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  • What grid distributed computing frameworks are currently favoured for trading systems

    - by Rich
    There seems to a quite a few grid computing frameworks out there, but which ones are actually being used to any great extent by the investment banks for purposes of low latency distributing calculation? I'd be interested to hear answers covering both windows,Linux and cross platform. Also, what RPC mechanisms seem to be favoured most? I've heard that for reason of low latency and speed, the calculations themselves are quite often written in C++/C as calculations running on VMs are several orders of magnitude slower than native code. Does this seem to be a common scenario in practice? e.g distributed .NET grid framework running calculations written in native c++/c?

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  • Progressbar: Force element.innerHTML update before javascript sort call

    - by maras
    Hi, what is the best practice for this scenario: 1) User clicks "Sort huge javascript array" 2) Browser shows "Sorting..." through element.innerHTML="Sorting" 3) Browser sorts huge javascript array (100% CPU for several seconds) while displaying "Sorting..." message. 4) Browser shows result. Pseudo code: ... <a href="#" onclick="sortHugeArray();return false">Sort huge array</a> ... function sortHugeArray(){ document.getElementById("progress").innerHTML="Sorting..."; ...do huge sort ... ...render result... document.getElementById("progress").innerHTML=result; } When i do that this way, browser never shows "Sorting...", it freezes browser for several seconds and shows result without noticing user... Thank you for advice.

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  • django url tag performance

    - by zxygentoo
    I was trying to integrate django-voting into my project following the RedditStyleVoting instruction. In my urls.py, i did something like this: url(r'^sections/(?P<object_id>\d+)/(?P<direction>up|down|clear)vote/?$', vote_on_object, dict( model=Section, template_object_name='section', template_name='script/section_confirm_vote.html', allow_xmlhttprequest=True ), name="section_vote", then, in my template: {% vote_by_user user on section as vote %} {% score_for_object section as score %} {% vote_by_user user on section as vote %} {% score_for_object section as score %} {{ score.score|default:0 }} It takes over 1.3s to load the page, but by hard coding it like this: {% vote_by_user user on section as vote %} {% score_for_object section as score %} {{ score.score|default:0 }} I got 50ms. Just avoid the url tag resolving stuff I got a 20+ times performance improvement. Is there something I did wrong? If not, then what's the best practice here, should we do things the right way or the fast way?

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  • Page inheritance in mixed asp.net Forms and MVC application

    - by Rising Star
    I'm working on a web application. One of my co-workers has written some asp.net forms pages. The page classes all inherit from BasePageClass, which of course inherits from the Page class. I wish to add some MVC controllers that I've been told need to use the same logic implemented in the BasePageClass. Ordinarily, I would want to inherit the functions in the BasePageClass in the controller classes, but this breaks the inheritance heirarchy. What is the best practice for solving this problem?

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  • better understanding of JSF Life cycle

    - by gurupriyan.e
    I need your help to understand this better. This is my case. I have a custom validator for each of my input controls in the form. So when there is any validation error,I add a corresponding FacesMessage in the validate method. My understanding was that when there is any validation error - or when there are any FacesMessages added in the validate method of the Custom Validator, it would skip the INVOKE APPLICATION phase and would directly call the RENDER RESPONSE PHASE - showing the FacesMessage that was added in the PROCESS VALIDATION Phase - Is this correct? The problem I'm facing is - I add a FacesMessage in the PROCESS VALIDATION Phase - because of a validation error - and I add a confirmation message for the action that was taken by the user in the INVOKE APPLICATION PHASE - Now both are shown in the page in the RENDER RESPONSE Phase ? - If my understanding is correct in the above question - is it the best practice to conditionally add a confirmation FacesMessage after confirming that there are no FacesMessages in the currect FacesContext ? Appreciate your help.

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  • Sinatra: How do I provide access to a login form while preventing access to the rest of my Sinatra a

    - by Brandon Toone
    I recently created a Sinatra app with a login form (no basic auth). To prevent access to the app unless the user logged in I put a before block in place before do unless request.path_info == '/login' authenticated? end end I quickly realized that this prevented me from accessing resources in the public directory like my style sheet and logo unless authenticated first as well. To get around that I changed my filter to the following: before do unless request.path_info == '/login' || request.path_info == "/stylesheets/master.css" || request.path_info == "/images/logo.png" authenticated? end end If there were lots of resources I needed to provide exceptions to this way of making them would quickly become overwhelming. What is a better way to code this so I can make exceptions for the public directory or even its specific sub-directories and files like /stylesheets, /images, /images/bg.png but not /secret or /secret/eyes-only.pdf? Or ... Is there a completely different best-practice to handle this situation of locking down everything except the stuff related to logging in (handlers, views, resources)?

