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• Possible to change the alpha value of certain pixels on iPhone?

  - by emi1faber

  Is it possible to change just a portion of a Sprite's alpha in response to user interaction? A good example of what I mean is iFog or iSteam, where the user can wipe "steam" off the iPhone's screen. Swapping images out wouldn't be feasible due to the sheer number of possibilities where the user could touch and move... For example, say you have a simple app that has a brick wall in the background that has graffiti on it, so there'd be two sprites, one of the brick wall, then one of the graffiti that has a higher z value than the brick wall. Then, based upon where the user touches (assuming their touch controls a sandblaster), some of the graffiti should be removed, but not all of it, which could be accomplished by changing the alpha value on a portion of the graffiti sprite. Is there any way to do this in cocos2d-iphone? Or, do I need to drop down into openGL, and if so, where would be a good place to start my search on how to accomplish this? Ideally, I'd like to accomplish this on a cocos2d-iphone Sprite, but if it's not possible, where's the best place to start looking? Thanks in advance, Ben

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• Status of VB6/ Best Desktop Application Language with Native Compilation

  - by Sandeep Jindal

  I was looking for a Desktop Application Programming Language with one of the biggest constraint: - “I need to output as native executable”. I explored multiple options: Java is not a very good option for desktop programming, but still you can use it. But Java to Exe is a problem. Only GCJ and Excelsior-Jet provides this. .Net platform does not support native compilation. Only very few expensive tools are available which can do the job. Python is not an option for native compilation. Right? VB6 is the option I am left with. From the above list, if I am correct, VB6 is the only and probably the best option I have. But VB6 itself has issues like: It is no more under development since There are questions on support of VB6 IDE with Vista Thus my questions are: From the list of programming language options, do you want to add any more? If VB6 is good/best option, looking at its development status, would you suggest using VB6 in this era?

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• New to MVVM - Best practices for seperating Data processing thread and UI Thread?

  - by OffApps Cory

  Good day. I have started messing around with the MVVP pattern, and I am having some problems with UI responsiveness versus data processing. I have a program that tracks packages. Shipment and package entities are persisted in SQL database, and are displayed in a WPF view. Upon initial retrieval of the records, there is a noticeable pause before displaying the new shipments view, and I have not even implemented the code that counts shipments that are overdue/active yet (which will necessitate a tracking check via web service, and a lot of time). I have built this with the Ocean framework, and all appears to be doing well, except when I first started my foray into multi-threading. It broke, and it appeared to break something in Ocean... Here is what I did: Private QueryThread As New System.Threading.Thread(AddressOf GetShipments) Public Sub New() ' Insert code required on object creation below this point. Me.New(ViewManagerService.CreateInstance, ViewModelUIService.CreateInstance) 'Perform initial query of shipments 'QueryThread.Start() GetShipments() Console.WriteLine(Me.Shipments.Count) End Sub Public Sub New(ByVal objIViewManagerService As IViewManagerService, ByVal objIViewModelUIService As IViewModelUIService) MyBase.New(objIViewModelUIService) End Sub Public Sub GetShipments() Dim InitialResults = From shipment In db.Shipment.Include("Packages") _ Select shipment Me.Shipments = New ShipmentsCollection(InitialResults, db) End Sub So I declared a new Thread, assigned it the GetShipments method and instanced it in the default constructor. Ocean freaks out at this, so there must be a better way of doing it. I have not had the chance to figure out the usage of the SQL ORM thing in Ocean so I am using Entity Framework (perhaps one of these days i will look at NHibernate or something too). Any information would be greatly appreciated. I have looked at a number of articles and they all have examples of simple uses. Some have mentioned the Dispatcher, but none really go very far into how it is used. Anyone know any good tutorials? Cory

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• Ruby on rails generates tests for you. Do those give a false sense of a safety net?

  - by Hamish Grubijan

  Disclaimer: I have not used RoR, and I have not generated tests. But, I will still dare to post this question. Quality Assurance is theoretically impossible to get 100% right in general (Undecidable problem ;), and it is hard in practice. So many developers do not understand that writing good automated tests is an art, and it is hard. When I hear that RoR generates the tests for you, I get very skeptical. It cannot be that easy. Testing is a general concept; it applies across languages. So does the concept of code contracts, it is similar for languages that support it. Code contracts do not generate themselves. The programmer must add the requirements and the promises manually, after doing some thinking about the algorithm / function. If a human gets it wrong, then the tools will propagate the error. Similarly with testing - it takes human judgement about what should happen. Tests do not write themselves, and we are far from the day when a business analyst can just have a conversation with a computer and tell it informally what the requirements are and have the computer do all the work. There is no magic ... how can RoR generate good tests for you? Please shed some light on this. Opinions are ok, for this is a community wiki. Thanks!

