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• Formal Languages, Inductive Proofs &amp; Regular Expressions

  - by MarkPearl

  So I am slogging away at my UNISA stuff. I have just finished doing the initial once non stop read through the first 11 chapters of my COS 201 Textbook - “Introduction to Computer Theory 2nd Edition” by Daniel Cohen. It has been an interesting couple of days, with familiar concepts coming up as well as some new territory. In this posting I am going to cover the first couple of chapters of the book. Let start with Formal Languages… What exactly is a formal language? Pretty much a no duh question for me but still a good one to ask – a formal language is a language that is defined in a precise mathematical way. Does that mean that the English language is a formal language? I would say no – and my main motivation for this is that one can have an English sentence that is correct grammatically that is also ambiguous. For example the ambiguous sentence: "I once shot an elephant in my pyjamas.” For this and possibly many other reasons that I am unaware of, English is termed a “Natural Language”. So why the importance of formal languages in computer science? Again a no duh question in my mind… If we want computers to be effective and useful tools then we need them to be able to evaluate a series of commands in some form of language that when interpreted by the device no confusion will exist as to what we were requesting. Imagine the mayhem that would exist if a computer misinterpreted a command to print a document and instead decided to delete it. So what is a Formal Language made up of… For my study purposes a language is made up of a finite alphabet. For a formal language to exist there needs to be a specification on the language that will describe whether a string of characters has membership in the language or not. There are two basic ways to do this: By a “machine” that will recognize strings of the language (e.g. Finite Automata). By a rule that describes how strings of a language can be formed (e.g. Regular Expressions). When we use the phrase “string of characters”, we can also be referring to a “word”. What is an Inductive Proof? So I am not to far into my textbook and of course it starts referring to proofs and different types. I have had to go through several different approaches of proofs in the past, but I can never remember their formal names , so when I saw “inductive proof” I thought to myself – what the heck is that? Google to the rescue… An inductive proof is like a normal proof but it employs a neat trick which allows you to prove a statement about an arbitrary number n by first proving it is true when n is 1 and then assuming it is true for n=k and showing it is true for n=k+1. The idea is that if you want to show that someone can climb to the nth floor of a fire escape, you need only show that you can climb the ladder up to the fire escape (n=1) and then show that you know how to climb the stairs from any level of the fire escape (n=k) to the next level (n=k+1). Does this sound like a form of recursion? No surprise then that in the same chapter they deal with recursive definitions. An example of a recursive definition for the language EVEN would the 3 rules below: 2 is in EVEN If x is in EVEN then so is x+2 The only elements in the set EVEN are those that be produced by the rules above. Nothing to exciting… So if a definition for a language is done recursively, then it makes sense that the language can be proved using induction. Regular Expressions So I am wondering to myself what use is this all – in fact – I find this the biggest challenge to any university material is that it is quite hard to find the immediate practical applications of some theory in real life stuff. How great was my joy when I suddenly saw the word regular expression being introduced. I had been introduced to regular expressions on Stack Overflow where I was trying to recognize if some text measurement put in by a user was in a valid form or not. For instance, the imperial system of measurement where you have feet and inches can be represented in so many different ways. I had eventually turned to regular expressions as an easy way to check if my parser could correctly parse the text or not and convert it to a normalize measurement. So some rules about languages and regular expressions… Any finite language can be represented by at least one if not more regular expressions A regular expressions is almost a rule syntax for expressing how regular languages can be formed regular expressions are cool For a regular expression to be valid for a language it must be able to generate all the words in the language and no other words. This is important. It doesn’t help me if my regular expression parses 100% of my measurement texts but also lets one or two invalid texts to pass as well. Okay, so this posting jumps around a bit – but introduces some very basic fundamentals for the subject which will be built on in later postings… Time to go and do some practical examples now…

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• How do multipass shaders work in OpenGL?

  - by Boreal

  In Direct3D, multipass shaders are simple to use because you can literally define passes within a program. In OpenGL, it seems a bit more complex because it is possible to give a shader program as many vertex, geometry, and fragment shaders as you want. A popular example of a multipass shader is a toon shader. One pass does the actual cel-shading effect and the other creates the outline. If I have two vertex shaders, "cel.vert" and "outline.vert", and two fragment shaders, "cel.frag" and "outline.frag" (similar to the way you do it in HLSL), how can I combine them to create the full toon shader? I don't want you saying that a geometry shader can be used for this because I just want to know the theory behind multipass GLSL shaders ;)

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• Programmaticaly finding the Landau notation (Big O or Theta notation) of an algorithm?

  - by Julien L

  I'm used to search for the Landau (Big O, Theta...) notation of my algorithms by hand to make sure they are as optimized as they can be, but when the functions are getting really big and complex, it's taking way too much time to do it by hand. it's also prone to human errors. I spent some time on Codility (coding/algo exercises), and noticed they will give you the Landau notation for your submitted solution (both in Time and Memory usage). I was wondering how they do that... How would you do it? Is there another way besides Lexical Analysis or parsing of the code? PS: This question concerns mainly PHP and or JavaScript, but I'm opened to any language and theory.

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• Is it illegal to rewrite every line of an open source project in a slightly different way, and use it in a closed source project?

  - by optician

  There is some code which is GPL or LGPL that I am considering using for an iPhone project. If I took that code (javascript) and rewrote it in a different language for use on the iPhone would that be a legal issue? In theory the process that has happened is that I have gone through each line of the project, learnt what it is doing, and then re implemented the ideas in a new language. To me it seems this is like learning how to implement something, but then re-implementing it separate from the original licence. Therefore you have only copied the algorithm, which arguably you could have learnt from somewhere else other than the original project. Does the licence cover the specific implementation or the algorithm as well?

