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• Generating jquery 'rules' from business model to UI in asp.net mvc

  - by jim

  Hi all, I've had a good look around and am certain that there's no matching question on SO, so here goes. Has anyone created a 'helper' method on their model that generates jquery (or plain javascript) rules validation dynamically, based on the criteria/rules that are contained within the object and taken from a repository (i.e. DB). What i'm thinking of is a discrete set of partial views (and associated models) that have rules at the business logic 'level' and rather than (or in combination with) validating the rule(s) at postback, translating the same rules into tightly focussed jquery methods that work identically at client (js) and server (c#) levels. I can see benefits here re performance. Also, the rules definitions could be created in a single place (in c#) and the jquery generated off of that, thus allowing single edits to update both code streams. I appreciate that there would be limitations imposed by language specific contstraints but the general principle could be quite interesting if used appropriately. I'm also aware that testibility could be an issue when using two different language structures and hoping to achieve similar test outcomes - but those aside... any thoughts or experiences of similar out there?? cheers jimi

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• Can you stop a defered callback in jquery 1.5?

  - by chobo2

  Hi I am wondering say you have something like this // Assign handlers immediately after making the request, // and remember the jqxhr object for this request var jqxhr = $.ajax({ url: "example.php" }) .success(function(response) { alert("success"); }) // perform other work here ... // Set another success function for the request above jqxhr.success(function(response){ alert("second success"); }); So I am thinking this. I have a general function that I want to use on all my responses that would be passed into my success. This function basically does a check to see if the server validation found any errors. If it did they it formats it and displays a message. Now I am wondering if I could some how have the second success function to then do specific stuff. Like say One ajax request needs to add a row into a table. So this should be possible. I just do what I have above and in the second success I just add the row. Is it possible though that if the first success runs through and see that there are validation errors from the server that I can stop the second success from happening? Sort of If(first success finds errors) { // print out errors // don't continue onto next success } else { // go to next success } Edit I found that there is something call deferred.reject and this does stop it but I am wondering how can I specify to stop only the success one. Since my thinking is if there are other deffered ones like complete on it will the be rejected too?

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• do the Python libraries have a natural dependence on the global namespace?

  - by msw

  I first ran into this when trying to determine the relative performance of two generators: t = timeit.repeat('g.get()', setup='g = my_generator()') So I dug into the timeit module and found that the setup and statement are evaluated with their own private, initially empty namespaces so naturally the binding of g never becomes accessible to the g.get() statement. The obvious solution is to wrap them into a class, thus adding to the global namespace. I bumped into this again when attempting, in another project, to use the multiprocessing module to divide a task among workers. I even bundled everything nicely into a class but unfortunately the call pool.apply_async(runmc, arg) fails with a PicklingError because buried inside the work object that runmc instantiates is (effectively) an assignment: self.predicate = lambda x, y: x > y so the whole object can't be (understandably) pickled and whereas: def foo(x, y): return x > y pickle.dumps(foo) is fine, the sequence bar = lambda x, y: x > y yields True from callable(bar) and from type(bar), but it Can't pickle <function <lambda> at 0xb759b764>: it's not found as __main__.<lambda>. I've given only code fragments because I can easily fix these cases by merely pulling them out into module or object level defs. The bug here appears to be in my understanding of the semantics of namespace use in general. If the nature of the language requires that I create more def statements I'll happily do so; I fear that I'm missing an essential concept though. Why is there such a strong reliance on the global namespace? Or, what am I failing to understand? Namespaces are one honking great idea -- let's do more of those!

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• Load page for validation but do not display it to user in ASP.NET

  - by Kevin

  We have a site requiring users pay $2 to view the details of a record. We occasionally get complaints because we send them to the payment page, and once they pay it turns out the record isn't valid, or it was lost, or the data couldn't be generated. So we want to add in a check to ensure the page constructs properly before the user is required to pay for it. However, we don't want the user to have access to the page until they pay for it. Is there anything in ASP.NET 3.5 or just general web design that would allow something like this? The data on the record is real time and computed on a backend server before sent to the client. Occasionally this computation fails for whatever reason. Our alternative is to call all of the loading methods and validate the data, then redirect them to the payment page. The problem is A) this will be a relatively involved process rewriting all of these methods to return validation information, and B) it still doesn't guarentee us the page will load properly. Any thoughts?

