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  • Interpreters: How much simplification?

    - by Ray
    In my interpreter, code like the following x=(y+4)*z echo x parses and "optimizes" down to four single operations performed by the interpreter, pretty much assembly-like: add 4 to y multiply <last operation result> with z set x to <last operation result> echo x In modern interpreters (for example: CPython, Ruby, PHP), how simplified are the "opcodes" for which are in end-effect run by the interpreter? Could I achieve better performance when trying to keep the structures and commands for the interpreter more complex and high-level? That would be surely a lot harder, or?

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  • Database structure for storing Bank-like accounts and transactions

    - by user1241320
    We're in the process of adding a bank-like sub-system to our own shop. We already have customers, so each will be given a sort of account and transactions of some kind will be possible (adding to the account or subtracting from it). So we at least need the account entity, the transaction one and operations will then have to recalculate overall balances. How would you structure your database to handle this? Is there any standard bank system have to use that I could mock? By the way, we're on mysql but will also look at some nosql solution for performance boost.

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  • How Do I See The Final Text Of A Query Resulting From A Call To mysqli->prepare?

    - by Joshua
    After code like this: $stmt = $mysqli->prepare("SELECT District FROM City WHERE Name=?")) { $stmt->bind_param("s", $city); $stmt->execute(); $stmt->bind_result($district); $stmt->fetch(); printf("%s is in district %s\n", $city, $district); How Do I See The Actual SQL Statement That Was Executed? (It Should Look Something Like "SELECT District FROM City WHERE Name='Simi Valley';") I already realize that in this simplistic case it would be very easy to simply reconstruct the query... but how can I access it in a general way that will work for very complicated prepared statements, and cases where I don't necessarily already understand the intended structure of the query, etc. Isn't there some function or method that can be called on the statement object that will return the actual text of the SQL query, after binding?

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  • Jquery background overlay/alert without .onclick event - php responder?

    - by Philip
    Hi guys, I have no experience with jquery or javascript for that matter. I am trying to implement this technique to respond to users for errors or messages in general. lights-out-dimmingcovering-background-content-with-jquery This method uses the onclick event and that's not what im after, I have tried to replace .onclick with .load but that doesn't seem to work. I'm after a quick fix as I really don't have the time to learn jquery or its event handlers. The goal is to catch any errors or message's and once these are called the alert box is called without any further actions such as .onclick. How my code would look: {PHP} $forms = new forms(); if(count($forms->showErrors) > 0 // or == true) { foreach($forms->showErrors as $error) { print('<p class="alert">'.htmlspecialchars($error, ENT_QUOTES).'</p>'); } }

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  • Surface Detection in 2d Game?

    - by GamiShini
    I'm working on a 2D Platform game, and I was wondering what's the best (performance-wise) way to implement Surface (Collision) Detection. So far I'm thinking of constructing a list of level objects constructed of a list of lines, and I draw tiles along the lines. ( http://img375.imageshack.us/img375/1704/lines.png ). I'm thinking every object holds the ID of the surface that he walks on, in order to easily manipulate his y position while walking up/downhill. Something like this: //Player/MovableObject class MoveLeft() { this.Position.Y = Helper.GetSurfaceById(this.SurfaceId).GetYWhenXIs(this.Position.X) } So the logic I use to detect "droping/walking on surface" is a simple point (player's lower legs)-touches-line (surface) check (with some safety approximation - let`s say 1-2 pixels over the line). Is this approach OK? I`ve been having difficulty trying to find reading material for this problem, so feel free to drop links/advice.

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  • Is loading a video in a browser multithreaded?

    - by mwilcox
    It's hard to know what is multithreaded in a browser and what isn't. It seems while a video streams or progressively downloads, it does not affect page performance, so my guess it is. Note I'm using Flash video, but it's really about video in general. Any other tips on what else is multithreaded (image loads?) is also helpful. I know JavaScript is not, and I thought Flash wasn't but I heard somewhere that it may be (or it could be done), but I think they were not well informed.

