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  • aio_write on linux with rtkaio is sometimes long

    - by Drakosha
    I'm using async io on linux with rtkaio library. In my tests everything works perfectly, but, in my real application i see that aio_write which is supposed to return very fast, is very slow. It can take more than 100 milis to write a 128KB to a O_DIRECT padded file. Both my test and the application use same I/O size, i check on the same file system (GFS). I added counting and i see that there are about 50% of async io operations that are short (shorter then 2 milis) and 50% that are long (longer than 2 milis). I also checked that the test and the application both use the same rtkaio library. I'm pretty lost, anyone any ideas where should i look? Another my related question: http://stackoverflow.com/questions/1799537/proc-sys-fs-aio-nr-is-never-higher-than-1024-aio-on-linux

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  • Can't access annotation property of subclassed uibutton

    - by Tzur Gazit
    I have a mapView to which I add annotations. The pin's callout have a button (rightCalloutAccessoryView). In order to be able to display various information when the button is pushed, i've subclassed uibutton and added a class called "Annotation". @interface CustomButton : UIButton { NSIndexPath *indexPath; Annotation *mAnnotation; } @property (nonatomic, retain) NSIndexPath *indexPath; @property (nonatomic, copy) Annotation *mAnnotation; - (id) setAnnotation2:(Annotation *)annotation; @end Here is "Annotation": @interface Annotation : NSObject <MKAnnotation> { CLLocationCoordinate2D coordinate; NSString *mPhotoID; NSString *mPhotoUrl; NSString *mPhotoName; NSString *mOwner; NSString *mAddress; } @property (nonatomic, assign) CLLocationCoordinate2D coordinate; @property (nonatomic, copy) NSString *mPhotoID; @property (nonatomic, copy) NSString *mPhotoUrl; @property (nonatomic, copy) NSString *mPhotoName; @property (nonatomic, copy) NSString *mOwner; @property (nonatomic, copy) NSString *mAddress; - (id) initWithCoordinates:(CLLocationCoordinate2D)coordinate; - (id) setPhotoId:(NSString *)id url:(NSString *)url owner:(NSString *)owner address:(NSString *)address andName:(NSString *)name; @end I want to set the annotation property of the uibutton at - (MKAnnotationView *)mapView:(MKMapView *)pMapView viewForAnnotation:(id )annotation, in order to refer to it at the button push handler (-(IBAction) showDetails:(id)sender). The problem is that I can't set the annotation property of the button. I get the following message at run time: 2010-04-27 08:15:11.781 HotLocations[487:207] *** -[UIButton setMAnnotation:]: unrecognized selector sent to instance 0x5063400 2010-04-27 08:15:11.781 HotLocations[487:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIButton setMAnnotation:]: unrecognized selector sent to instance 0x5063400' 2010-04-27 08:15:11.781 HotLocations[487:207] Stack: ( 32080987, 2472563977, 32462907, 32032374, 31884994, 55885, 30695992, 30679095, 30662137, 30514190, 30553882, 30481385, 30479684, 30496027, 30588515, 63333386, 31865536, 31861832, 40171029, 40171226, 2846639 ) I appreciate the help. Tzur.

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  • How can I extend this SQL query to find the k nearest neighbors?

    - by Smigs
    I have a database full of two-dimensional data - points on a map. Each record has a field of the geometry type. What I need to be able to do is pass a point to a stored procedure which returns the k nearest points (k would also be passed to the sproc, but that's easy). I've found a query at http://blogs.msdn.com/isaac/archive/2008/10/23/nearest-neighbors.aspx which gets the single nearest neighbour, but I can't figure how to extend it to find the k nearest neighbours. This is the current query - T is the table, g is the geometry field, @x is the point to search around, Numbers is a table with integers 1 to n: DECLARE @start FLOAT = 1000; WITH NearestPoints AS ( SELECT TOP(1) WITH TIES *, T.g.STDistance(@x) AS dist FROM Numbers JOIN T WITH(INDEX(spatial_index)) ON T.g.STDistance(@x) < @start*POWER(2,Numbers.n) ORDER BY n ) SELECT TOP(1) * FROM NearestPoints ORDER BY n, dist The inner query selects the nearest non-empty region and the outer query then selects the top result from that region; the outer query can easily be changed to (e.g.) SELECT TOP(20), but if the nearest region only contains one result, you're stuck with that. I figure I probably need to recursively search for the first region containing k records, but without using a table variable (which would cause maintenance problems as you have to create the table structure and it's liable to change - there're lots of fields), I can't see how.

