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  • Will fixed-point arithmetic be worth my trouble?

    - by Thomas
    I'm working on a fluid dynamics Navier-Stokes solver that should run in real time. Hence, performance is important. Right now, I'm looking at a number of tight loops that each account for a significant fraction of the execution time: there is no single bottleneck. Most of these loops do some floating-point arithmetic, but there's a lot of branching in between. The floating-point operations are mostly limited to additions, subtractions, multiplications, divisions and comparisons. All this is done using 32-bit floats. My target platform is x86 with at least SSE1 instructions. (I've verified in the assembler output that the compiler indeed generates SSE instructions.) Most of the floating-point values that I'm working with have a reasonably small upper bound, and precision for near-zero values isn't very important. So the thought occurred to me: maybe switching to fixed-point arithmetic could speed things up? I know the only way to be really sure is to measure it, that might take days, so I'd like to know the odds of success beforehand. Fixed-point was all the rage back in the days of Doom, but I'm not sure where it stands anno 2010. Considering how much silicon is nowadays pumped into floating-point performance, is there a chance that fixed-point arithmetic will still give me a significant speed boost? Does anyone have any real-world experience that may apply to my situation?

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  • How do you prevent file confusion if version-control keywords are forbidden?

    - by Thomas L Holaday
    At least two brilliant programmers, Linus Torvalds and Guido von Rossum, disparage the practice of putting keywords into a file that expand to show the version number, last author, etc. I know how keyword differences clutter up diffs. One of the reasons I like SlickEdit's DiffZilla is because it can be set to skip leading comments. However, I have vivid memories of team-programming where we had four versions of a file (two different releases, a customer one-off, and the development version) all open for patching at the same time, and was quite helpful to verify with a glance that each time we navigated to an included header we got the proper one, and each time we pasted code the source and destination were what we expected. There is also the where-did-this-file-come-from problem that arises when a hasty developer copies a file from one place to another using the file system, rather than checking it out of the repository using the tool; or, more defensibly, when files under control in locations A, B, and C need to be marshalled (with cherry-picking) into a distribution location D. In places where VCS keywords are banned, how do you cope?

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  • Visitor and templated virtual methods

    - by Thomas Matthews
    In a typical implementation of the Visitor pattern, the class must account for all variations (descendants) of the base class. There are many instances where the same method content in the visitor is applied to the different methods. A templated virtual method would be ideal in this case, but for now, this is not allowed. So, can templated methods be used to resolve virtual methods of the parent class? Given (the foundation): struct Visitor_Base; // Forward declaration. struct Base { virtual accept_visitor(Visitor_Base& visitor) = 0; }; // More forward declarations struct Base_Int; struct Base_Long; struct Base_Short; struct Base_UInt; struct Base_ULong; struct Base_UShort; struct Visitor_Base { virtual void operator()(Base_Int& b) = 0; virtual void operator()(Base_Long& b) = 0; virtual void operator()(Base_Short& b) = 0; virtual void operator()(Base_UInt& b) = 0; virtual void operator()(Base_ULong& b) = 0; virtual void operator()(Base_UShort& b) = 0; }; struct Base_Int : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_Long : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_Short : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_UInt : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_ULong : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_UShort : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; Now that the foundation is laid, here is where the kicker comes in (templated methods): struct Visitor_Cout : public Visitor { template <class Receiver> void operator() (Receiver& r) { std::cout << "Visitor_Cout method not implemented.\n"; } }; Intentionally, Visitor_Cout does not contain the keyword virtual in the method declaration. All the other attributes of the method signatures match the parent declaration (or perhaps specification). In the big picture, this design allows developers to implement common visitation functionality that differs only by the type of the target object (the object receiving the visit). The implementation above is my suggestion for alerts when the derived visitor implementation hasn't implement an optional method. Is this legal by the C++ specification? (I don't trust when some says that it works with compiler XXX. This is a question against the general language.)

