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  • C++ STL: Array vs Vector: Raw element accessing performance

    - by oh boy
    I'm building an interpreter and as I'm aiming for raw speed this time, every clock cycle matters for me in this (raw) case. Do you have any experience or information what of the both is faster: Vector or Array? All what matters is the speed I can access an element (opcode receiving), I don't care about inserting, allocation, sorting, etc. I'm going to lean myself out of the window now and say: Arrays are at least a bit faster than vectors in terms of accessing an element i. It seems really logical for me. With vectors you have all those security and controlling overhead which doesn't exist for arrays. (Why) Am I wrong? No, I can't ignore the performance difference - even if it is so small - I have already optimized and minimized every other part of the VM which executes the opcodes :)

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  • Preferred way of filling up a C++ vector of structs

    - by henle
    Alternative 1, reusing a temporary variable: Sticker sticker; sticker.x = x + foreground.x; sticker.y = foreground.y; sticker.width = foreground.width; sticker.height = foreground.height; board.push_back(sticker); sticker.x = x + outline.x; sticker.y = outline.y; sticker.width = outline.width; sticker.height = outline.height; board.push_back(sticker); Alternative 2, scoping the temporary variable: { Sticker sticker; sticker.x = x + foreground.x; sticker.y = foreground.y; sticker.width = foreground.width; sticker.height = foreground.height; board.push_back(sticker); } { Sticker sticker; sticker.x = x + outline.x; sticker.y = outline.y; sticker.width = outline.width; sticker.height = outline.height; board.push_back(sticker); } Alternative 3, writing straight to the vector memory: { board.push_back(Sticker()); Sticker &sticker = board.back(); sticker.x = x + foreground.x; sticker.y = foreground.y; sticker.width = foreground.width; sticker.height = foreground.height; } { board.push_back(Sticker()); Sticker &sticker = board.back(); sticker.x = x + outline.x; sticker.y = outline.y; sticker.width = outline.width; sticker.height = outline.height; } Which approach do you prefer?

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  • Points on lines where the two lines are the closest together

    - by James Bedford
    Hey guys, I'm trying to find the points on two lines where the two lines are the closest. I've implemented the following method (Points and Vectors are as you'd expect, and a Line consists of a Point on the line and a non-normalized direction Vector from that point): void CDClosestPointsOnTwoLines(Line line1, Line line2, Point* closestPoints) { closestPoints[0] = line1.pointOnLine; closestPoints[1] = line2.pointOnLine; Vector d1 = line1.direction; Vector d2 = line2.direction; float a = d1.dot(d1); float b = d1.dot(d2); float e = d2.dot(d2); float d = a*e - b*b; if (d != 0) // If the two lines are not parallel. { Vector r = Vector(line1.pointOnLine) - Vector(line2.pointOnLine); float c = d1.dot(r); float f = d2.dot(r); float s = (b*f - c*e) / d; float t = (a*f - b*c) / d; closestPoints[0] = line1.positionOnLine(s); closestPoints[1] = line2.positionOnLine(t); } else { printf("Lines were parallel.\n"); } } I'm using OpenGL to draw three lines that move around the world, the third of which should be the line that most closely connects the other two lines, the two end points of which are calculated using this function. The problem is that the first point of closestPoints after this function is called will lie on line1, but the second point won't lie on line2, let alone at the closest point on line2! I've checked over the function many times but I can't see where the mistake in my implementation is. I've checked my dot product function, scalar multiplication, subtraction, positionOnLine() etc. etc. So my assumption is that the problem is within this method implementation. If it helps to find the answer, this is function supposed to be an implementation of section 5.1.8 from 'Real-Time Collision Detection' by Christer Ericson. Many thanks for any help!

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  • Line Intersection from parametric equation

    - by Sidar
    I'm sure this question has been asked before. However, I'm trying to connect the dots by translating an equation on paper into an actual function. I thought It would be interesting to ask here instead on the Math sites (since it's going to be used for games anyway ). Let's say we have our vector equation : x = s + Lr; where x is the resulting vector, s our starting point/vector. L our parameter and r our direction vector. The ( not sure it's called like this, please correct me ) normal equation is : x.n = c; If we substitute our vector equation we get: (s+Lr).n = c. We now need to isolate L which results in L = (c - s.n) / (r.n); L needs to be 0 < L < 1. Meaning it needs to be between 0 and 1. My question: I want to know what L is so if I were to substitute L for both vector equation (or two lines) they should give me the same intersection coordinates. That is if they intersect. But I can't wrap my head around on how to use this for two lines and find the parameter that fits the intersection point. Could someone with a simple example show how I could translate this to a function/method?