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• BufferedImage.getGraphics() resulting in memory leak, is there a fix?

  - by user359202

  Hi friends, I'm having problem with some framework API calling BufferedImage.getGraphics() method and thus causing memory leak. What this method does is that it always calls BufferedImage.createGraphics(). On a windows machine, createGraphics() is handled by Win32GraphicsEnvironment which keeps a listeners list inside its field displayChanger. When I call getGraphics on my BufferedImage someChart, someChart's SurfaceManager(which retains a reference to someChart) is added to the listeners map in Win32GraphicsEnvironment, preventing someChart to be garbage collected. Nothing afterwards removes someChart's SurfaceManager from the listeners map. In general, the summarized path stopping a BufferedImage from being garbage collected, once getGraphics is called, is as follows: GC Root - localGraphicsEnvironment(Win32GraphicsEnvironment) - displayChanger(SunDisplayChanger) - listeners(Map) - key(D3DChachingSurfaceManager) - bImg(BufferedImage) I could have changed the framework's code so that after every called to BufferedImage.getGraphics(), I keep a reference to the BufferedImage's SurfaceManager. Then, I get hold of localGraphicsEnvironment, cast it to Win32GraphicsEnvironment, then call removeDisplayChangedListener() using the reference to the BufferedImage's SurfaceManager. But I don't think this is a proper way to solve the problem. Could someone please help me with this issue? Thanks a lot!

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• How to design authentication in a thick client, to be fail safe?

  - by Jay

  Here's a use case: I have a desktop application (built using Eclipse RCP) which on start, pops open a dialog box with 'UserName' and 'Password' fields in it. Once the end user, inputs his UserName and Password, a server is contacted (a spring remote-servlet, with the client side being a spring httpclient: similar to the approaches here.), and authentication is performed on the server side. A few questions related to the above mentioned scenario: If said this authentication service were to go down, what would be the best way to handle further proceedings? Authentication is something that I cannot do away with. Would running the desktop client in a "limited" mode be a good idea? For instance, important features/menus/views will be disabled, rest of the application will be accessible? Should I have a back up authentication service running on a different machine, working as a backup? What are the general best-practices in this scenario? I remember reading about google gears and how it would let you edit and do stuff offline - should something like this be designed? Please let me know your design/architectural comments/suggestions. Appreciate your help.

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• Project Euler, Problem 10 java solution now working

  - by Dennis S

  Hi, I'm trying to find the sum of the prime numbers < 2'000'000. This is my solution in java but I can't seem get the correct answer. Please give some input on what could be wrong and general advice on the code is appreciated. Printing 'sum' gives: 1308111344, which is incorrect. /* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. */ class Helper{ public void run(){ Integer sum = 0; for(int i = 2; i < 2000000; i++){ if(isPrime(i)) sum += i; } System.out.println(sum); } private boolean isPrime(int nr){ if(nr == 2) return true; else if(nr == 1) return false; if(nr % 2 == 0) return false; for(int i = 3; i < Math.sqrt(nr); i += 2){ if(nr % i == 0) return false; } return true; } } class Problem{ public static void main(String[] args){ Helper p = new Helper(); p.run(); } }

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• AJAX or a server side framework?

  - by Romansky

  I am working with a friend on building a web site, in general this web site will be a custom web app along with a very custom social network type of thing.. Currently I have a mock-up site that uses simple PHP with AJAX and JSON and JQUERY and I love how it works, I love the way it all fits together. But for a mock-up I did not implement any of the Social Network design patterns such as a login, rating, groups etc.. This brought me to a higher level of decision making requirement, I need to decide if I want to develop all this functionality by hand or use some kind of a framework. I spent this entire day researching, and it would seem that using Drupal and such frameworks will make the Social Network part easy (overlooking the customization requirement for now..) but will make client side Web App development less so. I found some other frameworks that are more developer friendly (customizable) such as Zend and Symfony etc.. but these seem to take allot of the power from the client and implement it in the server side, to me this seems a waste (and an unjustified performance bottleneck) .. Finally I found Aptana Jaxer framework that seems to think the same way I feel. That said it seems a bit under-developed, I didn't find modules for a social network and the community around it seems thin.. (searching Jaxer in StackOverflow returns few results) So other then making server side DB comm a bit simpler it does not help me greatly.. My requirements are a good facility to develop web apps on while containing all the user centric logic usually used for social networks in advance. What would you recommend? EDIT: OK, lats fine tune this question, after considering this abit further, is there a good down loadable source of a social network site in PHP that I can work around in building my web app? (I really like using JQUERY AJAX JSON etc..)