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  • Manually setting object's position or have the object do it all?

    - by N. Lucas
    I'm stuck thinking about the best way to go about setting a line segment's position, I have a class Line(length, angle, previous) being called from a class Polygon.. Right now I have: public function Line(length:Number, angle:Number, previous:Line = null) { if (previous != null) { this.x = previous.end.x; this.y = previous.end.y; } /**/ } Now, is this the best practice or should I be doing: Polygon.addLine(length:Number, angle:Number):void { var previous = _line[_line.length - 1]; // Array containing all Lines var line:Line = new Line(length, angle, previous); line.x = previous.end.x; line.y = previous.end.y; /**/ }

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  • ASP.NET Controls with Highly Customizable GUI

    - by micha12
    We are developing an ASP.NET web application where some of the features that we will need to implement are quite standard: for example, a chat between users, a forum, etc. There are ASP.NET chats and forums components available. However, they all have a predetermined GUI and html markup that is almost impossible to change and very difficult to customize. And this is a very common situation for most controls like grids, etc.: you have very low control over the html markup that is being generated by the control. In our case, our web app will have its own web design created by a professional web designer in PhotoShop, and then it will but transformed into html markup that will then be transformed in aspx pages. We would ideally like to create the html markup for the forum and chat by ourselves, and use only the non-GUI part of the ASP.NET components. Is this approach feasible? Has anyone dealt with such approach in practice?

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  • Reusing of a PreparedStatement between methods?

    - by MRalwasser
    We all know that we should rather reuse a JDBC PreparedStatement than creating a new instance within a loop. But how to deal with PreparedStatement reuse between different method invocations? Does the reuse-"rule" still count? Should I really consider using a field for the PreparedStatement or should I close and re-create the prepared statement in every invocation? (Of course an instance of such a class would be bound to a Connection which might be a disadvantage) I am aware that the ideal answer might be "it depends". But I am looking for a best practice for less experienced developers that they will do the right choice in most of the cases.

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  • Java Web App: Passing form parameters across multiple pages

    - by digiarnie
    Hi, what is the best practice or best way of passing form parameters from page to page in a flow? If I have a flow where a user enters data in a form and hits next and repeats this process until they get to an approval page, what ways could I approach this problem to make the retention of data as simple as possible over the flow? I guess you could put all the information as you go in the session but could you get into memory issues if a lot of people are using your app and going through the flow at the same time?

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  • Consolidating files in a single directory before you link them into the final executable

    - by David
    I am working on Solaris 10, Sun Studio 11. I am refactoring some old code, and trying to write unit tests for them. My make file looks like: my_model.o:my_model.cc CC -c my_model.cc -I/../../include -library=stlport4 -instances=extern unit_test: unit_test.o my_model.o symbol_dictionary.o CC -o unit_test unit_test.o my_model.o symbol_dictionary.o -I../../include \ -library=stlport4 -instances=extern unit_test.o: unit_test.cc CC -c unit_test.cc -I/../../include -library=stlport4 -instances=extern symbol_dictionary.o: cd ../../test-fixtures && ($MAKE) symbol_dictionary.o mv ../../test-fixtures/symbol_dictionary.o . In the ../../test-fixtures makefile, I have the following target: symbol_dictionary.o: CC -c symbol_dictionary.cc -I/../../include -library=stlport4 -instances=extern I do the instances=extern because I had linking problems before, and this was the recommended solution. The consequence is in each directory that is being compiled, a SunWS_Cache directory is created to store the template instances. This is the long way to get to this question. Is it a standard practice to consolidate object files in a single directory before you link them?

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  • Address calling class

    - by Samuel
    I have an abstract class Moveable with the method abstract void move() which is extended by the class Bullet and the abstract class Character, and Character is extended by the class Survivor and the class Zombie. In Survivor and Bullet the move() method doesnt require any parameters while in the class Zombie the move() method depends on the actual position of the survivor. The survivor and multiple zombies are created in the class Gui. I wanted to access the survivor in Zombie - what's the best way of doing this? In Gui i wrote a method getSurvivor() but i don't see how to access this method in Zombie? I am aware that as a workaround i could just pass a [Survivor survivor] as parameter in move() and ignore it in Bullet and Survivor, but that feels so ... bad practice.

