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  • Minimal-change algorithm which maximises 'swapping'

    - by Kim Bastin
    This is a question on combinatorics from a non-mathematician, so please try to bear with me! Given an array of n distinct characters, I want to generate subsets of k characters in a minimal-change order, i.e. an order in which generation n+1 contains exactly one character that was not in generation n. That's not too hard in itself. However, I also want to maximise the number of cases in which the character that is swapped out in generation n+1 is the same character that was swapped in in generation n. To illustrate, for n=7, k=3: abc abd abe* abf* abg* afg aeg* adg* acg* acd ace* acf* aef adf* ade bde bdf bef bcf* bce bcd* bcg* bdg beg* bfg* cfg ceg* cdg* cde cdf* cef def deg dfg efg The asterisked strings indicate the case I want to maximise; e.g. the e that is new in generation 3, abe, replaces a d that was new in generation 2, abd. It doesn't seem possible to have this happen in every generation, but I want it to happen as often as possible. Typical array sizes that I use are 20-30 and subset sizes around 5-8. I'm using an odd language, Icon (or actually its derivative Unicon), so I don't expect anyone to post code that I can used directly. But I will be grateful for answers or hints in pseudo-code, and will do my best to translate C etc. Also, I have noticed that problems of this kind are often discussed in terms of arrays of integers, and I can certainly apply solutions posted in such terms to my own problem. Thanks Kim Bastin

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  • Geometry instancing in OpenGL ES 2.0

    - by seahorse
    I am planning to do geometry instancing in OpenGL ES 2.0 Basically I plan to render the same geometry(a chair) maybe 1000 times in my scene. What is the best way to do this in OpenGL ES 2.0? I am considering passing model view mat4 as an attribute. Since attributes are per vertex data do I need to pass this same mat4, three times for each vertex of the same triangle(since modelview remains constant across vertices of the triangle). That would amount to a lot of extra data sent to the GPU( 2 extra vertices*16 floats*(Number of triangles) amount of extra data). Or should I be sending the mat4 only once per triangle?But how is that possible using attributes since attributes are defined as "per vertex" data? What is the best and efficient way to do instancing in OpenGL ES 2.0?

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  • What's the most efficient way to find barycentric coordinates?

    - by bobobobo
    In my profiler, finding barycentric coordinates is apparently somewhat of a bottleneck. I am looking to make it more efficient. It follows the method in shirley, where you compute the area of the triangles formed by embedding the point P inside the triangle. Code: Vector Triangle::getBarycentricCoordinatesAt( const Vector & P ) const { Vector bary ; // The area of a triangle is real areaABC = DOT( normal, CROSS( (b - a), (c - a) ) ) ; real areaPBC = DOT( normal, CROSS( (b - P), (c - P) ) ) ; real areaPCA = DOT( normal, CROSS( (c - P), (a - P) ) ) ; bary.x = areaPBC / areaABC ; // alpha bary.y = areaPCA / areaABC ; // beta bary.z = 1.0f - bary.x - bary.y ; // gamma return bary ; } This method works, but I'm looking for a more efficient one!

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  • Rotate an object given only by its points?

    - by d33tah
    I was recently writing a simple 3D maze FPP game. Once I was done fiddling with planes in OpenGL, I wanted to add support for importing Blender objects. The approach I used was triangulization of the object, then using Three.js to export the points to plaintext and then parsing the result JSON in my app. The example file can be seen here: https://github.com/d33tah/tinyfpp/blob/master/Data/Models/cross.txt The numbers represent x,y,z,u,v of a single vertex, which combined in three make a triangle. Then I rendered such an object triangle-by-triangle and played with it. I could move it back and forth and sideways, but I still have no idea how to rotate it by some axis. Let's say I'd like to rotate all the points by five degrees to the left, how would a code doing it look like?

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  • Collision for mobile game

    - by zemiguel12
    I'm writing a little game in as3 using Starling, and I need to check collision between 2 boats that can rotate. I don't need the pixel perfect collision, but bounds collision is not enough too. The boat look more or less like this: I was thinking about create one square on the back of the boat and a triangle on the front, than for each boat, check if the square collide with the other boat square or triangle, and the same for the triangle. I just don't know how to do that, I don't know if it's possible with the Shape.hitTest, or if it's the best way to do that. What can I do?

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  • Tuning garbage collections for low latency

    - by elec
    I'm looking for arguments as to how best to size the young generation (with respect to the old generation) in an environment where low latency is critical. My own testing tends to show that latency is lowest when the young generation is fairly large (eg. -XX:NewRatio <3), however I cannot reconcile this with the intuition that the larger the young generation the more time it should take to garbage collect. The application runs on linux, jdk 6 before update 14, i.e G1 not available.

