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• Safe to update separate regions of a BufferedImage in separate threads?

  - by finnw

  I have a collection of BufferedImage instances, one main image and some subimages created by calling getSubImage on the main image. The subimages do not overlap. I am also making modifications to the subimage and I want to split this into multiple threads, one per subimage. From my understanding of how BufferedImage, Raster and DataBuffer work, this should be safe because: Each instance of BufferedImage (and its respective WritableRaster) is accessed from only one thread. The shared ColorModel is immutable The DataBuffer has no fields that can be modified (the only thing that can change is elements of the backing array.) Modifying disjoint segments of an array in separate threads is safe. However I cannot find anything in the documentation that says that it is definitely safe to do this. Can I assume it is safe? I know that it is possible to work on copies of the child Rasters but I would prefer to avoid this because of memory constraints. Otherwise, is it possible to make the operation thread-safe without copying regions of the parent image?

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• How to localize an app on Google App Engine?

  - by Petri Pennanen

  What options are there for localizing an app on Google App Engine? How do you do it using Webapp, Django, web2py or [insert framework here]. 1. Readable URLs and entity key names Readable URLs are good for usability and search engine optimization (Stack Overflow is a good example on how to do it). On Google App Engine, key based queries are recommended for performance reasons. It follows that it is good practice to use the entity key name in the URL, so that the entity can be fetched from the datastore as quickly as possible. Currently I use the function below to create key names: import re import unicodedata def urlify(unicode_string): """Translates latin1 unicode strings to url friendly ASCII. Converts accented latin1 characters to their non-accented ASCII counterparts, converts to lowercase, converts spaces to hyphens and removes all characters that are not alphanumeric ASCII. Arguments unicode_string: Unicode encoded string. Returns String consisting of alphanumeric (ASCII) characters and hyphens. """ str = unicodedata.normalize('NFKD', unicode_string).encode('ASCII', 'ignore') str = re.sub('[^\w\s-]', '', str).strip().lower() return re.sub('[-\s]+', '-', str) This works fine for English and Swedish, however it will fail for non-western scripts and remove letters from some western ones (like Norwegian and Danish with their œ and ø). Can anyone suggest a method that works with more languages? 2. Translating templates Does Django internationalization and localization work on Google App Engine? Are there any extra steps that must be performed? Is it possible to use Django i18n and l10n for Django templates while using Webapp? The Jinja2 template language provides integration with Babel. How well does this work, in your experience? What options are avilable for your chosen template language? 3. Translated datastore content When serving content from (or storing it to) the datastore: Is there a better way than getting the *accept_language* parameter from the HTTP request and matching this with a language property that you have set with each entity?

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• Video-codec rater by image comparison algorithm?

  - by Andreas Hornig

  Hi, perhaps anyone knows if this is possible. comparing image quality is almost imposible to describe without subjective influences. When someone rates an image quality as good there is at least one person, that doesn't think so. human preferences are always different. So, I would like to know if there is away to "rate" the image quality by an algorithm that compares the original image to the produced one in following issues colour change(difference pixel by pixel blur rate artifacts and macroblocking the first one would be the easiest one because you could check just the diffeence in colours and can give 3 values in +- of each hex-value both last once I don't know if this is possible, but the blocking could be detected by edge-finding. and the king's quest would be to do that for more then just one image, because video is done with several frames. perhaps you expert programmers could tell me, if such an automated algo can be done to bring some objective measurement divice into rating image quality. this could perhaps calm down some h.264 is better than x264 and better than vp8 and blaaah people :) Andreas 1st posted here http://www.hdtvtotal.com/index.php?name=PNphpBB2&file=viewtopic&p=9705

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• Which Database to choose?

  - by Sundar

  I have the following criteria Database should be protected with a username and password. It should not be possible to copy the database file and use it else were like MS Access. There will be no central database server. Each machine will run their own database server locally and user will initiate synchronization. Concept is inspired from distributed version control system like Git. So it should have good replication support. Strong consistency is not needed. Users will synchronize each other database when they need. In case of conflicts it should be possible to find the conflict and present it (from application) to the user for fixing it. Revisions of data if available it will be good. e.g. Entire history of change to a invoice. I explored document oriented database and inclined towards the same. But I dont know what to choose. Database is small it will not reach even 1GB in the next few years (say 3 years). Please feel free to suggest any database which you think might be suitable. Any pointers is highly appreciated. Thanks in advance.

