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  • Why don't computers store decimal numbers as a second whole number?

    - by SomeKittens
    Computers have trouble storing fractional numbers where the denominator is something other than a solution to 2^x. This is because the first digit after the decimal is worth 1/2, the second 1/4 (or 1/(2^1) and 1/(2^2)) etc. Why deal with all sorts of rounding errors when the computer could have just stored the decimal part of the number as another whole number (which is therefore accurate?) The only thing I can think of is dealing with repeating decimals (in base 10), but there could have been an edge solution to that (like we currently have with infinity).

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  • How does an Engine like Source process entities?

    - by Júlio Souza
    [background information] On the Source engine (and it's antecessor, goldsrc, quake's) the game objects are divided on two types, world and entities. The world is the map geometry and the entities are players, particles, sounds, scores, etc (for the Source Engine). Every entity has a think function, which do all the logic for that entity. So, if everything that needs to be processed comes from a base class with the think function, the game engine could store everything on a list and, on every frame, loop through it and call that function. On a first look, this idea is reasonable, but it can take too much resources, if the game has a lot of entities.. [end of background information] So, how does a engine like Source take care (process, update, draw, etc) of the game objects?

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  • Some mail details about Orange Mauritius

    Being an internet service provider is not easy after all for a lot of companies. Luckily, there are quite some good international operators in this world. For example Orange Mauritius aka Mauritius Telecom aka Wanadoo(?) aka MyT here in Mauritius. The local circumstances give them a quasi-monopol position on fixed lines for telephony and therefore cable-based DSL internet connectivity. So far, not bad but as usual... the details. Just for the records, I am only using the services of Orange for mobile but friends and customers are bound, eh stuck, with other services of Orange Mauritius. And usually, being the IT guy, they get in touch with me to complain about problems or to ask questions on either their ADSL / MyT connection, mail services or whatever. Most of those issues are user-related and easily to solve by tweaking the configuration of their computer a little bit but sometimes it's getting weird. Using Orange ADSL... somewhere else Now, let's imagine we are an Orange ADSL customer for ages and we are using their mail services with our very own mail address like "[email protected]". We configured our mail client like Thunderbird, Outlook Express, Outlook or Windows Mail as publicly described, and we are able to receive and send emails like a champion. No problems at all, the world is green. Did I mention that we have a laptop? Ok, let's take our movable piece of information technology and visit a friend here on the island. Not surprising, he is also customer of Orange, so we can read and answer emails. But Orange is not the online internet service provider and one day, we happen to hang out with someone that uses Emtel via WiMAX or UMTS.. And the fun starts... We can still receive and read emails from our Orange mail account and the IT world is still bright but try to send mails to someone outside the domain "@intnet.mu" or "@orange.mu". Your mail client will deny sending mail with SMTP message 5.1.0 "blah not allowed". First guess, there is problem with the mail client, maybe magically the configuration changed over-night. But no it is still working at home... So, there is for sure a problem with the guy's internet connection. At least, it is his fault not to have Orange internet services, so it can not work properly... The Orange Mail FAQ After some more frustation we finally checkout the Orange Mail FAQ to see whether this (obviously?) common problem has been described already. Sorry, but those FAQ entries are even more confusing as it is not really clear how to handle this scenario. Best of all is that most of the entries are still refering to use servers of the domain "intnet.mu". I mean Orange will disable those systems in favour of the domain "orange.mu" in the near future and does not amend their FAQs. Come on, guys! Ok, settings for POP3 are there. Hm, what about the secure version POP3S? No signs at all... Even changing your mail client to use password encryption with STARTTLS is not allowed at all. Use "bow.intnet.mu" for incoming mail... Ahhh, pretty obvious host name. I mean, at least something like pop.intnet.mu or pop3.intnet.mu would have been more accurate. Funny of all, the hostname "pop.orange.mu" is accessible to receive your mail account. Alright, checking SMTP options for authentication or other like POP-before-SMTP or whatever well-known and established mechanism to send emails are described. I guess that spotting a whale or shark in Mauritian waters would be easier. Trial and error on SMTP settings reveal that neither STARTTLS or any other connection / password encryption is available. Using SSL/TLS on SMTP only reveals that there is no service answering your request. Calling customer service So, we have to bite into the bitter apple and get in touch with Orange customer service and complain/explain them our case and ask for advice. After some hiccups, we finally manage to get hold of someone competent in mail services and we receive the golden spoon of mail configuration made by Orange Mauritius: SMTP hostname: smtpauth.intnet.mu And the world of IT is surprisingly green again. Customer satisfaction? Dear Orange Mauritius, what's the problem with this information? Are you scared of mail spammer? Why isn't there any case in your FAQs? Ok, talking about your FAQs - simply said: they are badly outdated! Configure your mail client to use server name based in the domain intnet.mu but specify your account username with orange.mu as domain part. Although, that there are servers available on the domain orange.mu after all. So, why don't you provide current information like this: POP3 server name: pop.orange.muSMTP server name: smtp.orange.muSMTP authenticated: smtpauth.orange.mu It's not difficult, is it? In my humble opinion not really and you would provide clean, consistent and up-to-date information for your customers. This would produce less frustation and so less traffic on your customer service lines. Which after all, would improve the total user experience and satisfaction level on both sides. Without knowing these facts. Now, imagine you would take your laptop abroad and have to use other internet service providers to be able to be online... Calling your customer service would be unnecessary expensive!