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• Windows Embedded Compact 7 and Silverlight for Windows Embedded

  - by Valter Minute

  If you want to see a preview of Windows Embedded Compact 7 you can attend a one-day workshop in Milan on the 7th of February. During the workshop you’ll have a chance to use the new tools and see the OS image running on a ARMv7 device. You can register here for the event (registration may already be overbooked, but if you register you’ll notified of other events in your area): http://www.arroweurope.com/it/news-events/arrow-events/dettaglio/article/microsoft-embedded-windows-ce-products-seminar-compact-7-1.html If you want to discover the potential of Silverlight for Windows Embedded running on CE 6.0 R3 or Windows Embedded Compact 7 you can attend a one day workshop at the Microsoft Innovation Center in Tourin on the 14th of February. In a full-day event you’ll be able to learn the theory and use the tools in practice, getting a good overview of this technology and a chance to experiment with the tools. You can register here: https://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032473933&Culture=it-IT

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• UKOUG Application Server & Middleware SIG Meeting

  - by JuergenKress

  Date: Wednesday 10th Oct 2012 Time: 09:00 - 16:00 Location: Reading Venue: Oracle, Thames Valley Park, Reading Agenda: 09:00 Registration and Coffee 10:00 Welcome Application Server & Middleware Committee 10:10 Oracle Support Updates Nick Pounder, Oracle Customer Services 10:30 OpenWorld 2012 - News Round-up for Middleware Admins Simon Haslam, Veriton Limited 11:00 Coffee break 11:20 Oracle Single-Sign on to Oracle Access Manager Migration Rob Otto, Oracle Consulting Services UK 12:05 Supporting Fusion Middleware through First Failure Capture (theory) Greg Cook, Oracle 12:50 Lunch and Network 13:35 Deputy Chair Elections UKOUG 13:45 Supporting Fusion Middleware through First Failure Capture (demos) Greg Cook, Oracle 14:15 Networking session including tea/coffee 14:45 Real Life WebLogic Performance Tuning: Tales and Techniques from the Field Steve Millidge, C2B2 Consulting Limited 15:30 WLST: WebLogic's Swiss Army Knife Simon Haslam, Veriton Limited 15:45 AOB and Close For details please visit the registration page. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. BlogTwitterLinkedInMixForumWiki Technorati Tags: UK user group,Simon Haslam,WebLogic Community,Oracle,OPN,Jürgen Kress

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• Best way of storing voxels

  - by opiop65

  This should be a pretty easy question to answer, and I'm not looking for how to store the voxels data wise, I'm looking for the theory. Currently, my voxel engine has no global list of tiles. Each chunk has it's own list, and its hard to do things like collision detection or anything that may use tiles that are outside of its own chunk. I recently worked on procedural terrain with a non voxel engine. Now, I want to start using heightmaps in my voxel engine. But, I have a problem. If each chunk has its own list, then it will be pretty difficult to implement the heightmaps. My real question is, is should I store a global list of voxels independent of the chunks? And then I can just easily perform collision detection and terrain generation. However, it would probably be harder to do things such as frustum culling. So how should I store them?

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• Behaviour Driven Maturity Model

  - by Michael Stephenson

  Originally posted on: http://geekswithblogs.net/michaelstephenson/archive/2013/07/02/153326.aspxFor anyone who is interested I have written a small paper about the theory behind the BizTalk Maturity Assessment using a generic framework I have called the "Behaviour Driven Maturity Model" and then how it could be applied to the assessment of other subjects.The paper is on the following link:http://btsmaturity.blob.core.windows.net/behaviour-driven-model/Behaviour%20Based%20Maturity%20Model%20-%20Introduction.pdfIf you would like to create a model for a different subject area based on the details of this paper then I would encourage this as much as possible, all I ask is the following:1. Let us know your doing it so we can help tell people about each others activities2. Make it free to the community3. Reference back to BizTalkMaturity.com as the source of your model