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  • Python: using doctests for classes

    - by Adam Matan
    Hi, Is it possible to use Python's doctest concept for classes, not just functions? If so, where shall I put the doctests - at the class' docstring, or at the constructor's docstring? To clarify, I'm looking for something like: class Test: """ >>> a=Test(5) >>> a.multiply_by_2() 10 """ def __init__(self, number): self._number=number def multiply_by_2(self): return self._number*2 Thanks in advance, Adam

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  • Creating/Maintaining a large project-agnostic code library

    - by bufferz
    In order to reduce repetition and streamline testing/debugging, I'm trying to find the best way to develop a group of libraries that many projects can utilize. I'd like to keep individual executable relatively small, and have shared libraries for math, database, collections, graphics, etc. that were previously scattered among several projects and in many cases duplicated (bad!). This library is to be in an SVN repo and several programmers will be working on it. This library will be in constant development along with the executables that utilize it. For example, I want a code file in ProjectA to look something like the following: using MyCompany.Math.2D; //static 2D math methods using MyCompany.Math.3D; //static #D math methods using MyCompany.Comms.SQL; //static methods for doing simple SQLDB I/O using MyCompany.Graphics.BitmapOperations; //static methods that play with bitmaps So in my ProjectA solution file in VisualStudio, in order to develop/debug the MyCompany library I have to add several projects (Math, Comms, Graphics). Things get pretty cluttered and Solution files get out of date quickly between programmer SVN commits. I'm just looking for a high level approach to maintaining a large, shared code base in an SCN repository. I am fully willing to radically redesign my approach. I'm looking for that warm fuzzy feeling you get when you're design approach is spot on and development is fluid and natural. And ideas? Thanks!!

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  • Having trouble using jQuery to set meta tag values

    - by Zhami
    I'm trying to set meta tags using jQuery (please don't reply that this doesn't make sense since search engines blah-blah-blah... I am loading invoking 3rd party Javascript functions that examine these vales, such as Tweetmeme and Facebook). If I use: $('meta[name=some-name]').attr('content', 'some value'); it does work to set the value of an existing meta tag, but does not create a meta tag if such a named one does not exist. If you have insight or experience with this, please reply...

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  • Runtime C function details

    - by Sridhar
    Hi, Is there any way to find particular C language function's input and output parameters from a framework (apple's ARM) during the runtime or from any method with out knowing the headers. It is a framework and there are no header files for it.I decompile it with IDA Pro and it gives me the function names but not input and output parameters information. I am able to load those private functions using dlsym. Is it possible to find the parameters info in runtime (C language or Objective C) or from IDA Pro ? Regards, Raghu

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  • How to have member variables and public methods in a jQuery plugin?

    - by user169867
    I'm trying to create a jQuery plugin that will create something like an autoCompleteBox but with custom features. How do I store member variables for each matching jQuery element? For example I'll need to store a timerID for each. I'd also like to store references to some of the DOM elements that make up the control. I'd like to be able to make a public method that works something like: $("#myCtrl").autoCompleteEx.addItem("1"); But in the implementation of addItem() how can I access the member variables for that particular object like its timerID or whatever? Below is what I have so far... Thanks for any help or suggestions! (function($) { //Attach this new method to jQuery $.fn.autoCompleteEx = function(options) { //Merge Given Options W/ Defaults, But Don't Alter Either var opts = $.extend({}, $.fn.autoCompleteEx.defaults, options); //Iterate over the current set of matched elements return this.each(function() { var acx = $(this); //Get JQuery Version Of Element (Should Be Div) //Give Div Correct Class & Add <ul> w/ input item to it acx.addClass("autoCompleteEx"); acx.html("<ul><li class=\"input\"><input type=\"text\"/></li></ul>"); //Grab Input As JQ Object var input = $("input", acx); //Wireup Div acx.click(function() { input.focus().val( input.val() ); }); //Wireup Input input.keydown(function(e) { var kc = e.keyCode; if(kc == 13) //Enter { } else if(kc == 27) //Esc { } else { //Resize TextArea To Input var width = 50 + (_txtArea.val().length*10); _txtArea.css("width", width+"px"); } }); }); //End Each JQ Element }; //End autoCompleteEx() //Private Functions function junk() { }; //Public Functions $.fn.autoCompleteEx.addItem = function(id,txt) { var x = this; var y = 0; }; //Default Settings $.fn.autoCompleteEx.defaults = { minChars: 2, delay: 300, maxItems: 1 }; //End Of Closure })(jQuery);

