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  • Light on every model and not in the whole scene

    - by alecnash
    I am using a custom shader and try to pass the effect on my Models like that: foreach (ModelMesh mesh in Model.Meshes) { foreach (ModelMeshPart part in mesh.MeshParts) { part.Effect = effect; } mesh.Draw(); } My only issue is that every Model now has its own light source in it. Why is this happening and is this a problem of my shader? Edit: These are the parameters passed to the shader: private void Get_lambertEffect() { if (_lambertEffect == null) _lambertEffect = Engine.LambertEffect; //Lambert technique (LambertWithShadows, LambertWithShadows2x2PCF, LambertWithShadows3x3PCF) _lambertEffect.CurrentTechnique = _lambertEffect.Techniques["LambertWithShadows3x3PCF"]; _lambertEffect.Parameters["texelSize"].SetValue(Engine.ShadowMap.TexelSize); //ShadowMap parameters _lambertEffect.Parameters["lightViewProjection"].SetValue(Engine.ShadowMap.LightViewProjectionMatrix); _lambertEffect.Parameters["textureScaleBias"].SetValue(Engine.ShadowMap.TextureScaleBiasMatrix); _lambertEffect.Parameters["depthBias"].SetValue(Engine.ShadowMap.DepthBias); _lambertEffect.Parameters["shadowMap"].SetValue(Engine.ShadowMap.ShadowMapTexture); //Camera view and projection parameters _lambertEffect.Parameters["view"].SetValue(Engine._camera.ViewMatrix); _lambertEffect.Parameters["projection"].SetValue(Engine._camera.ProjectionMatrix); _lambertEffect.Parameters["world"].SetValue( Matrix.CreateScale(Size) * world ); //Light and color _lambertEffect.Parameters["lightDir"].SetValue(Engine._sourceLight.Direction); _lambertEffect.Parameters["lightColor"].SetValue(Engine._sourceLight.Color); _lambertEffect.Parameters["materialAmbient"].SetValue(Engine.Material.Ambient); _lambertEffect.Parameters["materialDiffuse"].SetValue(Engine.Material.Diffuse); _lambertEffect.Parameters["colorMap"].SetValue(ColorTexture.Create(Engine.GraphicsDevice, Color.Red)); }

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  • Spherical to Cartesian Coordinates

    - by user1258455
    Well I'm reading the Frank's Luna DirectX10 book and, while I'm trying to understand the first demo, I found something that's not very clear at least for me. In the updateScene method, when I press A, S, W or D, the angles mTheta and mPhi change, but after that, there are three lines of code that I don't understand exactly what they do: // Convert Spherical to Cartesian coordinates: mPhi measured from +y // and mTheta measured counterclockwise from -z. float x = 5.0f*sinf(mPhi)*sinf(mTheta); float z = -5.0f*sinf(mPhi)*cosf(mTheta); float y = 5.0f*cosf(mPhi); I mean, this explains that they do, it says that it converts the spherical coordinates to cartesian coordinates, but, mathematically, why? why the x value is calculated by the product of the sins of both angles? And the z by the product of the sine and cosine? and why the y just uses the cosine? After that, those values (x, y and z) are used to build the view matrix. The book doesn't explain (mathematically) why those values are calculated like that (and I didn't find anything to help me to understand it at the first Part of the book: "Mathematical prerequisites"), so it would be good if someone could explain me what exactly happen in those code lines or just give me a link that helps me to understand the math part. Thanks in advance!

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  • Why isn't my other two constant buffers being updated to the shader?

    - by Paul Ske
    I posted previously before about my two dynamic buffers not being dynamically updating the constant shader. The tessellation buffer isn't working because I have to manually update the tessellation factor inside the hull shader. I believe the camera position isn't updating either because when I perform distance adaptation the far edges are more tessellated then the what's truly in front of the camera. I have all the buffers set to dynamic. Inside the render loop I have them set as: ID3D11Buffer *multiBuffers[3]; devcon->VSSetConstantBuffers(0,3,multiBuffers); ... devcon->DSSetConstantBuffers(0,3,multiBuffers); I only got that from a directX Sample. Inside the shader file I have the three cbuffer structs. cbuffer ConstantBuffer { float4x4 WorldMatrix; float4x4 viewMatrix; float4x4 projectionMatrix; float4x4 modelWorldMatrix; // the rotation matrix float3 lightvec; // the light's vector float4 lightcol; // the light's color float4 ambientcol; // the ambient light's color bool isSelected; } cbuffer cameraBuffer { float3 cameraDirection; float padding; } cbuffer TessellationBuffer { float tessellationAmount; float3 padding2; } Am I missing something or would anyone know why wouldn't my buffers update to the shader file?