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  • Filtering documents against a dictionary key in MongoDB

    - by Thomas
    I have a collection of articles in MongoDB that has the following structure: { 'category': 'Legislature', 'updated': datetime.datetime(2010, 3, 19, 15, 32, 22, 107000), 'byline': None, 'tags': { 'party': ['Peter Hoekstra', 'Virg Bernero', 'Alma Smith', 'Mike Bouchard', 'Tom George', 'Rick Snyder'], 'geography': ['Michigan', 'United States', 'North America'] }, 'headline': '2 Mich. gubernatorial candidates speak to students', 'text': [ 'BEVERLY HILLS, Mich. (AP) \u2014 Two Democratic and Republican gubernatorial candidates found common ground while speaking to private school students in suburban Detroit', "Democratic House Speaker state Rep. Andy Dillon and Republican U.S. Rep. Pete Hoekstra said Friday a more business-friendly government can help reduce Michigan's nation-leading unemployment rate.", "The candidates were invited to Detroit Country Day Upper School in Beverly Hills to offer ideas for Michigan's future.", 'Besides Dillon, the Democratic field includes Lansing Mayor Virg Bernero and state Rep. Alma Wheeler Smith. Other Republicans running are Oakland County Sheriff Mike Bouchard, Attorney General Mike Cox, state Sen. Tom George and Ann Arbor business leader Rick Snyder.', 'Former Republican U.S. Rep. Joe Schwarz is considering running as an independent.' ], 'dateline': 'BEVERLY HILLS, Mich.', 'published': datetime.datetime(2010, 3, 19, 8, 0, 31), 'keywords': "Governor's Race", '_id': ObjectId('4ba39721e0e16cb25fadbb40'), 'article_id': 'urn:publicid:ap.org:0611e36fb084458aa620c0187999db7e', 'slug': "BC-MI--Governor's Race,2nd Ld-Writethr" } If I wanted to write a query that looked for all articles that had at least 1 geography tag, how would I do that? I have tried writing db.articles.find( {'tags': 'geography'} ), but that doesn't appear to work. I've also thought about changing the search parameter to 'tags.geography', but am having a devil of a time figuring out what the search predicate would be.

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  • Easy way to observe user activity - how improve my database structure.

    - by Thomas
    Welcome, I need some advise to improve perfomence my web application. In the begin I had this structure of database: USER -id (Primary Key) -name -password -email .... PROFILE -user Primary Key, Foreign Key (USER) -birthday -region -photoFile ... PAGES -id (Primary Key) -user Foreign Key(USER) -page -date COMMENTS -id (Primary Key) -user Foreign Key(USER) -page Foreign Key(PAGE) -comment -date FAVOURITES_PAGES -id (Primary Key) -user Foreign Key(USER) -favourite_page Foreign Key(PAGE) -date but now one of the most important page of website is observatory, when everyone can observe activity others users. So I need select all pages, comments and favourites pages some users and display it in one list, sorted by date. For better perfomance (I think) I changed my structure to this: table USER and PROFILE without changes ACTIVITY (additional table- have common fields: user,date) -id (Primary Key) -user Foreign Key(USER) -date -page Foreign Key(PAGE) -comment Foreign Key(COMMENTS) -favourite_page Foreign Key(FAVOURITES_PAGES) PAGES -id (Primary Key) -page COMMENTS -id (Primary Key) -page Foreign Key(PAGE) -comment FAVOURITES_PAGES -id (Primary Key) -favourite_page Foreign Key(PAGE) So now it is very easy get sorted records from all tables. But I have no only foreign key to PAGES, COMMENTS and FAVOURITES_PAGES in ACTIVITY table - there is about ten Foreign Key fields and in one record only one have value, others have None: ACTIVITY id user date page comment ... 1 2 2010-02-23 None 1 2 1 2010-02-21 1 None .... It is corect solution. When I display about 40 records in one page (pagination) I must wait about one secound, but database is almost emty (a few users and about 100 records in others tables). It is depends on amount records per page - I have checked it, but why it takes too long time, becouse of relationships? The website is built in Python/Django. Any advices/opinion?

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  • How do I align ReSharpers "cleanup code" with Visual Studio's "format document"

    - by Thomas Jespersen
    I'm a big fan of ReSharpers "cleanup code" feature. Especially the Solution wide clean up. But I use Visual Studio's Ctrl+K+D (Format document), it formats the code slightly differed than ReSharper. I'm on a quest to align ReSharper with Visual Studio (not the other way... because you can not share Visual Studio settings in the solution/source control system). So I'm after something like this: <Configuration> <CodeStyleSettings> <Sharing>SOLUTION</Sharing> <CSharp> <FormatSettings> <SPACE_AROUND_MULTIPLICATIVE_OP>True</SPACE_AROUND_MULTIPLICATIVE_OP> <SPACE_BEFORE_TYPEOF_PARENTHESES>False</SPACE_BEFORE_TYPEOF_PARENTHESES> </FormatSettings> </CSharp> </CodeStyleSettings> </Configuration> Which other settings will help ReSharper format code like Visual Studio?

