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  • Help with Assembly/SSE Multiplication

    - by Brett
    I've been trying to figure out how to gain some improvement in my code at a very crucial couple lines: float x = a*b; float y = c*d; float z = e*f; float w = g*h; all a, b, c... are floats. I decided to look into using SSE, but can't seem to find any improvement, in fact it turns out to be twice as slow. My SSE code is: Vector4 abcd, efgh, result; abcd = [float a, float b, float c, float d]; efgh = [float e, float f, float g, float h]; _asm { movups xmm1, abcd movups xmm2, efgh mulps xmm1, xmm2 movups result, xmm1 } I also attempted using standard inline assembly, but it doesn't appear that I can pack the register with the four floating points like I can with SSE. Any comments, or help would be greatly appreciated, I mainly need to understand why my calculations using SSE are slower than the serial C++ code? I'm compiling in Visual Studio 2005, on a Windows XP, using a Pentium 4 with HT if that provides any additional information to assit. Thanks in advance!

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  • question about polynomial multiplication

    - by davit-datuashvili
    i know that horners method for polynomial pultiplication is faster but here i dont know what is happening here is code public class horner{ public static final int n=10; public static final int x=7; public static void main(String[] args){ //non fast version int a[]=new int[]{1,2,3,4,5,6,7,8,9,10}; int xi=1; int y=a[0]; for (int i=1;i<n;i++){ xi=x*xi; y=y+a[i]*xi; } System.out.println(y); //fast method int y1=a[n-1]; for (int i=n-2;i>=0;i--){ y1=x*y+a[i]; } System.out.println(y1); } } result of this two methods are not same result of first method is 462945547 and result of second method is -1054348465 please help

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  • List multiplication

    - by Schitti
    Hi, Python newbie here. I have a list L = [a, b, c] and I want to generate a list of tuples : [(a,a), (a,b), (a,c), (b,a), (b,b), (b,c)...] I tried doing L * L but it didn't work. Can someone tell me how to get this in python.

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  • NSDecimalNumber multiplication strangeness

    - by rein
    ExclusivePrice, quantity are both NSDecimalNumbers. NSDecimalNumber *price = [exclusivePrice decimalNumberByMultiplyingBy:quantity]; NSLog(@"%@ * %@ = %@", exclusivePrice, quantity, price); The result I get: 2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = -0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000007169919476068871316457914368 What I expected: 2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = 130 Can anyone explain this please?

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  • Understanding The Convolution Matrix

    - by Ryan Naddy
    I am learning about the Convolution Matrix, and I understand how they work, but I don't understand how to know before hand what the output of a Matrix will look like. For example lets say I want to add a blur to an image, I could guess 10,000+ different combinations of numbers before I get the correct one. I do know though that this formula will give me a blur effect, but I have no idea why. float[] sharpen = new float[] { 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f }; Can anyone either explain to me how this works or point me to some article, that explains this? I would like to know before hand what a possible output of the matrix will be without guessing. Basically I would like to know why do we put that number in the filed, and why not some other number?

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  • Multiplying two matrices from two text files with unknown dimensions