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• Auto DOP and Concurrency

  - by jean-pierre.dijcks

  After spending some time in the cloud, I figured it is time to come down to earth and start discussing some of the new Auto DOP features some more. As Database Machines (the v2 machine runs Oracle Database 11.2) are effectively selling like hotcakes, it makes some sense to talk about the new parallel features in more detail. For basic understanding make sure you have read the initial post. The focus there is on Auto DOP and queuing, which is to some extend the focus here. But now I want to discuss the concurrency a little and explain some of the relevant parameters and their impact, specifically in a situation with concurrency on the system. The goal of Auto DOP The idea behind calculating the Automatic Degree of Parallelism is to find the highest possible DOP (ideal DOP) that still scales. In other words, if we were to increase the DOP even more  above a certain DOP we would see a tailing off of the performance curve and the resource cost / performance would become less optimal. Therefore the ideal DOP is the best resource/performance point for that statement. The goal of Queuing On a normal production system we should see statements running concurrently. On a Database Machine we typically see high concurrency rates, so we need to find a way to deal with both high DOP’s and high concurrency. Queuing is intended to make sure we Don’t throttle down a DOP because other statements are running on the system Stay within the physical limits of a system’s processing power Instead of making statements go at a lower DOP we queue them to make sure they will get all the resources they want to run efficiently without trashing the system. The theory – and hopefully – practice is that by giving a statement the optimal DOP the sum of all statements runs faster with queuing than without queuing. Increasing the Number of Potential Parallel Statements To determine how many statements we will consider running in parallel a single parameter should be looked at. That parameter is called PARALLEL_MIN_TIME_THRESHOLD. The default value is set to 10 seconds. So far there is nothing new here…, but do realize that anything serial (e.g. that stays under the threshold) goes straight into processing as is not considered in the rest of this post. Now, if you have a system where you have two groups of queries, serial short running and potentially parallel long running ones, you may want to worry only about the long running ones with this parallel statement threshold. As an example, lets assume the short running stuff runs on average between 1 and 15 seconds in serial (and the business is quite happy with that). The long running stuff is in the realm of 1 – 5 minutes. It might be a good choice to set the threshold to somewhere north of 30 seconds. That way the short running queries all run serial as they do today (if it ain’t broken, don’t fix it) and allows the long running ones to be evaluated for (higher degrees of) parallelism. This makes sense because the longer running ones are (at least in theory) more interesting to unleash a parallel processing model on and the benefits of running these in parallel are much more significant (again, that is mostly the case). Setting a Maximum DOP for a Statement Now that you know how to control how many of your statements are considered to run in parallel, lets talk about the specific degree of any given statement that will be evaluated. As the initial post describes this is controlled by PARALLEL_DEGREE_LIMIT. This parameter controls the degree on the entire cluster and by default it is CPU (meaning it equals Default DOP). For the sake of an example, let’s say our Default DOP is 32. Looking at our 5 minute queries from the previous paragraph, the limit to 32 means that none of the statements that are evaluated for Auto DOP ever runs at more than DOP of 32. Concurrently Running a High DOP A basic assumption about running high DOP statements at high concurrency is that you at some point in time (and this is true on any parallel processing platform!) will run into a resource limitation. And yes, you can then buy more hardware (e.g. expand the Database Machine in Oracle’s case), but that is not the point of this post… The goal is to find a balance between the highest possible DOP for each statement and the number of statements running concurrently, but with an emphasis on running each statement at that highest efficiency DOP. The PARALLEL_SERVER_TARGET parameter is the all important concurrency slider here. Setting this parameter to a higher number means more statements get to run at their maximum parallel degree before queuing kicks in.  PARALLEL_SERVER_TARGET is set per instance (so needs to be set to the same value on all 8 nodes in a full rack Database Machine). Just as a side note, this parameter is set in processes, not in DOP, which equates to 4* Default DOP (2 processes for a DOP, default value is 2 * Default DOP, hence a default of 4 * Default DOP). Let’s say we have PARALLEL_SERVER_TARGET set to 128. With our limit set to 32 (the default) we are able to run 4 statements concurrently at the highest DOP possible on this system before we start queuing. If these 4 statements are running, any next statement will be queued. To run a system at high concurrency the PARALLEL_SERVER_TARGET should be raised from its default to be much closer (start with 60% or so) to PARALLEL_MAX_SERVERS. By using both PARALLEL_SERVER_TARGET and PARALLEL_DEGREE_LIMIT you can control easily how many statements run concurrently at good DOPs without excessive queuing. Because each workload is a little different, it makes sense to plan ahead and look at these parameters and set these based on your requirements.

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• Going into Web Development without a C.S. Degree - Suggestions

  - by Klaint Cokeman

  I plan on seeking a career in web development and I'm about two semesters away from graduating with a CIS degree. Although I'm very satisfied with my choice of degree, I'm concerned that I may be lacking knowledge in a few areas because of not majoring in computer science. The programming side of things is no problem for me, I'm just wondering to what extent data structures/theory/etc. might benefit me to learn over spending more time with hands-on programming... and also what aspects of C.S. would be most appropriate to look into you would think would be most applicable to web development. In short, I'd like to expand my horizons a little bit. I'd very much appreciate and advice/suggestions/book or tutorial recommendations, etc. Thanks.

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• Changing enum in a different class for screen

  - by user2434321

  I'm trying to make a start menu for my game and my code uses Enum's to moniter the screen state. Now i want to change the screenstate declared in the main class, in my Background class Screen screen = new Screen(); is declared in the Game1 class Background(ref screen); This is in the update method for the Background Class KeyboardState keystate = Keyboard.GetState(); switch (screen) { case Screen.Start: if (isPressed && keystate.IsKeyUp(Keys.Up) && keystate.IsKeyUp(Keys.Down) && keystate.IsKeyUp(Keys.Enter)) { isPressed = false; } if (keystate.IsKeyDown(Keys.Down) && isPressed != true) { if (menuState == MenuState.Options) menuState = MenuState.Credits; if (menuState == MenuState.Play) menuState = MenuState.Options; isPressed = true; } if (keystate.IsKeyDown(Keys.Up) && isPressed != true) { if (menuState == MenuState.Options) menuState = MenuState.Play; if (menuState == MenuState.Credits) menuState = MenuState.Options; isPressed = true; } switch (menuState) { case MenuState.Play: arrowRect.X = 450; arrowRect.Y = 220; if (keystate.IsKeyDown(Keys.Enter) && isPressed != true) screen = Screen.Play; break; case MenuState.Options: arrowRect.X = 419; arrowRect.Y = 340; if (keystate.IsKeyDown(Keys.Enter) && isPressed != true) screen = Screen.Options; break; case MenuState.Credits: arrowRect.X = 425; arrowRect.Y = 460; if (keystate.IsKeyDown(Keys.Enter) && isPressed != true) screen = Screen.Credits; break; } break; } } For some reason when I play this and I hit the enter button the Background class's screen is changed but the main class's screen isn't how can i change this? EDIT 1* class Background { private Texture2D background; private Rectangle backgroundRect; private Texture2D arrow; private Rectangle arrowRect; private Screen screen; private MenuState menuState; private bool isPressed = false; public Screen getScreenState(ref Screen screen) { this.screen = screen; return this.screen; } public Background(ref Screen screen) { this.screen = screen; } public void Update() { KeyboardState keystate = Keyboard.GetState(); switch (screen) { case Screen.Start: if (isPressed && keystate.IsKeyUp(Keys.Up) && keystate.IsKeyUp(Keys.Down) && keystate.IsKeyUp(Keys.Enter)) { isPressed = false; } if (keystate.IsKeyDown(Keys.Down) && isPressed != true) { if (menuState == MenuState.Options) menuState = MenuState.Credits; if (menuState == MenuState.Play) menuState = MenuState.Options; isPressed = true; } if (keystate.IsKeyDown(Keys.Up) && isPressed != true) { if (menuState == MenuState.Options) menuState = MenuState.Play; if (menuState == MenuState.Credits) menuState = MenuState.Options; isPressed = true; } switch (menuState) { case MenuState.Play: arrowRect.X = 450; arrowRect.Y = 220; if (keystate.IsKeyDown(Keys.Enter) && isPressed != true) screen = Screen.Play; break; case MenuState.Options: arrowRect.X = 419; arrowRect.Y = 340; if (keystate.IsKeyDown(Keys.Enter) && isPressed != true) screen = Screen.Options; break; case MenuState.Credits: arrowRect.X = 425; arrowRect.Y = 460; if (keystate.IsKeyDown(Keys.Enter) && isPressed != true) screen = Screen.Credits; break; } break; case Screen.Pause: break; case Screen.Over: break; } } public void LoadStartContent(ContentManager Content, GraphicsDeviceManager graphics) { background = Content.Load<Texture2D>("startBackground"); arrow = Content.Load<Texture2D>("arrow"); backgroundRect = new Rectangle(0, 0, graphics.GraphicsDevice.Viewport.Width, graphics.GraphicsDevice.Viewport.Height); arrowRect = new Rectangle(450, 225, arrow.Width, arrow.Height); screen = Screen.Start; } public void LoadPlayContent(ContentManager Content, GraphicsDeviceManager graphics) { background = Content.Load<Texture2D>("Background"); backgroundRect = new Rectangle(0, 0, graphics.GraphicsDevice.Viewport.Width, graphics.GraphicsDevice.Viewport.Height); screen = Screen.Play; } public void LoadOverContent(ContentManager Content, GraphicsDeviceManager graphics) { } public void Draw(SpriteBatch spritebatch) { if (screen == Screen.Start) { spritebatch.Draw(background, backgroundRect, Color.White); spritebatch.Draw(arrow, arrowRect, Color.White); } else spritebatch.Draw(background, backgroundRect, Color.White); } } Thats my background class!