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  • AES acceleration for Java

    - by chris_l
    I want to encrypt/decrypt lots of small (2-10kB) pieces of data. The performance is ok for now: On a Core2Duo, I get about 90 MBytes/s AES256 (when using 2 threads). But I may need to improve that in the future - or at least reduce the impact on the CPU. Is it possible to use dedicated AES encryption hardware with Java (using JCE, or maybe a different API)? Would Java take advantage of special CPU features (SSE5?!), if I get a better CPU? Or are there faster JCE providers? (I tried SunJCE and BouncyCastle - no big difference.) Other possiblilities?

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  • What parallel programming model do you recommend today to take advantage of the manycore processors

    - by Doctor J
    If you were writing a new application from scratch today, and wanted it to scale to all the cores you could throw at it tomorrow, what parallel programming model/system/language/library would you choose? Why? I am particularly interested in answers along these axes: Programmer productivity / ease of use (can mortals successfully use it?) Target application domain (what problems is it (not) good at?) Concurrency style (does it support tasks, pipelines, data parallelism, messages...?) Maintainability / future-proofing (will anybody still be using it in 20 years?) Performance (how does it scale on what kinds of hardware?) I am being deliberately vauge on the nature of the application in anticipation of getting good general answers useful for a variety of applications.

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  • How to scale an image (in data URI format) in JavaScript (real scaling, not using styling)

    - by 103067513055141045393
    We are capturing a visible tab in a Chrome browser (by using the extensions API chrome.tabs.captureVisibleTab) and receiving a snapshot in the data URI scheme (Base64 encoded string). Is there a JavaScript library that can be used to scale down an image to a certain size? Currently we are styling it via CSS, but have to pay performance penalties as pictures are mostly 100 times bigger than required. Additional concern is also the load on the localStorage we use to save our snapshots. Does anyone know of a way to process this data URI scheme formatted pictures and reduce their size by scaling them down? References: Data URI scheme on http://en.wikipedia.org/wiki/Data_URI_scheme Chrome Extensions API onhttp://code.google.com/chrome/extensions/tabs.html The "Recently Closed Tabs" Chrome Extension onhttp://code.google.com/p/recently-closed-tabs

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  • Flex 4.5 - to long build process

    - by Idob
    We are developing an app using flex 4.5. The app runs just fine (no performance issues at all) but it takes us forever to compile and build it. A minor change, like just add a comment or press enter in an mxml file and rebuild takes about 3 minutes. You just cant work that way. It is a large project with about 1300 files. We also use Parsley as IOC container and a beat of cairngorm navigation. We also use Maven (Flex mojos) but I am talking about a normal eclipse build (Ctrl + B). We separated some of the code to a different SWC and all of our graphics are stored in a different resource SWF. Please, Do you have any suggestions? Regards, Ido

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  • What are annotations and how do they actually work for frameworks like Spring?

    - by Rachel
    I am new to Spring and now a days I hear a lot about Spring Framework. I have two sets of very specific questions: Set No. 1: What are annotations in general ? How does annotations works specifically with Spring framework ? Can annotations be used outside Spring Framework or are they Framework specific ? Set No. 2: What module of Spring Framework is widely used in Industry ? I think it is Spring MVC but why it is the most used module, if am correct or correct me on this ? I am newbie to Spring and so feel free to edit this questions to make more sense.

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  • Best way to test a batch email script

    - by John
    I have a php mail script sitting on a LAMP vps server. The script grabs about 1000 emails and sends them each an html email. I tested the script with about half a dozen of my own test email accounts and things worked fine. But I am concerned something may go wrong when I actually use this script for 1000 emails. Some things I would like to test for are 1) Confirm all 1000 emails were sent and received 2) Test to make sure emails did not end up in people's spam folders 3) Detect any other general failures Does anyone have suggestions on how I can test for the above cases? I would like to read about your experiences building batch email scripts.