    - by wes schwertner
    This is my first post here. I've been working on this c++ question for a while now and have gotten nowhere. Maybe you guys can give me some hints to get me started. My program has to read two .txt files each containing one matrix. Then it has to multiply them and output it to another .txt file. My confusion here though is how the .txt files are setup and how to get the dimensions. Here is an example of matrix 1.txt. #ivalue #jvalue value 1 1 1.0 2 2 1 The dimension of the matrix is 2x2. 1.0 0 0 1 Before I can start multiplying these matrices I need to get the i and j value from the text file. The only way I have found out to do this is int main() { ifstream file("a.txt"); int numcol; float col; for(int x=0; x<3;x++) { file>>col; cout<<col; if(x==1) //grabs the number of columns numcol=col; } cout<<numcol; } The problem is I don't know how to get to the second line to read the number of rows. And on top of that I don't think this will give me accurate results for other matrices files. Let me know if anything is unclear. UPDATE Thanks! I got getline to work correctly. But now I am running into another problem. In matrix B it is setup like: #ivalue #jvalue Value 1 1 0.1 1 2 0.2 2 1 0.3 2 2 0.4 I need to let the program know that it needs to go down 4 lines, maybe even more (The matrices dimensions are unknown. My matrix B example is a 2x2, but it could be a 20x20). I have a while(!file.eof()) loop my program to let it loop until the end of file. I know I need a dynamic array for multiplying, but would I need one here also? #include <iostream> #include <fstream> using namespace std; int main() { ifstream file("a.txt"); //reads matrix A while(!file.eof()) { int temp; int numcol; string numrow; float row; float col; for(int x=0; x<3;x++) { file>>col; if(x==1) { numcol=col; //number of columns } } string test; getline(file, test); //next line to get rows for(int x=0; x<3; x++) { file>>test; if(x==1) { numrow=test; //sets number of rows } } cout<<numrow; cout<<numcol<<endl; } ifstream file1("b.txt"); //reads matrix 2 while(!file1.eof()) { int temp1; int numcol1; string numrow1; float row1; float col1; for(int x=0; x<2;x++) { file1>>col1; if(x==1) numcol1=col1; //sets number of columns } string test1; getline(file1, test1); //In matrix B there are four rows. getline(file1, test1); //These getlines go down a row. getline(file1, test1); //Need help here. for(int x=0; x<2; x++) { file1>>test1; if(x==1) numrow1=test1; } cout<<numrow1; cout<<numcol1<<endl; } }

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  • Matlab: Randomize and Split

    - by Null-Hypothesis
    I have following data matrix in Matlab, I am trying to actually split this into multiple segments by passing a variable to a matlab function. But before splitting I would like to shuffle the matrix. The size of my matrix is 150X4 s.data 5.1000 3.5000 1.4000 0.2000 4.9000 3.0000 1.4000 0.2000 4.7000 3.2000 1.3000 0.2000 4.6000 3.1000 1.5000 0.2000 5.0000 3.6000 1.4000 0.2000 .. s = data: [150x4 double] labels: [150x1 double] Coming from R environment I find MatLab is very strange. Initially I thought the columns in matrix has a relationshop like in a R dataframe but thats wrong in my assumption.

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  • C++ template typedef

    - by Notinlist
    I have a class template<size_t N, size_t M> class Matrix { // .... }; I want to make a typedef which creates a Vector (column vector) which is equivalent to a Matrix with sizes N and 1. Something like that: typedef Matrix<N,1> Vector<N>; Which produces compile error. The following creates something similar, but not exactly what I want: template <int N> class Vector: public Matrix<N,1> { }; Is there a solution or a not too expensive workaround / best-practice for it? Thanks in advance!

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  • optimization math computation (multiplication and summing)

    - by wiso
    Suppose you want to compute the sum of the square of the differences of items: $\sum_{i=1}^{N-1} (x_i - x_{i+1})^2$, the simplest code (the input is std::vector<double> xs, the ouput sum2) is: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (prev - (*i)) * (prev - (*i)); // only 1 - with compiler optimization prev = (*i); } I hope that the compiler do the optimization in the comment above. If N is the length of xs you have N-1 multiplications and 2N-3 sums (sums means + or -). Now suppose you know this variable: sum = $x_1^2 + x_N^2 + 2 sum_{i=2}^{N-1} x_i^2$ Expanding the binomial square: $sum_i^{N-1} (x_i-x_{i+1})^2 = sum - 2\sum_{i=1}^{N-1} x_i x_{i+1}$ so the code becomes: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (*i) * prev; prev = (*i); } sum2 = -sum2 * 2. + sum; Here I have N multiplications and N-1 additions. In my case N is about 100. Well, compiling with g++ -O2 I got no speed up (I try calling the inlined function 2M times), why?

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  • Doubling a number - shift left vs. multiplication

    - by ToxicAvenger
    What are the differences between int size = (int)((length * 200L) / 100L); // (1) and int size = length << 1; // (2) (length is int in both cases) I assume both code snippets want to double the length parameter. I'd be tempted to use (2) ... so are there any advantages for using (1)? I looked at the edge cases when overflow occurs, and both versions seem to have the same behavior. Please tell me what am I missing.

