiceQuery<CmsChunk> query = asyncResult.AsyncState as DataServiceQuery<CmsChunk>; if (query != null) { //create a tracked DataServiceCollection from the result of the asynchronous query. QueryOperationResponse<CmsChunk> queryResponse = query.EndExecute(asyncResult) as QueryOperationResponse<CmsChunk>; data = new DataServiceCollection<CmsChunk>(queryResponse); handler(data); } } catch { handler(data); } } ); }, theQuery ); } This compiles and runs as expected. A very, very similar function (shown below) fails... public void LoadAllPagesExpandAll(DataHelperReturnHandler handler, string orderby) { DataServiceCollection<CmsPage> data = null; DataServiceQuery<CmsPage> theQuery = _dataservice .CmsPages .Expand("CmsChildPages") .Expand("CmsParentPage") .Expand("CmsItemState") .AddQueryOption("$orderby", orderby); theQuery.BeginExecute( delegate(IAsyncResult asyncResult) { _callback_dispatcher.BeginInvoke( () => { try { DataServiceQuery<CmsPage> query = asyncResult.AsyncState as DataServiceQuery<CmsPage>; if (query != null) { //create a tracked DataServiceCollection from the result of the asynchronous query. QueryOperationResponse<CmsPage> queryResponse = query.EndExecute(asyncResult) as QueryOperationResponse<CmsPage>; data = new DataServiceCollection<CmsPage>(queryResponse); handler(data); } } catch { handler(data); } } ); }, theQuery ); } Clearly the issue is the Expand projections that involve a self referencing relationship (pages can contain other pages). This is under SL4 or SL3 using ADONETDataServices SL3 Update CTP3. I am open to any work around or pointers to goo information, a Google search for the error results in two hits, neither particularly helpful that I can decipher. The short error is "An item could not be added to the collection. When items in a DataServiceCollection are tracked by the DataServiceContext, new items cannot be added before items have been loaded into the collection." The full error is... System.Reflection.TargetInvocationException was caught Message=Exception has been thrown by the target of an invocation. StackTrace: at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters) at System.Data.Services.Client.ClientType.ClientProperty.SetValue(Object instance, Object value, String propertyName, Boolean allowAdd) at System.Data.Services.Client.AtomMaterializer.ApplyItemsToCollection(AtomEntry entry, ClientProperty property, IEnumerable items, Uri nextLink, ProjectionPlan continuationPlan) at System.Data.Services.Client.AtomMaterializer.ApplyFeedToCollection(AtomEntry entry, ClientProperty property, AtomFeed feed, Boolean includeLinks) at System.Data.Services.Client.AtomMaterializer.MaterializeResolvedEntry(AtomEntry entry, Boolean includeLinks) at System.Data.Services.Client.AtomMaterializer.Materialize(AtomEntry entry, Type expectedEntryType, Boolean includeLinks) at System.Data.Services.Client.AtomMaterializer.DirectMaterializePlan(AtomMaterializer materializer, AtomEntry entry, Type expectedEntryType) at System.Data.Services.Client.AtomMaterializerInvoker.DirectMaterializePlan(Object materializer, Object entry, Type expectedEntryType) at System.Data.Services.Client.ProjectionPlan.Run(AtomMaterializer materializer, AtomEntry entry, Type expectedType) at System.Data.Services.Client.AtomMaterializer.Read() at System.Data.Services.Client.MaterializeAtom.MoveNextInternal() at System.Data.Services.Client.MaterializeAtom.MoveNext() at System.Linq.Enumerable.d_b11.MoveNext() at System.Data.Services.Client.DataServiceCollection1.InternalLoadCollection(IEnumerable1 items) at System.Data.Services.Client.DataServiceCollection1.StartTracking(DataServiceContext context, IEnumerable1 items, String entitySet, Func2 entityChanged, Func2 collectionChanged) at System.Data.Services.Client.DataServiceCollection1..ctor(DataServiceContext context, IEnumerable1 items, TrackingMode trackingMode, String entitySetName, Func2 entityChangedCallback, Func2 collectionChangedCallback) at System.Data.Services.Client.DataServiceCollection1..ctor(IEnumerable1 items) at Phinli.Dashboard.Silverlight.Helpers.DataHelper.<>c__DisplayClass44.<>c__DisplayClass46.<LoadAllPagesExpandAll>b__43() InnerException: System.InvalidOperationException Message=An item could not be added to the collection. When items in a DataServiceCollection are tracked by the DataServiceContext, new items cannot be added before items have been loaded into the collection. StackTrace: at System.Data.Services.Client.DataServiceCollection1.InsertItem(Int32 index, T item) at System.Collections.ObjectModel.Collection`1.Add(T item) InnerException: Thanks for any help!