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  • Joining links together in a dictionary

    - by ptabatt
    Hi guys, I'm student here, new to python and programming in general. I have a dictionary links which holds a tuple mapped to a number. How can I join the second url in the second tuple together with the urljoin() function? What I'm trying to do is get complete links so I can run a recursive function search() which takes a complete url as an arguement, finds all the links in each url and stores the number of links mapped to the links in a database. So far, I have: links {('href', 'http://reed.cs.depaul.edu/lperkovic/csc242/test2.html'): 1, ('href', 'test3.html'): 1} I want http://reed.cs.depaul.edu/lperkovic/csc242/test3.html...

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  • a quick overview on access

    - by masfenix
    Hey I am a university student (math major), but programming since I was little (read: 14). I am starting a new programming job tomorrow at a very big company. However I just found out that I might be just working with access for a couple of weeks (macros and whatnot). Can someone just give me a general rundown on how to create and use VB in access. What I mean is how do tables refer to themselves (as objects? as what name?) how to run queries through vb and such. thanks all.

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  • Why does Java not have any destructor like C++?

    - by Abhishek Jain
    Java has its own garbage collection implementation so it does not require any destructor like C++ . This makes Java developer lazy in implementing memory management. And Garbage Collection is very expensive. Still we can have destructor along with garbage collector where developer can free resources and which can save garbage collector's work. This might improves the performance of application. Why does Java not provide any destructor kind of mechanism? Developer does not have control over GC but he/she can control or create object. Then why not give them ability to destruct the objects?

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  • Lock HTML select element, allow value to be sent on submit

    - by ILMV
    I have a select box (for a customer field) on a complex order form, when the user starts to add lines to the order they should not be allowed to change the customer select box (unless all lines are deleted). My immediate thought was that I could use the disabled attribute, but when the box is disabled the selected value is no longer passed to the target. When the problem arose a while ago one of the other developers worked around this by looping through all the options and disabling all but the selected option, and sure enough the value was passed to the target and we've been using since. But now I'm looking for a proper solution, I don't want to loop through all the options because are data is expanding and it's starting to introduce performance issues. I'd prefer not to enable this / all the elements when the submit button is hit. How can I lock the input, whilst maintaining the selected option and passing that value to the target script? I would prefer a non-JavaScript solution if possible, but if needed we are running jQuery 1.4.2 so that could be used.

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  • Expert system for writing programs?

    - by aaa
    I am brainstorming an idea of developing a high level software to manipulate matrix algebra equations, tensor manipulations to be exact, to produce optimized C++ code using several criteria such as sizes of dimensions, available memory on the system, etc. Something which is similar in spirit to tensor contraction engine, TCE, but specifically oriented towards producing optimized rather than general code. The end result desired is software which is expert in producing parallel program in my domain. Does this sort of development fall on the category of expert systems? What other projects out there work in the same area of producing code given the constraints?

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  • How to organise a php based website

    - by bsandrabr
    I am putting my php /mysql website up and this is my scenario The users are grouped into sites each site with their own unique database. There will be about 40 users per site. the two options I'm trying to decide between are have a central website running the php and directing the users off to their own database using sub domains for each user each with their own php in htdocs I dont even know if 2 is possible/stupid but if it was, would it make any difference to performance as they're all being run by the same server. Any other ideas/ advice much appreciated as I want to organise it the best way from the start

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  • Speed up the loop operation in R

    - by Kay
    Hi, i have a big performance problem in R. I wrote a function that iterates over an data.frame object. It simply adds a new col to a data.frame and accumulate sth. (simple operation). The data.frame has round about 850.000 rows. My PC is still working about 10h now and i have no idea about the runtime. dayloop2 <- function(temp){ for (i in 1:nrow(temp)){ temp[i,10] <- i if (i > 1) { if ((temp[i,6] == temp[i-1,6]) & (temp[i,3] == temp[i-1,3])) { temp[i,10] <- temp[i,9] + temp[i-1,10] } else { temp[i,10] <- temp[i,9] } } else { temp[i,10] <- temp[i,9] } } names(temp)[names(temp) == "V10"] <- "Kumm." return(temp) } Any ideas how to speed up this operation ?