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• How to delete duplicate records in MySQL by retaining those fields with data in the duplicate item b

  - by NJTechGuy

  I have few thousands of records with few 100 fields in a MySQL Table. Some records are duplicates and are marked as such. Now while I can simply delete the dupes, I want to retain any other possible valuable non-null data which is not present in the original version of the record. Hope I made sense. For instance : a b c d e f key dupe -------------------- 1 d c f k l 1 x 2 g h j 1 3 i h u u 2 4 u r t 2 x From the above sample table, the desired output is : a b c d e f key dupe -------------------- 2 g c h k j 1 3 i r h u u 2 If you look at it closely, the duplicate is determined by using the key (it is the same for 2 records, so the one that has an 'x' for dupe field is the one to be deleted by retaining some of the fields from the dupe (like c, e values for key 1). Please let me know if you need more info about this puzzling problem. Thanks a tonne! p.s : If it is not possible using MySQL, a PERL/Python script sample would be awesome! Thanks!

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• Fork or copy a users browser session in IE

  - by jmoeller

  Is it possible to fork a users session (or do something similar) in a Internet Explorer plugin? I want to process the page the user is on when they click a button in the toolbar. To avoid interrupting the users browsing, I'd like to "copy" everything so I can parse and process the page in the background. The processing can involve things such as loading the content of the result links on a Google search, if that's where the button was clicked. So - what I basically want is to imitate "Ctrl+N" but hide the window from the user, so they won't be interrupted. As you can see, if you fill out and submit the form on http://www.snee.com/xml/crud/posttest.html and press "Ctrl+N", everything posted will still appear in the new window, but it won't post the data twice. I was thinking of somehow copying the IWebBrowser2, but: I'm not sure if that's possible (I haven't been able to find any information on MSDN) I don't know if it copies the sessions as well. Creating a new instance of the IWebBrowser2 and simply navigating to the current URL isn't a valid solution as POST-variables of course doesn't get carried over.

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• How to hide items under the options from one select box upon selection of an item in another select

  - by jl

  Hi, I am new to jQuery and would like to know how is it possible for me to hide an option in a selection box based on the selection of another selection box. I have 5 selection boxes, this is for the administrator to select the users of a limited criteria. The <options> are create dynamically from the results of a database query and php, and they all have the same <options>. e.g. this is an example of the selection boxes with their option values. userbox1 - Amy, Bosh, Cathy, Daniel, Ethan userbox2 - Amy, Bosh, Cathy, Daniel, Ethan userbox3 - Amy, Bosh, Cathy, Daniel, Ethan userbox4 - Amy, Bosh, Cathy, Daniel, Ethan userbox5 - Amy, Bosh, Cathy, Daniel, Ethan So if the administrator selects Cathy in userbox1, Cathy will be automatically be hidden from the selection on the rest of the userbox. And if the administrator changes his/her mind and reselect another user call Ethan. The userboxes should be able to show the availability of Cathy in the selection. I am not sure is hide/show the correct status to be used in such cases. May I know how is it possible to write the function as stated above? If I am missing some current references, kindly point me to it. Thanks in advance.

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• Mingling C++ classes with Objective C classes

  - by Joey

  I am using the iphone SDK and coding primarily in C++ while using parts of the SDK in obj-c. Is it possible to designate a C++ class in situations where an obj-c class is needed? For instance: 1) when setting delegates to obj-c objects. I cannot make a C++ class derive from a Delegate protocol so this and possibly other reasons prevent me from making my C++ class a delegate for various obj-c objects. What I do as a solution is create an obj-c adapter class that contains a ptr to the C++ class and is used as the delegate (notifying the C++ class when it is called). It feels cumbersome to write these every time I need to get delegate notifications to a C++ class. 2) when setting selectors This goes hand in hand with item 1. Say I want to set a callback to fire when something is done, like a button press or a setAnimationDidStopSelector in the UIView animation functionality. It would be nice to be able to designate a C++ function along with the relevant delegate for setAnimationDelegate. Well, I suspect this isn't readily possible, but if anyone has any suggestions on how to do it if it is, or on how to write such things more easily, I would love to hear them. Thanks.