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  • XNA 3D coordinates seem off

    - by Peteyslatts
    I'm going through a book, and the example it gave me seems like is should work, but when I try and implement it, it falls short. My Camera class takes three vectors in to generate View and Projection matrices. I'm giving it a position vector of (0,0,5), a target vector of Vector.Zero and a top vector (which way is up) of Vector.Up. My Three vertices are placed at (0,1,0), (-1,-1,0), (1,-1,0). It seems like it should work because the vertices are centered around the origin, and thats where I'm telling the camera to look but when I run the game, the only way to get the camera to see the vertices is to set its position to (0,0,-5) and even then the triangle is skewed. Not sure what's wrong here. Any suggestions would be helpful. Just to make sure I've given you guys everything (I don't think these are important as the problem seems to be related to the coordinates, not the ability of the game to draw them): I'm using a VertexBuffer and a BasicEffect. My render code is as follows: effect.World = Matrix.Identity; effect.View = camera.view; effect.Projection = camera.projection; effect.VertexColorEnabled = true; foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Apply(); GraphicsDevice.DrawUserPrimitives<VertexPositionColor> (PrimitiveType.TriangleStrip, verts, 0, 1); }

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  • Find methods related to testcases in Java

    - by user3623718
    I want to automatically change some methods in the program. These methods contain some compiler error and my program aims to fix these compiler errors. After fixing compiler errors I need to run test cases related to the changed method (or class) to know it is correct and if not which test cases failed. As the programs under investigation are very big, I only need to run test cases related to changes. As an example, if I change one method, then I need to only run test cases related to this method. Therefore, what I need is to programmatically be able to find test cases related to each method, and class. It is also useful if there is a tool that can do that for me. As an example, a tool which creates a matrix shows each test case is related to which method(s) One easy way to do that is to run all test cases and save functions they accessed. However, the problem is at the beginning the input program contains compiler error and it is not possible to run test cases because of these compiler error. Please let me know what is the best way to do that. An API or a tool that I can be used programmatically is the best for me.

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  • Cube rotation DX10

    - by German
    Well I'm reading the Frank's Luna DirectX10 book and, while I'm trying to understand the first demo, I found something that's not very clear at least for me. In the updateScene method, when I press A, S, W or D, the angles mTheta and mPhi change, but after that, there are three lines of code that I don't understand exactly what they do: // Convert Spherical to Cartesian coordinates: mPhi measured from +y // and mTheta measured counterclockwise from -z. float x = 5.0f*sinf(mPhi)*sinf(mTheta); float z = -5.0f*sinf(mPhi)*cosf(mTheta); float y = 5.0f*cosf(mPhi); I mean, this explains that they do, it says that it converts the spherical coordinates to cartesian coordinates, but, mathematically, why? why the x value is calculated by the product of the sins of both angles? And the z by the product of the sine and cosine? and why the y just uses the cosine? After that, those values (x, y and z) are used to build the view matrix. The book doesn't explain (mathematically) why those values are calculated like that (and I didn't find anything to help me to understand it at the first Part of the book: "Mathematical prerequisites"), so it would be good if someone could explain me what exactly happen in those code lines or just give me a link that helps me to understand the math part. Thanks in advance!

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  • Which version management design methodology to be used in a Dependent System nodes?

    - by actiononmail
    This is my first question so please indicate if my question is too vague and not understandable. My question is more related to High Level Design. We have a system (specifically an ATCA Chassis) configured in a Star Topology, having Master Node (MN) and other sub-ordinate nodes(SN). All nodes are connected via Ethernet and shall run on Linux OS with other proprietary applications. I have to build a recovery Framework Design so that any software entity, whether its Linux, Ramdisk or application can be rollback to previous good versions if something bad happens. Thus I think of maintaining a State Version Matrix over MN, where each State(1,2....n) represents Good Kernel, Ramdisk and application versions for each SN. It may happen that one SN version can dependent on other SN's version. Please see following diagram:- So I am in dilemma whether to use Package Management Methodology used by Debian Distributions (Like Ubuntu) or GIT repository methodology; in order to do a Rollback to previous good versions on either one SN or on all the dependent SNs. The method should also be easier for upgrading SNs along with MNs. Some of the features which I am trying to achieve:- 1) Upgrade of even single software entity is achievable without hindering others. 2) Dependency checks must be done before applying rollback or upgrade on each of the SN 3) User Prompt should be given in case dependency fails.If User still go for rollback, all the SNs should get notification to rollback there own releases (if required). 4) The binaries should be distributed on SNs accordingly so that recovery process is faster; rather fetching every time from MN. 5) Release Patches from developer for bug fixes, feature enhancement can be applied on running system. 6) Each version can be easily tracked and distinguishable. Thanks