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  • Use pt-table-sync to setup a new MySQL DB

    - by Generation D Systems
    I have 2 hosts (A and B). B contains a MySQL server with a database called mydb, and A contains a MySQL server with nothing (fresh install). I want to replicate the entire mydb from B to A, by running a script on A (I do not have shell access to B). Can I run this on A: pt-table-sync --execute h=b.mydomain.com,D=mydb h=a.mydomain.com I've read the docs but don't get a 100% comfort feeling (perhaps because of all the warnings about damaging your data if you don't know what you're doing). Will this work? as well, is h=a.mydomin.com necessary? (Will it route all traffic back in/out the local NIC?) can I use localhost or nothing at all?

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  • Using mongodump with an auth enabled mongodb server

    - by bb-generation
    I'm trying to do a daily backup of my mongodb server (auth enabled) using the mongodump tool. mongodump provides two parameters to set the credentials: -u [ --username ] arg username -p [ --password ] arg password Unfortunately they don't provide any parameter to read the password from stdin. Therefore everytime I run this command, everyone on the server can read the password (e.g. by using ps aux). The only workaround I have found is stopping the database and directly accessing the database files using the --dbpath parameter. Is there any other solution which allows me to backup the mongodb database without stopping the server and without "publishing" my password? I am using Debian squeeze 6.0.5 amd64 with mongodb 1.4.4-3.

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  • How can I draw an arrow at the edge of the screen pointing to an object that is off screen?

    - by Adam Henderson
    I am wishing to do what is described in this topic: http://www.allegro.cc/forums/print-thread/283220 I have attempted a variety of the methods mentioned here. First I tried to use the method described by Carrus85: Just take the ratio of the two triangle hypontenuses (doesn't matter which triagle you use for the other, I suggest point 1 and point 2 as the distance you calculate). This will give you the aspect ratio percentage of the triangle in the corner from the larger triangle. Then you simply multiply deltax by that value to get the x-coordinate offset, and deltay by that value to get the y-coordinate offset. But I could not find a way to calculate how far the object is away from the edge of the screen. I then tried using ray casting (which I have never done before) suggested by 23yrold3yrold: Fire a ray from the center of the screen to the offscreen object. Calculate where on the rectangle the ray intersects. There's your coordinates. I first calculated the hypotenuse of the triangle formed by the difference in x and y positions of the two points. I used this to create a unit vector along that line. I looped through that vector until either the x coordinate or the y coordinate was off the screen. The two current x and y values then form the x and y of the arrow. Here is the code for my ray casting method (written in C++ and Allegro 5) void renderArrows(Object* i) { float x1 = i->getX() + (i->getWidth() / 2); float y1 = i->getY() + (i->getHeight() / 2); float x2 = screenCentreX; float y2 = ScreenCentreY; float dx = x2 - x1; float dy = y2 - y1; float hypotSquared = (dx * dx) + (dy * dy); float hypot = sqrt(hypotSquared); float unitX = dx / hypot; float unitY = dy / hypot; float rayX = x2 - view->getViewportX(); float rayY = y2 - view->getViewportY(); float arrowX = 0; float arrowY = 0; bool posFound = false; while(posFound == false) { rayX += unitX; rayY += unitY; if(rayX <= 0 || rayX >= screenWidth || rayY <= 0 || rayY >= screenHeight) { arrowX = rayX; arrowY = rayY; posFound = true; } } al_draw_bitmap(sprite, arrowX - spriteWidth, arrowY - spriteHeight, 0); } This was relatively successful. Arrows are displayed in the bottom right section of the screen when objects are located above and left of the screen as if the locations of the where the arrows are drawn have been rotated 180 degrees around the center of the screen. I assumed this was due to the fact that when I was calculating the hypotenuse of the triangle, it would always be positive regardless of whether or not the difference in x or difference in y is negative. Thinking about it, ray casting does not seem like a good way of solving the problem (due to the fact that it involves using sqrt() and a large for loop). Any help finding a suitable solution would be greatly appreciated, Thanks Adam