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• Is VB Really Case Insensitive?

  - by Otaku

  I'm not trying to start an argument here, but for whatever reason it's typically stated that VB is case insensitive and C languages aren't (and somehow that is a good thing). But here's my question: Where exactly is VB case insensitive? When I type... Dim ss As String Dim SS As String ...into the VS2008 IDE the second one has a warning of "Local variable 'SS' is already declared in the current block". In VBA VBE, it doesn't immediately kick an error, but rather just auto-corrects the case. Am I missing something here with this argument that VB is not case sensitive? (Also, if you know or care to answer, why would that be a bad thing?) EDIT: Why am I even asking this question? I've used VB in many of it's dialects for years now, sometimes as a hobbyist, sometimes for small business-related programs in a workgroup. As of the last 6 months I've been working on a big project, much bigger than I anticipated. Much of the sample source code out there is in C#. I don't have any burning desire to learn C#, but if there are things I'm missing out on that C# offers that VB doesn't (an opposite would be VB.NET offers XML Literals), then I'd like to know more about that feature. So in this case, it's often argued that C languages are case sensitive and that's good and VB is case insensitive and that is bad. I'd like to know A) how exactly is VB case insensitive because every single example in the code editor becomes case sensititive (meaning case gets corrected) whether I want it or not and B) is this compelling enough for me to consider moving to C# if VB.NET case is somehow limiting what I could do with code?

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• Django queryset not returning the same values as the generated sql

  - by HRCerqueira

  Hello guys, I have the following queryset: subscribers = User.objects.values('email', 'username').filter( Q(subscription_settings__new_question='i') | Q(subscription_settings__new_question_watched_tags='i', marked_tags__id__in=question.tags.values('id'), tag_selections__reason='good') ).exclude(id=question.author.id) The problem is that when I evaluate the query I get only the values that are filtered by the first Q object (even if I reverse the order of the objects). So lets say that I was expecting the user A, B, C and D, where A and B are filtered by the first Q object and C and D by the second. But the queryset only returns A and B. I used the django debug toolbar to see the query that was actually being executed (and then I used a direct print statement like "print subscriber.query.as_sql()" just to be sure) and then evaluated the query directly using psql (I'm using postgres by the way), and I get the results I expect. Here's the query btw: SELECT "auth_user"."email", "auth_user"."username" FROM "auth_user" LEFT OUTER JOIN "forum_markedtag" ON ("auth_user"."id" = "forum_markedtag"."user_id") INNER JOIN "forum_defaultsubscriptionsetting" ON ("auth_user"."id" = "forum_defaultsubscriptionsetting"."user_id") WHERE ((("forum_markedtag"."reason" = E'good' AND "forum_defaultsubscriptionsetting"."new_question_watched_tags" = E'i' AND "forum_markedtag"."tag_id" IN (SELECT U0."id" FROM "tag" U0 INNER JOIN "question_tags" U1 ON (U0."id" = U1."tag_id") WHERE U1."question_id" = 64 )) OR "forum_defaultsubscriptionsetting"."new_question" = E'i' ) AND NOT ("auth_user"."id" = 10 )) Thanks in advance EDIT: I tried to break the queryset into two, one that uses the first Q object as the filter and another one with the second Q object, and although the second queryset produces the correct sql that returns the correct values when evaluated directly, it still doesn't return nothing when evaluated as a django queryset. heres the alternative code: subscribers = User.objects.values('email', 'username').filter( subscription_settings__new_question='i').exclude(id=question.author.id) subscribers2 = User.objects.values('email', 'username').filter( subscription_settings__new_question_watched_tags='i', marked_tags__id__in=question.tags.values('id'), tag_selections__reason='good').exclude(id=question.author.id)

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• WCF Service Layer in n-layered application: performance considerations