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  • Why isn't one of the constant buffers being loaded inside the shader?

    - by Paul Ske
    I however got the model to load under tessellation; only problem is that one of the constant buffers aren't actually updating the shader's tessellation factor inside the hullshader. I created a messagebox at the rendering point so I know for sure the tessellation factor is assigned to the dynamic constant buffer. Inside the shader code where it says .Edges[1] = tessellationAmount; the tessellationAmount is suppose to be sent from the dynamic buffer to the shader. Otherwise it's just a plain box. In better explanation; there's a matrixBuffer, cameraBuffer, TessellationBuffer for constant. There's a multiBuffer array that assigns the matrix, camera, tesselation. So, when I set the Hull Shader, PixelShader, VertexShader, DomainShader it gets assigned by the multibuffer. E.G. devcon-HSSetConstantBuffers(0,3,multibuffer); The only way around the whole ideal would be to go in the shader and change how much the edges tessellate and inside the edges as well with the same number. My question is why wouldn't the tessellationBuffer not work in the shader?

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  • Proper way to encapsulate a Shader into different modules

    - by y7haar
    I am planning to build a Shader system which can be accessed through different components/modules in C++. Each component has its own functionality like transform-relevated stuff (handle the MVP matrix, ...), texture handler, light calculation, etc... So here's an example: I would like to display an object which has a texture and a toon shading material applied and it should be moveable. So I could write ONE shading program that handles all 3 functionalities and they are accessed through 3 different components (texture-handler, toon-shading, transform). This means I have to take care of feeding a GLSL shader with different uniforms/attributes. This implies to know all necessary uniform locations and attribute locations, that the GLSL shader owns. And it would also necessary to provide different algorithms to calculate the value for each input variable. Similar functions would be grouped together in one component. A possible way would be, to wrap all shaders in a own definition file written in JSON/XML and parse that file in C++ to get all input members and create and compile the resulting GLSL. But maybe there is another way that is not so complex? So I'm searching for a way to build a system like that, but I'm not sure yet which is the best approach.

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  • Installation questions

    - by user12609425
    I've gotten a couple more questions about the installation process for Ops Center. "Can I install on any SPARC / X86 based platform?" Ops Center can run on Oracle Solaris on either architecture, or on Linux. The Certified Systems Matrix lists the supported OSes, and the Linux and Solaris install guides go into more detail about the hardware and OS requirements. "Can we install it on local zones or LDOMS?" Zones, yes; LDOMS, sort of. You can install the Enterprise Controller in a local zone. There are a few caveats, which are explained in the Preparing a Non-Global Zone section. You can also install a Proxy Controller in an Oracle Solaris 11 zone. Agent Controllers, which are the part of the infrastructure that's installed on managed systems, can be put on zones or LDOMS. "Do we need any dedicated network ports from all agent monitoring systems?"  Yes. The port requirements are covered in the Network Port Requirements and Protocols table, which is in the feature reference guide as well as in the install guides.

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  • How to make other semantics behave like SV_Position?

    - by object
    I'm having a lot of trouble with shadow mapping, and I believe I've found the problem. When passing vectors from the vertex shader to the pixel shader, does the hardware automatically change any of the values based on the semantic? I've compiled a barebones pair of shaders which should illustrate the problem. Vertex shader : struct Vertex { float3 position : POSITION; }; struct Pixel { float4 position : SV_Position; float4 light_position : POSITION; }; cbuffer Matrices { matrix projection; }; Pixel RenderVertexShader(Vertex input) { Pixel output; output.position = mul(float4(input.position, 1.0f), projection); output.light_position = output.position; // We simply pass the same vector in screenspace through different semantics. return output; } And a simple pixel shader to go along with it: struct Pixel { float4 position : SV_Position; float4 light_position : POSITION; }; float4 RenderPixelShader(Pixel input) : SV_Target { // At this point, (input.position.z / input.position.w) is a normal depth value. // However, (input.light_position.z / input.light_position.w) is 0.999f or similar. // If the primitive is touching the near plane, it very quickly goes to 0. return (0.0f).rrrr; } How is it possible to make the hardware treat light_position in the same way which position is being treated between the vertex and pixel shaders? EDIT: Aha! (input.position.z) without dividing by W is the same as (input.light_position.z / input.light_position.w). Not sure why this is.