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  • WPF TreeView Virtualization

    - by Carlo
    I'm trying to figure out this virtualization feature, I'm not sure if I'm understanding it wrong or what's going on, but I'm using the ANTS memory profiler to check the number of items in a virtualized TreeView, and it just keeps increasing. I have a TreeView with 1,001 items (1 root, 1000 sub-items), and I always get up to 1,001 TreeViewItems, 1,001 ToggleButtons and 1,001 TextBlocks. Isn't virtualization supposed to re-use the items? If so, why would I have 1,001 of each? Also, the CleanUpVirtualizedItem never fires. Let me know if I'm understanding this wrong and if you have resources on how to use this. I've searched over the internet but haven't found anything useful. EDIT: Even the memory used by the tree grows from aporx. 4mb to 12mb when I expand and scroll through all the items. Let me know thanks. This is my code. XAML: <Window x:Class="RadTreeViewExpandedProblem.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300"> <Grid> <TreeView x:Name="treeView" VirtualizingStackPanel.IsVirtualizing="True" VirtualizingStackPanel.CleanUpVirtualizedItem="TreeView_CleanUpVirtualizedItem"> <TreeView.ItemsPanel> <ItemsPanelTemplate> <VirtualizingStackPanel /> </ItemsPanelTemplate> </TreeView.ItemsPanel> </TreeView> </Grid> </Window> C#: public partial class Window1 : Window { public Window1() { InitializeComponent(); TreeViewItem rootItem = new TreeViewItem() { Header = "Item Level 0" }; for (int i = 0; i < 1000; i++) { TreeViewItem itemLevel1 = new TreeViewItem() { Header = "Item Level 1" }; itemLevel1.Items.Add(new TreeViewItem()); rootItem.Items.Add(itemLevel1); } treeView.Items.Add(rootItem); } private void TreeView_CleanUpVirtualizedItem(object sender, CleanUpVirtualizedItemEventArgs e) { } }

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  • C# LINQ: How to remove element from IQueryable<T>

    - by aximili
    How do you loop through IQueryable and remove some elements I don't need. I am looking for something like this var items = MyDataContext.Items.Where(x => x.Container.ID == myContainerId); foreach(Item item in items) { if(IsNotWhatINeed(item)) items.Remove(item); } Is it possible? Thanks in advance

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  • WPF TreeView - How to scroll so expanded branch is visible

    - by Jared
    When I expand items in my treeview so that scrolling is necessary, a scrollbar appears. However, it doesn't scroll down for the newly expanded branch of items - they get cropped by the bottom of the control. So as I continue expanding items at the bottom of the tree, I have to keep manually scrolling down to see the new children. Anyone have a suggestion for how make it automatically scroll to show the newly expanded items?

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  • LINQ: How to remove element from IQueryable<T>

    - by aximili
    How do you loop through IQueryable and remove some elements I don't need. I am looking for something like this var items = MyDataContext.Items.Where(x => x.Container.ID == myContainerId); foreach(Item item in items) { if(IsNotWhatINeed(item)) items.Remove(item); } Is it possible? Thanks in advance

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  • c# Properties.Settings.Default Doesn't work as expected