  - by Marconline

  Hi all. When I went to University, teachers used to say that in good structured application you have presentation layer, business layer and data layer. This is what I heard for more than 5 years. When I started working I discovered that this is true but sometimes is better to have more than just three layers. Two or three days ago I discovered this article by John Papa that explain how to use Entity Framework in layered application. According to that article you should have: UI Layer and Presentation Layer (Model View Pattern) Service Layer (WCF) Business Layer Data Access Layer Service Layer is, to me, one of the best ideas I've ever heard since I work. Your UI is then completely "diconnected" from Business and Data Layer. Now when I went deeper by looking into provided source code, I began to have some questions. Can you help me in answering them? Question #0: is this a good enterpise application template in your opinion? Question #1: where should I host the service layer? Should it be a Windows Service or what else? Question #2: in the source code provided the service layer expose just an endpoint with WSHttpBinding. This is the most interoperable binding but (I think) the worst in terms of performances (due to serialization and deserializations of objects). Do you agree? Question #3: if you agree with me at Question 2, which kind of binding would you use? Looking forward to hear from you. Have a nice weekend! Marco

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• Can't ssh to ec2 permission denied (publickey)

  - by Chris Barnes

  I have existing instances running and I can connect to them fine. Even if I start a new instance from one of my saved ami's I can connect to it fine but any new public or community ami (I've tried 2 offical Ubuntu ami's and 1 Fedora quickstart ami) I get permission denied (publickey). The permissions are good on my key file. I've also tried creating a new keyfile. My ec2 firewall rules are good, I've also tried creating a new group. This is the error I'm getting. ssh -v -i ec2-keypair [email protected] OpenSSH_5.2p1, OpenSSL 0.9.7l 28 Sep 2006 debug1: Reading configuration data /Users/chris/.ssh/config debug1: Reading configuration data /etc/ssh_config debug1: Connecting to ec2-xxx.xxx.xxx.xxx.compute-1.amazonaws.com [xxx.xxx.xxx.xxx] port 22. debug1: Connection established. debug1: identity file ec2-keypair type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.1p1 Debian-6ubuntu2 debug1: match: OpenSSH_5.1p1 Debian-6ubuntu2 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.2 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Host 'ec2-xxx.xxx.xxx.xxx.compute-1.amazonaws.com' is known and matches the RSA host key. debug1: Found key in /Users/chris/.ssh/known_hosts:13 debug1: ssh_rsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey debug1: Next authentication method: publickey debug1: Trying private key: ec2-keypair debug1: read PEM private key done: type RSA debug1: Authentications that can continue: publickey debug1: No more authentication methods to try. Permission denied (publickey).

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• REST tools support for development and testing

  - by nzpcmad

  There is a similar question here but it only covers some of the issues below. We have a client who requires web services using REST. We have tons of experience using SOAP and over time have gathered together a really good set of tools for SOAP development and testing e.g. soapUI Eclipse plugins wsdl2java WSStudio By "tools" I mean a product "out of the box" that we can start using. I'm not talking about cutting code to "roll our own" using Ajax or whatever. The tool set for REST doesn't seem to be nearly as mature? What tools are out there (we use C# and Java mainly) ? Do the tools handle GET, POST, PUT, and DELETE? Is there a decent Eclipse plugin? Is there a decent client testing application like WSStudio where you point the tool to the WSDL and it generates a proxy on the fly with the appropriate methods and inputs and you simple type the data in? Are there any good package monitoring tools that allow you to look at the data? (I'm not thinking about sniffers like Wireshark here but rather things like soapUI that allow you to see the request / response) ?

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• Site Security/Access management for asp.net mvc application

  - by minal

  I am trying to find a good pattern to use for user access validation. Basically on a webforms application I had a framework which used user roles to define access, ie, users were assigned into roles, and "pages" were granted access to a page. I had a table in the database with all the pages listed in it. Pages could have child pages that got their access inherited from the parent. When defining access, I assigned the roles access to the pages. Users in the role then had access to the pages. It is fairly simple to manage as well. The way I implemented this was on a base class that every page inherited. On pageload/init I would check the page url and validate access and act appropriately. However I am now working on a MVC application and need to implement something similar, however I can't find a good way to make my previous solution work. Purely because I don't have static pages as url paths. Also I am not sure how best to approach this as I now have controllers rather then aspx pages. I have looked at the MVCSitemapprovider, but that does not work off a database, it needs a sitemap file. I need control of changing user persmissions on the fly. Any thoughts/suggestions/pointers would be greatly appreciated.