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  • What would be the fastest way of storing or calculating legal move sets for chess pieces?

    - by ioSamurai
    For example if a move is attempted I could just loop through a list of legal moves and compare the x,y but I have to write logic to calculate those at least every time the piece is moved. Or, I can store in an array [,] and then check if x and y are not 0 then it is a legal move and then I save the data like this [0][1][0][0] etc etc for each row where 1 is a legal move, but I still have to populate it. I wonder what the fastest way to store and read a legal move on a piece object for calculation. I could use matrix math as well I suppose but I don't know. Basically I want to persist the rules for a given piece so I can assign a piece object a little template of all it's possible moves considering it is starting from it's current location, which should be just one table of data. But is it faster to loop or write LINQ queries or store arrays and matrices? public class Move { public int x; public int y; } public class ChessPiece : Move { private List<Move> possibleMoves { get; set; } public bool LegalMove(int x, int y){ foreach(var p in possibleMoves) { if(p.x == x && p.y == y) { return true; } } } } Anyone know?

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  • Checking validation of entries in a Sudoku game written in Java

    - by Mico0
    I'm building a simple Sudoku game in Java which is based on a matrix (an array[9][9]) and I need to validate my board state according to these rules: all rows have 1-9 digits all columns have 1-9 digits. each 3x3 grid has 1-9 digits. This function should be efficient as possible for example if first case is not valid I believe there's no need to check other cases and so on (correct me if I'm wrong). When I tried doing this I had a conflict. Should I do one large for loop and inside check columns and row (in two other loops) or should I do each test separately and verify every case by it's own? (Please don't suggest too advanced solutions with other class/object helpers.) This is what I thought about: Main validating function (which I want pretty clean): public boolean testBoard() { boolean isBoardValid = false; if (validRows()) { if (validColumns()) { if (validCube()) { isBoardValid = true; } } } return isBoardValid; } Different methods to do the specific test such as: private boolean validRows() { int rowsDigitsCount = 0; for (int num = 1; num <= 9; num++) { boolean foundDigit = false; for (int row = 0; (row < board.length) && (!foundDigit); row++) { for (int col = 0; col < board[row].length; col++) { if (board[row][col] == num) { rowsDigitsCount++; foundDigit = true; break; } } } } return rowsDigitsCount == 9 ? true : false; } I don't know if I should keep doing tests separately because it looks like I'm duplicating my code.

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  • How to setup my texture cordinates correctly in GLSL 150 and OpenGL 3.3?

    - by RubyKing
    I'm trying to do texture mapping in GLSL 150 and OpenGL 3.3 Here are my shaders I've tried my best to get this correct as possible hopefully this is :) I'm guessing you want to know what the problem is well my texture shows but not in its fullest form just one section of it not the full texture on the quad. All I can think of is its the texture cordinates in the main.cpp which is at the bottom of this post. FRAGMENT SHADER #version 150 in vec2 Texcoord_VSPS; out vec4 color; // Values that stay constant for the whole mesh. uniform sampler2D myTextureSampler; //Main Entry Point void main() { // Output color = color of the texture at the specified UV color = texture2D( myTextureSampler, Texcoord_VSPS ); } VERTEX SHADER #version 150 //Position Container in vec3 position; //Container for TexCoords attribute vec2 Texcoord0; out vec2 Texcoord_VSPS; //out vec2 ex_texcoord; //TO USE A DIFFERENT COORDINATE SYSTEM JUST MULTIPLY THE MATRIX YOU WANT //Main Entry Point void main() { //Translations and w Cordinates stuff gl_Position = vec4(position.xyz, 1.0); Texcoord_VSPS = Texcoord0; } LINK TO MAIN.CPP http://pastebin.com/t7Vg9L0k

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  • Getting Requirements Right