    - by Jack
    I've been working on a program to automate my backup checks with LogMeIn backup (a windows forms based program). I now need a way to store user settings, to save information easily. I've never worked with the Application/User settings that is somewhat "built-in" - and decided to try it, but ran into problems. I added four settings for now: IncludeCriteria (Specialized.StringCollection) ExcludeCriteria (Specialized.StringCollection) ReportPath (string) ReportType (int) But the behavior doesn't act as expected (go figure). After saving some values in my program, I go back into edit/view my settings values using the VS 2008 settings editor. None of my values are stored. While I think this may be because those values are just default values, wouldn't that be where they can be stored/read/changed? Here is my load form code (still very unrefined): private void setupForm() { txtPath.Text = BackupReport.Properties.Settings.Default.ReportPath == null ? "" : BackupReport.Properties.Settings.Default.ReportPath; if (BackupReport.Properties.Settings.Default.ReportType == 0) { radioHTML.Checked = true; } else radioExcel.Checked = true; if (BackupReport.Properties.Settings.Default.IncludeCriteria.Count > 0) { listIncludeCriteria.DataSource = Properties.Settings.Default.IncludeCriteria; //foreach (string s in Properties.Settings.Default.IncludeCriteria) // listIncludeCriteria.Items.Add(s); } if (BackupReport.Properties.Settings.Default.ExcludeCriteria.Count > 0) { listExcludeCriteria.DataSource = BackupReport.Properties.Settings.Default.ExcludeCriteria; //foreach (string s in Properties.Settings.Default.ExcludeCriteria) // listExcludeCriteria.Items.Add(s); } } listIncludeCriteria is just a listbox. When the user saves I call this method: private void saveSettings() { //var settings = BackupReport.Properties.Settings; if (txtPath.Text != "") { BackupReport.Properties.Settings.Default.ReportPath = txtPath.Text; } if (listIncludeCriteria.Items.Count > 0) { //BackupReport.Properties.Settings.Default.IncludeCriteria = (StringCollection)listIncludeCriteria.Items.AsQueryable(); foreach (var i in listIncludeCriteria.Items) { if (!isIncludeDuplicate(i.ToString())) BackupReport.Properties.Settings.Default.IncludeCriteria.Add(i.ToString()); } } if (listExcludeCriteria.Items.Count > 0) { //BackupReport.Properties.Settings.Default.ExcludeCriteria = (StringCollection)listExcludeCriteria.Items.AsQueryable(); foreach (var i in listExcludeCriteria.Items) { if (!isExcludeDuplicate(i.ToString())) Properties.Settings.Default.ExcludeCriteria.Add(i.ToString()); } } if (radioExcel.Checked == true) BackupReport.Properties.Settings.Default.ReportType = 1; else BackupReport.Properties.Settings.Default.ReportType = 0; BackupReport.Properties.Settings.Default.Save(); //Properties.Settings.Default.Save(); this.DialogResult = DialogResult.OK; this.Close(); } The wierd thing is when the form loads, the path I put in the first time seems to come up (ReportPath) - even the listBoxes are populated with a bunch of crap I put in - yet I cant find these values anywhere. Any help would be appreciated! Josh

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  • What is the fastest cyclic synchronization in Java (ExecutorService vs. CyclicBarrier vs. X)?