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• maintaining a large list in python

  - by Oren

  I need to maintain a large list of python pickleable objects that will quickly execute the following algorithm: The list will have 4 pointers and can: Read\Write each of the 4 pointed nodes Insert new nodes before the pointed nodes Increase a pointer by 1 Pop nodes from the beginning of the list (without overlapping the pointers) Add nodes at the end of the list The list can be very large (300-400 MB), so it shouldnt be contained in the RAM. The nodes are small (100-200 bytes) but can contain various types of data. The most efficient way it can be done, in my opinion, is to implement some paging-mechanism. On the harddrive there will be some database of a linked-list of pages where in every moment up to 5 of them are loaded in the memory. On insertion, if some max-page-size was reached, the page will be splitted to 2 small pages, and on pointer increment, if a pointer is increased beyond its loaded page, the following page will be loaded instead. This is a good solution, but I don't have the time to write it, especially if I want to make it generic and implement all the python-list features. Using a SQL tables is not good either, since I'll need to implement a complex index-key mechanism. I tried ZODB and zc.blist, which implement a BTree based list that can be stored in a ZODB database file, but I don't know how to configure it so the above features will run in reasonable time. I don't need all the multi-threading\transactioning features. No one else will touch the database-file except for my single-thread program. Can anyone explain me how to configure the ZODB\zc.blist so the above features will run fast, or show me a different large-list implementation?

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• Currency exchange rates for paypal

  - by Jacco

  Does anyone know a way to get the currency exchange rates for paypal? We have custom shopping cart and use Paypal (Website Payments Standard) to handle payments. Our 'home' currency is Euro, but we would like to present our customers the option to pay in different currencies (USD, CAD, AUD and GBP). PayPal offers the option to:     a) automatically convert our Euro quoted prices to, for example, USD upon checkout     b) checkout in USD directly With option a): We get paid in Euro, the customer pays for the currency exchange (good). The customer does not know what he/she is going to be charged in USD until checkout. (bad) With option b) The customer pays in USD, then the currency is converted into EUR and we pay the the currency exchange. The customer never has to worry about the different currencies (excellent) We do not know the exchange rate PayPal is going to use so we cannot quote the correct prices to our customer (showstopper) So my question is:   Does anybody know a way to get the PayPal exchange rates? or   Does anybody know how to make a good estimate? Update: PayPal updates it's exchange rate 2 times a day. (at least, that is what they state). They use the Interbank Exchange Rate provided by ??? and add a 2.5% spread above this rate to determine their retail foreign exchange rates. Unforunately, there the Interbank Exchange Rates vary from source to source and from minute to minute. We have been monitoring the PayPal exchange rates and cross referenced them with the Official reference rates provides by the European Central Bank. the results vary widely, somewhere from 1 to 6 ! percent...

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• Python coding test problem for interviews

  - by Kal

  I'm trying to come up with a good coding problem to ask interview candidates to solve with Python. They'll have an hour to work on the problem, with an IDE and access to documentation (we don't care what people have memorized). I'm not looking for a tough algorithmic problem - there are other sections of the interview where we do that kind of thing. The point of this section is to sit and watch them actually write code. So it should be something that makes them use just the data structures which are the everyday tools of the application developer - lists, hashtables (dictionaries in Python), etc, to solve a quasi-realistic task. They shouldn't be blocked completely if they can't think of something really clever. We have a problem which we use for Java coding tests, which involves reading a file and doing a little processing on the contents. It works well with candidates who are familiar with Java (or even C++). But we're running into a number of candidates who just don't know Java or C++ or C# or anything like that, but do know Python or Ruby. Which shouldn't exclude them, but leaves us with a dilemma: On the one hand, we don't learn much from watching someone struggle with the basics of a totally unfamiliar language. On the other hand, the problem we use for Java turns out to be pretty trivial in Python (or Ruby, etc) - anyone halfway competent can do it in 15 minutes. So, I'm trying to come up with something better. Surprisingly, Google doesn't show me anyone doing something like this, unless I'm just too dumb to enter the obvious search term. The best idea I've come up with involves scheduling workers to time slots, but it's maybe a little too open-ended. Have you run into a good example? Or a bad one? Or do you just have an idea?