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  • Rotating 2D Object

    - by Vico Pelaez
    Well I am trying to learn openGL and want to make a triangle move one unit (0.1) everytime I press one of the keyboard arrows. However i want the triangle to turn first pointing the direction where i will move one unit. So if my triangle is pointing up and I press right the it should point right first and then move one unit in the x axis. I have implemented the code to move the object one unit in any direction, however I can not get it to turn pointing to the direction it is going. The initial position of the Triangle is pointing up. #define LENGTH 0.05 float posX = -0.5, posY = -0.5, posZ = 0; float inX = 0.0 ,inY = 0.0 ,inZ = 0.0; // what values???? void rect(){ glMatrixMode(GL_PROJECTION); glLoadIdentity(); glPushMatrix(); glTranslatef(posX,posY,posZ); glRotatef(rotate, inX, inY, inZ); glBegin(GL_TRIANGLES); glColor3f(0.0, 0.0, 1.0); glVertex2f(-LENGTH,-LENGTH); glVertex2f(LENGTH-LENGTH, LENGTH); glVertex2f(LENGTH, -LENGTH); glEnd(); glPopMatrix(); } void display(){ //Clear Window glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); rect(); glFlush(); } void init(){ glClearColor(0.0, 0.0, 0.0, 0.0); glColor3f(1.0, 1.0, 1.0); } float move_unit = 0.01; bool change = false; void keyboardown(int key, int x, int y) { switch (key){ case GLUT_KEY_UP: if(rotate = 0) posY += move_unit; else{ inX = 1.0; rotate = 0; } break; case GLUT_KEY_RIGHT: if(rotate = -90) posX += move_unit; else{ inX = 1.0; // is this value ok?? rotate -= 90; } break; case GLUT_KEY_LEFT: if(rotate = 90) posX -= move_unit; else{ inX = 1.0; // is this value ok??? rotate += 90; } break; case GLUT_KEY_DOWN: if(rotate = 180) posY -= move_unit; else{ inX = 1.0; rotate += 180; } break; case 27: // Escape button exit(0); break; default: break; } glutPostRedisplay(); } int main(int argc, char** argv){ glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowSize(500,500); glutInitWindowPosition(0, 0); glutCreateWindow("Triangle turn"); glutSpecialFunc(keyboardown); glutDisplayFunc(display); init(); glutMainLoop()

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  • how can i use ORM tool like My Generation?

    - by ykaratoprak
    i downloaded MyGeneration from net. And run. it has got connection string. "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;Data Source=localhost " on the other hand; my connection string : Data Source=.\sqlexpress; Initial Catalog=NetTanitimTest; Integrated Security=True if i click save or connect button it throws to me connection error. Who used it can you hel p me?

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  • CGPath and Quartz 2D

    - by iphonedevnoob
    I want to create a triangle using Quartz 2D functions. The 3 edges of the triangle should be in different colors. I am able to create the triangle but not able to set the color of each edge or subpath separately. Any suggestions or sample code are much appreciated.

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  • Why does this thumbnail generation code throw OutOfMemoryException on large files?

    - by tsilb
    This code works great for generating thumbnails, but when given a very large (100MB+) TIFF file, it throws OutOfMemoryExceptions. When I do it manually in Paint.NET on the same machine, it works fine. How can I improve this code to stop throwing on very large files? In this case I'm loading a 721MB TIF on a machine with 8GB RAM. The Task Manager shows 2GB used so something is preventing it from using all that memory. Specifically it throws when I load the Image to calculate the size of the original. What gives? /// <summary>Creates a thumbnail of a given image.</summary> /// <param name="inFile">Fully qualified path to file to create a thumbnail of</param> /// <param name="outFile">Fully qualified path to created thumbnail</param> /// <param name="x">Width of thumbnail</param> /// <returns>flag; result = is success</returns> public static bool CreateThumbnail(string inFile, string outFile, int x) { // Validation - assume 16x16 icon is smallest useful size. Smaller than that is just not going to do us any good anyway. I consider that an "Exceptional" case. if (string.IsNullOrEmpty(inFile)) throw new ArgumentNullException("inFile"); if (string.IsNullOrEmpty(outFile)) throw new ArgumentNullException("outFile"); if (x < 16) throw new ArgumentOutOfRangeException("x"); if (!File.Exists(inFile)) throw new ArgumentOutOfRangeException("inFile", "File does not exist: " + inFile); // Mathematically determine Y dimension int y; using (Image img = Image.FromFile(inFile)) { // OutOfMemoryException double xyRatio = (double)x / (double)img.Width; y = (int)((double)img.Height * xyRatio); } // All this crap could have easily been Image.Save(filename, x, y)... but nooooo.... using (Bitmap bmp = new Bitmap(inFile)) using (Bitmap thumb = new Bitmap((Image)bmp, new Size(x, y))) using (Graphics g = Graphics.FromImage(thumb)) { g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; System.Drawing.Imaging.ImageCodecInfo codec = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[1]; System.Drawing.Imaging.EncoderParameters ep2 = new System.Drawing.Imaging.EncoderParameters(1); ep2.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L); g.DrawImage(bmp, new Rectangle(0,0,thumb.Width, thumb.Height)); try { thumb.Save(outFile, codec, ep2); return true; } catch { return false; } } }

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  • Binding DynamicObject to a DataGrid with automatic column generation?