    - by Tim Murphy
    Originally posted on: http://geekswithblogs.net/tmurphy/archive/2013/10/28/getting-requirements-right.aspxI had a meeting with a stakeholder who stated “I bet you wish I wasn’t in these meetings”.  She said this because she kept changing what we thought the end product should look like.  My reply was that it would be much worse if she came in at the end of the project and told us we had just built the wrong solution. You have to take the time to get the requirements right.  Be honest with all involved parties as to the amount of time it is taking to refine the requirements.  The only thing worse than wrong requirements is a surprise in budget overages.  If you give open visibility to your progress then management has the ability to shift priorities if needed. In order to capture the best requirements use different approaches to help your stakeholders to articulate their needs.  Use mock ups and matrix spread sheets to allow them to visualize and confirm that everyone has the same understanding.  The goals isn’t to record every last detail, but to have the major landmarks identified so there are fewer surprises along the way. Help the team members to understand that you all have the same goal.  You want to create the best possible solution for the given business problem.  If you do this everyone involved will do there best to outline a picture of what is to be built and you will be able to design an appropriate solution to fill those needs more easily. Technorati Tags: requirements gathering,PSC Group,PSC

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  • Scale an image with unscalable parts

    - by Uko
    Brief description of problem: imagine having some vector picture(s) and text annotations on the sides outside of the picture(s). Now the task is to scale the whole composition while preserving the aspect ratio in order to fit some view-port. The tricky part is that the text is not scalable only the picture(s). The distance between text and the image is still relative to the whole image, but the text size is always a constant. Example: let's assume that our total composition is two times larger than a view-port. Then we can just scale it by 1/2. But because the text parts are a fixed font size, they will become larger than we expect and won't fit in the view-port. One option I can think of is an iterative process where we repeatedly scale our composition until the delta between it and the view-port satisfies some precision. But this algorithm is quite costly as it involves working with the graphics and the image may be composed of a lot of components which will lead to a lot of matrix computations. What's more, this solution seems to be hard to debug, extend, etc. Are there any other approaches to solving this scaling problem?

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  • Help improving a simple assembly function

    - by MPelletier
    I just handed in this function in an assignment. It is done (hence no homework tag). But I would like to see how this can be improved. Essentially, the function sums the squares of all the integers between 1 and the given number, using the following formula: n(n+1)(2n+1)/6 Where n is the maximum number. The function below is made to catch any overflow and return 0 should any occur. UInt32 sumSquares(const UInt32 number) { int result = 0; __asm { mov eax, number //move number in eax mov edx, 2 //move 2 in edx mul edx //multiply (2n) jo end //jump to end if overflow add eax, 1 //addition (2n+1) jo end //jump to end if overflow mov ecx, eax //move (2n+1) in ecx mov ebx, number //move number in ebx add ebx, 1 //addition (n+1) jo end //jump to end if overflow mov eax, number //move number in eax for multiplication mul ebx //multiply n(n+1) jo end //jump to end if overflow mul ecx //multiply n(n+1)(2n+1) jo end //jump to end if overflow mov ebx, 6 //move 6 in ebx div ebx //divide by 6, the result will be in eax mov result, eax //move eax in result end: } return result; } Basically, I want to know what I can improve in there. In terms of best-practices mostly. One thing sounds obvious: smarter overflow check (with a single check for whatever maximum input would cause an overflow).

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  • nth ugly number

    - by Anil Katti
    Numbers whose only prime factors are 2, 3 or 5 are called ugly numbers. Example: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, ... 1 can be considered as 2^0. I am working on finding nth ugly number. Note that these numbers are extremely sparsely distributed as n gets large. I wrote a trivial program that computes if a given number is ugly or not. For n 500 - it became super slow. I tried using memoization - observation: ugly_number * 2, ugly_number * 3, ugly_number * 5 are all ugly. Even with that it is slow. I tried using some properties of log - since that will reduce this problem from multiplication to addition - but, not much luck yet. Thought of sharing this with you all. Any interesting ideas? Using a concept similar to "Sieve of Eratosthenes" (thanks Anon) for (int i(2), uglyCount(0); ; i++) { if (i % 2 == 0) continue; if (i % 3 == 0) continue; if (i % 5 == 0) continue; uglyCount++; if (uglyCount == n - 1) break; } i is the nth ugly number. Even this is pretty slow. I am trying to find 1500th ugly number.