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  • New A-Team Web Site Launched

    - by .raja
    The A-Team has launched a new web site – the A-Team Chronicles which aggregates and organizes content produced by The A-Team members (including your humble blogger). The A-Team is a central, outbound, highly technical team comprised of Enterprise Architects, Solution Specialists and Software Engineers within the Fusion Middleware Product Development Organization that works with customers and partners, world wide, providing guidance on implementation best practices, architecture, troubleshooting and how best to use Oracle products to solve customer business needs. This content captures best practices, tips and tricks and guidance that the A-Team members gain from real-world experiences, working with customers and partners on implementation projects, through Architecture reviews, issue resolution and more. A-Team Chronicles makes this content available, through short and to the point articles to all our customers and partners in a consistent, easy to find and organized way. If you like the articles we post here, you might find even more interesting articles at the new A-Team Chronicles site, covering a wider range of Fusion Middleware topics. We will be decommissioning this site shortly in favor of A-Team Chronicles site and all new contents will be posted there.

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  • FigurePrint Brings Your Minecraft Creations to Life

    - by Jason Fitzpatrick
    If you love Minecraft so much you wish your finest creations could sit on your desk, FigurePrint is happy to oblige with a little 3D printing magic. Using their helper app you can export a section of your Minecraft world, big or small, upload it to their servers, and receive a full-color 3D printed model of it in the mail. The pricing is based on the size and complexity of model. Hit up the link to read more about their Minecraft printing services (as well as their Xbox Live avatar printing and World of War Craft printing). FigurePrint: Minecraft [via Wired] How To Delete, Move, or Rename Locked Files in Windows HTG Explains: Why Screen Savers Are No Longer Necessary 6 Ways Windows 8 Is More Secure Than Windows 7

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  • 3D engine for an online city/country simulation game (SimCity, Civilization)

    - by Dmitri
    I want to create a browser game, in which the user can control the development of a certain region (like SimCity or Civilization). One part of the task is rendering of the virtual world in a browser (3D or pseudo-3D). The rendering engine should a) work in a browser and b) ideally - be compatible with mobile devices (i. e. the representation of the virtual world should be visible both on desktop computer and mobile devices with the same codebase). Question: Which rendering engines (for SimCity-style games) fulfill aforementioned requirements (open and closed source) ?

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  • For normal mapping, why can we not simply add the tangent normal to the surface normal?

    - by sebf
    I am looking at implementing bump mapping (which in all implementations I have seen is really normal mapping), and so far all I have read says that to do this, we create a matrix to convert from world-space to tangent-space, in order to transform the lights and eye direction vectors into tangent space, so that the vectors from the normal map may be used directly in place of those passed through from the vertex shader. What I do not understand though, is why we cannot just use the normalised sum of the sampled-normal vector, and the surface-normal? (assuming we already transform and pass through the surface normal for the existing lighting functions) Take the diagram below; the normal is simply the deviation from the 'reference normal' for any given coordinate system, correct? And transforming the surface normal of a mapped surface from world space to tangent space makes it equivalent to the tangent space 'reference normal', no? If so, why do we transform all lighting vectors into tangent space, instead of simply transforming the sampled tangent once in the pixel shader?

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  • C Problem with Compiler?

    - by Solomon081
    I just started learning C, and wrote my hello world program: #include <stdio.h> main() { printf("Hello World"); return 0; } When I run the code, I get a really long error: Apple Mach-O Linker (id) Error Ld /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug/CProj normal x86_64 cd /Users/Solomon/Desktop/C/CProj setenv MACOSX_DEPLOYMENT_TARGET 10.7 /Developer/usr/bin/clang -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.7.sdk -L/Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug -F/Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug -filelist /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/CProj.LinkFileList -mmacosx-version-min=10.7 -o /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug/CProj ld: duplicate symbol _main in /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/helloworld.o and /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/main.o for architecture x86_64 Command /Developer/usr/bin/clang failed with exit code 1 I am running xCode Should I reinstall DevTools?