    - by Alex Dunlop
    Which Java synchronization construct is likely to provide the best performance for a concurrent, iterative processing scenario with a fixed number of threads like the one outlined below? After experimenting on my own for a while (using ExecutorService and CyclicBarrier) and being somewhat surprised by the results, I would be grateful for some expert advice and maybe some new ideas. Existing questions here do not seem to focus primarily on performance, hence this new one. Thanks in advance! The core of the app is a simple iterative data processing algorithm, parallelized to the spread the computational load across 8 cores on a Mac Pro, running OS X 10.6 and Java 1.6.0_07. The data to be processed is split into 8 blocks and each block is fed to a Runnable to be executed by one of a fixed number of threads. Parallelizing the algorithm was fairly straightforward, and it functionally works as desired, but its performance is not yet what I think it could be. The app seems to spend a lot of time in system calls synchronizing, so after some profiling I wonder whether I selected the most appropriate synchronization mechanism(s). A key requirement of the algorithm is that it needs to proceed in stages, so the threads need to sync up at the end of each stage. The main thread prepares the work (very low overhead), passes it to the threads, lets them work on it, then proceeds when all threads are done, rearranges the work (again very low overhead) and repeats the cycle. The machine is dedicated to this task, Garbage Collection is minimized by using per-thread pools of pre-allocated items, and the number of threads can be fixed (no incoming requests or the like, just one thread per CPU core). V1 - ExecutorService My first implementation used an ExecutorService with 8 worker threads. The program creates 8 tasks holding the work and then lets them work on it, roughly like this: // create one thread per CPU executorService = Executors.newFixedThreadPool( 8 ); ... // now process data in cycles while( ...) { // package data into 8 work items ... // create one Callable task per work item ... // submit the Callables to the worker threads executorService.invokeAll( taskList ); } This works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as much as the processing algorithm would be expected to allow (some work items will finish faster than others, then idle). However, as the work items become smaller (and this is not really under the program's control), the user CPU load shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.8% 85% 1.30 64k 2.5% 77% 5.6 16k 4% 64% 22.5 4096 8% 56% 86 1024 13% 38% 227 256 17% 19% 420 64 19% 17% 948 16 19% 13% 1626 Legend: - block size = size of the work item (= computational steps) - system = system load, as shown in OS X Activity Monitor (red bar) - user = user load, as shown in OS X Activity Monitor (green bar) - cycles/sec = iterations through the main while loop, more is better The primary area of concern here is the high percentage of time spent in the system, which appears to be driven by thread synchronization calls. As expected, for smaller work items, ExecutorService.invokeAll() will require relatively more effort to sync up the threads versus the amount of work being performed in each thread. But since ExecutorService is more generic than it would need to be for this use case (it can queue tasks for threads if there are more tasks than cores), I though maybe there would be a leaner synchronization construct. V2 - CyclicBarrier The next implementation used a CyclicBarrier to sync up the threads before receiving work and after completing it, roughly as follows: main() { // create the barrier barrier = new CyclicBarrier( 8 + 1 ); // create Runable for thread, tell it about the barrier Runnable task = new WorkerThreadRunnable( barrier ); // start the threads for( int i = 0; i < 8; i++ ) { // create one thread per core new Thread( task ).start(); } while( ... ) { // tell threads about the work ... // N threads + this will call await(), then system proceeds barrier.await(); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; } public void run() { while( true ) { // wait for work barrier.await(); // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as before. However, as the work items become smaller, the load still shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.7% 78% 6.1 16k 5.5% 52% 25 4096 9% 29% 64 1024 11% 15% 117 256 12% 8% 169 64 12% 6.5% 285 16 12% 6% 377 For large work items, synchronization is negligible and the performance is identical to V1. But unexpectedly, the results of the (highly specialized) CyclicBarrier seem MUCH WORSE than those for the (generic) ExecutorService: throughput (cycles/sec) is only about 1/4th of V1. A preliminary conclusion would be that even though this seems to be the advertised ideal use case for CyclicBarrier, it performs much worse than the generic ExecutorService. V3 - Wait/Notify + CyclicBarrier It seemed worth a try to replace the first cyclic barrier await() with a simple wait/notify mechanism: main() { // create the barrier // create Runable for thread, tell it about the barrier // start the threads while( ... ) { // tell threads about the work // for each: workerThreadRunnable.setWorkItem( ... ); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; @NotNull volatile private Callable<Integer> workItem; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; this.workItem = NO_WORK; } final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { synchronized( this ) { workItem = callable; notify(); } } public void run() { while( true ) { // wait for work while( true ) { synchronized( this ) { if( workItem != NO_WORK ) break; try { wait(); } catch( InterruptedException e ) { e.printStackTrace(); } } } // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.4% 80% 6.3 16k 4.6% 60% 30.1 4096 8.6% 41% 98.5 1024 12% 23% 202 256 14% 11.6% 299 64 14% 10.0% 518 16 14.8% 8.7% 679 The throughput for small work items is still much worse than that of the ExecutorService, but about 2x that of the CyclicBarrier. Eliminating one CyclicBarrier eliminates half of the gap. V4 - Busy wait instead of wait/notify Since this app is the primary one running on the system and the cores idle anyway if they're not busy with a work item, why not try a busy wait for work items in each thread, even if that spins the CPU needlessly. The worker thread code changes as follows: class WorkerThreadRunnable implements Runnable { // as before final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { workItem = callable; } public void run() { while( true ) { // busy-wait for work while( true ) { if( workItem != NO_WORK ) break; } // do the work ... // wait for everyone else to finish barrier.await(); } } } Also works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.2% 81% 6.3 16k 4.2% 62% 33 4096 7.5% 40% 107 1024 10.4% 23% 210 256 12.0% 12.0% 310 64 11.9% 10.2% 550 16 12.2% 8.6% 741 For small work items, this increases throughput by a further 10% over the CyclicBarrier + wait/notify variant, which is not insignificant. But it is still much lower-throughput than V1 with the ExecutorService. V5 - ? So what is the best synchronization mechanism for such a (presumably not uncommon) problem? I am weary of writing my own sync mechanism to completely replace ExecutorService (assuming that it is too generic and there has to be something that can still be taken out to make it more efficient). It is not my area of expertise and I'm concerned that I'd spend a lot of time debugging it (since I'm not even sure my wait/notify and busy wait variants are correct) for uncertain gain. Any advice would be greatly appreciated.