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  • Polynomial operations using operator overloading

    - by Vlad
    I'm trying to use operator overloading to define the basic operations (+,-,*,/) for my polynomial class but when i run the program it crashes and my computer frozes. Update3 Ok i successfully done the first two operations(+,-). Now at multiplication, after multiplying each term of the first polynomial with each of the second i want to sort the poly list descending and then if there are more than one term with the same power to merge them in only one term, but for some reason it doesn't compile because of the sort function which doesn't work. Here's what I got: polinom operator*(const polinom& P) const { polinom Result; constIter i, j, lastItem = Result.poly.end(); Iter it1, it2; int nr_matches; for (i = poly.begin() ; i != poly.end(); i++) { for (j = P.poly.begin(); j != P.poly.end(); j++) Result.insert(i->coef * j->coef, i->pow + j->pow); } sort(Result.poly.begin(), Result.poly.end(), SortDescending()); lastItem--; while (true) { nr_matches = 0; for (it1 = Result.poly.begin(); it < lastItem; it1++) { for (it2 = it1 + 1;; it2 <= lastItem; it2++){ if (it2->pow == it1->pow) { it1->coef += it2->coef; nr_matches++; } } Result.poly.erase(it1 + 1, it1 + (nr_matches + 1)); } return Result; } Also here's SortDescending: struct SortDescending { bool operator()(const term& t1, const term& t2) { return t2.pow < t1.pow; } }; What did i do wrong? Thanks!

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  • Worse is better. Is there an example?

    - by J.F. Sebastian
    Is there a widely-used algorithm that has time complexity worse than that of another known algorithm but it is a better choice in all practical situations (worse complexity but better otherwise)? An acceptable answer might be in a form: There are algorithms A and B that have O(N**2) and O(N) time complexity correspondingly, but B has such a big constant that it has no advantages over A for inputs less then a number of atoms in the Universe. Examples highlights from the answers: Simplex algorithm -- worst-case is exponential time -- vs. known polynomial-time algorithms for convex optimization problems. A naive median of medians algorithm -- worst-case O(N**2) vs. known O(N) algorithm. Backtracking regex engines -- worst-case exponential vs. O(N) Thompson NFA -based engines. All these examples exploit worst-case vs. average scenarios. Are there examples that do not rely on the difference between the worst case vs. average case scenario? Related: The Rise of ``Worse is Better''. (For the purpose of this question the "Worse is Better" phrase is used in a narrower (namely -- algorithmic time-complexity) sense than in the article) Python's Design Philosophy: The ABC group strived for perfection. For example, they used tree-based data structure algorithms that were proven to be optimal for asymptotically large collections (but were not so great for small collections). This example would be the answer if there were no computers capable of storing these large collections (in other words large is not large enough in this case). Coppersmith–Winograd algorithm for square matrix multiplication is a good example (it is the fastest (2008) but it is inferior to worse algorithms). Any others? From the wikipedia article: "It is not used in practice because it only provides an advantage for matrices so large that they cannot be processed by modern hardware (Robinson 2005)."

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  • How to create Fibonacci Sequence in Java

    - by rfkrocktk
    I really suck at math. I mean, I REALLY suck at math. I'm trying to make a simple fibonacci sequence class for an algorithm I'll be using. I have seen the python example which looks something like this: a = 0 b = 1 while b < 10: print b a, b = b, b+a The problem is that I can't really make this work in any other language. I'd like to make it work in Java, since I can pretty much translate it into the other languages I use from there. This is the general thought: public class FibonacciAlgorithm { private Integer a = 0; private Integer b = 1; public FibonacciAlgorithm() { } public Integer increment() { a = b; b = a + b; return value; } public Integer getValue() { return b; } } All that I end up with is doubling, which I could do with multiplication :( Can anyone help me out? Math pwns me.

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  • RFC regarding WAM

    - by Noctis Skytower
    Request For Comment regarding Whitespace's Assembly Mnemonics What follows in a first generation attempt at creating mnemonics for a whitespace assembly language. STACK ===== push number copy copy number swap away away number MATH ==== add sub mul div mod HEAP ==== set get FLOW ==== part label call label goto label zero label less label back exit I/O === ochr oint ichr iint In the interest of making improvements to this small and simple instruction set, this is a second attempt. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo save Store load Retrieve L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller exit End the program print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack What do you think of the following revised list for Whitespace's assembly instructions? I'm still thinking outside of the box somewhat and trying to come up with a better mnemonic set than last time. When the previous interpreter was written, it was completed over two contiguous, rushed evenings. This rewrite deserves significantly more time now that it is the summer. Of course, the next version of Whitespace (0.4) may have its instructions revised even more, but this is just a redesign of what originally was done in a very short amount of time. Hopefully, the instructions make more sense once someone new to programmings thinks about them.