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• GLSL Atmospheric Scattering Issue

  - by mtf1200

  I am attempting to use Sean O'Neil's shaders to accomplish atmospheric scattering. For now I am just using SkyFromSpace and GroundFromSpace. The atmosphere works fine but the planet itself is just a giant dark sphere with a white blotch that follows the camera. I think the problem might rest in the "v3Attenuation" variable as when this is removed the sphere is show (albeit without scattering). Here is the vertex shader. Thanks for the time! uniform mat4 g_WorldViewProjectionMatrix; uniform mat4 g_WorldMatrix; uniform vec3 m_v3CameraPos; // The camera's current position uniform vec3 m_v3LightPos; // The direction vector to the light source uniform vec3 m_v3InvWavelength; // 1 / pow(wavelength, 4) for the red, green, and blue channels uniform float m_fCameraHeight; // The camera's current height uniform float m_fCameraHeight2; // fCameraHeight^2 uniform float m_fOuterRadius; // The outer (atmosphere) radius uniform float m_fOuterRadius2; // fOuterRadius^2 uniform float m_fInnerRadius; // The inner (planetary) radius uniform float m_fInnerRadius2; // fInnerRadius^2 uniform float m_fKrESun; // Kr * ESun uniform float m_fKmESun; // Km * ESun uniform float m_fKr4PI; // Kr * 4 * PI uniform float m_fKm4PI; // Km * 4 * PI uniform float m_fScale; // 1 / (fOuterRadius - fInnerRadius) uniform float m_fScaleDepth; // The scale depth (i.e. the altitude at which the atmosphere's average density is found) uniform float m_fScaleOverScaleDepth; // fScale / fScaleDepth attribute vec4 inPosition; vec3 v3ELightPos = vec3(g_WorldMatrix * vec4(m_v3LightPos, 1.0)); vec3 v3ECameraPos= vec3(g_WorldMatrix * vec4(m_v3CameraPos, 1.0)); const int nSamples = 2; const float fSamples = 2.0; varying vec4 color; float scale(float fCos) { float x = 1.0 - fCos; return m_fScaleDepth * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25)))); } void main(void) { gl_Position = g_WorldViewProjectionMatrix * inPosition; // Get the ray from the camera to the vertex and its length (which is the far point of the ray passing through the atmosphere) vec3 v3Pos = vec3(g_WorldMatrix * inPosition); vec3 v3Ray = v3Pos - v3ECameraPos; float fFar = length(v3Ray); v3Ray /= fFar; // Calculate the closest intersection of the ray with the outer atmosphere (which is the near point of the ray passing through the atmosphere) float B = 2.0 * dot(m_v3CameraPos, v3Ray); float C = m_fCameraHeight2 - m_fOuterRadius2; float fDet = max(0.0, B*B - 4.0 * C); float fNear = 0.5 * (-B - sqrt(fDet)); // Calculate the ray's starting position, then calculate its scattering offset vec3 v3Start = m_v3CameraPos + v3Ray * fNear; fFar -= fNear; float fDepth = exp((m_fInnerRadius - m_fOuterRadius) / m_fScaleDepth); float fCameraAngle = dot(-v3Ray, v3Pos) / fFar; float fLightAngle = dot(v3ELightPos, v3Pos) / fFar; float fCameraScale = scale(fCameraAngle); float fLightScale = scale(fLightAngle); float fCameraOffset = fDepth*fCameraScale; float fTemp = (fLightScale + fCameraScale); // Initialize the scattering loop variables float fSampleLength = fFar / fSamples; float fScaledLength = fSampleLength * m_fScale; vec3 v3SampleRay = v3Ray * fSampleLength; vec3 v3SamplePoint = v3Start + v3SampleRay * 0.5; // Now loop through the sample rays vec3 v3FrontColor = vec3(0.0, 0.0, 0.0); vec3 v3Attenuate; for(int i=0; i<nSamples; i++) { float fHeight = length(v3SamplePoint); float fDepth = exp(m_fScaleOverScaleDepth * (m_fInnerRadius - fHeight)); float fScatter = fDepth*fTemp - fCameraOffset; v3Attenuate = exp(-fScatter * (m_v3InvWavelength * m_fKr4PI + m_fKm4PI)); v3FrontColor += v3Attenuate * (fDepth * fScaledLength); v3SamplePoint += v3SampleRay; } vec3 first = v3FrontColor * (m_v3InvWavelength * m_fKrESun + m_fKmESun); vec3 secondary = v3Attenuate; color = vec4((first + vec3(0.25,0.25,0.25) * secondary), 1.0); // ^^ that color is passed to the frag shader and is used as the gl_FragColor } Here is also an image of the problem image