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  • Python Parse regex

    - by Nemo
    Let's say I have string in the form given below: myString={"name", "age", "address", "contacts", "Email"} I need to get all the items of myString into a List using python. Here's what I did r= re.search("myString=\{\"(.+)\", $\}", line) if r: items.append(r.group(1)) print(items) Here line is the variable that holds the content of my text file. What change do I have to make to my regex to get all the items in myString? Please kindly help me out. Thanks.

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  • linq get sum of two columns in one query

    - by Axarydax
    Hi, let's say that I have a table called Items (ID int, Done int, Total int) I can do it by two queries: int total = m.Items.Sum(p=>p.Total) int done = m.Items.Sum(p=>p.Done) But I'd like to do it in one query, something like this: var x = from p in m.Items select new { Sum(p.Total), Sum(p.Done)}; Surely there is a way to call aggregate functions from LINQ syntax...?

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  • Mail server hammering

    - by Rodrigo
    I've noticed a quick increase on smtp connections coming to my server, investigating it further i figured out that there's a botnet hammering my smtp server. I've tried to stop it by adding a rule at iptables: -N SMTP-BLOCK -A SMTP-BLOCK -m limit --limit 1/m --limit-burst 3 -j LOG --log-level notice --log-prefix "iptables SMTP-BLOCK " -A SMTP-BLOCK -m recent --name SMTPBLOCK --set -j DROP -A INPUT -p tcp --dport 25 -m state --state NEW -m recent --name SMTPBLOCK --rcheck --seconds 360 -j SMTP-BLOCK -A INPUT -p tcp --dport 25 -m state --state NEW -m recent --name SMTP --set -A INPUT -p tcp --dport 25 -m state --state NEW -m recent --name SMTP --rcheck --seconds 60 --hitcount 3 -j SMTP-BLOCK -A INPUT -p tcp --dport 25 -m state --state NEW -j ACCEPT That would avoid them from hammering "too fast", however the problem still, there's like 5 tries per second, it's going insane, i had to incrase the maximum number of childs of sendmail/dovecot. There's too many ips to filter out manually and simply changing the smtp to another port is not practical since i got many other clients on that server. I'm using sendmail with dovecot, any ideas to have this filtered out more efficiently?

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  • C# to VB conversion query

    - by Jim
    This C# code successfully gets the 2 relevant records into _currentUserRegisteredEventIds: ctx.FetchEventsForWhichCurrentUserIsRegistered((op) => { if (!op.HasError) { var items = op.Value; _currentUserRegisteredEventIds = new HashSet<int>(items); UpdateRegistrationButtons(); } }, null); but VB code trying to do the same thing has nothing in _currentUserRegisteredEventIds: ctx.FetchEventsForWhichCurrentUserIsRegistered(Function(op) If Not op.HasError Then Dim items = op.Value _currentUserRegisteredEventIds = New HashSet(Of Integer)(items) UpdateRegistrationButtons() End If Any help appreciated.