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  • Efficiency of iterators and alternatives? [migrated]

    - by user48037
    I have the following code for my game tiles: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { for (it = gameTiles[x][y].tiles.begin() ; it != gameTiles[x][y].tiles.end(); ++it) {}}} tiles is: struct Game_Tile { // More specific object types will be added here eventually vector<GameObject_Tile*> tiles; }; My problem is that if I change the vector to just be a single GameObject_Tile* instead and remove the iterator line in the loop I go from about 200fps to 450fps. Some context: The vector/pointer only contains one object in both scenarios. I will eventually need to store multiple, but for testing I just set it to a single pointer. The loop goes through 2,300 objects each frame and draws them. I would like to point out that if I remove the Draw (not seen int he example) method, I gain about 30 frames in both scenarios, the issue is the iteration. So I am wondering why having this as a vector being looped through by an iterator (to get at a single object) is costing me over 200 frames when compared to it being a single pointer? The 200+ frames faster code is: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { //gameTiles[x][y].tiles is used as a pointer here instead of using *it }} tiles is: struct Game_Tile { // More specific object types will be added here eventually GameObject_Tile* tiles; };

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  • Vector math, finding coördinates on a planar between 2 vectors

    - by Will Kru
    I am trying to generate a 3d tube along a spline. I have the coördinates of the spline (x1,y1,z1 - x2,y2,z2 - etc) which you can see in the illustration in yellow. At those points I need to generate circles, whose vertices are to be connected at a later stadium. The circles need to be perpendicular to the 'corners' of two line segments of the spline to form a correct tube. Note that the segments are kept low for illustration purpose. [apparently I'm not allowed to post images so please view the image at this link] http://img191.imageshack.us/img191/6863/18720019.jpg I am as far as being able to calculate the vertices of each ring at each point of the spline, but they are all on the same planar ie same angled. I need them to be rotated according to their 'legs' (which A & B are to C for instance). I've been thinking this over and thought of the following: two line segments can be seen as 2 vectors (in illustration A & B) the corner (in illustraton C) is where a ring of vertices need to be calculated I need to find the planar on which all of the vertices will reside I then can use this planar (=vector?) to calculate new vectors from the center point, which is C and find their x,y,z using radius * sin and cos However, I'm really confused on the math part of this. I read about the dot product but that returns a scalar which I don't know how to apply in this case. Can someone point me into the right direction? [edit] To give a bit more info on the situation: I need to construct a buffer of floats, which -in groups of 3- describe vertex positions and will be connected by OpenGL ES, given another buffer with indices to form polygons. To give shape to the tube, I first created an array of floats, which -in groups of 3- describe control points in 3d space. Then along with a variable for segment density, I pass these control points to a function that uses these control points to create a CatmullRom spline and returns this in the form of another array of floats which -again in groups of 3- describe vertices of the catmull rom spline. On each of these vertices, I want to create a ring of vertices which also can differ in density (amount of smoothness / vertices per ring). All former vertices (control points and those that describe the catmull rom spline) are discarded. Only the vertices that form the tube rings will be passed to OpenGL, which in turn will connect those to form the final tube. I am as far as being able to create the catmullrom spline, and create rings at the position of its vertices, however, they are all on a planars that are in the same angle, instead of following the splines path. [/edit] Thanks!