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• How can I abstract out the core functionality of several Rails applications?

  - by hornairs

  I'd like to develop a number of non-trivial Rails applications which all implement a core set of functionality but each have certain particular customizations, extensions, and aesthetic differences. How can I pull the core functionality (models, controllers, helpers, support classes, tests) common to all these systems out in such a way that updating the core will benefit every application based upon it? I've seen Rails Engines but they seem to be too detached, almost too abstracted to be built upon. I can seem them being useful for adding one component to an existing app, for example bolting on a blog engine to your existing e-commerce site. Since engines seem to be mostly self contained, it seems difficult and inconvenient to override their functionality and views while keeping DRY. I've also considered abstracting the code into a gem, but this seems a little odd. Do I make the gem depend on the Rails gems, and the define models & controllers inside it, and then subclass them in my various applications? Or do I define many modules inside the gem that I include in the different spots inside my various applications? How do I test the gem and then test the set of customizations and overridden functionality on top of it? I'm also concerned with how I'll develop the gem and the Rails apps in tandem, can I vendor a git repository of the gem into the app and push from that so I don't have to build a new gem every iteration? Also, are there private gem hosts/can I set my own gem source up? Also, any general suggestions for this kind of undertaking? Abstraction paradigms to adhere to? Required reading? Comments from the wise who have done this before? Thanks!

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• Should a developer write their own test plan for Q/A?

  - by Mat Nadrofsky

  Who writes the test plans in your shop? Who should write them? I realize developers (like me) regularly do their own unit testing whilst developing and in some cases even their own Q/A depending on the size of the shop and the nature of the business, but in a big software shop with a full development team and Q/A team, who should be writing those official "my changes are done now" test plans? Soon, we'll be bringing on another Q/A member to our development team. My question is, going forward, is it a good practice to get your developers to write their own test plans? Something tells me that part of that might make sense but another part might not... What I like about that: Developer is very familiar with the changes made, thus it's easy to produce a document... What I don't like about that: Developer knows how it's supposed to work and might write a test plan that caters to this without knowing it. So, with the above in mind, what is the general stance on this topic? I'm of course already reading books like the Mythical Man-Month, Code Complete and a few others which really do help, but I'd like to get some input from the group as well.

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• Table index design

  - by Swoosh

  I would like to add index(s) to my table. I am looking for general ideas how to add more indexes to a table. Other than the PK clustered. I would like to know what to look for when I am doing this. So, my example: This table (let's call it TASK table) is going to be the biggest table of the whole application. Expecting millions records. IMPORTANT: massive bulk-insert is adding data in this table table has 27 columns: (so far, and counting :D ) int x 9 columns = id-s varchar x 10 columns bit x 2 columns datetime x 5 columns INT COLUMNS all of these are INT ID-s but from tables that are usually smaller than Task table (10-50 records max), example: Status table (with values like "open", "closed") or Priority table (with values like "important", "not so important", "normal") there is also a column like "parent-ID" (self - ID) join: all the "small" tables have PK, the usual way ... clustered STRING COLUMNS there is a (Company) column (string!) that is something like "5 characters long all the time" and every user will be restricted using this one. If in Task there are 15 different "Companies" the logged in user would only see one. So there's always a filter on this one. Might be a good idea to add an index to this column? DATE COLUMNS I think they don't index these ... right? Or can / should be?