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• x86 opcode alignment references and guidelines

  - by mrjoltcola

  I'm generating some opcodes dynamically in a JIT compiler and I'm looking for guidelines for opcode alignment. 1) I've read comments that briefly "recommend" alignment by adding nops after calls 2) I've also read about using nop for optimizing sequences for parallelism. 3) I've read that alignment of ops is good for "cache" performance Usually these comments don't give any supporting references. Its one thing to read a blog or a comment that says, "its a good idea to do such and such", but its another to actually write a compiler that implements specific op sequences and realize most material online, especially blogs, are not useful for practical application. So I'm a believer in finding things out myself (disassembly, etc. to see what real world apps do). This is one case where I need some outside info. I notice compilers will usually start an odd byte instruction immediately after whatever previous instruction sequence there was. So the compiler is not taking any special care in most cases. I see "nop" here or there, but usually it seems nop is used sparingly, if at all. How critical is opcode alignment? Can you provide references for cases that I can actually use for implementation? Thanks.

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• Natural language processing - Ideas for beginner's projects

  - by Microkernel

  Hi guys, I am a beginner in NLP and NLTK. I am very interested in NLP and hence joined a weekend course on AI in some local institution, which requires me to do a project for completion of the course, and I decided to do it in NLP. The problem is,the instructor is not good at all for this course (According to me she is just a charlatan) (or may not be very interested in teaching as this is her last batch here after which the institute is going to send her out). So I am stuck in a situation where where I got to finish this project in a month to one and half months period, but as a naive person in the field I am feeling it very difficult to comprehend the things required to decide on project. (Also, as I am working full time, I am not finding enough time to dedicate on this). I considered using NLTK toolkit in python for the project for following reasons. (1) Python is famous for ease of use, rapid prototyping and very active community (considering very short span of time I have, and as I am a C programmer by profession, I need a language that I can learn fast and is simple to use). (2) NLTk has good review, and extensive documentation and a very active community. So the problem is what project should I take up, so that I can learn something and will be able to finish project in time. (I know almost nothing in NLP, don't even know what exactly corpora is... :( ) So, please suggest me some topics that I should consider for the project. Regards, MicroKernel :)

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• method for specialized pathfinding?

  - by rlbond

  I am working on a roguelike in my (very little) free time. Each level will basically be a few rectangular rooms connected together by paths. I want the paths between rooms to be natural-looking and windy, however. For example, I would not consider the following natural-looking: B X X X XX XX XX AXX I really want something more like this: B X XXXX X X X X AXXXXXXXX These paths must satisfy a few properties: I must be able to specify an area inside which they are bounded, I must be able to parameterize how windy and lengthy they are, The lines should not look like they started at one path and ended at the other. For example, the first example above looks as if it started at A and ended at B, because it basically changed directions repeatedly until it lined up with B and then just went straight there. I was hoping to use A*, but honestly I have no idea what my heuristic would be. I have also considered using a genetic algorithm, but I don't know how practical that method might end up. My question is, what is a good way to get the results I want? Please do not just specify a method like "A*" or "Dijkstra's algorithm," because I also need help with a good heuristic.

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• Ideas for networking project

  - by Chris Thompson

  Hi all, I'm a graduating senior in computer science taking a computer networks class and I'm trying to figure out my final project. I normally am not at a loss for ideas but be it senioritis or straight burn out, I've got nothing. I've done some fun stuff in the past, but I just can't seem to come up with a good idea. Given the mass of brilliance on this site, I figured it would be a good place to request some suggestions. To give you an idea of scope, it's due in about a month and I would consider myself proficient with mobile architectures like Android (although I have no iPhone experience) along with Java, C++, etc. If you can suggest an idea, I'd be happy to make it work in whatever language I know. Like I said, I'm a senior and will be graduating so I'd rather not take on something that would kill me... Also, I'd be happy to make it open source if it's an idea you'd always wanted to work on but didn't have the time to start. Thanks in advance for the help! Chris Edit 1: Thanks so much for the suggestions everyone! Unfortunately I've actually already written a chat client (for a network security class) and I think I'd run into some honor code issues if I did that again, although that's always a great option. I like the game idea and that's actually something I've never attempted before (in any capacity) although given that, I'm a little scared about time...

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• Advice for Future Programmers?