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  • Optimizing Vector elements swaps using CUDA

    - by Orion Nebula
    Hi all, Since I am new to cuda .. I need your kind help I have this long vector, for each group of 24 elements, I need to do the following: for the first 12 elements, the even numbered elements are multiplied by -1, for the second 12 elements, the odd numbered elements are multiplied by -1 then the following swap takes place: Graph: because I don't yet have enough points, I couldn't post the image so here it is: http://www.freeimagehosting.net/image.php?e4b88fb666.png I have written this piece of code, and wonder if you could help me further optimize it to solve for divergence or bank conflicts .. //subvector is a multiple of 24, Mds and Nds are shared memory _shared_ double Mds[subVector]; _shared_ double Nds[subVector]; int tx = threadIdx.x; int tx_mod = tx ^ 0x0001; int basex = __umul24(blockDim.x, blockIdx.x); Mds[tx] = M.elements[basex + tx]; __syncthreads(); // flip the signs if (tx < (tx/24)*24 + 12) { //if < 12 and even if ((tx & 0x0001)==0) Mds[tx] = -Mds[tx]; } else if (tx < (tx/24)*24 + 24) { //if >12 and < 24 and odd if ((tx & 0x0001)==1) Mds[tx] = -Mds[tx]; } __syncthreads(); if (tx < (tx/24)*24 + 6) { //for the first 6 elements .. swap with last six in the 24elements group (see graph) Nds[tx] = Mds[tx_mod + 18]; Mds [tx_mod + 18] = Mds [tx]; Mds[tx] = Nds[tx]; } else if (tx < (tx/24)*24 + 12) { // for the second 6 elements .. swp with next adjacent group (see graph) Nds[tx] = Mds[tx_mod + 6]; Mds [tx_mod + 6] = Mds [tx]; Mds[tx] = Nds[tx]; } __syncthreads(); Thanks in advance ..

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  • Acessing a struct member, using a pointer to a vector of structs. Error:base operand of '->' has non-pointer type

    - by Matt Munson
    #include <iostream> #include <vector> using namespace std; struct s_Astruct { vector <int> z; }; int main () { vector <s_Astruct> v_a; for(int q=0;q<10;q++) { v_a.push_back(s_Astruct()); for(int w =0;w<5;w++) v_a[q].z.push_back(8); } vector <s_Astruct> * p_v_a = & v_a; cout << p_v_a[0]->z[4]; //error: base operand of '->' has non-pointer type //'__gnu_debug_def::vector<s_Astruct, std::allocator<s_Astruct> >' } There seems to be some issue with this sort of operation that I don't understand. In the code that I'm working on I actually have things like p_class-vector[]-vector[]-int; and I'm getting a similar error.

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  • is there a way to condense a vector (C++)?

    - by zebraman
    I have a sparsely populated vector that I populated via hashing, so elements are scattered randomly in the vector. Now what I want to do is iterate over every element in that vector. What I had in mind was essentially condensing the vector to fit the number of elements present, removing any empty spaces. Is there a way I can do this?

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  • Why did I get this error : java.lang.Exception: XMLEncoder: discarding statement Vector.add() ?

    - by Frank
    My Java program look like this : public class Biz_Manager { static Contact_Info_Setting Customer_Contact_Info_Panel; static XMLEncoder XML_Encoder; ...... void Get_Customer_Agent_Shipping_Company_And_Shipping_Agent_Net_Worth_Info() { try { XML_Encoder=new XMLEncoder(new BufferedOutputStream(new FileOutputStream(Customer_Contact_Info_Panel.Contact_Info_File_Path))); XML_Encoder.writeObject(Customer_Contact_Info_Panel.Contacts_Vector); } catch (Exception e) { e.printStackTrace(); } finally { if (XML_Encoder!=null) { XML_Encoder.close(); // <== Error here , line : 9459 XML_Encoder=null; } } } } // ======================================================================= public class Contact_Info_Setting extends JPanel implements ActionListener,KeyListener,ItemListener { public static final long serialVersionUID=26362862L; ...... Vector<Contact_Info_Entry> Contacts_Vector=new Vector<Contact_Info_Entry>(); ...... } // ======================================================================= package Utility; import java.io.*; import java.util.*; import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) public Long Id; public static final long serialVersionUID=26362862L; public String Contact_Id="",First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country=""; ...... public boolean B_1; public Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } public Contact_Info_Entry(String Other_Id) { this.Other_Id=Other_Id; } ...... public void setId(Long value) { Id=value; } public Long getId() { return Id; } public void setContact_Id(String value) { Contact_Id=value; } public String getContact_Id() { return Contact_Id; } public void setFirst_Name(String value) { First_Name=value; } public String getFirst_Name() { return First_Name; } public void setLast_Name(String value) { Last_Name=value; } public String getLast_Name() { return Last_Name; } public void setCompany_Name(String value) { Company_Name=value; } public String getCompany_Name() { return Company_Name; } ...... } I got this error message : java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... Exception in thread "Thread-8" java.lang.NullPointerException at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:611) at java.beans.XMLEncoder.outputValue(XMLEncoder.java:552) at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:682) at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:687) at java.beans.XMLEncoder.outputValue(XMLEncoder.java:552) at java.beans.XMLEncoder.flush(XMLEncoder.java:398) at java.beans.XMLEncoder.close(XMLEncoder.java:429) at Biz_Manager.Get_Customer_Agent_Shipping_Company_And_Shipping_Agent_Net_Worth_Info(Biz_Manager.java:9459) Seems it can't deal with vector, why ? Anything wrong ? How to fix it ? Frank