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  • Frame Interpolation issues for skeletal animation

    - by sebby_man
    I'm trying to animate in-between keyframes for skeletal animation but having some issues. Each joint is represented by a quaternion and there is no translation component. When I try to slerp between the orientations at the two key frames, I got a very wacky animation. I know my skinning equation is right because the animation is perfectly fine when the animation is directly on a keyframe rather than in-between two. I'm using glm's built in mix function to do the slerp, so I don't think there are any problems with the actual slerp implementation. There's really one thing left that could be wrong here. I must not be in the correct space to do slerp. Right now the orientations are in joint local space. Do I have to be in world space? In some other space along the way? I have the bind pose matrix and world-space transformation matrix at my disposal if those are needed.

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  • Even More New ADF Bloggers

    - by Shay Shmeltzer
    A couple of weeks back I posted an entry about new ADF related blogs that I found out about. Well as they say "when it rain it pours"  - and over the past few days I came across several other new bloggers that cover ADF. So here are a few others that you might want to add to your ADF blog aggregator: http://adfplus.blogspot.com - Paco van der Lindenhttps://blogs.oracle.com/aramamoo/ - Arunhttp://e20labs.org - Chad Thompsonhttp://oracleadfhowto.blogspot.com/ - Vinay Agarwalhttp://javaosdev.blogspot.com - Donovan Sherriffs https://blogs.oracle.com/prajkumar - Phil Wanghttp://oracle-itself.tumblr.com - Wael Abdeenhttps://blogs.oracle.com/adfthoughts - Raphael Rodriguehttp://adfwithejb.blogspot.com - Prateek Kumar shaw And here are a few more that are not just about ADF but do have the occasional ADF related entry:http://yonaweb.be - Yannick Ongenahttp://blog.whitehorses.nl - whitehorseshttps://blogs.oracle.com/imc - ISV Migration Center Team and the usual reminder here: To keep track of all things new in the ADF blog world follow the JDeveloper twitter or like JDeveloper on facebook to get notified of the latest entries we find for you around the world.

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  • Xna model parts are overlying others

    - by Federico Chiaravalli
    I am trying to import in XNA an .fbx model exported with blender. Here is my drawing code public void Draw() { Matrix[] modelTransforms = new Matrix[Model.Bones.Count]; Model.CopyAbsoluteBoneTransformsTo(modelTransforms); foreach (ModelMesh mesh in Model.Meshes) { foreach (BasicEffect be in mesh.Effects) { be.EnableDefaultLighting(); be.World = modelTransforms[mesh.ParentBone.Index] * GameCamera.World * Translation; be.View = GameCamera.View; be.Projection = GameCamera.Projection; } mesh.Draw(); } } The problem is that when I start the game some model parts are overlying others instead of being behind. I've tried to download other models from internet but they have the same problem.

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  • DOAG 2011

    - by Grant Ronald
    This week is the German Oracle User Group (DOAG) one of the largest Oracle User Groups in Europe.  We have a strong representation from Oracle's Product Management Team.  I kick of things with Dummies Guide to ADF on Tuesday 10am Frank Nimphius explains Task Flows in 60 minutes Duncan Mills give an insight into Real World Performance Tuning for ADF. Susan Duncan explains the Amazing World of Application Lifecycle Management and Duncan Mills finished the day with ADF Mobile Development There is also a load of interesting sessions on Forms, Apex and ADF from customers, partners and Oracle employees from Oracle Germany.  Looking to be a great conference.

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  • Programmatically updating one update panel elements from another update panel elements

    - by Jalpesh P. Vadgama
    While taking interviews for asp.net candidate I am often asking this question but most peoples are not able to give this answer. So I decided to write a blog post about this. Here is the scenario. There are two update panels in my html code in first update panel there is textbox hello world and another update panel there is a button called btnHelloWorld. Now I want to update textbox text in button click event without post back. But in normal scenario It will not update the textbox text as both are in different update panel. Here is the code for that. <form id="form1" runat="server"> <asp:ScriptManager ID="myScriptManager" runat="server" EnableCdn="true"></asp:ScriptManager> <asp:UpdatePanel ID="firstUpdatePanel" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:TextBox ID="txtHelloWorld" runat="server"></asp:TextBox> </ContentTemplate> </asp:UpdatePanel> <asp:UpdatePanel ID="secondUpdatePanel" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:Button ID="btnHelloWorld" runat="server" Text="Print Hello World" onclick="btnHelloWorld_Click" /> </ContentTemplate> </asp:UpdatePanel> </form> Here comes magic!!. Lots of people don’t know that update panel are providing the Update method from which we can programmatically update the update panel elements without post back. Below is code for that. protected void btnHelloWorld_Click(object sender, System.EventArgs e) { txtHelloWorld.Text = "Hello World!!!"; firstUpdatePanel.Update(); } That’s it here I have updated the firstUpdatePanel from the code!!!. Hope you liked it.. Stay tuned for more..Happy Programming.. Technorati Tags: UpdatePanel,ASP.NET

