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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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• 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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• Is SELECT INTO able to affect data from its original table during UPDATE

  - by driveby

  Whilst asking this question asp.net scheduling timed events user murph posted some insightful information: Point about this is that its very, very simple - you have an process for exchange that is performing a clearly defined task and you have a high frequency task that is not doing anything particularly complex, its a straightforward query (select from table where sent = false and send at < value) - probably into temporary table so that you can run a single query update after you've done the sends - that you can optimise the index for. You're not trying to queue up a huge pile of event triggers, just one that fires once a minute and processes things that are due. Is it possible to SELECT data from table X INTO table Y and have the UPDATES that are performed on table Y pushed into table X? I guess the alternative would be that the data gets updated in table Y then an update command can be run on table X based on the data in table Y. What would be the advantage of selecting into another table? Thank you,

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• Screening (multi)collinearity in a regression model

  - by aL3xa

  I hope that this one is not going to be "ask-and-answer" question... here goes: (multi)collinearity refers to extremely high correlations between predictors in the regression model. How to cure them... well, sometimes you don't need to "cure" collinearity, since it doesn't affect regression model itself, but interpretation of an effect of individual predictors. One way to spot collinearity is to put each predictor as a dependent variable, and other predictors as independent variables, determine R2, and if it's larger than .9 (or .95), we can consider predictor redundant. This is one "method"... what about other approaches? Some of them are time consuming, like excluding predictors from model and watching for b-coefficient changes - they should be noticeably different. Of course, we must always bare in mind specific context/goal of analysis... Sometimes, only remedy is to repeat a research, but right now, I'm interested in various ways of screening redundant predictors when (multi)collinearity occurs in a regression model.

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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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• 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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• 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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• Sticky Footers that move down when dynamic content gets loaded

  - by Dominic Rodger

  I've been using this snippet of jQuery to get a sticky footer: if($(document.body).height() < $(window).height()){ $("#footer").css({position: "absolute",top:($(window).scrollTop()+$(window).height()-$("#footer").height())+"px", width: "100%"}); } $(window).scroll(positionFooter).resize(positionFooter); However, that breaks when I've got expandable/collapsible divs lying around where the original content was less high than the window, since it is then stuck to the bottom of the window, rather than the bottom of the document. Is there a way of fixing this, or a better way of doing it? Please bear in mind that I don't have much control over the HTML, since I need to do this in Django's admin interface, which doesn't allow much injection of HTML in the places you might want to to accomplish this sort of thing (i.e. this answer and this answer don't work for me).

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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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• 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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• 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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• 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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• SDL versus GLFW?

  - by user697111

  What are the pros and cons to each? It seems they serve the same purpose. I have a few demos with each and they seem about the same. Performance or cross platform wise, is one better than the other? The only thing I notice is that SDL seems to have more "helper" libraries (fonts, images, mixer, built in sound support, etc). On its site, GLFW claims to be more "OpenGL" focused, but still have to use a GLEW to get any newer OpenGL features (same with SDL). I guess I'm leaning towards using SDL now (more mature, more features, more community). Are there any reasons I've missed why GLFW stands out and I should use it instead of SDL?

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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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• 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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• 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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• std::for_each on a member function with 1 argument

  - by Person

  I'm wondering how to implement what is stated in the title. I've tried something like... std::for_each( a.begin(), a.end(), std::mem_fun_ref( &myClass::someFunc ) ) but I get an error saying that the "term" (I"m assuming it means the 3rd argument) doesn't evaluate to a function with 1 argument, even though someFunc does take one argument - the type of the objects stored in a. I'm wondering if what I'm trying to do is possible using the standard library (I know I can do it easily using boost). P.S. Does using for_each and mem_fun_ref have any performance implications in comparison to just iterating through a manually and passing the object to someFunc?