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  • Can't load vector font in Nuclex Framework

    - by ProgrammerAtWork
    I've been trying to get this to work for the last 2 hours and I'm not getting what I'm doing wrong... I've added Nuclex.TrueTypeImporter to my references in my content and I've added Nuclex.Fonts & Nuclex.Graphics in my main project. I've put Arial-24-Vector.spritefont & Lindsey.spritefont in the root of my content directory. _spriteFont = Content.Load<SpriteFont>("Lindsey"); // works _testFont = Content.Load<VectorFont>("Arial-24-Vector"); // crashes I get this error on the _testFont line: File contains Microsoft.Xna.Framework.Graphics.SpriteFont but trying to load as Nuclex.Fonts.VectorFont. So I've searched around and by the looks of it it has something to do with the content importer & the content processor. For the content importer I have no new choices, so I leave it as it is, Sprite Font Description - XNA Framework for content processor and I select Vector Font - Nuclex Framework And then I try to run it. _testFont = Content.Load<VectorFont>("Arial-24-Vector"); // crashes again I get the following error Error loading "Arial-24-Vector". It does work if I load a sprite, so it's not a pathing problem. I've checked the samples, they do work, but I think they also use a different version of the XNA framework because in my version the "Content" class starts with a capital letter. I'm at a loss, so I ask here. Edit: Something super weird is going on. I've just added the following two lines to a method inside FreeTypeFontProcessor::FreeTypeFontProcessor( Microsoft::Xna::Framework::Content::Pipeline::Graphics::FontDescription ^fontDescription, FontHinter hinter, just to check if code would even get there: System::Console::WriteLine("I AM HEEREEE"); System::Console::ReadLine(); So, I compile it, put it in my project, I run it and... it works! What the hell?? This is weird because I've downloaded the binaries, they didn't work, I've compiled the binaries myself. didn't work either, but now I make a small change to the code and it works? _. So, now I remove the two lines, compile it again and it works again. Someone care to elaborate what is going on? Probably some weird caching problem!

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  • Matlab - binary vector with high concentration of 1s (or 0s)

    - by JohnIdol
    What's the best way to generate a number X of random binary vectors of size N with concentration of 1s (or, simmetrically, of 0s) that spans from very low to very high? Using randint or unidrnd (as in this question) will generate binary vectors with uniform distributions, which is not what I need in this case. Any help appreciated!

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  • ImageMagick vs. Cairo on Vector Graphics rasterization

    - by Sherwood Hu
    I am working on a project that needs rasterizing of drawings into image files. I have already got it work using GDI+. Wanting to create a portable solution, I am also looking into other solutions and found two - cairo and imagemagick. I am new to both, but it seems that ImageMagick can do almost all the stuff - drawing lines, arcs, circles, text etc.. plus many bitmap manipulation. However, Cairo is mentioned as competitor to GDI+ in web sites. ImageMagick is never mentioned for this purpose. I do not have time to invest on both libraries. I need to decide which one is worthy. I prefer to ImageMagick, as it seems much more powerful. What's your opinion on the two graphic libs?