    - by SeveQ
    I'm still experimenting with DynamicObjects. Now I need some information: I'm trying to bind an object inheriting from DynamicObject to a WPF DataGrid (not Silverlight). How do I get the DataGrid to automatically create its columns from the available public properties of the object that are typically generated at runtime? Is that possible actually?

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  • Skip makefile dependency generation for certain targets (e.g. `clean`)

    - by Shtééf
    I have several C and C++ projects that all follow a basic structure I've been using for a while now. My source files go in src/*.c, intermediate files in obj/*.[do], and the actual executable in the top level directory. My makefiles follow roughly this template: # The final executable TARGET := something # Source files (without src/) INPUTS := foo.c bar.c baz.c # OBJECTS will contain: obj/foo.o obj/bar.o obj/baz.o OBJECTS := $(INPUTS:%.cpp=obj/%.o) # DEPFILES will contain: obj/foo.d obj/bar.d obj/baz.d DEPFILES := $(OBJECTS:%.o=%.d) all: $(TARGET) obj/%.o: src/%.cpp $(CC) $(CFLAGS) -c -o $@ $< obj/%.d: src/%.cpp $(CC) $(CFLAGS) -M -MF $@ -MT $(@:%.d=%.o) $< $(TARGET): $(OBJECTS) $(LD) $(LDFLAGS) -o $@ $(OBJECTS) .PHONY: clean clean: -rm -f $(OBJECTS) $(DEPFILES) $(RPOFILES) $(TARGET) -include $(DEPFILES) Now I'm at the point where I'm packaging this for a Debian system. I'm using debuild to build the Debian source package, and pbuilder to build the binary package. The debuild step only has to execute the clean target, but even this causes the dependency files to be generated and included. In short, my question is really: Can I somehow prevent make from generating dependencies when all I want is to run the clean target?

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  • How to add page title in url in asp.net mvc? (url generation)

    - by Ante
    How to dynamically create urls/links like: www.restaurant.com/restaurant/restaurant-name-without-some-characters-like-space-coma-etc/132 what are the keywords i can use to google some articles on this topic? (how to genererate and handle this kind of urls inside asp.net mvc) There are some questions: How to generate links? (store slugs in db?) Redirect or not if slug isn't canonical? edit: apparently they are called slugs

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  • Can you change VS Win Forms designer code generation?

    - by Big Endian
    We implemented new standards, which call for our private members to have a leading underscore. Like so: private System.Windows.Forms.Label _label; Unfortunately VS will put out the default below when you drag a new label onto your form: private System.Windows.Forms.Label label1; Is there a way to change that to: private System.Windows.Forms.Label _label1; Cheers, Plamen

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  • How can i automate eclipe plugin update site generation ??

    - by Ibrahim Cakirlar
    Hi, In our project many eclipse plugins are prepared. I want use tycho to build eclipse plugins automatically. But while executing "mvn install" in an update site project tycho can not find required features. Is there anything wrong?? My Update site --- packaging : eclipse-update-site My feature --- packaging : eclipse-feature my plugin --- packaing : eclipse-plugin How can i use tycho to install my plugin and feature in my target platform (eclipse) ??

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  • What are the programming religious wars of the generations before our current generation?

    - by Christopher Altman
    Being 32 years old, I did not follow debates in programming, language design, and platforms in the 1960s, 1970s, 1980s, and most of the 1990s. I sometimes hear glimpse of what the major debates were and how they turned the course of history. It makes me wonder what I take for granted. I am curious, what were the debates. The ones I know are: Procedural vs. Object Orientated Programming Lisp vs. C Software vs. Chips with Embedded Code

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  • Are there any general guidelines for increasing the generation of reports?

    - by David Thielen
    Yes a lot of what you need to do is specific not only to the vendor you use, but also to the specific reports you are creating. However, there are also good general rules that hold for most reports. Vendor Best Practices BIRT Best Practices (more why you need a 3 day class to learn all of them) Crystal Reports Best Practices Microsoft Sql Server Best Practices Oracle B.I. Publisher Best Practices Windward Reports Best Practices General tips on designing a report Note: posted to self answer

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