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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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• database design suggesion

  - by Bharanikumar

  Hi , am going to start new travel site, I want some advise from guru's regarding database design , Things coming to picture are, Book taxi online , This is the core idea, So i like to implement lot of jquery,ajax stuff in my site , Main thing site must run veryt fast,safe,security, In mysql , which typw shall i use, MYISAM OR INNODB Which is best type for ajax works, fast,safe ,secure ,performance view . This is my demo site, Just look this site, i implemented some ajax stuff here, my-url In this site please choose the postcode in the taxifrom tab, It ask you value please enter, just enter nw7 , See How long it will take for response,some time no response and system goes to hang or idle mode, Also please look the diversion , select No diversion, There you will list of textbox, enter the nw3 then hit the search icon , See after 80seconds only , you will get response from DB, See this too bad response ... This is DB , my Database type if myisam ,no idexing , no fulltext and nothing...no constraints, So please advise me , which database type i choose, Myisam or innodb, Thanks Bharanikumar

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• How do you handle passwords or credentials for standalone applications?

  - by Abel Morelos

  Let's say that you have a standalone application (a Java application in my case) and that this application has a configuration file (a XML file in my case) where you store the credentials (user and password) for a bunch of databases you need to connect. Everything works great, but now you discover (or your are given a new requirement like me) that you have to put this application in a different server and that you can't have these credentials in the configuration files because of security and/or compliance considerations. I'm considering to use data sources hosted in the application server (a WAS server), but I think this could have poor performance and maybe it's not the best approach since I'm connecting from a standalone application. I was also considering to use some sort of encryption, but I would like to keep things as simple as possible. How would you handle this case? Where would you put these credentials or protect them from being compromised? Or how would you connect to your databases in this scenario?

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• creating a wordpress dev enviornment and uploading to production

  - by Jeff

  I am an old school java developer who is considering a using wordpress. I'm used to developing locally on my PC (yeah yeah not even a mac) and then ftping my files up to a production environment on a remote server. My high level review of wordpress gives me the impression that typically there is no concept of lower environments and that all updates occur directly in production. Is this the case? If not, can someone explain how one goes about uploading the files to a web site? Thanks, Jeff

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• What goes between SQL Server and Client?

  - by worlds-apart89

  This question is an updated version of a previous question I have asked on here. I am new to client-server model with SQL Server as the relational database. I have read that public access to SQL Server is not secure. If direct access to the database is not a good practice, then what kind of layer should be placed between the server and the client? Note that I have a desktop application that will serve as the client and a remote SQL Server database that will provide data to the client. The client will input their username and password in order to see their data. I have heard of terms like VPN, ISA, TMG, Terminal Services, proxy server, and so on. I need a fast and secure n-tier architecture. P.S. I have heard of web services in front of the database. Can I use WCF to retrieve, update, insert data? Would it be a good approach in terms of security and performance?

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• Javascript - Determine if String Is In List

  - by Emtucifor

  In SQL we can see if a string is in a list like so: Column IN ('a', 'b', 'c') What's a good way to do this in javascript? I realize one can use the switch function: var str = 'a' var flag = false; switch (str) { case 'a': case 'b': case 'c': flag = true; default: } if (thisthing || thatthing || flag === true) { // do something } But this is a horrible mess. It's also clunky to do this: if (thisthing || thatthing || str === 'a' || str === 'b' || str = 'c') { // do something } And I'm not sure about the performance or clarity of this: if (thisthing || thatthing || {a:1, b:1, c:1}[str]) { // do something } Any ideas?

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• Is Pex (Test generation) really usefull tool?

  - by Yauheni Sivukha

  Yes, it is possible to generate tests on boundary values for functions like "Sum" or "Divide". Pex is a good tool here. But more often we create tests on business behaviour. Let's consider example from classic Beck's tdd book: [Test] public void ShouldRoundOnCreation() { Money money = new Money(20.678); Assert.AreEqual(20.68,money.Amount); Assert.AreEqual(2068,money.Cents); } Can this test be generated? No :) 95 % of tests in my projects check business logic, and can not be generated. Pex (Especially in pair with Moles) can give 100% code coverage, but a high code coverage rate of a test suite does never indicate, that code is well tested - It only gives false confidence that everything is tested. And this is very dangerous. So, the question is - Is Pex really usefull tool?

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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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