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• Looking for Simplified Overview of EJB3

  - by sdoca

  Hi I'm looking for a simplified overview of EJB3 components. I seem to understand most of the pieces of the puzzle, but can't quite get them to fit together in my brain as a full picture. I've developed numerous web applications (wars) that have been deployed on Tomcat before, but not a full-fledged EE application (ear). I would like the overview to be as generic as possible. I'm not looking for a tutorial on how to set up EJB3 on Glassfish built in NetBeans or some other vendor specific tutorial that's more about the IDE than the technology. I keep reading about Java, ejb-jar, web and ear modules but am not clear on what these different modules contain and how to use them to put together my app. In my case, I want to write a simple database CRUD web application. The first step is simple; create entity classes that model the database tables my app will be using. I plan on using annotations. Should I create a jar that contains just these enity classes? Is this the ejb-jar module (sometimes referred to as the Java module)? Next, I'll need some business logic classes that make use of the entity classes. These are the session beans (stateless or stateful) correct? Should these be packaged in the same jar as the entity classes or a separate jar? Finally, I'll need some sort of web interface (I'll be creating a JSF portlet) application that makes use of the both the session and entity beans. Together with the above jar(s), this will be my war? Assuming the above to be correct, what is involved in creating an ear? Forgive me if this post is vague, but I'm having a hard time defining what it is I don't understand. Thanks for any help!

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• Can Haskell's monads be thought of as using and returning a hidden state parameter?

  - by AJM

  I don't understand the exact algebra and theory behind Haskell's monads. However, when I think about functional programming in general I get the impression that state would be modelled by taking an initial state and generating a copy of it to represent the next state. This is like when one list is appended to another; neither list gets modified, but a third list is created and returned. Is it therefore valid to think of monadic operations as implicitly taking an initial state object as a parameter and implicitly returning a final state object? These state objects would be hidden so that the programmer doesn't have to worry about them and to control how they gets accessed. So, the programmer would not try to copy the object representing the IO stream as it was ten minutes ago. In other words, if we have this code: main = do putStrLn "Enter your name:" name <- getLine putStrLn ( "Hello " ++ name ) ...is it OK to think of the IO monad and the "do" syntax as representing this style of code? putStrLn :: IOState -> String -> IOState getLine :: IOState -> (IOState, String) main :: IOState -> IOState -- main returns an IOState we can call "state3" main state0 = putStrLn state2 ("Hello " ++ name) where (state2, name) = getLine state1 state1 = putStrLn state0 "Enter your name:"

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• Click behaviour - Difference in IE and FF ?!

  - by OlliD

  Hey folks, i just came to the conclusion that a project i am currently working on might have a "logical" error in functionality. Currently I'am using server technology with PHP/MySQL and JQuery. Within the page there's a normal link reference with tag <a href="contentpage?page=xxx">next step</a> The pain point now seems to be the given jquery click event on the same element. The intension was to save the (current) content of the page (- form elements) via another php script using the php session command. For any reason, IE can handle the click event of Jquery right before executing the standard html command, that reloads the current page again with the new page parameter. By using FF the behaviour is different. I assume, that FF first execute the html command and afterwards execute the javascript code which handles the click event. Therefore the resultset here is wrong respectivly empty. My question now is whether you made the same experience and how you handled / wordarrounded this problem. I'd be thankful fur any of your tips or further feedback. Maybe you also have a solution on how to rethink about the current architecture. Regards, Oliver

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• Bruteforcing Blackberry PersistentStore?

  - by Haoest

  Hello, I am experimenting with Blackberry's Persistent Store, but I have gotten nowhere so far, which is good, I guess. So I have written a a short program that attempts iterator through 0 to a specific upper bound to search for persisted objects. Blackberry seems to intentionally slow the loop. Check this out: String result = "result: \n"; int ub = 3000; Date start = Calendar.getInstance().getTime(); for(int i=0; i<ub; i++){ PersistentObject o = PersistentStore.getPersistentObject(i); if (o.getContents() != null){ result += (String) o.getContents() + "\n"; } } result += "end result\n"; result += "from 0 to " + ub + " took " + (Calendar.getInstance().getTime().getTime() - start.getTime()) / 1000 + " seconds"; From 0 to 3000 took 20 seconds. Is this enough to conclude that brute-forcing is not a practical method to breach the Blackberry? In general, how secure is BB Persistent Store?