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  • Is it ok to Swallow SocketExceptions in some situations?

    - by NoPyGod
    Let's say I've programmed an application which connects to a server using the Socket Class (TCP). If I encounter a SocketException while reading or writing, then obviously I have to do go ahead and run a disconnection routine to change the application's state to Disconnected. But what if I've started to Disconnect, and while I'm cleaning up, a SocketException occurs? The SocketException doesn't really mean anything to me, as I was going to shutdown the socket myself anyway.. so is it ok to swallow it? I really want to know what the best practice for this situation is.

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  • What is the optimal number of threads for performing IO operations in java?

    - by marc
    In Goetz's "Java Concurrency in Practice", in a footnote on page 101, he writes "For computational problems like this that do not I/O and access no shared data, Ncpu or Ncpu+1 threads yield optimal throughput; more threads do not help, and may in fact degrade performance..." My question is, when performing I/O operations such as file writing, file reading, file deleting, etc, are there guidelines for the number of threads to use to achieve maximum performance? I understand this will be just a guide number, since disk speeds and a host of other factors play into this. Still, I'm wondering: can 20 threads write 1000 separate files to disk faster than 4 threads can on a 4-cpu machine?

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  • JavaScript constructors inside a namespace

    - by Joe
    I have read that creating a namespace for JavaScript projects helps to reduce conflicts with other libraries. I have some code with a lot of different types of objects for which I have defined constructor functions. Is it good practice to put these inside the namespace as well? For example: var shapes = { Rectangle: function(w, h) { this.width = w; this.height = h; } }; which can be called via: var square = new shapes.Rectangle(10,10);

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  • -1 as a return value

    - by dimadima
    This question is specifically about PHP, but I'm guessing it might be applicable to other languages as well. I've noticed that between PHP4 and PHP5, the designers of the language shifted away from using -1 as a return value to using constants or other forms of output. This makes sense, as -1 is not particularly evocative, and I'm guessing this practice led to confusion. That said, I am sometimes inclined to return -1 when I want to quickly add another return option to a function, and -1 often seems like a perfectly valid way to express the outcome I am coding for. So here are my questions: Is my observation generally correct, regarding the move away from -1 as a return value in PHP5 vs PHP4? What are the cons of returning -1, beyond for the reason I mentioned above, wherein the -1 return value doesn't contribute positively to code clarity?

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  • How do I use a UIView subclass as a container?

    - by dxq
    I'm trying to subclass UIView to create a custom view that is essentially a container. The subclass contains a UILabel and a UIImageView- I can't make either of them show up. Here's an example of what I've been trying: In my main view controller: - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) { ViewClass *myView = [[ViewClass alloc] initWithFrame:CGRectMake(100, 100, 150, 150)]; [view addSubview:myView]; } return self; } In my UIView subclass: - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { UILabel *word = [[[UILabel alloc] initWithFrame:[self bounds]] autorelease]; word.text = @"WHY ISN'T THIS SHOWING UP!?"; [self addSubview:word]; } return self; } Can anyone explain what I'm doing wrong? I'm way out of practice with UIKit and Obj-C, and I figure I'm probably missing something obvious.

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  • Decorators vs. classes in python web development.

    - by Tristan
    I've noticed three main ways Python web frameworks deal request handing: decorators, controller classes with methods for individual requests, and request classes with methods for GET/POST. I'm curious about the virtues of these three approaches. Are there major advantages or disadvantages to any of these approaches? To fix ideas, here are three examples. Bottle uses decorators: @route('/') def index(): return 'Hello World!' Pylons uses controller classes: class HelloController(BaseController): def index(self): return 'Hello World' Tornado uses request handler classes with methods for types: class MainHandler(tornado.web.RequestHandler): def get(self): self.write("Hello, world") Which style is the best practice?

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  • Console App Mouse-Click X Y Coordinate Detection/Comparison

    - by Bloodyaugust
    I have a game that I am working on in a C# console application, purely as practice before going on to better methods. As opposed to using something such as a Windows Forms App, which has button functionality built in, I am endeavoring to grab the cursor position (which I know how to do) and compare it to a number of area's inside a console application as defined by perhaps pixel location, but I also do not know if there is some sort of built in unit of space other than pixels (this last bit is the part I am unable to figure). P.S. I know this is in general terms, with no code already provided, but I do not feel that it is needed as all I am asking for is a brief explanation of how to grab X Y coordinates inside a console application, and stick them in int variables. Many Thanks in advance! :D

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  • Constantly changing frameworks/APIs - how do we keep up?