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  • Better ways to implement a modulo operation (algorithm question)

    - by ryxxui
    I've been trying to implement a modular exponentiator recently. I'm writing the code in VHDL, but I'm looking for advice of a more algorithmic nature. The main component of the modular exponentiator is a modular multiplier which I also have to implement myself. I haven't had any problems with the multiplication algorithm- it's just adding and shifting and I've done a good job of figuring out what all of my variables mean so that I can multiply in a pretty reasonable amount of time. The problem that I'm having is with implementing the modulus operation in the multiplier. I know that performing repeated subtractions will work, but it will also be slow. I found out that I could shift the modulus to effectively subtract large multiples of the modulus but I think there might still be better ways to do this. The algorithm that I'm using works something like this (weird pseudocode follows): result,modulus : integer (n bits) (previously defined) shiftcount : integer (initialized to zero) while( (modulus<result) and (modulus(n-1) != 1) ){ modulus = modulus << 1 shiftcount++ } for(i=shiftcount;i>=0;i++){ if(modulus<result){result = result-modulus} if(i!=0){modulus = modulus << 1} } So...is this a good algorithm, or at least a good place to start? Wikipedia doesn't really discuss algorithms for implementing the modulo operation, and whenever I try to search elsewhere I find really interesting but incredibly complicated (and often unrelated) research papers and publications. If there's an obvious way to implement this that I'm not seeing, I'd really appreciate some feedback.

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  • F# passing an operator with arguments to a function

    - by dan
    Can you pass in an operation like "divide by 2" or "subtract 1" using just a partially applied operator, where "add 1" looks like this: List.map ((+) 1) [1..5];; //equals [2..6] // instead of having to write: List.map (fun x-> x+1) [1..5] What's happening is 1 is being applied to (+) as it's first argument, and the list item is being applied as the second argument. For addition and multiplication, this argument ordering doesn't matter. Suppose I want to subtract 1 from every element (this will probably be a common beginners mistake): List.map ((-) 1) [1..5];; //equals [0 .. -4], the opposite of what we wanted 1 is applied to the (-) as its first argument, so instead of (list_item - 1), I get (1 - list_item). I can rewrite it as adding negative one instead of subtracting positive one: List.map ((+) -1) [1..5];; List.map (fun x -> x-1) [1..5];; // this works too I'm looking for a more expressive way to write it, something like ((-) _ 1), where _ denotes a placeholder, like in the Arc language. This would cause 1 to be the second argument to -, so in List.map, it would evaluate to list_item - 1. So if you wanted to map divide by 2 to the list, you could write: List.map ((/) _ 2) [2;4;6] //not real syntax, but would equal [1;2;3] List.map (fun x -> x/2) [2;4;6] //real syntax equivalent of the above Can this be done or do I have to use (fun x -> x/2)? It seems that the closest we can get to the placeholder syntax is to use a lambda with a named argument.

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  • floating exception using icc compiler

    - by Hristo
    I'm compiling my code via the following command: icc -ltbb test.cxx -o test Then when I run the program: time ./mp6 100 > output.modified Floating exception 4.871u 0.405s 0:05.28 99.8% 0+0k 0+0io 0pf+0w I get a "Floating exception". This following is code in C++ that I had before the exception and after: // before if (j < E[i]) { temp += foo(0, trr[i], ex[i+j*N]); } // after temp += (j < E[i])*foo(0, trr[i], ex[i+j*N]); This is boolean algebra... so (j < E[i]) is either going to be a 0 or a 1 so the multiplication would result either in 0 or the foo() result. I don't see why this would cause a floating exception. This is what foo() does: int foo(int s, int t, int e) { switch(s % 4) { case 0: return abs(t - e)/e; case 1: return (t == e) ? 0 : 1; case 2: return (t < e) ? 5 : (t - e)/t; case 3: return abs(t - e)/t; } return 0; } foo() isn't a function I wrote so I'm not too sure as to what it does... but I don't think the problem is with the function foo(). Is there something about boolean algebra that I don't understand or something that works differently in C++ than I know of? Any ideas why this causes an exception? Thanks, Hristo

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