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  • web grid server pagination trigger multiple controller call when changing page

    - by Thomas Scattolin
    When I server-filter on "au" my web grid and change page, multiple call to the controller are done : the first with 0 filtering, the second with "a" filtering, the third with "au" filtering. My table load huge data so the first call is longer than others. I see the grid displaying firstly the third call result, then the second, and finally the first call (this order correspond to the response time of my controller due to filter parameter) Why are all that controller call made ? Can't just my controller be called once with my total filter "au" ? What should I do ? Here is my grid : $("#" + gridId).kendoGrid({ selectable: "row", pageable: true, filterable:true, scrollable : true, //scrollable: { // virtual: true //false // Bug : Génère un affichage multiple... //}, navigatable: true, groupable: true, sortable: { mode: "multiple", // enables multi-column sorting allowUnsort: true }, dataSource: { type: "json", serverPaging: true, serverSorting: true, serverFiltering: true, serverGrouping:false, // Ne fonctionne pas... pageSize: '@ViewBag.Pagination', transport: { read: { url: Procvalue + "/LOV", type: "POST", dataType: "json", contentType: "application/json; charset=utf-8" }, parameterMap: function (options, type) { // Mise à jour du format d'envoi des paramètres // pour qu'ils puissent être correctement interprétés côté serveur. // Construction du paramètre sort : if (options.sort != null) { var sort = options.sort; var sort2 = ""; for (i = 0; i < sort.length; i++) { sort2 = sort2 + sort[i].field + '-' + sort[i].dir + '~'; } options.sort = sort2; } if (options.group != null) { var group = options.group; var group2 = ""; for (i = 0; i < group.length; i++) { group2 = group2 + group[i].field + '-' + group[i].dir + '~'; } options.group = group2; } if (options.filter != null) { var filter = options.filter.filters; var filter2 = ""; for (i = 0; i < filter.length; i++) { // Vérification si type colonne == string. // Parcours des colonnes pour trouver celle qui a le même nom de champ. var type = ""; for (j = 0 ; j < colonnes.length ; j++) { if (colonnes[j].champ == filter[i].field) { type = colonnes[j].type; break; } } if (filter2.length == 0) { if (type == "string") { // Avec '' autour de la valeur. filter2 = filter2 + filter[i].field + '~' + filter[i].operator + "~'" + filter[i].value + "'"; } else { // Sans '' autour de la valeur. filter2 = filter2 + filter[i].field + '~' + filter[i].operator + "~" + filter[i].value; } } else { if (type == "string") { // Avec '' autour de la valeur. filter2 = filter2 + '~' + options.filter.logic + '~' + filter[i].field + '~' + filter[i].operator + "~'" + filter[i].value + "'"; }else{ filter2 = filter2 + '~' + options.filter.logic + '~' + filter[i].field + '~' + filter[i].operator + "~" + filter[i].value; } } } options.filter = filter2; } var json = JSON.stringify(options); return json; } }, schema: { data: function (data) { return eval(data.data.Data); }, total: function (data) { return eval(data.data.Total); } }, filter: { logic: "or", filters:filtre(valeur) } }, columns: getColonnes(colonnes) }); Here is my controller : [HttpPost] public ActionResult LOV([DataSourceRequest] DataSourceRequest request) { return Json(CProduitsManager.GetProduits().ToDataSourceResult(request)); }

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  • Reference methods defined in one JScript file from another JScript

    - by Thomas Svensen
    I am writing some server-side scripts using jscript and WSH. The scripts are getting quite long, and some common functions and variables would fit better in a general library script which I included in my various script instances. But, I cannot find a way reference one JScript file from another. For a moment, I though reading the file contents and passing it to "eval()" could work. But, as it says on MSDN: "Note that new variables or types defined in the eval statement are not visible to the enclosing program." (http://msdn.microsoft.com/en-us/library/b51a45x6.aspx) Is there any way to include/refence a JScript from another one?

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  • Clear default values using onsubmit

    - by Thomas
    I need to clear the default values from input fields using js, but all of my attempts so far have failed to target and clear the fields. I was hoping to use onSubmit to excute a function to clear all default values (if the user has not changed them) before the form is submitted. <form method='get' class='custom_search widget custom_search_custom_fields__search' onSubmit='clearDefaults' action='http://www.example.com' > <input name='cs-Price-2' id='cs-Price-2' class='short_form' value='Min. Price' /> <input name='cs-Price-3' id='cs-Price-3' class='short_form' value='Max Price' /> <input type='submit' name='search' class='formbutton' value=''/> </form> How would you accomplish this?

