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• Why is this loop over mysql resultset slow? (1.4ms per cycle)

  - by pawpro

  The $res contains around 488k rows the whole loop takes 61s! that's over 1.25ms per cycle! What is taking all that time? while($row = $res->fetch_assoc()) { $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['std'] = $row['cost_std']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['ecn'] = $row['cost_ecn']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['wnd'] = $row['cost_wnd']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['other_destination'] = $row['destination_id']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['carrier_destination'] = $row['carrier_destination_id']; } Now resultset of 10 rows, smaller arrays and performance 30 times higher (0.041ms) not the fastest still but better. while($row = $res->fetch_assoc()) { $customer[$row['id']]['name'] = $row['name']; $customer[$row['id']]['code'] = $row['customer']; }

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• Take advantage of multiple cores executing SQL statements

  - by willvv

  I have a small application that reads XML files and inserts the information on a SQL DB. There are ~ 300 000 files to import, each one with ~ 1000 records. I started the application on 20% of the files and it has been running for 18 hours now, I hope I can improve this time for the rest of the files. I'm not using a multi-thread approach, but since the computer I'm running the process on has 4 cores I was thinking on doing it to get some improvement on the performance (although I guess the main problem is the I/O and not only the processing). I was thinking on using the BeginExecutingNonQuery() method on the SqlCommand object I create for each insertion, but I don't know if I should limit the max amount of simultaneous threads (nor I know how to do it). What's your advice to get the best CPU utilization? Thanks

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• How to safely remove a USB drive on Windows CE 5.0?

  - by Radu C

  Until today, I assumed that Windows CE was writing everything to disk and I wouldn't end up with a broken FAT16 when I removed the USB stick. Today, I was proven wrong. I use a USB stick to test things on a WinCE 5.0 device. I don't write anything from the app or WinCE to the stick. I just execute my app, and my app reads its settings and pictures from the stick. Today, just this order of operations broke my stick filesystem (and I have to fix it). Is there a way to tell WinCE 5.0 to unmount the stick before I remove it? It sees it as a "Hard Drive", and the tap-and-hold menu has nothing along the lines of "safely remove drive". I'm happy with both code to do this operation and some trick that I didn't find in Windows CE yet. Thank you.

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• Separate one-off code paths

  - by DeadMG

  I'm implementing an application with different code paths that shall be chosen once at startup and then fixed forevermore for that execution- for example, choosing D3D11 or D3D9 rendering path. Obviously I don't want to duplicate all my other code. Is run-time inheritance (no virtual inheritance) a fair solution? I don't want to waste a bunch of performance making virtual lookups when the type was fixed long ago. Not just that, but it makes me nervous that the functions can't be inlined and whether or not it affects RVO and NRVO and such. Am I just being over-concerned about this?

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• SQL Server, fetching data from multiple joined tables. Why is slow?

  - by user562192

  I have problem with performance when retrieving data from SQL Server. My sql query looks something like this: SELECT table_1.id, table_1.value, table_2.id, table_2.value,..., table_20.id, table_20.value From table_1 INNER JOIN table_2 ON table_1.id = table_2.table_1_id INNER JOIN table_3 ON table_2.id = table_3.table_2_id... WHERE table_1.row_number BETWEEN 1 AND 20 So, I am fetching 20 results. This query takes about 5 seconds to execute. When I select only table_1.id, it returns results instantly. Because of that, I guess that problem is not in JOINs, it is in retrieving data from multiple tables. Any suggestions how I would speed up this query?

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• IDL-like parser that turns a document definition into powerful classes?