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  • Rails paginate array items one-by-one instead of page-by-page

    - by hnovick
    Hi Guys, I have a group of assets, let's call them "practitioners". I'm displaying these practitioners in the header of a calendar interface. There are 7 columns to the calendar. 7 columns = 7 practitioners per view/page. Right now: if the first page shows you practitioners 1-7, when you go the next page you will see practitioners 8-15, next page 16-23, etc. etc. i am wondering how to page the practitioners so that if the first page shows you practitioners 1-7, the next page will show you practitioners 2-8, then 3-9, etc. etc. i would greatly appreciate any help you can offer. here is the rails code i am working with. best regards, harris novick # get the default sort order sort_order = RESOURCE_SORT_ORDER # if we've been given asset ids, start our list with them unless params[:asset_ids].blank? params[:asset_ids] = params[:asset_ids].values unless params[:asset_ids].is_a?(Array) sort_order = "#{params[:asset_ids].collect{|id| "service_provider_resources.id = #{id} DESC"}.join(",")}, #{sort_order}" end @asset_set = @provider.active_resources(:include => {:active_services => :latest_approved_version}).paginate( :per_page => RESOURCES_IN_DAY_VIEW, :page => params[:page], :order => sort_order )

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • What happens in memory when a C++ class is instantiated

    - by Jo Bucher
    I'm interested in the nuts and boltw of C++ and I wondered what actually changes when an object is instantiated. I'm particularly interested if the functions are then added to memory, if they are there from runtime or if they are never stored in memory at all. If anyone could direct me to a good site on some of the core bolts of C and C++, I'd love that too. Thanks, Jo

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  • Android - read and delete new SMS of a specific sender only

    - by John
    I'm trying to write the next function: 1) Send SMS to a service number 2) Read the response SMS content (the service's auto sent-back message that tells me if I succeed/failed to turn on the service) 3) Delete the service's auto-sent SMS I know how to do the first step, and I should be able to do the second with both: getMessageBody () getOriginatingAddress () but: 1) how can I refer the last incoming message to use the above functions? 2) how can I delete that specific message? Thanks, John

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  • Android: how to convert a Drawable to Bitmap

    - by Rob
    How can I convert a Drawable to a Bitmap? I would like to set a certain drawable as the device's wallpaper, but all wallpaper functions accept Bitmaps only (I cannot use WallpaperManager - I'm pre 2.1). Also, my drawables are downloaded from the web and do not reside in R.drawable. Thanks, Rob

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  • wrong operator() overload called