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• Slot Machine Pay Out

  - by Kris.Mitchell

  I have done a lot of research into random number generators for slot machines, reel stop calculations and how to physically give the user a good chance on winning. What I can't figure out is how to properly insure that the machine is going to have a payout rating of (lets say) 95%. So, I have a reel set up wit 22 spaces on it. Filled with 16 different symbols. When I get my random number, mod divide it by 64 and get the remainder, I hop over to a loop up table to see how the virtual stop relates to the reel position. Now that I have how the reels are going to stop, do I make sure the payout ratio is correct? For every dollar they put in, how to I make sure the machine will pay out .95 cents? Thanks for the ideas. I am working in actionscript, if that helps with the language issues, but in general I am just looking for theory.

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• openGL migration from SFML to glut, vertices arrays or display lists are not displayed

  - by user3714670

  Due to using quad buffered stereo 3D (which i have not included yet), i need to migrate my openGL program from a SFML window to a glut window. With SFML my vertices and display list were properly displayed, now with glut my window is blank white (or another color depending on the way i clear it). Here is the code to initialise the window : int type; int stereoMode = 0; if ( stereoMode == 0 ) type = GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH; else type = GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_STEREO; glutInitDisplayMode(type); int argc = 0; char *argv = ""; glewExperimental = GL_TRUE; glutInit(&argc, &argv); bool fullscreen = false; glutInitWindowSize(width,height); int win = glutCreateWindow(title.c_str()); glutSetWindow(win); assert(win != 0); if ( fullscreen ) { glutFullScreen(); width = glutGet(GLUT_SCREEN_WIDTH); height = glutGet(GLUT_SCREEN_HEIGHT); } GLenum err = glewInit(); if (GLEW_OK != err) { fprintf(stderr, "Error: %s\n", glewGetErrorString(err)); } glutDisplayFunc(loop_function); This is the only code i had to change for now, but here is the code i used with sfml and displayed my objects in the loop, if i change the value of glClearColor, the window's background does change color : glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glClearColor(255.0f, 255.0f, 255.0f, 0.0f); glLoadIdentity(); sf::Time elapsed_time = clock.getElapsedTime(); clock.restart(); camera->animate(elapsed_time.asMilliseconds()); camera->look(); for (auto i = objects->cbegin(); i != objects->cend(); ++i) (*i)->draw(camera); glutSwapBuffers(); Is there any other changes i should have done switching to glut ? that would be great if someone could enlighten me on the subject. In addition to that, i found out that adding too many objects (that were well handled before with SFML), openGL gives error 1285: out of memory. Maybe this is related. EDIT : Here is the code i use to draw each object, maybe it is the problem : GLuint LightID = glGetUniformLocation(this->shaderProgram, "LightPosition_worldspace"); if(LightID ==-1) cout << "LightID not found ..." << endl; GLuint MaterialAmbientID = glGetUniformLocation(this->shaderProgram, "MaterialAmbient"); if(LightID ==-1) cout << "LightID not found ..." << endl; GLuint MaterialSpecularID = glGetUniformLocation(this->shaderProgram, "MaterialSpecular"); if(LightID ==-1) cout << "LightID not found ..." << endl; glm::vec3 lightPos = glm::vec3(0,150,150); glUniform3f(LightID, lightPos.x, lightPos.y, lightPos.z); glUniform3f(MaterialAmbientID, MaterialAmbient.x, MaterialAmbient.y, MaterialAmbient.z); glUniform3f(MaterialSpecularID, MaterialSpecular.x, MaterialSpecular.y, MaterialSpecular.z); // Get a handle for our "myTextureSampler" uniform GLuint TextureID = glGetUniformLocation(shaderProgram, "myTextureSampler"); if(!TextureID) cout << "TextureID not found ..." << endl; glActiveTexture(GL_TEXTURE0); sf::Texture::bind(texture); glUniform1i(TextureID, 0); // 2nd attribute buffer : UVs GLuint vertexUVID = glGetAttribLocation(shaderProgram, "color"); if(vertexUVID==-1) cout << "vertexUVID not found ..." << endl; glEnableVertexAttribArray(vertexUVID); glBindBuffer(GL_ARRAY_BUFFER, color_array_buffer); glVertexAttribPointer(vertexUVID, 2, GL_FLOAT, GL_FALSE, 0, 0); GLuint vertexNormal_modelspaceID = glGetAttribLocation(shaderProgram, "normal"); if(!vertexNormal_modelspaceID) cout << "vertexNormal_modelspaceID not found ..." << endl; glEnableVertexAttribArray(vertexNormal_modelspaceID); glBindBuffer(GL_ARRAY_BUFFER, normal_array_buffer); glVertexAttribPointer(vertexNormal_modelspaceID, 3, GL_FLOAT, GL_FALSE, 0, 0 ); GLint posAttrib; posAttrib = glGetAttribLocation(shaderProgram, "position"); if(!posAttrib) cout << "posAttrib not found ..." << endl; glEnableVertexAttribArray(posAttrib); glBindBuffer(GL_ARRAY_BUFFER, position_array_buffer); glVertexAttribPointer(posAttrib, 3, GL_FLOAT, GL_FALSE, 0, 0); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elements_array_buffer); glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0); GLuint error; while ((error = glGetError()) != GL_NO_ERROR) { cerr << "OpenGL error: " << error << endl; } disableShaders();