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• More than one location provider at same time

  - by Rabarama

  I have some problems with location systems. I have a service that implements locationlistener. I want to get the best location using network when possible, gps if network is not enough accurate (accuracy greater than 300mt). The problem is this. I need location (accurate if possible, inaccuarte otherways) every 5 minutes. I start with a : LocationManager lm=(LocationManager)getApplicationContext().getSystemService(LOCATION_SERVICE); Criteria criteria = new Criteria(); criteria.setAccuracy(Criteria.ACCURACY_COARSE); criteria.setAltitudeRequired(false); criteria.setBearingRequired(false); String provider=lm.getBestProvider(criteria, true); if(provider!=null){ lm.requestLocationUpdates( provider,5*60*1000,0,this); In "onLocationChanged" i listen to locations and when i get a location with accuracy greater than 300mt, i want to change to gps location system. If I remove allupdates and then request for gps updates, like this: lm.removeUpdates((android.location.LocationListener) this); Criteria criteria = new Criteria(); criteria.setAccuracy(Criteria.ACCURACY_FINE); criteria.setAltitudeRequired(false); criteria.setBearingRequired(false); String provider=lm.getBestProvider(criteria, true); if(provider!=null){ lm.requestLocationUpdates( provider,5*60*1000,0,this); } system stops waiting for gpsupdate, and if i'm in a close room it can stay without location updates for hours, ignoring timeupdate indications. Is there a way to tell locationprovider to switch to network if gps is not giving a location in "x" seconds? or how to understand when gps is not localizing? or if i requestlocationupdates from 2 providers at same time (network and gps), can be a problem? Any suggestion?

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• Overriding MSBuildExtensionsPath in the MSBuild task is flaky

  - by Stuart Lange

  This is already cross-posted at MS Connect: https://connect.microsoft.com/VisualStudio/feedback/details/560451 I am attempting to override the property $(MSBuildExtensionsPath) when building a solution containing a C# web application project via msbuild. I am doing this because a web application csproj file imports the file "$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v9.0\WebApplications\Microsoft.WebApplication.targets". This file is installed by Visual Studio to the standard $(MSBuildExtensionsPath) location (C:\Program Files\MSBuild). I would like to eliminate the dependency on this file being installed on the machine (I would like to keep my build servers as "clean" as possible). In order to do this, I would like to include the Microsoft.WebApplication.targets in source control with my project, and then override $(MSBuildExtensionsPath) so that the csproj will import this included version of Microsoft.WebApplication.targets. This approach allows me to remove the dependency without requiring me to manually modify the web application csproj file. This scheme works fine when I build my solution file from the command line, supplying the custom value of $(MSBuildExtensionsPath) at the command line to msbuild via the /p flag. However, if I attempt to build the solution using the MSBuild task in a custom msbuild project file (overriding MSBuildExtensionsPath using the "Properties" attribute), it fails because the web app csproj file is attempting to import the Microsoft.WebApplication.targets from the "standard" Microsoft.WebApplication.targets location (C:\Program Files\MSBuild). Notably, if I run msbuild using the "Exec" task in my custom project file, it works. Even more notably, the FIRST time I run the build using the "MSBuild" task AFTER I have run the build using the "EXEC" task (or directly from the command line), the build works. Has anyone seen behavior like this before? Am I crazy? Is anyone aware of the root cause of this problem, a possible workaround, or whether this is a legitimate bug in MSBuild?

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• Returning from dll (Asynchronous sockets)

  - by Juha

  I am trying to do a simple http-server in (c++) dll-file that I can use from managed (C#) application with P/Invoke. I was trying to do this with asynchronous functions (WSAAsyncSelect() and stuff), so that I could manage server by calling functions inside dll whenever needed and after that it would return to my main program. Now I'm not sure if that is even possible. It seems that "main function" in dll, the function that starts the server, has to include message loop or something and since it's a loop, it doesn't return from dll ever. Could I somehow do this message stuff in my managed application and call some function in dll when there is something to do? Or is it even possible to do this stuff in one thred? I would really like to avoid all concurrency stuff. The dll looks now basicly the same as here, main function is the one that I call from managed C# program and would like to return to there after calling the function. http://www.winsocketdotnetworkprogramming.com/winsock2programming/winsock2advancediomethod5b.html I'm quite noob in windows programming, and never even heard of this message-queue or message-loop.