    - by user313202
    okay, I am writing a matrix class and have overloaded the function call operator twice. The core of the matrix is a 2D double array. I am using the MinGW GCC compiler called from a windows console. the first overload is meant to return a double from the array (for viewing an element). the second overload is meant to return a reference to a location in the array (for changing the data in that location. double operator()(int row, int col) const ; //allows view of element double &operator()(int row, int col); //allows assignment of element I am writing a testing routine and have discovered that the "viewing" overload never gets called. for some reason the compiler "defaults" to calling the overload that returns a reference when the following printf() statement is used. fprintf(outp, "%6.2f\t", testMatD(i,j)); I understand that I'm insulting the gods by writing my own matrix class without using vectors and testing with C I/O functions. I will be punished thoroughly in the afterlife, no need to do it here. Ultimately I'd like to know what is going on here and how to fix it. I'd prefer to use the cleaner looking operator overloads rather than member functions. Any ideas? -Cal the matrix class: irrelevant code omitted class Matrix { public: double getElement(int row, int col)const; //returns the element at row,col //operator overloads double operator()(int row, int col) const ; //allows view of element double &operator()(int row, int col); //allows assignment of element private: //data members double **array; //pointer to data array }; double Matrix::getElement(int row, int col)const{ //transform indices into true coordinates (from sorted coordinates //only row needs to be transformed (user can only sort by row) row = sortedArray[row]; result = array[usrZeroRow+row][usrZeroCol+col]; return result; } //operator overloads double Matrix::operator()(int row, int col) const { //this overload is used when viewing an element return getElement(row,col); } double &Matrix::operator()(int row, int col){ //this overload is used when placing an element return array[row+usrZeroRow][col+usrZeroCol]; } The testing program: irrelevant code omitted int main(void){ FILE *outp; outp = fopen("test_output.txt", "w+"); Matrix testMatD(5,7); //construct 5x7 matrix //some initializations omitted fprintf(outp, "%6.2f\t", testMatD(i,j)); //calls the wrong overload }

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  • Operator Overloading in C

    - by Leif Andersen
    In C++, I can change the operator on a specific class by doing something like this: MyClass::operator==/*Or some other operator such as =, >, etc.*/(Const MyClass rhs) { /* Do Stuff*/; } But with there being no classes (built in by default) in C. So, how could I do operator overloading for just general functions? For example, if I remember correctly, importing stdlib.h gives you the - operator, which is just syntactic sugar for (*strcut_name).struct_element. So how can I do this in C? Thank you.

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  • C - floating point rounding

    - by hatorade
    I'm trying to understand how floating point numbers work. I think I'd like to test out what I know / need to learn by evaluating the following: I would like to find the smallest x such that x + 1 = x, where x is a floating point number. As I understand it, this would happen in the case where x is large enough so that x + 1 is closer to x than the next number higher than x representable by floating point. So intuitively it seems it would be the case where I don't have enough digits in the significand. Would this number x then be the number where the significand is all 1's. But then I can't seem to figure out what the exponent would have to be. Obviously it would have to be big (relative to 10^0, anyway).

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  • What is causing Apache2 to display PHP as plain text in this config file?

    - by rxgx
    I am trying to run PHP and Rails in the same virtual host, however, PHP is being displayed as plain/text. When I create a test host without all the rewrites and proxy-ing, Apache2 will process the PHP as desired. Where in my config file have I gone wrong? <VirtualHost *:80> #ServerName staging.domain.com #ServerAlias www.domain.com DocumentRoot /home/demo/vhosts/domain/public <Directory /> Options FollowSymLinks AllowOverride None </Directory> <Directory /home/demo/vhosts/domain/public> Options Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> RewriteEngine On <Proxy balancer://thinservers> BalancerMember http://127.0.0.1:5000 BalancerMember http://127.0.0.1:5001 BalancerMember http://127.0.0.1:5002 </Proxy> # Redirect all non-static requests to thin RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f RewriteRule ^/(.*)$ balancer://thinservers%{REQUEST_URI} [P,QSA,L] ProxyPass / balancer://thinservers/ ProxyPassReverse / balancer://thinservers/ ProxyPreserveHost on <Proxy *> Order deny,allow Allow from all </Proxy> # Custom log file locations ErrorLog /home/demo/vhosts/domain/log/error.log CustomLog /home/demo/vhosts/domain/log/access.log combined </VirtualHost>

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  • What language is to binary, as Perl is to text?

    - by ehdr
    I am looking for a scripting (or higher level programming) language (or e.g. modules for Python or similar languages) for effortlessly analyzing and manipulating binary data in files (e.g. core dumps), much like Perl allows manipulating text files very smoothly. Things I want to do include presenting arbitrary chunks of the data in various forms (binary, decimal, hex), convert data from one endianess to another, etc. That is, things you normally would use C or assembly for, but I'm looking for a language which allows for writing tiny pieces of code for highly specific, one-time purposes very quickly. Any suggestions?