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• Any idea for a master thesis in software engineering

  - by medusa

  Hi! I have to choose a thesis for my master degree. Time is limited to about 6 months. Do you have any idea? Any personal thesis that was successful? After searching around for some time now, i see the most famous topics are related to artificial intelligence, but i don't want something like that, because most of it would be just theory and boring. A lot of students present these kind of studies because those are the most difficult. I would prefer something that does not necessary include that mathematical complexity but which is an everyday-life topic, and gives concrete ideas, hypothesis, or solutions to some actual problems. Hope i gave my whole idea: i am looking for something that is different from the majority of what all students do, and able to impress the audience... :) I would really really appreciate any your suggestion, Thank you!

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• How often is software speed evident in the eyes of customers?

  - by rwong

  In theory, customers should be able to feel the software performance improvements from first-hand experience. In practice, sometimes the improvements are not noticible enough, such that in order to monetize from the improvements, it is necessary to use quotable performance figures in marketing in order to attract customers. We already know the difference between perceived performance (GUI latency, etc) and server-side performance (machines, networks, infrastructure, etc). How often is it that programmers need to go the extra length to "write up" performance analyses for which the audience is not fellow programmers, but managers and customers?

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• Easy to use cross-platform 3D engines for C++ game development?

  - by davr

  I want to try my hand at writing a 3D game. However I don't want to start at such a low level of drawing individual triangles and writing my own 3D object loader and so on. I've heard of things like Irrlicht, Crystal Space 3D, and Cafu, but I don't have any experience with any of them. I'm looking for suggestions from people who have experience with these or other engines on which ones are well written, and are easy to get started using, without having to learn a ton of 3D math theory and how GPU's work internally.

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• What's the real benefit of meta-modeling?

  - by Jakob

  After reading several texts about meta-modeling I still do not really get the practical benefit. Sometimes I think it is only an interesting mind game but no useful tool. Sure it is wise to clarify your modeling vocabulary: some may say class where others say entity or concept, but this is just simple documentation your modeling terminology. Meta-modeling, as I understand it, is more complex, as it tries to formalize and abstract modeling. Some good examples are Keet's formal comparison of conceptual data modeling languages (UML, ERM and ORM) from academia and the Meta Object Facility (MOF) from industry. To me MOF looks as impractical as CORBA, which was also created by OMG. In theory you could use meta-modeling to transform and integrate models in different modeling languages, but is anyone actually doing this?

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• Bring Office 2003 Menus Back to 2010 with UBitMenu

  - by Matthew Guay

  Are you having trouble getting used to the Ribbon interface in Office 2010?  Here’s how you can roll back the clock a bit and bring back the familiar menus and toolbars from 2003. The Office 2007 Ribbon was both praised and criticized.  While many users felt they were more productive with the new interface, others felt frustrated searching for commands they had memorized in older versions of Office.  Now, with Office 2010, the ribbon interface has been brought to every app in the Office suite, and is integrated into many newer programs from Microsoft. If you’re moving from Office 2003, using UBitMenu allows you to add the old familiar menus back along with the new Ribbon interface for an easier learning curve. Also, with the customizability of Office 2010, we can strip away the extra Ribbon tabs to make it more like 2003. Get the 2003 Menus and Toolbars Back in Office 2010 Download UBitMenu (link below), and install as normal.  Make sure all of your Office programs are closed during the installation.  This handy utility is very small, and installed amazingly quick. Open Word, Excel, or PowerPoint and there’s now a new Menu tab beside Home in the Ribbon.  Now you can access all of your favorite old Office commands in the familiar menus, and access many of the newer Office features such as SmartArt.   Here’s a close-up of the toolbar.  Notice that the layout is very similar to that of Word 2003. You can access all of the new Transitions in PowerPoint 2010 from the menu bar.   The menu in Excel even included support for the new PivotTable and PivotCharts Wizard. One problem we noticed was that the toolbars were condensed to a drop-down menu if the Office window was less than 870px wide.  This may be a frustration to users with low-resolution displays, and you might want to use the Office Apps maximized. Get Rid of the Ribbon Now that you’ve got the old menus back, you can get rid of the extra ribbon tabs if you’d like.  Office 2010 lets you customize your ribbon and remove tabs, so let’s get rid of all the other tabs except for our new Menu tab.  In our example we’re using Word, but you can do it in Excel or PowerPoint the same way. Click the File tab and select Options. Alternately, in the Menu tab, select Tools and then Word Options. Select Customize Ribbon on the left sidebar, then uncheck the boxes beside all the ribbon tabs you want to hide on the right.  Click Ok when you’re finished. While you’re at it, you can change the default color scheme as well. Note: The color change will automatically change the color scheme in all of the Office apps, so you’ll only need to do that once. Now the ribbon only has 2 tabs…the File tab for the new Backstage View, and the UBitMenu tab we just installed.  It almost has the appearance Word 2003, but with the new features of Word 2010!  You’ll need to repeat these steps in Excel and PowerPoint if you want to customize their ribbon the same.   Conclusion If you’ve been having a hard time getting used to Office 2010, UBitMenu is a great way to get familiar with the new interface, or simply stay productive with your old tricks.  We do wish it supported the other Office applications like OneNote and Outlook. That doesn’t make it a deal breaker though, it can make the learning curve easier in Word, PowerPoint, and Excel. UBitMenu is free for personal use, and available at a very reasonable price for businesses. If you’re using Office 2007 and not a fan of the Ribbon, UBitMenu works for it as well. Download UBitMenu Similar Articles Productive Geek Tips How To Bring Back the Old Menus in Office 2007Upgrade Office 2003 to 2010 on XP or Run them Side by SideHow to Find Office 2003 Commands in Office 2010Make Word 2007 Always Save in Word 2003 FormatMake Excel 2007 Always Save in Excel 2003 Format TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips HippoRemote Pro 2.2 Xobni Plus for Outlook All My Movies 5.9 CloudBerry Online Backup 1.5 for Windows Home Server Speed Up Windows With ReadyBoost Awesome World Cup Soccer Calendar Nice Websites To Watch TV Shows Online 24 Million Sites Windows Media Player Glass Icons (icons we like) How to Forecast Weather, without Gadgets

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• Online Introduction to Relational Databases (and not only) with Stanford University!