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  • AddObjectsFromArray does not work properly

    - by Sheehan Alam
    I have two NSMutableArrays: NSMutableArray* currentMessages NSMutableArray* items I am trying to copy the contents of items into currentMessages as such: [self.currentMessages addObjectsFromArray:self.items]; When I am debugging self.items contains 30 objects. After this operation self.currentMessages contains 0 objects. Why is the copy not working?

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  • Get sum of two columns in one LINQ query

    - by Axarydax
    Hi, let's say that I have a table called Items (ID int, Done int, Total int) I can do it by two queries: int total = m.Items.Sum(p=>p.Total) int done = m.Items.Sum(p=>p.Done) But I'd like to do it in one query, something like this: var x = from p in m.Items select new { Sum(p.Total), Sum(p.Done)}; Surely there is a way to call aggregate functions from LINQ syntax...?

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  • Move options between multiple dropdown lists

    - by Martha
    We currently have a form with the standard multi-select functionality of "here are the available options, here are the selected options, here are some buttons to move stuff back and forth." However, the client now wants the ability to not just select certain items, but to also categorize them. For example, given a list of books, they want to not just select the ones they own, but also the ones they've read, the ones they would like to read, and the ones they've heard about. (All examples fictional.) Thankfully, a selected item can only be in one category at a time. I can find many examples of moving items between listboxes, but not a single one for moving items between multiple listboxes. To add to the complication, the form needs to have two sets of list+categories, e.g. a list of movies that need to be categorized in addition to the aforementioned books. An additional problem is that sorting between lists is all well and good in the javascript-enabled world, but I can't really think of a good fallback interface for, say, mobile browsers. Maybe a pseudo-listbox with radio buttons next to each item? The master list of items will in general be very long - over 100 items, certainly, possibly many more. Any given category will most likely contain one or two selected items, but the possibility exists for a category to have dozens of selected items, or zero selected items. As far as OS and stuff, the site is in classic asp (quit snickering!), the server-side code is VBScript, and so far we've avoided the various Javascript libraries by the simple expedient of almost never using client-side scripting. This one form for this one client is currently the big exception. Give 'em an inch and they want a mile... Oh, and I have to add: I suck at Javascript, or really at any C-descendant language. Curly braces give me hives. I'd really, really like something I can just copy & paste into my page, maybe tweak some variable names, and never look at it again. A girl can dream, can't she? :)

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  • Changing the itemsSource of a treeview makes it's children invisible, when they were already display

    - by Marnix Kraus
    I found some strange problem in WPF, using the itemsSource of a treeview. I hope I can make this specific problem clear for you. First; a story. There is a treeview. It has a list with treeviewitems as itemsSource. This list is called _roots. There is another list, called _leafs. For as in a treeview, the _roots contain the _leafs in some hierarchical way. For example: <TreeviewItem Header="Jungle"> <TreeviewItem> <SpecialTreeviewItem Header="Monkey"/> <SpecialTreeviewItem Header="Apple"/> </TreeviewItem> </TreeviewItem> Now I am trying to switch between these two lists as itemsSource. It seemed to work fine, but it doesn't: When the Jungle-item is un-expanded, and I change the itemsSource to _leafs, and change it back again to _roots, everything works fine and all items can be expanded and showed. But when the Jungle-item is expanded (and the special items are already visible) and I change it to the _leafs itemsSource, and then change the itemsSource back to _roots, all special items have disappeared!! Also, when I do the same as case 2, but first un-expand the Jungle-item again, the special items also disappear. I did a lot of debugging, before posting this question here and come to the following conclusion: Printing on the event: visibility changed, the visibility is set to false for all items that were already visible (that is, when _roots become visible, the special items become invisible (because they were already visible)) So, IsVisible is false for the items, but Visibility = Visible. Which is a bit strange. The problem seems to depend on the use of the _roots list, which in a certain way contain the _leafs. When I change the itemsSource to different lists with special items in it, everything works fine. The hierarchical structure of the _roots make this thing broken. I hope that this is a complete overview of my problem. Help would be appreciated.