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  • Infrastructure and Platform As A Service in Private Cloud at Lawrence Livermore National Laboratory

    - by Anand Akela
    Scientists at the National Ignition Facility (NIF)— the world’s largest laser, at the Lawrence Livermore National Laboratory (LLNL)— need research environment that requires re-creating the physical environment and conditions that exist inside the sun. They have built private cloud infrastructure using Oracle VM and Oracle Enterprise Manager 12c to provision such an environment for research.  Tim Frazier of LLNL joined the "Managing Your Private Cloud With Oracle Enterprise Manager' session at Oracle Open World 2012 and discussed how the latest features in Oracle VM and Oracle Enterprise Manager 12c enables them to accelerate application provisioning in their private cloud. He also talked about how to increase service delivery agility, improve standardized roll outs, and do proactive management to gain total control of the private cloud environment. He also presented at the "Scene and Be Heard Theater" at Oracle OpenWorld 2012 and shared a lot of good information about his project and what they are doing in their private cloud environment. Learn more by looking at Tim's presentation .

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  • SQLAuthority News – A Conversation with an Old Friend – Sri Sridharan

    - by pinaldave
    Sri Sridharan is my old friend and we often talk on GTalk. The subject varies from Life in India/USA, movies, musics, and of course SQL. We have our differences when we talk about food or movie but we always agree when we talk about SQL. Yesterday while chatting with him we talked about SQLPASS and the conversation lasted for a long time. Here is the conversation between us on GTalk. I have removed a few of the personal talks and formatted into paragraphs as GTalk often shows stuff out of formatting. Pinal: Sri, Congrats on running for the PASS BoD again. You were so close last year. What made you decide to run again this year? Sri: Thank you Pinal for your leadership in the PASS India Community and all the things you do out there. After coming so close last year, there was no doubt in my mind that I will run again. I was truly humbled by the support I got from the community. Growing up in India for over 25 years, you are brought up in a very competitive part of the world. Right from the pressure of staying in the top of the class from kindergarten to your graduation, the relentless push from your parents about studying and getting good grades (and nothing else matters), you land up essentially living in a pressure cooker. To survive that relentless pressure, you need to have a thick skin, ability to stand up for who you really are , what you want to accomplish and in the process stay true those values. I am striving for a greater cause, to make PASS an organization that can help people with their SQL Server careers, to make PASS relevant to its chapter members, to make PASS an organization that every SQL professional in the world wants to be connected with. Just because I did not get elected or appointed last year does not mean that these causes are not worth fighting. Giving up upon failing the first time is simply not in me. If I did that, what message would I send to those who voted for me? What message would I send to my kids? Pinal: As someone who has such strong roots in India, what can the Indian PASS Community expect from you? Sri: First of all, I think fostering a regional leadership is something PASS must encourage as part of its global growth plan. For PASS global being able to understand all the issues in a region of the world and make sound decisions will be a tough thing to do on a continuous basis. I expect people like you, chapter leaders, regional mentors, MVPs of the region start playing a bigger role in shaping the next generation of PASS. That is something I said in my campaign and I still stand by it. I would like to see growth in the number of chapters in India. The current count does not truly represent the full potential of that region. I was pretty thrilled to see the Bangalore SQLSaturday happen early this year. I would like to see more of SQLSaturday events, at least in the major metro cities. I know the issues in India are very different from the rest of the world. So the formula needs to be tweaked a little for it to work better in India. Once the SQLSaturday model is vetted out, maybe there could be enough justification to have SQLRally India. PASS needs to have a premier SQL event in that region. Going to USA or Europe for that matter is incredibly hard due to VISA issues etc. So this could be a case of where PASS comes closer to where the community is. Pinal: What portfolio would take on if you are elected to the PASS Board? Sri: There are some very strong folks on the PASS Board today. The President discusses the portfolios with the group and makes the final call on the portfolios. I am also a fan of having a team associated with the portfolios. In that case, one person is the primary for a portfolio but secondary on a couple of other portfolios. This way people on the board have a direct vested interest in a few portfolios. Personally, I know I would these portfolios good justice – Chapters, Global Growth and Events (SQLSat, SQLRally). I would try to see if we can get a director to focus on Volunteers.  To me that is very critical for growth in the international regions. Pinal: This is an interesting conversation with you Sri. I know you so long time but this is indeed inspiring to many. India is a big country and we appreciate your thoughts. Sri: Thank you very much for taking time to chat with me today. Cheers. There are pretty strong candidates for SQLPASS Board of Elections this year. I know all of them in person and honestly it is going to be extremely difficult to not to vote for anybody. I am indeed in a crunch right now how to pick one over another. Though the choice is difficult, I encourage you to vote for them. I am extremely confident that the new board of directors will all have the same goal – Better SQL Server Community. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, DBA, PostADay, SQL, SQL Authority, SQL PASS, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology