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• [nHibernate] casting string to bool using nHibernate Criteria

  - by code-zoop

  I have an nHibernate query using Criteria, and I am trying to cast a string to bool in the query itself. I have done the same with casting a string to int, and that works well (the "DataField" property is "1" as a string): var result = Session .CreateCriteria<Car>() .Add(Restrictions.Eq((Projections.Cast(NHibernateUtil.Int32, Projections.Property("DataField"), 1)) .List<Car>(); tx.Commit(); But I am trying to do the same with bool, but I do not get the expected result: var result = Session .CreateCriteria<Car>() .Add(Restrictions.Eq((Projections.Cast(NHibernateUtil.bool, Projections.Property("DataField"), true)) .List<Car>(); tx.Commit(); "DataField" is the string "True", but the result in an empty list, where it should contain 100 elements with the "DataField" property string set to "True". I have tried with the string "true", and "1", but the result is still an empty List. [EDIT] As Commented below, I could check for the string "True" or "False", but I would say this is a more general question than just for the Boolean. Note that the idea is to have some sort of key value representation of the data, where the value can be different data types. I need the value table to contain all data, so storing the data as string seems like the cleanest solution! I have been able to use the method above to store both int and double as string, and to the cast in the query, but I have not succeeded using the same method for DateDime and Boolean. And for DateTime it is crucial to have the actual DateTime object. How can I make the cast from string to bool, and string to DateTime work in the queries? Thanks

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• As an Agile Java developer, what should I be looking for when hiring a C++ developer?

  - by agoudzwaard

  I come from an effective team of Agile Java developers. We've had a lot of success in hiring more people like ourselves - people passionate about technology with experience primarily in the Agile Java/J2EE space. We're looking to hire our first C++ developer to serve as an on-shore resource for maintaining and adding to the C++ portion of our code base. Up until now the entirety of our C++ development has been done out of an off-shore location. We consider our interview process to be fairly thorough: A phone screen centered on Object-Oriented Programming and Java A non-trivial at-home code project using Java An in-person interview covering technical and behavioral competency We look for a demonstration of Agile best practices (expressive code, test-driven development, continuous integration) throughout the entire process, however there is a common conception that Agility is primarily practiced by Java developers. If we retrofit our interview process for C++, should we still expect Agile qualities when interviewing for a C++ role? I'm asking on behalf of a team that has worked with Java too long to know what a good C++ developer looks like. Specifically we're looking to answer the following questions: Can we expect a demonstrated understanding of OO design and Separation of Concerns? In the code project we want the candidate to write unit tests. Would a good C++ developer be surprised by this expectation? Are there any "extra" competencies we can look for? For example with Java developers we always look for a familiarity with Dependency Injection.

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• Rotating png images using css in IE

  - by Ernest Shulikovski

  Here is a mockup for something called "Diversity Disc": http://diversity.iest.pl/ It is just three disks that you can rotate and read "results". I am using there just four png images, and rotate using jQuery f.i: $.fn.rleft = function() { return this.animate({ rotate: '-=45deg' }); }; It works not so bad in most new browser. But in all versions of IE things go terribly wrong. There is problem with rotation, and with png: after rotation, there is happening something very ugly with alpha transparency of those images. So my question is, is this possible to make it work in IE 8 and 7 (and, more or less IE 6?). If no I will be forced to order it in Flash. But I would like first to try to do it using just css and javascript (svg?). So what I am doing wrong? Do you have any tips, for using different technology, or js library? Thank you in advance for any answers.