  - by Luca Zavarella

  How many of you know exactly the definition of "relational database"? What exactly the adjective "relational" refers to? Many of you allow themselves to be deceived, thinking this adjective is related to foreign key constraints between tables. Instead this adjective lurks in a world based on set theory, relational algebra and the concept of relationship intended as a table.Well, for those who want to deep the fundamentals of relational model, relational algebra, XML, OLAP and emerging "NoSQL" systems, Stanford University School of Engineering offers a public and free online introductory course to databases. This is the related web page: http://www.db-class.com/ The course will last 2 months, after which there will be a final exam. Passing the final exam will entitle the participants to receive a statement of accomplishment. A syllabus and more information is available here. Happy eLearning to you!

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• Yet another blog about IValueConverter

  - by codingbloke

  After my previous blog on a Generic Boolean Value Converter I thought I might as well blog up another IValueConverter implementation that I use. The Generic Boolean Value Converter effectively converters an input which only has two possible values to one of two corresponding objects.  The next logical step would be to create a similar converter that can take an input which has multiple (but finite and discrete) values to one of multiple corresponding objects.  To put it more simply a Generic Enum Value Converter. Now we already have a tool that can help us in this area, the ResourceDictionary.  A simple IValueConverter implementation around it would create a StringToObjectConverter like so:- StringToObjectConverter using System; using System.Windows; using System.Windows.Data; using System.Linq; using System.Windows.Markup; namespace SilverlightApplication1 {     [ContentProperty("Items")]     public class StringToObjectConverter : IValueConverter     {         public ResourceDictionary Items { get; set; }         public string DefaultKey { get; set; }                  public StringToObjectConverter()         {             DefaultKey = "__default__";         }         public virtual object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)         {             if (value != null && Items.Contains(value.ToString()))                 return Items[value.ToString()];             else                 return Items[DefaultKey];         }         public virtual object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)         {             return Items.FirstOrDefault(kvp => value.Equals(kvp.Value)).Key;         }     } } There are some things to note here.  The bulk of managing the relationship between an object instance and the related string key is handled by the Items property being an ResourceDictionary.  Also there is a catch all “__default__” key value which allows for only a subset of the possible input values to mapped to an object with the rest falling through to the default. We can then set one of these up in Xaml:-             <local:StringToObjectConverter x:Key="StatusToBrush">                 <ResourceDictionary>                     <SolidColorBrush Color="Red" x:Key="Overdue" />                     <SolidColorBrush Color="Orange" x:Key="Urgent" />                     <SolidColorBrush Color="Silver" x:Key="__default__" />                 </ResourceDictionary>             </local:StringToObjectConverter> You could well imagine that in the model being bound these key names would actually be members of an enum.  This still works due to the use of ToString in the Convert method.  Hence the only requirement for the incoming object is that it has a ToString implementation which generates a sensible string instead of simply the type name. I can’t imagine right now a scenario where this converter would be used in a TwoWay binding but there is no reason why it can’t.  I prefer to avoid leaving the ConvertBack throwing an exception if that can be be avoided.  Hence it just enumerates the KeyValuePair entries to find a value that matches and returns the key its mapped to. Ah but now my sense of balance is assaulted again.  Whilst StringToObjectConverter is quite happy to accept an enum type via the Convert method it returns a string from the ConvertBack method not the original input enum type that arrived in the Convert.  Now I could address this by complicating the ConvertBack method and examining the targetType parameter etc.  However I prefer to a different approach, deriving a new EnumToObjectConverter class instead. EnumToObjectConverter using System; namespace SilverlightApplication1 {     public class EnumToObjectConverter : StringToObjectConverter     {         public override object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)         {             string key = Enum.GetName(value.GetType(), value);             return base.Convert(key, targetType, parameter, culture);         }         public override object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)         {             string key = (string)base.ConvertBack(value, typeof(String), parameter, culture);             return Enum.Parse(targetType, key, false);         }     } }   This is a more belts and braces solution with specific use of Enum.GetName and Enum.Parse.  Whilst its more explicit in that the a developer has to  choose to use it, it is only really necessary when using TwoWay binding, in OneWay binding the base StringToObjectConverter would serve just as well. The observant might note that there is actually no “Generic” aspect to this solution in the end.  The use of a ResourceDictionary eliminates the need for that.

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• Can't get heroku site updated on custom domain

  - by Joseph Brown

  I have hosayif.com registered at GoDaddy, and I set up a cname for rails.hosayif.com to point to my heroku app at sharp-meadow-6535.herokuapp.com. I set this up with a previous app, and it worked. I made a new app, renamed the old one, and then renamed the new one so that it is sharp-meadow-6535.herokuapp.com in hopes of not having to change anything at GoDaddy. In theory, rails.hosayif.com and sharp-meadow-6535.herokuapp.com should be the same site, but they are not. Can someone tell me what I am doing wrong?

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• What can Haskell's type system do that Java's can't?