    - by Jamie Chapman
    This question isn't really for any specific technology but more of general developer question. We all know from experience that things change. Frameworks evolve, new features are added and stuff gets removed. For example, how might a product using version 1.0 of the "ABC" framework adapt when version 2.0 comes along (ABC could be .NET, Java, Cocoa, or whatever you want)? One solution might be to make the frameworks backward compatible; so that code written for 1.0 will still work in version 2.0 of the framework. Another might be to selectively target only version 1.0 of the framework, but this might leave many fancy new features unused (many .NET 2.0 apps seem to do this) Any thoughts on what we as developers should do as best practice to keep our technologies up to date, whilst not breaking our applications?

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  • Using DAO's or static methods in Domain Object with nHibernate

    - by mickyjtwin
    I am using nHibernate for the first time, and after alot of reading/researching, plus looking at other projects done with nHibernate, have seen a couple of implementation practices. I am looking for opinions about which would be best to use and why. Essentially the two methods are as follows: Using Data Access Objects and a DAO Factory. Example usage: INotificationListDAO nListDAO = NHDaoFactory.GetNotificationListDAO(); NotificationList list = nListDAO.GetByListID(""); Use Static methods in the Domain Object. Example usage: NotificationList list = NotificationList.GetByListID(""); NHHelper.Session.Get(id); NHHelper.Session basically calls the NHibernateSessionManager.Instace.GetSessionFrom(""). While both look similar, it is more to do with best practice. From what I understand, the first option is more so if you are developing enterprise level applications, where my requirements are more for mid-range websites.

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  • Unreachable code detected in case statement

    - by alex
    I have a code: protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { switch (keyData) { case Keys.Alt|Keys.D1: if (this._condition1) { return true; } else { return base.ProcessCmdKey(ref msg, keyData); } break; case Keys.Control |Keys.U: if (this._condition2) { return true; } else { return base.ProcessCmdKey(ref msg, keyData); } break; default: return base.ProcessCmdKey(ref msg, keyData); } return true; It gives me "unreachable code detected" warning on breaks. Is it good practice not to use break operator here ? I don't want to turn off "unreachable code detected" warning. PS: There are many case in my ProcessCmdKey method.

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  • Unread email notifier, most practical approach

    - by Michael Pasqualone
    I'm in the process of writing a small php-cli script that will loop over over my personal inbox and then send me an SMS via a gateway. The question I have is: As will have the script launch via cron every 10 minutes, if there is an email sitting in my inbox that is not read before the next script launch then I will receive 2 sms. Does any one (pseudocode will do) have any idea what the best practice would be in php5 to ensure only 1 SMS is sent? What I am currently learning towards is towards storing the message ID in a sqlite DB and flagging a field whether an SMS has been sent or not - but wondering if there is an easier way?

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  • Enums With Default Throw Clause?

    - by Tom Tresansky
    I noticed the following in the Java Language spec in the section on enumerations here: link switch(this) { case PLUS: return x + y; case MINUS: return x - y; case TIMES: return x * y; case DIVIDE: return x / y; } throw new AssertionError("Unknown op: " + this); However, looking at the switch statement definition section, I didn't notice this particular syntax (the associated throw statement) anywhere. Can I use this sort of "default case is throw an exception" syntactic sugar outside of enum definitions? Does it have any special name? Is this considered a good/bad practice for short-cutting this behavior of "anything not in the list throws an exception"?

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  • Connection Pooling

    - by cshah
    I have the following code, If I use conn == null in finally do I still use connection pooling? I know it is a good practice to close your connection but how about disposing the whole connection object? public void ExecuteNonQuery(SqlCommand Cmd) { //========== Connection ==========// SqlConnection Conn = new SqlConnection(strConStr); try { //========== Open Connection ==========// Conn.Open(); //========== Execute Command ==========// Cmd.Connection = Conn; Cmd.CommandTimeout = 180; Cmd.ExecuteNonQuery(); } catch (Exception Exc) { throw Exc; } finally { //======== Closing Connection ========// if (Conn.State == ConnectionState.Open) { Conn.Close(); } //======== Disposing object ========// Conn = null; } }

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