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  • Problem using yaml-cpp on OS X

    - by Thomas
    So I'm having trouble compiling my application which is using yaml-cpp I'm including "yaml.h" in my source files (just like the examples in the yaml-cpp wiki) but when I try compiling the application I get the following error: g++ -c -o entityresourcemanager.o entityresourcemanager.cpp entityresourcemanager.cpp:2:18: error: yaml.h: No such file or directory make: *** [entityresourcemanager.o] Error 1 my makefile looks like this: CC = g++ CFLAGS = -Wall APPNAME = game UNAME = uname OBJECTS := $(patsubst %.cpp,%.o,$(wildcard *.cpp)) mac: $(OBJECTS) $(CC) `pkg-config --cflags --libs sdl` `pkg-config --cflags --libs yaml-cpp` $(CFLAGS) -o $(APPNAME) $(OBJECTS) pkg-config --cflags --libs yaml-cpp returns: -I/usr/local/include/yaml-cpp -L/usr/local/lib -lyaml-cpp and yaml.h is indeed located in /usr/local/include/yaml-cpp Any idea what I could do? Thanks

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  • Implementation of a general-purpose object structure (property bag)

    - by Thomas Wanner
    We need to implement some general-purpose object structure, much like an object in dynamic languages, that would give us a possibility of creating the whole object graph on-the-fly. This class has to be serializable and somehow user friendly. So far we have made some experiments with class derived from Dictionary<string, object> using the dot notation path to store properties and collections in the object tree. We have also find an article that implements something similar, but it doesn't seem to fit completely into our picture either. Do you know about some good implementations / libraries that deal with a similar problem or do you have any (non-trivial) ideas that could help us with our own implementation ? Also, I probably have to say that we are using .NET 3.5, so we can't take advantage of the new features in .NET 4.0 like dynamic type etc. (as far as I know it's also not possible to use any subset of it in .NET 3.5 solution).

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  • Send custom headers with UIWebView loadRequest

    - by Thomas Clayson
    I want to be able to send some extra headers with my UIWebView loadRequest method. I have tried: NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.reliply.org/tools/requestheaders.php"]]; [req addValue:@"hello" forHTTPHeaderField:@"aHeader"]; [self.theWebView loadRequest:req]; I have also tried subclassing the UIWebView and intercepting the - (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType method. In that method I had a block of code which looked like this: NSMutableURLRequest *newRequest = [request mutableCopy]; for(NSString *key in [customHeaders allKeys]) { [newRequest setValue:[customHeaders valueForKey:key] forHTTPHeaderField:key]; } [self loadRequest:newRequest]; But for some unknown reason it was causing the web view to not load anything (blank frame) and the error message NSURLErrorCancelled (-999) comes up (all known fixes don't fix it for me). So I am at a loss as to what to do. How can I send a custom header along with a UIWebView request? Many thanks!

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  • How do I set the UI language in vim?

    - by Daren Thomas
    I saw this on reddit, and it reminded me of one of my vim gripes: It shows the UI in German. Damn you, vim! I want English, but since my OS is set up in German (the standard at our office), I guess vim is actually trying to be helpfull. What magic incantations must I perform to get vim to switch the UI language? I have tried googling on various occasions, but can't seem to find an answer (No, Google, you're my friend *pat*, *pat*, but I allready know how to change the syntax highlighting, thank you!)...

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  • Guessing the time zone from an arbitrary "location" string?

    - by Thomas
    I'm trying to run some statistics over the Stack Overflow data dump, and for that I would like to know the time zone for each user. However, all I have to go on is the completely free-form "location" string. I'll stress that I'm only looking for an approximation of the time zone; of course, in general this is an unsolvable problem. However, many people fill out their country, state and/or city, which should give a pretty good indication. It's okay if it fails for other cases. It doesn't have to be reliable, it doesn't have to be accurate, it doesn't have to cover all bases. I don't want to waste too much time on this, so I'm wondering if there is some code out there that can make a reasonable guess. Any language, platform, API or library goes. Any ideas?