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• datanucleus enhancer & javaw: "the parameter is incorrect"

  - by Riley

  I'm on windows XP using eclipse and the datanucleus enhancer for a gwt + gae app. When I run the enhancer, I get an error: Error Thu Oct 21 16:33:57 CDT 2010 Cannot run program "C:\Program Files\Java\jdk1.6.0_18\bin\javaw.exe" (in directory "C:\ag\dev"): CreateProcess error=87, The parameter is incorrect java.io.IOException: Cannot run program "C:\Program Files\Java\jdk1.6.0_18\bin\javaw.exe" (in directory "C:\ag\dev"): CreateProcess error=87, The parameter is incorrect at java.lang.ProcessBuilder.start(Unknown Source) at com.google.gdt.eclipse.core.ProcessUtilities.launchProcessAndActivateOnError(ProcessUtilities.java:213) at com.google.appengine.eclipse.core.orm.enhancement.EnhancerJob.runInWorkspace(EnhancerJob.java:154) at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Caused by: java.io.IOException: CreateProcess error=87, The parameter is incorrect at java.lang.ProcessImpl.create(Native Method) at java.lang.ProcessImpl.<init>(Unknown Source) at java.lang.ProcessImpl.start(Unknown Source) ... 5 more I've had this problem before, and it was due to a long classpath. I just spent an hour and a half shortening my classpath by moving libraries around and even moving my eclipse install, but with no luck. Any ideas about where I should start to look for an answer? The error message doesn't include any information about what directory it's in or anything. It's kind of infuriating! Is it possible to make the output of javaw more verbose? Is it possible to get around this class-path size bug?

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• iPhone OpenGL Splash Screen? How?

  - by Kyle

  My app is based pretty much on the EAGLView in the SDK. It doesn't incorporate a ViewController. Rather it simply inits GL and starts painting immediately.. Currently, my app will load a very small PNG and displays it as quickly as possible. On a 3GS this is rather instant, but on a 3G it can take about 2 seconds. In the latter case of the 3G, the user is looking at a black screen for that time. Is this behavior allowed by Apple? Is there any way to alter this SDK example so that it makes use of 'default.png'? It doesn't seem so straight forward to me. I want my user to see an image as quickly as possible, and I also don't want to be rejected for such a little quirk like this as well. In the guidelines, they encourage you to use default.png for standard applications to show a sort of mockup of the interface while it actually loads. I want to initialize OpenGL, and ALSO display this. This default.png is loaded before the app screen launches. This is EXACLTY what I want to make use of. Any help is appreciated. Thanks!

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• Magento resource model for table with compound primary key

  - by sdek

  I am creating a custom module for a Magento ecommerce site, and the module will center around a new (ie, custom) table that has a compound/composite primary key, or rather the table has two columns that make up the primary key. Does anybody know how to create your models/resource models based on a table with a compound key? To give a few more details, I have looked up several tutorials and also used the excellent moduleCreator script. But it seems like all the tutorials revolve around the table having a PK with just one column in it. Something like this: class <Namespace>_<Module>_Model_Mysql4_<Module> extends Mage_Core_Model_Mysql4_Abstract { public function _construct(){ $this->_init('<module_alias>/<table_alias>', '<table_primary_key_id>'); } } Also, I just noticed that looking at the database model almost all tables have a single primary key. I understand this has much to do with the EAV-style db structure, but still is it possible to use a table with a compound PK? I want to stick with the Magento framework/conventions if possible. Is it discouraged? Should I just change the structure of my custom table to have some dummy id column? I do have the ability to do that, but geez! (Another side note that I thought I would mention is that it looks like the Zend Framework provides a way to base a class on a table with compound primary key (see Example #20 on this page - about half-way down), so it seems that the Magento framework should also provide for it... I just don't see how.)

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• Can Sql Server 2005 Pivot table have nText passed into it?