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  • An interesting case of delete and destructor (C++)

    - by Viet
    I have a piece of code where I can call destructor multiple times and access member functions even the destructor was called with member variables' values preserved. I was still able to access member functions after I called delete but the member variables were nullified (all to 0). And I can't double delete. Please kindly explain this. Thanks. #include <iostream> using namespace std; template <typename T> void destroy(T* ptr) { ptr->~T(); } class Testing { public: Testing() : test(20) { } ~Testing() { printf("Testing is being killed!\n"); } int getTest() const { return test; } private: int test; }; int main() { Testing *t = new Testing(); cout << "t->getTest() = " << t->getTest() << endl; destroy(t); cout << "t->getTest() = " << t->getTest() << endl; t->~Testing(); cout << "t->getTest() = " << t->getTest() << endl; delete t; cout << "t->getTest() = " << t->getTest() << endl; destroy(t); cout << "t->getTest() = " << t->getTest() << endl; t->~Testing(); cout << "t->getTest() = " << t->getTest() << endl; //delete t; // <======== Don't do it! Double free/delete! cout << "t->getTest() = " << t->getTest() << endl; return 0; }

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  • SQL Alchemy MVC and cross controller joins

    - by Khorkrak
    When using SQL Alchemy for abstracting your data access layer and using controllers as the way to access objects from that abstraction layer, how should joins be handled? So for example, say you have an Orders controller class that manages Order objects such that it provides getOrder, saveOrder, etc methods and likewise a similar controller for User objects. First of all do you even need these controllers? Should you instead just treat SQL Alchemy as "the" thing for handling data access. Why bother with object oriented controller stuff there when you instead have a clean declarative way to obtain and persist objects without having to write SQL directly either. Well one reason could be that perhaps you may want to replace SQL Alchemy with direct SQL or Storm or whatever else. So having controller classes there to act as an intermediate layer helps limit what would need to change then. Anyway - back to the main question - so assuming you have these two controllers, now lets say you want the list of orders for a certain set of users meeting some criteria. How do you go about doing this? Generally you don't want the controllers crossing domains - the Orders controllers knows only about Orders and the User controller just about Users - they don't mess with each other. You also don't want to go fetch all the Users that match and then feed a big list of user ids to the Orders controller to go find the matching Orders. What's needed is a join. Here's where I'm stuck - that seems to mean either the controllers must cross domains or perhaps they should be done away with altogether and you simply do the join via SQL Alchemy directly and get the resulting User and / or Order objects as needed. Thoughts?

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  • Format fixed-format text file lines

    - by EugeneP
    there's a text file first second third 1 2 3 yes no ok hmmmmmmm yep_a_long_word_it_is ahahahahahahha what java functions /libs to use to align words so that they are looked like this (fixed width based on the longest column's length), let's say center align: first second third 1 2 3 yes no ok hmmmmmmm yep_a_long_word_it_is ahahahahahahha

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  • Discover generic types

    - by vittore
    Thanks @dtb for help, he advised really need piece of code for generic service locator static class Locator { private static class LocatorEntry<T> where T : ... { public static IDataManager<T> instance; } public static void Register<T>(IDataManager<T> instance) where T : ... { LocatorEntry<T>.instance = instance; } public static IDataManager<T> GetInstance<T>() where T : ... { return LocatorEntry<T>.instance; } } However in my previous version I used reflection on assembly to discover a hundred of DataManager's I want to write an method discover like the following void Discover() { var pManager = new ProtocolSQLDataManager(); Register(pManager); var rManager = new ResultSQLDataManager(); Register(rManager); var gType = typeof(ISQLDataAccessManager<>); foreach (Type type in Assembly.GetExecutingAssembly().GetTypes()) { if (type.IsSubclassOf(gType) && !type.IsAbstract)) { var manager = Activator.CreateInstance(type); // put something here in order to make next line of code works Register<T>(manager); } } } How to cast type to appropriate type in order to make Register working( and call appropriate Register ?

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