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  • Hibernate criteria with projection not performing query for @OneToMany mapping

    - by Josh
    I have a domain object, Expense, that has a field called initialFields. It's annotated as so: @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true) @JoinTable(blah blah) private final List<Field> initialFields; Now I'm trying to use Projections in order to only pull certain fields for performance reasons, but when doing so the initialFields field is always null. It's the only OneToMany field and the only field I am trying to retrieve with the projection that is behaving this way. If I use a regular HQL query initialFields is populated appropriately, but of course I can't limit the fields. Anyone ever seen anything like this?

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  • What is the best way to convert a hexidecimal string to a byte array (.NET)?

    - by Robert Wagner
    I have a hexidecimal string that I need to convert to a byte array. The best way (ie efficient and least code) is: string hexstr = "683A2134"; byte[] bytes = new byte[hexstr.Length/2]; for(int x = 0; x < bytes.Length; x++) { bytes[x] = Convert.ToByte(hexstr.Substring(x * 2, 2), 16); } In the case where I have a 32bit value I can do the following: string hexstr = "683A2134"; byte[] bytes = BitConverter.GetBytes(Convert.ToInt32(hexstr, 16)); However what about in the general case? Is there a better built in function, or a clearer (doesn't have to be faster, but still performant) way of doing this? I would prefer a built in function as there seems to be one for everything (well common things) except this particular conversion.

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  • Is OpenId easier or harder for users?

    - by Spines
    I'm wondering if I should use OpenId for my website. My first exposure to OpenId was StackOverflow, and I found it confusing that they only had a login link, yet no register link. Now that I've learned about OpenId though I prefer it over the regular way of registration. I have a feeling that only a small percentage of the internet users know how to login with a third party account provider, and most would prefer just to create an account. It makes sense for StackOverflow to use OpenId since the target audience is tech-savvy, however my website caters to the general public. Does anyone have any statistics or first hand experience with using OpenId versus regular registration?

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  • EJB3.1 Remote invocation - is it distributed automatically? is it expensive?

    - by Hank
    I'm building a JEE6 application with performance and scalability in the forefront of my mind. Business logic and JPA2-facade is held in stateless session beans (EJB3.1). As of right now, the SLSBs implement only @Remote-interfaces. When a bean needs to access another bean, it does so via RMI. My reasoning behind this is the assumption that, once the application runs on a bunch of clustered application servers, the RMI-part allows the execution to be distributed across the whole cluster automagically. Is that a correct assumption? I'm fine with dealing with the downsides of that (objects lose entityManager session, pass-by-value), at least I think so. But I am wondering if constant remote invocation isn't adding more load then necessary.

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  • How to make a secure login using UDID or device token?

    - by Erik B
    So I'm making an app where I want the users to be able add, edit and rate content, but I do not want to force them to register. Instead I was planning on just using their device id or device token to identify them. I'm planning on making both an iPhone and Android version, so I'm looking for a general solution, but the iPhone version has higher priority, so an iPhone specific solution would also be welcome. The problem is that I don't want just anyone to be able to use my web service by sending a phony device id or someone else's device id. How would the client prove to the server that it is providing the correct device id?

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  • Getting pixel averages of a vector sitting atop a bitmap...

    - by user346511
    I'm currently involved in a hardware project where I am mapping triangular shaped LED to traditional bitmap images. I'd like to overlay a triangle vector onto an image and get the average pixel data within the bounds of that vector. However, I'm unfamiliar with the math needed to calculate this. Does anyone have an algorithm or a link that could send me in the right direction? (I tagged this as Python, which is preferred, but I'd be happy with the general algorithm!) I've created a basic image of what I'm trying to capture here: http://imgur.com/Isjip.gif

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