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  • How do I go about hosting facebook apps that are picking speed?

    - by Karthik
    My situation is this. I coded in php and built a facebook app. After 3 days it has 13,000 users. I have my own server at hostmonster. It is a regular plan costing me about $70 per year. It has unlimited bandwidth. I did not anticipate hosting apps or that it could pick up so many users. Already 1 Gb of data was transferred in the last few days. I am planning to build a few more apps(around 10 - 20) and reach atleast a million users in total. Should I continue hosting on the same server or move to a VPS? I am a student and I don't have too much of a disposable income. So I want to move only if it is necessary. Right now it shows 1 Gb/infinity in data transfer. Any help/suggestions highly appreciated.

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  • rts libgdx design?

    - by user36531
    I am attempting to create a simple rts multi-player strategy game using libgdx. I am stumped at the moment. I want the underlying game world to run at all times and be aware of where all items are on the map.. so if player A logs in and moves unit to some location on the grid and logs off, that unit info is still there and can be accessed again by player A when they log back on to move somewhere else (if it didnt get attacked during the playerA was logged off). How can i do this? Do i create a main game world on the server and when players connect make client just sequentially request whats in each visible tile? Is there an easier way to get this done? Or go SQL route? Whats better?

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  • How to implement fast search on Azure Blob?

    - by Vicky
    I am done with writing the code to upload files (text files) to azure blob storage. Now I want to provide search based on text files content. For ex. If I search for "Hello" then the name of files that contains "Hello" words should appear in search result. Here my code to search class BlobSearch { static void Main(string[] args) { string searchText = "Hello"; CloudStorageAccount account = CloudStorageAccount.Parse(azureConString); CloudBlobClient blobClient = account.CreateCloudBlobClient(); CloudBlobContainer blobContainer = blobClient.GetContainerReference("MyBlobContainer"); blobContainer.FetchAttributes(); var blobItemList = blobContainer.ListBlobs(); foreach (var item in blobItemList) { string line = string.Empty; CloudBlockBlob blockBlob = blobContainer.GetBlockBlobReference(item.Uri.ToString()); if(blockBlob.Name.Contains(".txt")) { int lineno = 1; using (var stream = blockBlob.OpenRead()) { using (StreamReader reader = new StreamReader(stream)) { while ((line = reader.ReadLine()) != null) { if (line.IndexOf(searchText) != -1) { Console.WriteLine("Line : " + lineno +" => "+ blockBlob.Name); } lineno++; } } } } } Console.WriteLine("SEARCH COMPLETE"); Console.ReadLine(); } } Above code is working but it is too slow. Is there any way to do it faster or Can improve above code.

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  • Best practices for periodically saving game state to disk

    - by Ben Morris
    I'm working on an MMO. All of the player and environment data lives on a server and is kept in memory. There's a "world" object which keeps track of all of the maps, characters, etc. and their relations to each other. To avoid data loss in case of a crash, I've been periodically serializing the world to disk. The trouble is, this object can be quite large, so when the server starts writing, there's noticeable in-game slowdown for a few seconds, which I'd like to avoid. Any pointers on how to go about this in a more efficient way?

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  • Should integer divide by zero halt execution?

    - by Pyrolistical
    I know that modern languages handle integer divide by zero as an error just like the hardware does, but what if we could design a whole new language? Ignoring existing hardware, what should a programming language does when an integer divide by zero occurs? Should it return a NaN of type integer? Or should it mirror IEEE 754 float and return +/- Infinity? Or is the existing design choice correct, and an error should be thrown? Is there a language that handles integer divide by zero nicely? EDIT When I said ignore existing hardware, I mean don't assume integer is represented as 32 bits, it can be represented in anyway you can to imagine.

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  • Insider Insights

    Insider rumours and gossip from the murky world of the Database Industry, and from the colourful characters that inhabit it.