  - by Nate Zaugg

  I have a buddy that is going to be giving some presentations to high-schoolers. Specifically he asked: What would you be looking for if they approached you about work? Perhaps you are in that age group right now. What do you want to know? Perhaps you are just a few years into the workforce. What do you wish someone had told you but never did? Perhaps you have children, relatives or friends in or soon to be in that age group. What are you worried they don't know about? I'm sure there are other perspectives and questions I'm not even thinking about. I'd like to hear what you have to say about it. Here was my list: Don't be afraid to try! Don't let the perception that something is too difficult stop you from experimenting. Curiosity may have killed the cat, but an un-inquisitive person is mostly useless. Stolen from Einstein: You don't really understand something until you can explain it to your grandmother. It's never enough to be smart, you also have to work well with others. Before you can be really smart, you must learn how to learn. There will always be someone smarter than you are -- Become their buddy! Get to know great minds and learn all you can. Some knowledge can only be expressed this way. Communication, Communication, Communication! Projects rarely fail because of technical reasons and the difference between good programmers and outstanding programmers is how well they communicate. A good work ethic never goes unnoticed. Know when to ask for help and when to figure something out for yourself.

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• How to resize a Flot graph when its containing div changes size

  - by Will Gorman

  I'm using the Flot graphing library jQuery plugin and I haven't found a good way to handle resizing the graph when it's containing <div> changes size (for example, due to window resizing). When handling the onresize event, I've made sure that the width and height of the containing <div>are updated to the correct size and then tried calling both setupGrid and draw on the plot object but with no effect. I've had some success with the approach of just removing and readding the containing <div> and replotting the graph in it. However, this seems to be prone to getting stuck in infinite resize event loops if I have to add other <div> elements to the document at the same time (like for tooltips for the graph) as I'm guessing those can trigger resize events as well? Is there a good way to handle it that I'm missing? (I'm also using ExplorerCanvas for IE in order to be able to use Flot, if that might have anything to do with it. I haven't really tried in any other browsers yet)

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• fast similarity detection

  - by reinierpost

  I have a large collection of objects and I need to figure out the similarities between them. To be exact: given two objects I can compute their dissimilarity as a number, a metric - higher values mean less similarity and 0 means the objects have identical contents. The cost of computing this number is proportional to the size of the smaller object (each object has a given size). I need the ability to quickly find, given an object, the set of objects similar to it. To be exact: I need to produce a data structure that maps any object o to the set of objects no more dissimilar to o than d, for some dissimilarity value d, such that listing the objects in the set takes no more time than if they were in an array or linked list (and perhaps they actually are). Typically, the set will be very much smaller than the total number of objects, so it is really worthwhile to perform this computation. It's good enough if the data structure assumes a fixed d, but if it works for an arbitrary d, even better. Have you seen this problem before, or something similar to it? What is a good solution? To be exact: a straightforward solution involves computing the dissimilarities between all pairs of objects, but this is slow - O(n2) where n is the number of objects. Is there a general solution with lower complexity?

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• Issues in Convergence of Sequential minimal optimization for SVM

  - by Amol Joshi

  I have been working on Support Vector Machine for about 2 months now. I have coded SVM myself and for the optimization problem of SVM, I have used Sequential Minimal Optimization(SMO) by Mr. John Platt. Right now I am in the phase where I am going to grid search to find optimal C value for my dataset. ( Please find details of my project application and dataset details here http://stackoverflow.com/questions/2284059/svm-classification-minimum-number-of-input-sets-for-each-class) I have successfully checked my custom implemented SVM`s accuracy for C values ranging from 2^0 to 2^6. But now I am having some issues regarding the convergence of the SMO for C 128. Like I have tried to find the alpha values for C=128 and it is taking long time before it actually converges and successfully gives alpha values. Time taken for the SMO to converge is about 5 hours for C=100. This huge I think ( because SMO is supposed to be fast. ) though I`m getting good accuracy? I am screwed right not because I can not test the accuracy for higher values of C. I am actually displaying number of alphas changed in every pass of SMO and getting 10, 13, 8... alphas changing continuously. The KKT conditions assures convergence so what is so weird happening here? Please note that my implementation is working fine for C<=100 with good accuracy though the execution time is long. Please give me inputs on this issue. Thank You and Cheers.

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• Can this be considered Clean Code / Best Practice?