  - by manemawanna

  Right bit of a simple question can I input nText into a pivot table? (SQL Server 2005) What I have is a table which records the answers to a questionnaire consisting of the following elements for example: UserID QuestionNumber Answer Mic 1 Yes Mic 2 No Mic 3 Yes Ste 1 Yes Ste 2 No Ste 3 Yes Bob 1 Yes Bob 2 No Bob 3 Yes With the answers being held in nText. Anyway what id like a Pivot table to do is: UserID 1 2 3 Mic Yes No Yes Ste Yes No Yes Bob Yes No Yes I have some test code, that creates a pivot table but at the moment it just shows the number of answers in each column (code can be found below). So I just want to know is it possible to add nText to a pivot table? As when I've tried it brings up errors and someone stated on another site that it wasn't possible, so I would like to check if this is the case or not. Just for further reference I don't have the opportunity to change the database as it's linked to other systems that I haven't created or have access too. Heres the SQL code I have at present below: DECLARE @query NVARCHAR(4000) DECLARE @count INT DECLARE @concatcolumns NVARCHAR(4000) SET @count = 1 SET @concatcolumns = '' WHILE (@count <=52) BEGIN IF @COUNT > 1 AND @COUNT <=52 SET @concatcolumns = (@concatcolumns + ' + ') SET @concatcolumns = (@concatcolumns + 'CAST ([' + CAST(@count AS NVARCHAR) + '] AS NVARCHAR)') SET @count = (@count+1) END DECLARE @columns NVARCHAR(4000) SET @count = 1 SET @columns = '' WHILE (@count <=52) BEGIN IF @COUNT > 1 AND @COUNT <=52 SET @columns = (@columns + ',') SET @columns = (@columns + '[' + CAST(@count AS NVARCHAR) + '] ') SET @count = (@count+1) END SET @query = ' SELECT UserID, ' + @concatcolumns + ' FROM( SELECT UserID, QuestionNumber AS qNum from QuestionnaireAnswers where QuestionnaireID = 7 ) AS t PIVOT ( COUNT (qNum) FOR qNum IN (' + @columns + ') ) AS PivotTable' select @query exec(@query)

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• XML Schema that describes a self-describing XML document

  - by Raegx

  Is it possible to write an XML Schema that describes an XML document that lists a set of elements and then requires other elements on that same XML document to use those values as either attributes and/or sub-elements? Example: define a list of locations, then force location attributes and/or location elements to be of those values. <root> <locations> <location>Home</location> <location>Office</location> <location>School</location> </locations> <addresses> <address location="Home">...</address> <address location="Office">...</address> </addresses> </root> or <root> <locations> <location>Home</location> <location>Office</location> <location>School</location> </locations> <addresses> <address> <location>Home</location> ... </address> <address> <location>Office</location> ... </address> </addresses> </root> I am failing hard at finding the proper way to search for this information. I suspect it is either not possible or I just don't know the right search terms.

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• open source business intelligence solutions

  - by opensas

  which open source business intelligence solution would you recommend? All I need is to build some cubes and let the end user play with dimensions, filter data, sort, etc, and once it's done being able to export it to excel... I'd like the solution to be as simple and easy on resources as possible, and also I'd like it to be as much open source as possible, by the way. I've heard that many solutions available do have many restrictions when it comes to there community version. I'd like to ear your advices and the pros/cons of each alternative, to help me choose the right tool, and if you could point me to some basic demo and tutorial to get started. thanks a lot ps: I'm using sql server databases, they aren't huge databases (in general less than a million records) and I doesn't necessarily have to work on "live" data... ps: some useful links: http://en.wikipedia.org/wiki/Business_intelligence_tools#Open_source_free_products http://www.manageability.org/blog/stuff/open-source-java-business-intelligence http://www.jaspersoft.com/jasperanalysis http://community.pentaho.com/projects/bi_platform/ http://community.pentaho.com/faq/platform_licensing.php http://www.eclipse.org/birt/phoenix/ http://www.spagoworld.org/xwiki/bin/view/SpagoWorld/ http://docs.google.com/viewer?a=v&q=cache:vhsqMQXwCUkJ:www.ow2.org/xwiki/bin/download/Activities/EuropeLocalChapterWebinars/ELCWebinarOSBI.pdf+open+source+business+intelligence&hl=en&pid=bl&srcid=ADGEESgpJJ2MqaKprJQOF2jX2UXCZQjg_asv8d7EVYtq0Vma-e-tR1tFxS-I0SOW0IhJC5acYc94rkDOrgP1WckCp_vk4qhKqR9y2Klp_u9cL8hlXoKoUpMkpAd5wabu61A4W0y15E5P&sig=AHIEtbRJ5FAI-3YK-qtayPjKkF_CwOgZag

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• Show WPF tooltip on disabled item only