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  • Solving Big Problems with Oracle R Enterprise, Part II

    - by dbayard
    Part II – Solving Big Problems with Oracle R Enterprise In the first post in this series (see https://blogs.oracle.com/R/entry/solving_big_problems_with_oracle), we showed how you can use R to perform historical rate of return calculations against investment data sourced from a spreadsheet.  We demonstrated the calculations against sample data for a small set of accounts.  While this worked fine, in the real-world the problem is much bigger because the amount of data is much bigger.  So much bigger that our approach in the previous post won’t scale to meet the real-world needs. From our previous post, here are the challenges we need to conquer: The actual data that needs to be used lives in a database, not in a spreadsheet The actual data is much, much bigger- too big to fit into the normal R memory space and too big to want to move across the network The overall process needs to run fast- much faster than a single processor The actual data needs to be kept secured- another reason to not want to move it from the database and across the network And the process of calculating the IRR needs to be integrated together with other database ETL activities, so that IRR’s can be calculated as part of the data warehouse refresh processes In this post, we will show how we moved from sample data environment to working with full-scale data.  This post is based on actual work we did for a financial services customer during a recent proof-of-concept. Getting started with the Database At this point, we have some sample data and our IRR function.  We were at a similar point in our customer proof-of-concept exercise- we had sample data but we did not have the full customer data yet.  So our database was empty.  But, this was easily rectified by leveraging the transparency features of Oracle R Enterprise (see https://blogs.oracle.com/R/entry/analyzing_big_data_using_the).  The following code shows how we took our sample data SimpleMWRRData and easily turned it into a new Oracle database table called IRR_DATA via ore.create().  The code also shows how we can access the database table IRR_DATA as if it was a normal R data.frame named IRR_DATA. If we go to sql*plus, we can also check out our new IRR_DATA table: At this point, we now have our sample data loaded in the database as a normal Oracle table called IRR_DATA.  So, we now proceeded to test our R function working with database data. As our first test, we retrieved the data from a single account from the IRR_DATA table, pull it into local R memory, then call our IRR function.  This worked.  No SQL coding required! Going from Crawling to Walking Now that we have shown using our R code with database-resident data for a single account, we wanted to experiment with doing this for multiple accounts.  In other words, we wanted to implement the split-apply-combine technique we discussed in our first post in this series.  Fortunately, Oracle R Enterprise provides a very scalable way to do this with a function called ore.groupApply().  You can read more about ore.groupApply() here: https://blogs.oracle.com/R/entry/analyzing_big_data_using_the1 Here is an example of how we ask ORE to take our IRR_DATA table in the database, split it by the ACCOUNT column, apply a function that calls our SimpleMWRR() calculation, and then combine the results. (If you are following along at home, be sure to have installed our myIRR package on your database server via  “R CMD INSTALL myIRR”). The interesting thing about ore.groupApply is that the calculation is not actually performed in my desktop R environment from which I am running.  What actually happens is that ore.groupApply uses the Oracle database to perform the work.  And the Oracle database is what actually splits the IRR_DATA table by ACCOUNT.  Then the Oracle database takes the data for each account and sends it to an embedded R engine running on the database server to apply our R function.  Then the Oracle database combines all the individual results from the calls to the R function. This is significant because now the embedded R engine only needs to deal with the data for a single account at a time.  Regardless of whether we have 20 accounts or 1 million accounts or more, the R engine that performs the calculation does not care.  Given that normal R has a finite amount of memory to hold data, the ore.groupApply approach overcomes the R memory scalability problem since we only need to fit the data from a single account in R memory (not all of the data for all of the accounts). Additionally, the IRR_DATA does not need to be sent from the database to my desktop R program.  Even though I am invoking ore.groupApply from my desktop R program, because the actual SimpleMWRR calculation is run by the embedded R engine on the database server, the IRR_DATA does not need to leave the database server- this is both a performance benefit because network transmission of large amounts of data take time and a security benefit because it is harder to protect private data once you start shipping around your intranet. Another benefit, which we will discuss in a few paragraphs, is the ability to leverage Oracle database parallelism to run these calculations for dozens of accounts at once. From Walking to Running ore.groupApply is rather nice, but it still has the drawback that I run this from a desktop R instance.  