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  • How can i use the Orientation correct for images

    - by user3578109
    I´m learning android/java by myself @the moment and i have a problem with a part of my app i´m learning on. I made the code with help of the www and my problem is that if i open an image from the gallery it´s send to the edit activity but in the activity pictures what are made in portrait mode are displayed always wrong (90° to the right side).... The codes are Matrix private Bitmap rotateBitmapToOrientation(Bitmap b, int orientation){ Matrix matrix = new Matrix(); matrix.postRotate(orientation); Canvas offscreenCanvas = new Canvas(); offscreenCanvas.drawBitmap(b, matrix, null); return b; } and the other one @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); switch (requestCode) { case PICK_IMAGE_FROM_GALLERY: { if (resultCode == RESULT_OK) { Log.d(TAG, "Got Picture!"); Log.d(TAG,"File type - " + data.getType()); Uri photoUri = data.getData(); if (photoUri != null) { try { String[] filePathColumn = {MediaStore.Images.Media.DATA}; String[] orientationColumn = {MediaStore.Images.Media.ORIENTATION}; int orientation = -1; Cursor cursor = getContentResolver().query(photoUri, filePathColumn, null, null, null); cursor.moveToFirst(); int columnIndex = cursor.getColumnIndex(filePathColumn[0]); String filePath = cursor.getString(columnIndex); cursor.close(); cursor = getContentResolver().query(photoUri, orientationColumn, null, null, null); if(cursor != null && cursor.moveToFirst()){ orientation = cursor.getInt(cursor.getColumnIndex(orientationColumn[0])); } cursor.close(); HashMap<String, Integer> pRes = this.getImageResolutionSetting(); Bitmap shrunkenBitmap = FileUtilsHelper.shrinkBitmap(filePath, pRes.get("width"), pRes.get("height")); shrunkenBitmap = rotateBitmapToOrientation(shrunkenBitmap, orientation); String res = FileUtilsHelper.saveBitmapAsJpeg(shrunkenBitmap, this); Log.d(TAG,"File Path: " + res); shrunkenBitmap.recycle(); Intent editImage = new Intent(this, EditImage.class); editImage.addFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT); editImage.putExtra("stuff.path", res); startActivity(editImage); }catch(Exception e){ Toast.makeText(this, R.string.cant_save_image,Toast.LENGTH_SHORT).show(); } } } } break; } }} I don´t know what i´m doing wrong... I could really need a teacher on that :) Thx for your help dudes!!

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  • C# - can you name a matrix with the contents of a string

    - by RHodgett
    Basically I have x amount of matrices I need to establish of y by y size. I was hoping to name the matrices: matrixnumber1 matrixnumber2..matrixnumbern I cannot use an array as its matrices I have to form. Is it possible to use a string to name a string (or a matrix in this case)? Thank you in advance for any help on this! for (int i = 1; i <= numberofmatricesrequired; i++) { string number = Convert.ToString(i); Matrix (matrixnumber+number) = new Matrix(matrixsize, matrixsize); }

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  • Stage3D Camera problem

    - by Thomas Versteeg
    I am trying to create a 2D Stage3D game where you can move the camera around the level in an RTS style. I thought about using Orthographic Matrix3D functions for this but when I try to scroll the whole "stage" also scrolls. This is the Camera code: public function Camera2D(width:int, height:int, zoom:Number = 1) { resize(width, height); _zoom = zoom; } public function resize(width:Number, height:Number):void { _width = width; _height = height; _projectionMatrix = makeMatrix(0, width, 0, height); _recalculate = true; } protected function makeMatrix(left:Number, right:Number, top:Number, bottom:Number, zNear:Number = 0, zFar:Number = 1):Matrix3D { return new Matrix3D(Vector.<Number>([ 2 / (right - left), 0, 0, 0, 0, 2 / (top - bottom), 0, 0, 0, 0, 1 / (zFar - zNear), 0, 0, 0, zNear / (zNear - zFar), 1 ])); } public function get viewMatrix():Matrix3D { if (_recalculate) { _recalculate = false; _viewMatrix.identity(); _viewMatrix.appendTranslation( -_width / 2 - _x, -_height / 2 - y, 0); _viewMatrix.appendScale(_zoom, _zoom, 1); _renderMatrix.identity(); _renderMatrix.append(_viewMatrix); _renderMatrix.append(_projectionMatrix); } return _renderMatrix; } Here are two screenshots to show what I mean: How do I only let the inside of the stage3D scroll and not the whole stage?