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• JavaScript onClick() Display

  - by junaidkaps

  I have an array consisting of several objects containing Strings. I am successfully able to display the array by using: <td><p onclick="theMiddle(this)">The Middle</td> As you see from the td tag this is part of a table. Issue is that the browser opens up a new page to display my text. I have been trying to display the array above my table in a p tag. //JavaScript var arrayTheMiddle = new Array (showName.theMiddle, beginingTime.theMiddle, network.abc, duration.thirty, rating.general, description.theMiddle, showImage.theMiddle); function theMiddle(obj){ for(i=0; i < arrayTheMiddle.length; i++) { document.write(arrayTheMiddle[i] + "<br>"); } } //HTML File <p>Would like the array/function displayed here while the user clicks within the table below (entire table has not been listed)</p> <td><p onclick="theMiddle(this)">The Middle</td> Unfortunately I am constantly failing at utilizing get element by id to call my function which consists of an array. I have searched for all sorts of stuff, yet frankly I'm lost. Not even sure if my approach is correct at this point. I'm sure this is one of those simple things that are blowing over my head!

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• jQuery.data() works in Mac OS WebKit, but not on iPhone OS?

  - by rpj

  I'm playing around with jQTouch for an iPhone OS app that I've been toying with off and on for a while. I wanted to try my hand building it as a web app so I started playing with jQTouch. For reference, here is the page+source (all my code is currently in index.html so you can just "View Source" to see it all): http://rpj.me/doughapp.com/wd/ Essentially, I'm trying to save pertinent JSON objects retrieved from Google Local into DOM objects using the data() method (in this example, obj is the Google Local object): $('#locPane').data('selected', obj); then later (in a different "pane"), retrieving that object to be used: $('#locPane').bind('pageAnimationEnd', function(e, inf) { var selobj = $(this).data('selected'); // use 'selobj' here ... } In Chromium and Safari on the desktop OS (Snow Leopard in my case), this works perfectly (try it out). However, the same code returns undefined for the call to $(this).data('selected') in the second snippet above. I've also tried $('#' + e.target.id).data('selected') and even the naive $('#locPane').data('selected'). All variants return undefined in the iPhone OS version of WebKit, but not on the desktop. Interestingly, the running this on Mobile Safari in the iPhone Simulator fails as well. If you look at the full source, you'll see that I even try to save this object into my global jQTouch object (named jqt in my code). This, too, fails on the mobile platform. Has anyone else ever ran into this? I'll admit to not being a web/javascript programmer by trade, so if I'm making an idiot's error please call me out on it. Thank you in advance for the help! -RPJ Update: I didn't make it clear in the original post, but I'm open to any workaround if it works consistently. Since I'm having trouble storing these objects in general, anything that allows me to keep them around is good enough for now. Thanks!

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• google maps api keys to be set webserver-wide, (as env var? inside apache?)

  - by ~knb

  I have a web site with many virtual hosts and each registered with several domain names (ending in .org, .de), site1.mysite.de, site2.mysite.org Then I have different templating systems based on several programming languages (perl and php) in use on the web server. The Google Maps Api requires a unique Google Maps api key for each vhost. I want to have something like a web-server wide variable $goomapkey that I can call from inside my code. In PHP code, Now I have a kludgy case-analysis solution like $domain = substr($_SERVER['SERVER_NAME'], -3); if (".de" == $domain){ //if ("xxxxxx" eq substr($ENV{SERVER_NAME}, 0, 5)){ // $gookey = "ABQIAAA..."; //} else { //site1.de $gookey = "ABQIAAAA1Js..."; //} } elseif ("dev" == substr($_SERVER['SERVER_NAME'], 0, 3)){ //dev.mysite.org $gookey = "ABQIAAAA1JsSb..."; } else { //www.mysite.org $gookey = "ABQIAAAA1JsS..."; //TODO: Add more keys for each virtual host, for my.machinename.de, IP-address based URL, ... } ... inside my php-based CMS. A non-ideal solution, because it is, php-only, and I still have to set it at several html templates inside the CMS, and there are too many cases. I want the google maps api key to be set by the apache web server who examines the request *early in the request loop before any php page template code is constructed and evaluated. is an environment variable a good solution? which technology should be used to set the $goomapkey variable? I'd prefer mod_perl2 Apache request handler, but the documentation is confusing (many API changes in the past ). Which Apache module could I use? Is there a built-in Apache module that does the same thing?

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• Programming texts and reference material for my Kindle DX, creating the ultimate reference device?