  - by MRFerocius

  Guys, How are you doing today? I have the following question because I will follow this strategy for all my helpers (to deal with the DB entities) Is this considered a good practice or is it going to be unmaintainable later? public class HelperArea : AbstractHelper { event OperationPerformed<Area> OnAreaInserting; event OperationPerformed<Area> OnAreaInserted; event OperationPerformed<Area> OnExceptionOccured; public void Insert(Area element) { try { if (OnAreaInserting != null) OnAreaInserting(element); DBase.Context.Areas.InsertOnSubmit(new AtlasWFM_Mapping.Mapping.Area { areaDescripcion = element.Description, areaNegocioID = element.BusinessID, areaGUID = Guid.NewGuid(), areaEstado = element.Status, }); DBase.Context.SubmitChanges(); if (OnAreaInserted != null) OnAreaInserted(element); } catch (Exception ex) { LogManager.ChangeStrategy(LogginStrategies.EVENT_VIEWER); LogManager.LogError(new LogInformation { logErrorType = ErrorType.CRITICAL, logException = ex, logMensaje = "Error inserting Area" }); if (OnExceptionOccured != null) OnExceptionOccured(elemento); } } I want to know if it is a good way to handle the event on the Exception to let subscribers know that there has been an exception inserting that Area. And the way to log the Exception, is is OK to do it this way? Any suggestion to make it better?

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• Getting a job in the games industry as a developer, just knowing a game engine

  - by numerical25

  I recently enrolled in a community college for games developement. But I am skeptical about the curriculum. I have no experience in the gaming industry so I wouldn't be able to tell whether it's a good investment or not. So I am asking you. I don't want to get too much into the details of all the classes I am taking so I will try to be brief. By the time I graduate, I should have a understanding of how a game engine works. I will be working with the Unreal Engine to develop a Multiplayer game from scratch. So in the process of my final project, I will learn how to work within the Unreal Engine, learn Python and learn how to use its API to connect to a remote server and build game mechanics. Overall I will also recieve an associates degree in game development. I learn C++ but not C. The director said he was trying to implement C in the program as well. What I notice is I will not learn how to build a 3D game engine from scratch. They do not teach any artificial intelligence (AI). I will not learn how to work with the graphics card using a graphics API such as DirectX or OpenGL. I know building a game engine from scratch is a little complex, but at the same time the track is requiring me to take some advanced mathematics courses such as calculus and geometry 1 and 2. I also got to take a physics class. I just think that's a little much for just learning how to use the Unreal Engine but not actually build one or try to learn the anatomy of a games engine. Is this good enough to possibly land my a job in the industry? If I left anything out or was not detail, please feel free to ask more questions. Edit: I do learn data structures and algorithms.

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• jsf and huge web site

  - by darko petreski

  Hi All, I need to program a very huge web site. The site should contain public part with search engine, user registration forms, cart and all other stuff. The private part should contain administrative web application with a lot of data grids, complex edit forms, security checks, services and so on. Also I need very good support for html mailing and pdf exports. Web services are also required. I am considering to use jsf. Can you recommend me books or other stuff where I can find all this info for building what i need? Is seam good option for this? I have looked their site and page seam on production. The sites listed there are far from professional and enterprise. Is there any book that explains how to build complete web site with jsf technology from login, security, sending mails, pdf conversion, time dependent background processes and everything else that big sites needs. I do not have time reading 20 books. In every php book all this stuff is explained but I have not seen a single java book that at least from high view will explain all of this. Regards

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• 2-step user registration with Django

  - by David S

  I'm creating a website with Django and want a fairly common 2-step user registration. What I mean by this is that the user fills in the some basic user information + some application specific information (sort of like a coupon value). Upon submit, an email is sent to ensure email address is valid. This email should contain a link to click on to "finish" the registration. When the link is clicked, the user is marked as validated and they are directed to a new page to complete optional "user profile" type information. So, pretty basic stuff. I have done some research and found django-registration by James Bennett. I do know who James is and have seen him at PyCons and DjanoCons in the past. There is obviously very few people in the world that know Django better than James (so, I know the quality of the code/app is good). But, it almost seems like a bit of over kill. I've read through the docs and was a bit confused (maybe I'm just being a bit dense today). I believe that if I do use django-registration, I will need to have some custom forms, etc. Is there anything else out there I should evaluate? Or are there any good tutorials or videos on using django-registration? I've done a bit of googling, but haven't found anything. But, I suspect that it might be a case of a lot of very common words that don't really find what you are looking for (django user registration tutorial/example). Or is just a case where it would be just about as easy to build your own solution with Django forms, etc? Here is the tech stack I'm using: Python 2.7.2 Django 1.3.1 PostgreSQL 9.1 psycopg2 2.4.1 Twitter Bootstrap 2.0.2

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