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  • Join query in doctrine symfony

    - by THOmas
    I have two tables userdetails and blog question The schema is UserDetails: connection: doctrine tableName: user_details columns: id: type: integer(8) fixed: false name: type: string(255) fixed: false BlogQuestion: connection: doctrine tableName: blog_question columns: question_id: type: integer(8) fixed: false unsigned: false primary: true autoincrement: true blog_id: type: integer(8) fixed: false user_id: type: integer(8) fixed: false question_title: type: string(255) I am using one join query for retrieving all the questions and user details from this two tables My join query is $q = Doctrine_Query::create() ->select('*') ->from('BlogQuestion u') ->leftJoin('u.UserDetails p'); $q->execute(); But it is showing this error Unknown relation alias UserDetails Pls anybody help me Thanks in advance

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  • Rookie PHP question

    - by Thomas
    I am hacking together a theme for wordpress and I am using the following code to pull out data from a custom field with several values: <?php $mykey_values = get_post_custom_values('services'); foreach ( $mykey_values as $key => $value ) { echo "<span>$value, </span>"; } ?> I use a comma to seperate the results, but I don't want a comma after the last result. How do I get around this?

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  • How best to convert CakePHP date picker form data to a PHP DateTime object?

    - by Daren Thomas
    I'm doing this in app/views/mymodel/add.ctp: <?php echo $form->input('Mymodel.mydatefield'); ?> And then, in app/controllers/mymodel_controller.php: function add() { # ... (if we have some submitted data) $datestring = $this->data['Mymodel']['mydatefield']['year'] . '-' . $this->data['Mymodel']['mydatefield']['month'] . '-' . $this->data['Mymodel']['mydatefield']['day']; $mydatefield = DateTime::createFromFormat('Y-m-d', $datestring); } There absolutly has to be a better way to do this - I just haven't found the CakePHP way yet... What I would like to do is: function add() { # ... (if we have some submitted data) $mydatefield = $this->data['Mymodel']['mydatefiled']; # obviously doesn't work }

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  • Using a checkbox input on a form to send the form data to different email addresses

    - by Cody Thomas
    I am building a form for a client. Here is the rundown. The form will be used as a request to have a staff member contact the person filling out the form. However, there is a list of staff members that will contact them depending on what the subject matter is. So, I want to create a checkbox input section on the form with each staff person's email address attached to a corresponding checkbox. So, the person filling out the form can check only the staff people necessary for their needs. Finally, when the person clicks "submit", the form will be emailed to only the staff members who were checked in the form. I'm at a loss of how to set this up.

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  • Makefile for DOS/Windows and Cygwin

    - by Thomas Matthews
    I need to have a makefile work under DOS (Windows) and Cygwin. I having problems with the makefile detecting the OS correctly and setting appropriate variables. The objective is to set variables for the following commands, then invoke the commands in rules using the variables: Delete file: rm in Cygwin, del in DOS. Remove directory: rmdir (different parameters in Cygwin and DOS) Copy file: cp in Cygwin, copy in DOS. Testing for file existance: test in Cygwin, IF EXIST in DOS. Listing contents of a file: cat in Cygwin, type in DOS. Here is my attempt, which always uses the else clause: OS_KIND = $(OSTYPE) #OSTYPE is an environment variable set by Cygwin. ifeq ($(OS_KIND), cygwin) ENV_OS = Cygwin RM = rm -f RMDIR = rmdir -r CP = cp REN = mv IF_EXIST = test -a IF_NOT_EXIST = ! test -a LIST_FILE = cat else ENV_OS = Win_Cmd RM = del -f -Q RMDIR = rmdir /S /Q IF_EXIST = if exist IF_NOT_EXIST = if not exist LIST_FILE = type endif I'm using the forward slash character, '/', as a directory separator. This is a problem with the DOS command, as it is interpreting it as program argument rather than a separator. Anybody know how to resolve this issue? Edit: I am using make with Mingw in both Windows Console (DOS) and Cygwin.

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  • Variadic templates in Scala

    - by Thomas Jung
    Suppose you want to have something like variadic templates (the ability to define n type parameters for a generic class) in Scala. For example you do not want to define Tuple2[+T1, +T2] and Tuple3[+T1, +T2, +T3] but Tuple[T*]. Are there other options than HLists?

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  • Visual C++/Studio: Application configuration incorrect?

    - by Thomas
    My C(++) program, written and compiled using Visual C(++)/Visual Studio, runs fine on my own machine, but refuses to run on another machine. The error message I get is "This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem."

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  • Handle a More Navigation Controller in an Interface Builder based TabBar Application

    - by Thomas Joulin
    Hi, I'm still not clear on how and when to use interface builder. I have a tabbar-based application, in which I added 6 navigations controllers. Instead of having 6 tabs, I would like 3 plus a "More" tab which allows the user to configure the tabs he wants. Is there any way to do that with IB ? And if not, how can I move from IB to a code-based tabbar (provided I already set up a class TabBarController which handles shouldAutoRotate:) Thanks in advance !

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