  - by mwilliams

  (Revisiting this topic with the release of the Kindle DX) Having owned both generation Kindle readers and now getting a Kindle DX; I'm very excited for true PDF handling on an e-ink device! An image of _Why's book on my Kindle (from my iPhone). This gives me a device capable of storing hundreds of thousands of pages that are full text search capable in the form factor of a magazine. What references (preferably PDF to preserve things such as code samples) would you recommend? Ultimately I would like reference material for every modern and applicable programming language (C, C++, Objective-C, Python, Ruby, Java, .NET (C#, Visual Basic, ASP.NET), Erlang, SQL references) as well as general programming texts and frameworks (algorithms, design patterns, theory, Rails, Django, Cocoa, ORMs, etc) and anything else that could be thought of. With so many developers here using such a wide array of languages, as a professional in your particular field, what books or references would you recommend to me for my Kindle? Creative Commons material a plus (translate that to free) as well as the material being in the PDF file format. File size is not an issue. If this turns out to be a success, I will update with a follow-up with a compiled list generated from all of the answers. Thanks for the assistance and contributing! UPDATE I have been using the Kindle DX a lot now for technical books. Check out this blog post I did for high resolution photos of different material: http://www.matthewdavidwilliams.com/2009/06/12/technical-document-pdfs-on-the-kindle-dx/

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• Which isolation level should I use for the following insert-if-not-present transaction?

  - by Steve Guidi

  I've written a linq-to-sql program that essentially performs an ETL task, and I've noticed many places where parallelization will improve its performance. However, I'm concerned about preventing uniquness constraint violations when two threads perform the following task (psuedo code). Record CreateRecord(string recordText) { using (MyDataContext database = GetDatabase()) { Record existingRecord = database.MyTable.FirstOrDefault(record.KeyPredicate()); if(existingRecord == null) { existingRecord = CreateRecord(recordText); database.MyTable.InsertOnSubmit(existingRecord); } database.SubmitChanges(); return existingRecord; } } In general, this code executes a SELECT statement to test for record existance, followed by an INSERT statement if the record doesn't exist. It is encapsulated by an implicit transaction. When two threads run this code for the same instance of recordText, I want to prevent them from simultaneously determining that the record doesn't exist, thereby both attempting to create the same record. An isolation level and explicit transaction will work well, except I'm not certain which isolation level I should use -- Serializable should work, but seems too strict. Is there a better choice?

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• numpy array assignment problem

  - by Sujan

  Hi All: I have a strange problem in Python 2.6.5 with Numpy. I assign a numpy array, then equate a new variable to it. When I perform any operation to the new array, the original's values also change. Why is that? Please see the example below. Kindly enlighten me, as I'm fairly new to Python, and programming in general. -Sujan >>> import numpy as np >>> a = np.array([[1,2],[3,4]]) >>> b = a >>> b array([[1, 2], [3, 4]]) >>> c = a >>> c array([[1, 2], [3, 4]]) >>> c[:,1] = c[:,1] + 5 >>> c array([[1, 7], [3, 9]]) >>> b array([[1, 7], [3, 9]]) >>> a array([[1, 7], [3, 9]])

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• Boost threading/mutexs, why does this work?

  - by Flamewires

  Code: #include <iostream> #include "stdafx.h" #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> using namespace std; boost::mutex mut; double results[10]; void doubler(int x) { //boost::mutex::scoped_lock lck(mut); results[x] = x*2; } int _tmain(int argc, _TCHAR* argv[]) { boost::thread_group thds; for (int x = 10; x>0; x--) { boost::thread *Thread = new boost::thread(&doubler, x); thds.add_thread(Thread); } thds.join_all(); for (int x = 0; x<10; x++) { cout << results[x] << endl; } return 0; } Output: 0 2 4 6 8 10 12 14 16 18 Press any key to continue . . . So...my question is why does this work(as far as i can tell, i ran it about 20 times), producing the above output, even with the locking commented out? I thought the general idea was: in each thread: calculate 2*x copy results to CPU register(s) store calculation in correct part of array copy results back to main(shared) memory I would think that under all but perfect conditions this would result in some part of the results array having 0 values. Is it only copying the required double of the array to a cpu register? Or is it just too short of a calculation to get preempted before it writes the result back to ram? Thanks.

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