This is not ideal for integrating into typical operational processes like nightly data warehouse refreshes or monthly statement generation.  But, this is not an issue for ORE.  Oracle R Enterprise lets us run this from the database using regular SQL, which is easily integrated into standard operations.  That is extremely exciting and the way we actually did these calculations in the customer proof. As part of Oracle R Enterprise, it provides a SQL equivalent to ore.groupApply which it refers to as “rqGroupEval”.  To use rqGroupEval via SQL, there is a bit of simple setup needed.  Basically, the Oracle Database needs to know the structure of the input table and the grouping column, which we are able to define using the database’s pipeline table function mechanisms. Here is the setup script: At this point, our initial setup of rqGroupEval is done for the IRR_DATA table.  The next step is to define our R function to the database.  We do that via a call to ORE’s rqScriptCreate. Now we can test it.  The SQL you use to run rqGroupEval uses the Oracle database pipeline table function syntax.  The first argument to irr_dataGroupEval is a cursor defining our input.  You can add additional where clauses and subqueries to this cursor as appropriate.  The second argument is any additional inputs to the R function.  The third argument is the text of a dummy select statement.  The dummy select statement is used by the database to identify the columns and datatypes to expect the R function to return.  The fourth argument is the column of the input table to split/group by.  The final argument is the name of the R function as you defined it when you called rqScriptCreate(). The Real-World Results In our real customer proof-of-concept, we had more sophisticated calculation requirements than shown in this simplified blog example.  For instance, we had to perform the rate of return calculations for 5 separate time periods, so the R code was enhanced to do so.  In addition, some accounts needed a time-weighted rate of return to be calculated, so we extended our approach and added an R function to do that.  And finally, there were also a few more real-world data irregularities that we needed to account for, so we added logic to our R functions to deal with those exceptions.  For the full-scale customer test, we loaded the customer data onto a Half-Rack Exadata X2-2 Database Machine.  As our half-rack had 48 physical cores (and 96 threads if you consider hyperthreading), we wanted to take advantage of that CPU horsepower to speed up our calculations.  To do so with ORE, it is as simple as leveraging the Oracle Database Parallel Query features.  Let’s look at the SQL used in the customer proof: Notice that we use a parallel hint on the cursor that is the input to our rqGroupEval function.  That is all we need to do to enable Oracle to use parallel R engines. Here are a few screenshots of what this SQL looked like in the Real-Time SQL Monitor when we ran this during the proof of concept (hint: you might need to right-click on these images to be able to view the images full-screen to see the entire image): From the above, you can notice a few things (numbers 1 thru 5 below correspond with highlighted numbers on the images above.  You may need to right click on the above images and view the images full-screen to see the entire image): The SQL completed in 110 seconds (1.8minutes) We calculated rate of returns for 5 time periods for each of 911k accounts (the number of actual rows returned by the IRRSTAGEGROUPEVAL operation) We accessed 103m rows of detailed cash flow/market value data (the number of actual rows returned by the IRR_STAGE2 operation) We ran with 72 degrees of parallelism spread across 4 database servers Most of our 110seconds was spent in the “External Procedure call” event On average, we performed 8,200 executions of our R function per second (110s/911k accounts) On average, each execution was passed 110 rows of data (103m detail rows/911k accounts) On average, we did 41,000 single time period rate of return calculations per second (each of the 8,200 executions of our R function did rate of return calculations for 5 time periods) On average, we processed over 900,000 rows of database data in R per second (103m detail rows/110s) R + Oracle R Enterprise: Best of R + Best of Oracle Database This blog post series started by describing a real customer problem: how to perform a lot of calculations on a lot of data in a short period of time.  While standard R proved to be a very good fit for writing the necessary calculations, the challenge of working with a lot of data in a short period of time remained. This blog post series showed how Oracle R Enterprise enables R to be used in conjunction with the Oracle Database to overcome the data volume and performance issues (as well as simplifying the operations and security issues).  It also showed that we could calculate 5 time periods of rate of returns for almost a million individual accounts in less than 2 minutes. In a future post, we will take the same R function and show how Oracle R Connector for Hadoop can be used in the Hadoop world.  In that next post, instead of having our data in an Oracle database, our data will live in Hadoop and we will how to use the Oracle R Connector for Hadoop and other Oracle Big Data Connectors to move data between Hadoop, R, and the Oracle Database easily.