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  • Bind xaml vector images dynamically

    - by Carl
    I'm looking for a way to bind xaml images dynamically in code. There are lots of examples online to show how to bind png or xaml images in the window's xaml, or to load png files in code. But I have found no examples for xaml files with build action=page. XmlReader can't handle them since they are compiled to baml. LoadComponent(new Uri("...filename.xaml") will apparently load the baml but what kind of image class do I load this into? BitmapImage(new Uri("...filename.xaml") does not seem to work, probably because it's not a bitmap. Thanks in advance.

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  • Can I use vector as index in map structure in c++?

    - by tsubasa
    I attempted to do something like this but it does not compile: class point { public: int x; int y; }; int main() { vector<point> vp1; vector<point> vp2; vector<point> vp3; map < vector<point>, int > m; m[vp1] = 1; m[vp2] = 2; m[vp3] = 3; map < vector<point>, int >::iterator it; for (it=m.begin(); it!=m.end(); it++) { cout<<m[it->first]<<endl; } return 0; }

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  • Characteristics of an Initialization Vector

    - by Jamie Chapman
    I'm by no means a cryptography expert, I have been reading a few questions around Stack Overflow and on Wikipedia but nothing is really 'clear cut' in terms of defining an IV and it's usage. Points I have discovered: An IV is pre-pended to a plaintext message in order to strengthen the encryption The IV is truely random Each message has it's own unique IV Timestamps and cryptographic hashes are sometimes used instead of random values, but these are considered to be insecure as timestamps can be predicted One of the weaknesses of WEP (in 802.11) is the fact that the IV will reset after a specific amount of encryptions, thus repeating the IV I'm sure there are many other points to be made, what have I missed? (or misread!)

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  • Vector deltas and moving in unknown areas

    - by dekz
    Hi All, I was in need of a little math help that I can't seem to find the answer to, any links to documentation would be greatly appreciated. Heres my situation, I have no idea where I am in this maze, but I need to move around and find my way back to the start. I was thinking of implementing a waypoint list of places i've been offset from my start at 0,0. This is a 2D cartesian plane. I've been given 2 properties, my translation speed from 0-1 and my rotation speed from -1 to 1. -1 is very left and +1 is very right. These are speed and not angles so thats where my problem lies. If I'm given 0 as a translation speed and 0.2 I will continually turn to my right at a slow speed. How do I figure out the offsets given these 2 variables? I can store it every time I take a 'step'. I just need to figure out the offsets in x and y terms given the translations and rotation speeds. And the rotation to get to those points. Any help is appreciated.

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  • replace NA in an R vector with adjacent values

    - by pssguy
    I have a dataframe which has merged player and team data for soccer seasons So for a particular player in a specific season I have data like df <- data.frame(team=c(NA,"CRP",NA,"CRP","CRP",NA), player=c(NA,"Ed",NA,"Ed","Ed",NA), playerGame= c(NA,1,NA,2,3,NA), teamGame =c(1,2,3,4,5,6)) Where the NA's indicate that the player did not appear in that specific team game How would I most efficiently replace the team and player NA's with "CRP" and "Ed" respectively and have a plGame output of, in this instance, 0,1,1,2,3,3

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  • How to access the element of a list/vector that passed by reference in C++

    - by bsoundra
    Hi all, The problem is passing lists/vectors by reference int main(){ list<int> arr; //Adding few ints here to arr func1(&arr); return 0; } void func1(list<int> * arr){ // How Can I print the values here ? //I tried all the below , but it is erroring out. cout<<arr[0]; // error cout<<*arr[0];// error cout<<(*arr)[0];//error //How do I modify the value at the index 0 ? func2(arr);// Since it is already a pointer, I am passing just the address } void func2(list<int> *arr){ //How do I print and modify the values here ? I believe it should be the same as above but // just in case. } Is the vectors any different from the lists ? Thanks in advance. Any links where these things are explained elaborately will be of great help. Thanks again.

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  • C++ STL vector iterator... but got runtime error

    - by nzer0
    I'm studying STL and made win32 project.. But I got stuck in runtime error.. I tried to debug it but.. please click to see picture this is very strange because in watch table, n1,p1,it are defined but n2 isn't and tmp is not either.. I can't find what is wrong... please help..

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