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  • nHibernate: limit the result set of a mapped collection

    - by HeavyWave
    How do you limit the result set of a mapped collection in nHibernate? For instance: Model.Items; will always return all the Items for the given Model. Is there any way to force it to return only, say, 20 Items without creating a specific query ? Something like Model.Items.SetMaxResults(20); In other words, I would like nHibernate to return IQueryable instead of a simple IList, when I access a collection.

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  • Help with Report Viewer

    - by DanSogaard
    My Items table contains items with each item has a specific date. I want to generate a report that displays items between two different dates. For example, I'd put two timedatepicker controls so the user selects From: 24/9/2009 To: 19/3/2010 and then press a button to generate a report of items between these dates. I'm using Report Viewer control btw not crystal report.

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  • C# menustrip designer

    - by Iceyoshi
    Hi, I'm not sure when this happened but when I was trying to edit a menustrip in my program (in the VS designer), I noticed that the menu items had be grouped or merged. Like: File Edit Format Insert ... Instead of being able to click each menu item and add sub-items to them in the designer, they all were grouped together so I couldn't edit the menu items separately, it's quite painful. I couldn't find any properties related to this, so how could I ungroup the menu items in the designer?

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  • Generic class for performing mass-parallel queries. Feedback?

    - by Aaron
    I don't understand why, but there appears to be no mechanism in the client library for performing many queries in parallel for Windows Azure Table Storage. I've created a template class that can be used to save considerable time, and you're welcome to use it however you wish. I would appreciate however, if you could pick it apart, and provide feedback on how to improve this class. public class AsyncDataQuery<T> where T: new() { public AsyncDataQuery(bool preserve_order) { m_preserve_order = preserve_order; this.Queries = new List<CloudTableQuery<T>>(1000); } public void AddQuery(IQueryable<T> query) { var data_query = (DataServiceQuery<T>)query; var uri = data_query.RequestUri; // required this.Queries.Add(new CloudTableQuery<T>(data_query)); } /// <summary> /// Blocking but still optimized. /// </summary> public List<T> Execute() { this.BeginAsync(); return this.EndAsync(); } public void BeginAsync() { if (m_preserve_order == true) { this.Items = new List<T>(Queries.Count); for (var i = 0; i < Queries.Count; i++) { this.Items.Add(new T()); } } else { this.Items = new List<T>(Queries.Count * 2); } m_wait = new ManualResetEvent(false); for (var i = 0; i < Queries.Count; i++) { var query = Queries[i]; query.BeginExecuteSegmented(callback, i); } } public List<T> EndAsync() { m_wait.WaitOne(); return this.Items; } private List<T> Items { get; set; } private List<CloudTableQuery<T>> Queries { get; set; } private bool m_preserve_order; private ManualResetEvent m_wait; private int m_completed = 0; private void callback(IAsyncResult ar) { int i = (int)ar.AsyncState; CloudTableQuery<T> query = Queries[i]; var response = query.EndExecuteSegmented(ar); if (m_preserve_order == true) { // preserve ordering only supports one result per query this.Items[i] = response.Results.First(); } else { // add any number of items this.Items.AddRange(response.Results); } if (response.HasMoreResults == true) { // more data to pull query.BeginExecuteSegmented(response.ContinuationToken, callback, i); return; } m_completed = Interlocked.Increment(ref m_completed); if (m_completed == Queries.Count) { m_wait.Set(); } } }

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  • Copying contents from one NSMutableArray to another

    - by Sheehan Alam
    I have two NSMutableArrays: NSMutableArray* currentMessages NSMutableArray* items I am trying to copy the contents of items into currentMessages as such: [self.currentMessages addObjectsFromArray:self.items]; When I am debugging self.items contains 30 objects. After this operation self.currentMessages contains 0 objects. Why is the copy not working?

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