  - by paniq

  I am looking for an IDL-like (or whatever) translator which turns a DOM- or JSON-like document definition into classes which are accessible from both C++ and Python, within the same application expose document properties as ints, floats, strings, binary blobs and compounds: array, string dict (both nestable) (basically the JSON type feature set) allow changes to be tracked to refresh views of an editing UI provide a change history to enable undo/redo operations can be serialized to and from JSON (can also be some kind of binary format) allow to keep large data chunks on disk, with parts only loaded on demand provide non-blocking thread-safe read/write access to exchange data with realtime threads allow multiple editors in different processes (or even on different machines) to view and modify the document The thing that comes closest so far is the Blender 2.5 DNA/RNA system, but it's not available as a separate library, and badly documented. I'm most of all trying to make sure that such a lib does not exist yet, so I know my time is not wasted when I start to design and write such a thing. It's supposed to provide a great foundation to write editing UI components.

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• How do search engines see dynamic profiles?

  - by Lumpy

  Recently search engines have been able to page dynamic content on social networking sites. I would like to understand how this is done. Are there static pages created by a site like Facebook that update semi frequently. Does Google attempt to store every possible user name? As I understand it, a page like www.facebook.com/username, is not an actual file stored on disk but is shorthand for a query like: select username from users and display the information on the page. How does Google know about every user, this gets even more complicated when things like tweets are involved.

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• Django: common template subsections

  - by Parand

  What's a good way to handle commonly occurring subsections of templates? For example, there is a sub-header section that's used across 4 different pages. The pages are different enough to not work well with template inheritance (ie. "extends" doesn't fit well). Is "include" the recommended method here? It feels a bit heavyweight, requiring each subsection or snippet to be in its own file. Are there any performance issues in using include or is it smart about forming template from the subsections (ie. if I make extensive use of it, do I pay any penalties)? I think what I'm looking for is something like template tags, but without the programming - a simple way to create a library of html template tags I can sprinkle in other templates.

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• Using pthread condition variable with rwlock

  - by Doomsday

  Hello, I'm looking for a way to use pthread rwlock structure with conditions routines in C++. I have two questions: First: How is it possible and if we can't, why ? Second: Why current POSIX pthread have not implemented this behaviour ? To understand my purpose, I explain what will be my use: I've a producer-consumer model dealing with one shared array. The consumer will cond_wait when the array is empty, but rdlock when reading some elems. The producer will wrlock when adding(+signal) or removing elems from the array. The benefit of using rdlock instead of mutex_lock is to improve performance: when using mutex_lock, several readers would block, whereas using rdlock several readers would not block.

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• How to reduce this IF-Else ladder in c#

  - by Rohit

  This is the IF -Else ladder which I have created to focus first visible control on my form.According to the requirement any control can be hidden on the form.So i had to find first visible control and focus it. if (ddlTranscriptionMethod.Visible) { ddlTranscriptionMethod.Focus(); } else if (ddlSpeechRecognition.Visible) { ddlSpeechRecognition.Focus(); } else if (!SliderControl1.SliderDisable) { SliderControl1.Focus(); } else if (ddlESignature.Visible) { ddlESignature.Focus(); } else { if (tblDistributionMethods.Visible) { if (chkViaFax.Visible) { chkViaFax.Focus(); } else if (chkViaInterface.Visible) { chkViaInterface.Focus(); } else if (chkViaPrint.Visible) { chkViaPrint.Focus(); } else { chkViaSelfService.Focus(); } } } Is there any other way of doing this. I thought using LINQ will hog the performance as i have to tranverse the whole page collection. I am deep on page which has masterpages.Please suggest.

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• Is select() Ok to implemnet single socket read/write timeout ?

  - by chmike

  I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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• What is the most "database independent" way of creating a variable length text field in a database

  - by Thibaut Colar

  I want to create a text field in the database, with no specific size (it will store text of length unknown in some case) - the particular text are serialized simple object (~ JSON) What is the most database independent way to do this : - a varchar with no size specified (don't think all db support this) - a 'text' field, this seems to be common, but I don't believe it's a standard - a blob or other object of that kind ? - a varchar of a a very large size (that's inefficient and wastes disk space probably) - Other ? I'm using JDBC, but I'd like to use something that is supported in most DB (oracle, mysql, postgresql, derby, HSQL, H2 etc...) Thanks.

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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• Tiny C Compiler and Virus warnings...