  - by DT

  Just wondering if it is possible to show a WPF on a disabled item ONLY (and not when the item is enabled). I would like to give the user a tooltip explaining why an item is currently disabled. I have an IValueConverter to invert the boolean IsEnabled property binding. But it doesn't seem to work in this situation. The tooltip is show both when the item is enabled and disabled. So is is possible to bind a tooltip.IsEnabled property exclusively to an item's own !IsEnabled? Pretty straightforward question I guess, but code example here anyway: public class BoolToOppositeBoolConverter : IValueConverter { #region IValueConverter Members public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (targetType != typeof(bool)) throw new InvalidOperationException("The target must be a boolean"); return !(bool)value; } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (targetType != typeof(bool)) throw new InvalidOperationException("The target must be a boolean"); return !(bool)value; } #endregion } And the binding: <TabItem Header="Tab 2" Name="tabItem2" ToolTip="Not enabled in this situation." ToolTipService.ShowOnDisabled="True" ToolTipService.IsEnabled="{Binding Path=IsEnabled, ElementName=tabItem2, Converter={StaticResource oppositeConverter}}"> <Label Content="Item content goes here" /> </TabItem> Thanks folks.

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• Lightweight spinlocks built from GCC atomic operations?

  - by Thomas

  I'd like to minimize synchronization and write lock-free code when possible in a project of mine. When absolutely necessary I'd love to substitute light-weight spinlocks built from atomic operations for pthread and win32 mutex locks. My understanding is that these are system calls underneath and could cause a context switch (which may be unnecessary for very quick critical sections where simply spinning a few times would be preferable). The atomic operations I'm referring to are well documented here: http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Atomic-Builtins.html Here is an example to illustrate what I'm talking about. Imagine a RB-tree with multiple readers and writers possible. RBTree::exists() is read-only and thread safe, RBTree::insert() would require exclusive access by a single writer (and no readers) to be safe. Some code: class IntSetTest { private: unsigned short lock; RBTree<int>* myset; public: // ... void add_number(int n) { // Aquire once locked==false (atomic) while (__sync_bool_compare_and_swap(&lock, 0, 0xffff) == false); // Perform a thread-unsafe operation on the set myset->insert(n); // Unlock (atomic) __sync_bool_compare_and_swap(&lock, 0xffff, 0); } bool check_number(int n) { // Increment once the lock is below 0xffff u16 savedlock = lock; while (savedlock == 0xffff || __sync_bool_compare_and_swap(&lock, savedlock, savedlock+1) == false) savedlock = lock; // Perform read-only operation bool exists = tree->exists(n); // Decrement savedlock = lock; while (__sync_bool_compare_and_swap(&lock, savedlock, savedlock-1) == false) savedlock = lock; return exists; } }; (lets assume it need not be exception-safe) Is this code indeed thread-safe? Are there any pros/cons to this idea? Any advice? Is the use of spinlocks like this a bad idea if the threads are not truly concurrent? Thanks in advance. ;)

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• Big-O of PHP functions?

  - by Kendall Hopkins

  After using PHP for a while now, I've noticed that not all PHP built in functions as fast as expected. Consider the below two possible implementations of a function that finds if a number is prime using a cached array of primes. //very slow for large $prime_array $prime_array = array( 2, 3, 5, 7, 11, 13, .... 104729, ... ); $result_array = array(); foreach( $array_of_number => $number ) { $result_array[$number] = in_array( $number, $large_prime_array ); } //still decent performance for large $prime_array $prime_array => array( 2 => NULL, 3 => NULL, 5 => NULL, 7 => NULL, 11 => NULL, 13 => NULL, .... 104729 => NULL, ... ); foreach( $array_of_number => $number ) { $result_array[$number] = array_key_exists( $number, $large_prime_array ); } This is because in_array is implemented with a linear search O(n) which will linearly slow down as $prime_array grows. Where the array_key_exists function is implemented with a hash lookup O(1) which will not slow down unless the hash table gets extremely populated (in which case it's only O(logn)). So far I've had to discover the big-O's via trial and error, and occasionally looking at the source code. Now for the question... I was wondering if there was a list of the theoretical (or practical) big O times for all* the PHP built in functions. *or at least the interesting ones For example find it very hard to predict what the big O of functions listed because the possible implementation depends on unknown core data structures of PHP: array_merge, array_merge_recursive, array_reverse, array_intersect, array_combine, str_replace (with array inputs), etc.