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  • HTG Explains: How Do Noise Reducing Headphones Work?

    - by YatriTrivedi
    Passive noise reduction, active noise cancellation, sound isolation… The world of headphones has become quite advanced in giving you your own private sound bubble. Here’s how these different technologies work. Latest Features How-To Geek ETC Should You Delete Windows 7 Service Pack Backup Files to Save Space? What Can Super Mario Teach Us About Graphics Technology? Windows 7 Service Pack 1 is Released: But Should You Install It? How To Make Hundreds of Complex Photo Edits in Seconds With Photoshop Actions How to Enable User-Specific Wireless Networks in Windows 7 How to Use Google Chrome as Your Default PDF Reader (the Easy Way) WizMouse Enables Mouse Over Scrolling on Any Window Enhance GIMP’s Image Editing Power with Gimp Paint Studio Reclaim Vertical UI Space by Moving Your Tabs to the Side in Firefox Wind and Water: Puzzle Battles – An Awesome Game for Linux and Windows How Star Wars Changed the World [Infographic] Tabs Visual Manager Adds Thumbnailed Tab Switching to Chrome

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  • Physics System ignores collision in some rare cases

    - by Gajoo
    I've been developing a simple physics engine for my game. since the game physics is very simple I've decided to increase accuracy a little bit. Instead of formal integration methods like fourier or RK4, I'm directly computing the results after delta time "dt". based on the very first laws of physics : dx = 0.5 * a * dt^2 + v0 * dt dv = a * dt where a is acceleration and v0 is object's previous velocity. Also to handle collisions I've used a method which is somehow different from those I've seen so far. I'm detecting all the collision in the given time frame, stepping the world forward to the nearest collision, resolving it and again check for possible collisions. As I said the world consist of very simple objects, so I'm not loosing any performance due to multiple collision checking. First I'm checking if the ball collides with any walls around it (which is working perfectly) and then I'm checking if it collides with the edges of the walls (yellow points in the picture). the algorithm seems to work without any problem except some rare cases, in which the collision with points are ignored. I've tested everything and all the variables seem to be what they should but after leaving the system work for a minute or two the system the ball passes through one of those points. Here is collision portion of my code, hopefully one of you guys can give me a hint where to look for a potential bug! void PhysicalWorld::checkForPointCollision(Vec2 acceleration, PhysicsComponent& ball, Vec2& collisionNormal, float& collisionTime, Vec2 target) { // this function checks if there will be any collision between a circle and a point // ball contains informations about the circle (it's current velocity, position and radius) // collisionNormal is an output variable // collisionTime is also an output varialbe // target is the point I want to check for collisions Vec2 V = ball.mVelocity; Vec2 A = acceleration; Vec2 P = ball.mPosition - target; float wallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; float r = ball.mRadius / (mMap->getWallWidth() + mMap->getHallWidth()); // r is ball radius scaled to match actual rendered object. if (A.any()) // todo : I need to first correctly solve the collisions in case there is no acceleration return; if (V.any()) // if object is not moving there will be no collisions! { float D = P.x * V.y - P.y * V.x; float Delta = r*r*V.length2() - D*D; if(Delta < eps) return; Delta = sqrt(Delta); float sgnvy = V.y > 0 ? 1: (V.y < 0?-1:0); Vec2 c1(( D*V.y+sgnvy*V.x*Delta) / V.length2(), (-D*V.x+fabs(V.y)*Delta) / V.length2()); Vec2 c2(( D*V.y-sgnvy*V.x*Delta) / V.length2(), (-D*V.x-fabs(V.y)*Delta) / V.length2()); float t1 = (c1.x - P.x) / V.x; float t2 = (c2.x - P.x) / V.x; if(t1 > eps && t1 <= collisionTime) { collisionTime = t1; collisionNormal = c1; } if(t2 > eps && t2 <= collisionTime) { collisionTime = t2; collisionNormal = c2; } } } // this function should step the world forward by dt. it doesn't check for collision of any two balls (components) // it just checks if there is a collision between the current component and 4 points forming a rectangle around it. void PhysicalWorld::step(float dt) { for (unsigned i=0;i<mObjects.size();i++) { PhysicsComponent &current = *mObjects[i]; Vec2 acceleration = current.mForces * current.mInvMass; float rt=dt; // stores how much more the world should advance while(rt > eps) { float collisionTime = rt; Vec2 collisionNormal = Vec2(0,0); float halfWallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; // we check if there is any collision with any of those 4 points around the ball // if there is a collision both collisionNormal and collisionTime variables will change // after these functions collisionTime will be exactly the value of nearest collision (if any) // and if there was, collisionNormal will report in which direction the ball should return. checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); // either if there is a collision or if there is not we step the forward since we are sure there will be no collision before collisionTime current.mPosition += collisionTime * (collisionTime * acceleration * 0.5 + current.mVelocity); current.mVelocity += collisionTime * acceleration; // if the ball collided with anything collisionNormal should be at least none zero in one of it's axis if (collisionNormal.any()) { collisionNormal *= Dot(collisionNormal, current.mVelocity) / collisionNormal.length2(); current.mVelocity -= 2 * collisionNormal; // simply reverse velocity along collision normal direction } rt -= collisionTime; } // reset all forces for current object so it'll be ready for later game event current.mForces.zero(); } }

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