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  • Screen space to world space

    - by user13414
    I am writing a 2D game where my game world has x axis running left to right, y axis running top to bottom, and z axis out of the screen: Whilst my game world is top-down, the game is rendered on a slight tilt: I'm working on projecting from world space to screen space, and vice-versa. I have the former working as follows: var viewport = new Viewport(0, 0, this.ScreenWidth, this.ScreenHeight); var screenPoint = viewport.Project(worldPoint.NegateY(), this.ProjectionMatrix, this.ViewMatrix, this.WorldMatrix); The NegateY() extension method does exactly what it sounds like, since XNA's y axis runs bottom to top instead of top to bottom. The screenshot above shows this all working. Basically, I have a bunch of points in 3D space that I then render in screen space. I can modify camera properties in real time and see it animate to the new position. Obviously my actual game will use sprites rather than points and the camera position will be fixed, but I'm just trying to get all the math in place before getting to that. Now, I am trying to convert back the other way. That is, given an x and y point in screen space above, determine the corresponding point in world space. So if I point the cursor at, say, the bottom-left of the green trapezoid, I want to get a world space reading of (0, 480). The z coordinate is irrelevant. Or, rather, the z coordinate will always be zero when mapping back to world space. Essentially, I want to implement this method signature: public Vector2 ScreenPointToWorld(Vector2 point) I've tried several things to get this working but am just having no luck. My latest thinking is that I need to call Viewport.Unproject twice with differing near/far z values, calculate the resultant Ray, normalize it, then calculate the intersection of the Ray with a Plane that basically represents ground-level of my world. However, I got stuck on the last step and wasn't sure whether I was over-complicating things. Can anyone point me in the right direction on how to achieve this?

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  • What's the standard location of a 3D clipping box?

    - by Kendall Frey
    The way I understand 3D rendering, polygons are transformed using several matrices, and they are then clipped if they are not inside a certain box, before projecting the box onto the screen. Before transformation, the visible area is typically a frustum, and after transformation, I am guessing it's a cube. This cube makes the clipping math easier than a frustum would. My question is, what's the 'standard' location/size for this clipping box? I can think of 3 possibilities: (0,0,0)-(1,1,1), (-0.5,-0.5,-0.5)-(0.5,0.5,0.5), (-1,-1,-1)-(1,1,1) Or is there no standard?

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  • How to Draw texture between 2 Vector3

    - by Sparky41
    My scenario: RTS combat style, 1 unit fires beam on another unit My problem is i want to draw a flat texture between 2 Vector3 points. I have looked at various Billboarding styles but that doesn't give me a proper solution. I looked at this: http://msdn.microsoft.com/en-us/library/bb464051.aspx is BasicEffect and DrawPrimitives the correct solution just stretch the texture to the distance between point of origin to target? I used the quad class they used but i found this it seemed to inflexible So my question to you is how would i go about this sort of problem? Regards

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  • Interpolating Matrices

    - by sebf
    Hello, Apologies if I am missing something very obvious (likely!) but is there anything wrong with interpolating between two matrices by: float d = (float)(targetTime.Ticks - keyframe_start.ticks) / (float)(keyframe_end.ticks - keyframe_start.ticks); return ((keyframe_start.Transform * (1 - d)) + (keyframe_end.Transform * d)); As in my app, when I try an use this to interpolate between two keyframes, the model begins to 'shrink' - the severity based on how far between the two keyframes the target time is; its worst when the transform split is ~50/50.

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  • Billboarding restricted to an axis (cylindrical)

    - by user8709
    I have succesfully created a GLSL shader for a billboarding effect. I want to tweak this to restrict the billboarding to an arbitrary axis, i.e. a billboarded quad only rotates itself about the y-axis. I use the y-axis as an example, but essentially I would like this to be an arbitrary axis. Can anyone show me how to modify my existing shader below, or if I need to start from scratch, point me towards some resources that could be helpful? precision mediump float; uniform mat4 u_modelViewProjectionMat; uniform mat4 u_modelMat; uniform mat4 u_viewTransposeMat; uniform vec3 u_axis; // <------------ !!! the arbitrary axis to restrict rotation around attribute vec3 a_position0; attribute vec2 a_texCoord0; varying vec2 v_texCoord0; void main() { vec3 pos = (a_position0.x * u_viewTransposeMat[0] + a_position0.y * u_viewTransposeMat[1]).xyz; vec4 position = vec4(pos, 1.0); v_texCoord0 = a_texCoord0; gl_Position = u_modelViewProjectionMat * position; }