  - by NoMoreZealots

  I wanted to try out the TCC and got the Win32 Binary zip file from the website. upon decompressing it I tried to compile the "hello_win.c" source from the example directory. As soon as the compiler tried to write to the disk McAfee Popped up a dialog box and identified a Trojan named "Generic.dx." Has anyone else experience this? Dropping a virus into a compiler would be a sneaky, but brilliant, delivery mechanizism. I just want to know if this is a legit threat.

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• Class.Class vs Namespace.Class for top level general use class libraries?

  - by Joan Venge

  Which one is more acceptable (best-practice)?: namespace NP public static class IO public static class Xml ... // extension methods using NP; IO.GetAvailableResources (); vs public static class NP public static class IO public static class Xml ... // extension methods NP.IO.GetAvailableResources (); Also for #2, the code size is managed by having partial classes so each nested class can be in a separate file, same for extension methods (except that there is no nested class for them) I prefer #2, for a couple of reasons like being able to use type names that are already commonly used, like IO, that I don't want to replace or collide. Which one do you prefer? Any pros and cons for each? What's the best practice for this case? EDIT: Also would there be a performance difference between the two?

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• Objective-C style question: do "release" or "nil" properties in dealloc?

  - by Piotr Czapla

  Hi, Apple usually release ivars in dealloc but is there anything wrong with nilling the properties in dealloc? I mean instead of this: - (void) dealoc(){ [myRetainedProperty release]; [super dealloc]; } write code like this: - (void) dealoc(){ self.myRetainedProperty = nil; [super dealloc]; } I know that it is one additional method call but on the other hand it is safer as it doesn't crashes when you change your property form retain to assign and forget to amend dealloc. What do you think? Can you think about any other reason to use release instead of setting nil besides performance?

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• Mac OS X 10.5 App "not supported on this architecture" cured by copying?

  - by JWWalker

  I have an app that updates itself over the internet, and the updated copy won't run on PowerPC machines (G5) running Leopard (10.5.8). Double-clicking the app produces a message saying "You can't open the application "appname" because it is not supported on this architecture." But here's the weird part: if I duplicate the app using the Finder or using a cp -R command, then the duplicate runs fine! And yet, if I do ls -laeR on both apps, the results are identical. I restarted the machine, and the difference between the two copies was still there. Sometimes, renaming the app made it run. After a few tries, I managed to rename it back to the original name and still have it run. If this was just on one machine, I'd dismiss it as disk corruption, cosmic rays, or a voodoo hex, but it was reported by a customer and then I reproduced it on my own machine. Any ideas what could cause this behavior?

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• Breaking One Big Graphic of MutablePaths into CAShapeLayers

  - by StackOverFlowRider

  I have a class called GraphicView that takes a Graphic object and draws it in its drawRect method. This Graphic object is basically an array of mutablePaths that comprise an icon that I want drawn. For performance and other issues, I was thinking of taking this icon that is comprised of mutablePaths, and dividing it into a bunch of CAShapeLayers. I'm wondering is this possible? Considering the points for the mutablePaths of the icon are all interwoven together (ie the icon was initially an SVG file that I converted to code), is it possible to divide different parts of the icon into CAShapeLayers, and reassemble them all together when assigning to the views layer? If so how would it be done? If I assign them as sublayers to a CALayer or CAShapeLayer, will it understand to mesh them all together?

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• Forced to use too many hidden fields; looking for an alternative approach

  - by harisri786

  I am looking for a better approach to do this. I have around 70 to 80 hidden fields in my page. This hidden fields are initialized at the server side and then used at the client side for validations, calculations, etc,. using java script. I wanted to know if there is any other alternative approach to using hidden fields in asp.net. I guess, these many hidden fields are increasing the page size and hence affecting the performance of my web page and I want to do away with it. FYI: I am working on an asp.net web application.