  - by Matt Fenwick

  I was talking to a friend about the differences between the type systems of Haskell and Java. He asked me what Haskell's could do that Java's couldn't, and I realized that I didn't know. After thinking for a while, I came up with a very short list of minor differences. Not being heavy into type theory, I'm left wondering whether they're formally equivalent. To try and keep this from becoming a subjective question, I'm asking: what are the major, non-syntactical differences between their type systems? I realize some things are easier/harder in one than in the other, and I'm not interested in talking about those. And to make it more specific, let's ignore Haskell type extensions since there's so many out there that do all kinds of crazy/cool stuff.

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• BizTalk Envelopes explained

  - by Robert Kokuti

  Recently I've been trying to get some order into an ESB-BizTalk pub/sub scenario, and decided to wrap the payload into standardized envelopes. I have used envelopes before in a 'light weight' fashion, and I found that they can be quite useful and powerful if used systematically. Here is what I learned. The Theory In my experience, Envelopes are often underutilised in a BizTalk solution, and quite often their full potential is not well understood. Here I try to simplify the theory behind the Envelopes within BizTalk.   Envelopes can be used to attach additional data to the ‘real’ data (payload). This additional data can contain all routing and processing information, and allows treating the business data as a ‘black box’, possibly compressed and/or encrypted etc. The point here is that the infrastructure does not need to know anything about the business data content, just as a post man does not need to know the letter within the envelope. BizTalk has built-in support for envelopes through the XMLDisassembler and XMLAssembler pipeline components (these are part of the XMLReceive and XMLSend default pipelines). These components, among other things, perform the following: XMLDisassembler Extracts the payload from the envelope into the Message Body Copies data from the envelope into the message context, as specified by the property schema(s) associated by the envelope schema. Typically, once the envelope is through the XMLDisassembler, the payload is submitted into the Messagebox, and the rest of the envelope data are copied into the context of the submitted message. The XMLDisassembler uses the Property Schemas, referenced by the Envelope Schema, to determine the name of the promoted Message Context element.   XMLAssembler Wraps the Message Body inside the specified envelope schema Populates the envelope values from the message context, as specified by the property schema(s) associated by the envelope schema. Notice that there are no requirements to use the receiving envelope schema when sending. The sent message can be wrapped within any suitable envelope, regardless whether the message was originally received within an envelope or not. However, by sharing Property Schemas between Envelopes, it is possible to pass values from the incoming envelope to the outgoing envelope via the Message Context. The Practice Creating the Envelope Add a new Schema to the BizTalk project:   Envelopes are defined as schemas, with the <Schema> Envelope property set to Yes, and the root node’s Body XPath property pointing to the node which contains the payload. Typically, you’d create an envelope structure similar to this: Click on the <Schema> node and set the Envelope property to Yes. Then, click on the Envelope node, and set the Body XPath property pointing to the ‘Body’ node:   The ‘Body’ node is a Child Element, and its Data Structure Type is set to xs:anyType.  This allows the Body node to carry any payload data. The XMLReceive pipeline will submit the data found in the Body node, while the XMLSend pipeline will copy the message into the Body node, before sending to the destination. Promoting Properties Once you defined the envelope, you may want to promote the envelope data (anything other than the Body) as Property Fields, in order to preserve their value in the message context. Anything not promoted will be lost when the XMLDisassembler extracts the payload from the Body. Typically, this means you promote everything in the Header node. Property promotion uses associated Property Schemas. These are special BizTalk schemas which have a flat field structure. Property Schemas define the name of the promoted values in the Message Context, by combining the Property Schema’s Namespace and the individual Field names. It is worth being systematic when it comes to naming your schemas, their namespace and type name. A coherent method will make your life easier when it comes to referencing the schemas during development, and managing subscriptions (filters) in BizTalk Administration. I developed a fairly coherent naming convention which I’ll probably share in another article. Because the property schema must be flat, I recommend creating one for each level in the envelope header hierarchy. Property schemas are very useful in passing data between incoming as outgoing envelopes. As I mentioned earlier, in/out envelopes do not have to be the same, but you can use the same property schema when you promote the outgoing envelope fields as you used for the incoming schema.  As you can reference many property schemas for field promotion, you can pick data from a variety of sources when you define your outgoing envelope. For example, the outgoing envelope can carry some of the incoming envelope’s promoted values, plus some values from the standard BizTalk message context, like the AdapterReceiveCompleteTime property from the BizTalk message-tracking properties. The values you promote for the outgoing envelope will be automatically populated from the Message Context by the XMLAssembler pipeline component. Using the Envelope Receiving Enveloped messages are automatically recognized by the XMLReceive pipeline, or any other custom pipeline which includes the XMLDisassembler component. The Body Path node will become the Message Body, while the rest of the envelope values will be added to the Message context, as defined by the Property Shemas referenced by the Envelope Schema. Sending The Send Port’s filter expression can use the promoted properties from the incoming envelope. If you want to enclose the sent message within an envelope, the Send Port XMLAssembler component must be configured with the fully qualified envelope name:   One way of obtaining the fully qualified envelope name is copy it off from the envelope schema property page: The full envelope schema name is constructed as <Name>, <Assembly> The outgoing envelope is populated by the XMLAssembler pipeline component. The Message Body is copied to the specified envelope’s Body Path node, while the rest of the envelope fields are populated from the Message Context, according to the Property Schemas associated with the Envelope Schema. That’s all for now, happy enveloping!

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• What can Haskell's type system do that Java's can't and vice versa?

  - by Matt Fenwick

  I was talking to a friend about the differences between the type systems of Haskell and Java. He asked me what Haskell's could do that Java's couldn't, and I realized that I didn't know. After thinking for a while, I came up with a very short list of minor differences. Not being heavy into type theory, I'm left wondering whether they're formally equivalent. To try and keep this from becoming a subjective question, I'm asking: what are the major, non-syntactical differences between their type systems? I realize some things are easier/harder in one than in the other, and I'm not interested in talking about those. And to make it more specific, let's ignore Haskell type extensions since there's so many out there that do all kinds of crazy/cool stuff.

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