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  • 2D Skeletal Animation Transformations

    - by Brad Zeis
    I have been trying to build a 2D skeletal animation system for a while, and I believe that I'm fairly close to finishing. Currently, I have the following data structures: struct Bone { Bone *parent; int child_count; Bone **children; double x, y; }; struct Vertex { double x, y; int bone_count; Bone **bones; double *weights; }; struct Mesh { int vertex_count; Vertex **vertices; Vertex **tex_coords; } Bone->x and Bone->y are the coordinates of the end point of the Bone. The starting point is given by (bone->parent->x, bone->parent->y) or (0, 0). Each entity in the game has a Mesh, and Mesh->vertices is used as the bounding area for the entity. Mesh->tex_coords are texture coordinates. In the entity's update function, the position of the Bone is used to change the coordinates of the Vertices that are bound to it. Currently what I have is: void Mesh_update(Mesh *mesh) { int i, j; double sx, sy; for (i = 0; i < vertex_count; i++) { if (mesh->vertices[i]->bone_count == 0) { continue; } sx, sy = 0; for (j = 0; j < mesh->vertices[i]->bone_count; j++) { sx += (/* ??? */) * mesh->vertices[i]->weights[j]; sy += (/* ??? */) * mesh->vertices[i]->weights[j]; } mesh->vertices[i]->x = sx; mesh->vertices[i]->y = sy; } } I think I have everything I need, I just don't know how to apply the transformations to the final mesh coordinates. What tranformations do I need here? Or is my approach just completely wrong?

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  • Stage3D: Camera pans the whole screen

    - by Thomas Versteeg
    I am trying to create a 2D Stage3D game where you can move the camera around the level in an RTS style. I thought about using Orthographic Matrix3D functions for this but when I try to scroll the whole "stage" also scrolls. This is the Camera code: public function Camera2D(width:int, height:int, zoom:Number = 1) { resize(width, height); _zoom = zoom; } public function resize(width:Number, height:Number):void { _width = width; _height = height; _projectionMatrix = makeMatrix(0, width, 0, height); _recalculate = true; } protected function makeMatrix(left:Number, right:Number, top:Number, bottom:Number, zNear:Number = 0, zFar:Number = 1):Matrix3D { return new Matrix3D(Vector.<Number>([ 2 / (right - left), 0, 0, 0, 0, 2 / (top - bottom), 0, 0, 0, 0, 1 / (zFar - zNear), 0, 0, 0, zNear / (zNear - zFar), 1 ])); } public function get viewMatrix():Matrix3D { if (_recalculate) { _recalculate = false; _viewMatrix.identity(); _viewMatrix.appendTranslation( -_width / 2 - _x, -_height / 2 - y, 0); _viewMatrix.appendScale(_zoom, _zoom, 1); _renderMatrix.identity(); _renderMatrix.append(_viewMatrix); _renderMatrix.append(_projectionMatrix); } return _renderMatrix; } And the camera is send directly to the GPU with: c3d.setProgramConstantsFromMatrix(Context3DProgramType.VERTEX, 0, cameraMatrix, true); And these are the shaders: ------Vertex Shader------ m44 op, va0, vc0 mov v0, va1.xy mov v0.z, va0.z ------Fragment Shader------ tex ft0, v0, fs0 <2d,linear,nomip> mov oc, ft1 Here is a example and here are two screenshots to show what I mean: How do I only let the inside of the stage3D scroll and not the whole stage?

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  • How to make an object stay relative to another object

    - by Nick
    In the following example there is a guy and a boat. They have both a position, orientation and velocity. The guy is standing on the shore and would like to board. He changes his position so he is now standing on the boat. The boat changes velocity and orientation and heads off. My character however has a velocity of 0,0,0 but I would like him to stay onboard. When I move my character around, I would like to move as if the boat was the ground I was standing on. How do keep my character aligned properly with the boat? It is exactly like in World Of Warcraft, when you board a boat or zeppelin. This is my physics code for the guy and boat: this.velocity.addSelf(acceleration.multiplyScalar(dTime)); this.position.addSelf(this.velocity.clone().multiplyScalar(dTime)); The guy already has a reference to the boat he's standing on, and thus knows the boat's position, velocity, orientation (even matrices or quaternions can be used).

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