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• Reference inherited class's <T>ype in a derived class

  - by DRapp

  I don't know if its possible or not, but here's what I need. I'm toying around with something and want to know if its possible since you can't create your own data type based on a sealed type such as int, Int32, Int64, etc. I want to create a top-level class that is defined of a given type with some common stuff. Then, derive this into two subclasses, but in this case, each class is based on either and int or Int64 type. From THAT instance, create an instance of either one and know its yped basis for parameter referenc / return settings. So when I need to create an instance of the "ThisClass", I don't have to know its type basis of either int or Int64, yet IT will know the type and be able to allow methods/functions to be called with the typed... This way, If I want to change my ThisClass definition from SubLevel1 to SubLevel2, I don't have to dance around all different data type definitions. Hope this makes sense.. public class TopLevel<T> { ... } pubic class SubLevel1 : TopLevel<int> { ... } public class SubLevel2 : TopLevel<Int64> { ... } public class ThisClass : SubLevel1 { ... public <based on the Int data type from SubLevel1> SomeFunc() { return <the Int value computed>; } }

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• Can you force a crash if a write occurs to a given memory location with finer than page granularity?

  - by Joseph Garvin

  I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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• Empty UIView with minimal drawRect: overhead

  - by Benjohn Barnes

  Hi, I have an application that has three nested views that are mechanically important, but have no visual elements: A vanila UIView that doesn't have any content of its own, and is simply used as a host for CALayers. A UIScrollView (that is queried for it's origin and used to position CALayers in 3d: I really only use this view to faithfully replicate the scroll view's "mechanics"), The scroll view's contents: a UIView subclass. It simply picks up touch events and passes them to a delegate - all that is important are its UIResponder machinery. The UIView hosting CALayers is a sibling of a UIImageView that is a background image over which the CALayers are drawn. I'd really like to ensure that none of these empty UIViews have any drawing or compositing overhead (in time, or storage) associated with them, or if that's not possible, to get this overhead as small as possible, and to understand it so that I can perhaps decide if I should try a different approach. In interface builder, I've set all of the views to not clear their context before drawing. I've not set them to be opaque though, because they definitely are not opaque - they are completely transparent. I've found that I need to give the scroll view contents a transparent clear colour (again in IB by setting the background colour's opacity to zero), and this suggests that it is being drawn, which I don't want. So, in short, I've not got much idea of what is and isn't getting drawn (anyone know of a tool like Quartz Debug for iPhone / simulator?), or how to go about stopping things from getting drawn. Advice would be very welcome! Thanks, Benjohn

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• Changing customErrors in web.config semi-dynamically

  - by Tom Ritter

  The basic idea is we have a test enviroment which mimics Production so customErrors="RemoteOnly". We just built a test harness that runs against the Test enviroment and detects breaks. We would like it to be able to pull back the detailed error. But we don't want to turn customErrors="On" because then it doesn't mimic Production. I've looked around and thought a lot, and everything I've come up with isn't possible. Am I wrong about any of these points? We can't turn customErrors on at runtime because when you call configuration.Save() - it writes the web.config to disk and now it's Off for every request. We can't symlink the files into a new top level directory with it's own web.config because we're on windows and subversion on windows doesn't do symlinks. We can't use URL-Mapping to make an empty folder dir2 with its own web.config and make the files in dir1 appear to be in dir2 - the web.config doesn't apply We can't copy all the aspx files into dir2 with it's own web.config because none of the links would be consistent and it's a horrible hacky solution. We can't change customErrors in web.config based on hostname (e.g. add another dns entry to the test server) because it's not possible/supported We can't do any virtual directory shenanigans to make it work. If I'm not, is there a way to accomplish what I'm trying to do? Turn on customErrors site-wide under certain circumstances (dns name or even a querystring value)?

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• Load Ruby on Rails models without loading the entire framework

  - by epochwolf

  I'm looking to create a custom daemon that will run various database tasks such as delaying mailings and user notifications (each notice is a separate row in the notifications table). I don't want to use script/runner or rake to do these tasks because it is possible that some of the tasks only require the create of one or two database rows or thousands of rows depending on the task. I don't want the overhead of launching a ruby process or loading the entire rails framework for each operation. I plan to keep this daemon in memory full time. To create this daemon I would like to use my models from my ruby on rails application. I have a number of rails plugins such as acts_as_tree and AASM that I will need loaded if I where to use the models. Some of the plugins I need to load are custom hacks on ActiveRecord::Base that I've created. (I am willing to accept removing or recoding some of the plugins if they need components from other parts of rails.) My questions are Is this a good idea? And - Is this possible to do in a way that doesn't have me manually including each file in my models and plugins? If not a good idea What is a good alternative? (I am not apposed to doing writing my own SQL queries but I would have to add database constraints and a separate user for the daemon to prevent any stupid accidents. Given my lack of familiarity with configuring a database, I would like to use active record as a crutch.)

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