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• Making simple tabs in android

  - by user2910566

  I am new to Android. I am making a tab Activity that has 3 tabs in it. . I came across reading some interesting articles that tab can be made in three ways:: Regular TabHost Using simple Fragments Using Action Bar Sherlock I have a set of questions Which is a better choice & why ? Which gives more flexibility, efficiency & performance ? Which would be the preferd choice in case of requirement changes happen in future ? My research indicate :: ActionBarsherlock is better ! Is there something better than this ? If so what is it ?

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• Does HTML5 only replace the video aspects of Flash/Silverlight?

  - by John

  I see a lot of talk how HTML5 video tag will kill Flash. But while video is the most widely used part of Flash/SL, it's only a small part of their technical abilities. For instance you can write a game using full 3D graphics and socket connections in Flex, and serious business applications, etc. Is the thinking that Javascript will kill those parts of Flash/Flex/SL? Because while that seems feasible now for even quite rich web-apps, what about any kind of high-performance app like real-time graphics?

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• C# asp.net MVC: When to update LastActivityDate?

  - by Oskar Kjellin

  I'm using asp.net mvc and creating a public website. I need to keep track of users that are online. I see that the standard way in asp.net of doing this is to keep track of LastActivityDate. My question is when should I update this? If I update it every time the users clicks somewhere, I will feel a performance draw back. However if I do not do that, people that only surf arround will be listed as offline. What is the best way to do this in asp.net MVC?

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• Endless saving of CoreData Context

  - by Robert

  Sometimes I noticed that a 'save:' operation an a ManagedObjectContext never returns and consumes 100% CPU. I'm using an SQL Store in a GarbageCollected environment (Mac OS X 10.6.3). The disk activity shows about 700 KB/s writing. While having a look at the folder that contains the sqlite database file the "-journal" file appears and disappears, appears and disappears, ... This is part of the call graph from the process analysis: 2203 -[NSManagedObjectContext save:] 1899 -[NSPersistentStoreCoordinator(_NSInternalMethods) executeRequest:withContext:] 1836 -[NSSQLCore executeRequest:withContext:] 1836 -[NSSQLCore saveChanges:] 1479 -[NSSQLCore performChanges] ... 335 -[NSSQLCore recordChangesInContext:] ... 20 -[NSSQLCore rollbackChanges] ... 2 -[NSSQLCore prepareForSave:] ... 62 -[NSPersistentStoreCoordinator(_NSInternalMethods) _checkRequestForStore:originalRequest:andOptimisticLocking:] ... 1 -[NSPersistentStore(_NSInternalMethods) _preflightCrossCheck] ... 184 -[NSMergePolicy resolveConflicts:] ... 120 -[NSManagedObjectContext(_NSInternalChangeProcessing) _prepareForPushChanges:] ... Everything a happening in the main GUI thread. Any ideas what I can to do to resolve the problem?

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• Password protect web pages on Windows CE 6

  - by Chris

  I am using the default web server for WinCE 6 and wish to password protect certain folders. The default VROOT /remoteadmin/ is password protected, and this works but my configuration doesn't work. I have tried mimicking these settings on my own folders but to little success. Here is how one looks: In the HKLM\Comm\HTTPD\VROOTS key I have created a subkey called /web/configuration (this folder actually exists on the box). The following values are in this key A = 1 DefaultPage = config.html Path = /hard disk/webroot/web/configuration/ UserList = ADMIN This is nigh on identical to the settings in /RemoteAdmin/ but /RemoteAdmin/ requests a password and /web/configuration doesn't (even after reboot).

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• C#. Struct design. Why 16 byte is recommended size?

  - by maxima120

  I read Cwalina book (recommendations on development and design of .NET apps). He says that good designed struct has to be less than 16 bytes in size (for performance purpose). My questions is - why exactly is this? And (more important) can I have larger struct with same efficiency if I run my .NET 3.5 (soon to be .NET 4.0) 64-bit application on i7 under Win7 x64 (is this limitation CPU / OS based)? Just to stress again - I need as efficient struct as it is possible. I try to keep it in stack all the time, the application is heavily multi-threaded and runs on sub-millisecond intervals, the current size of the struct is 64 byte.

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