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  • graphics programming

    - by PVB
    hi , i would like to program some graphic figures such as line, circle,etc. i have used turboc++ 3.0 for dos graphics. i would like to do the same with the compilers dev c++ or code blocks or vc++. i would like to implement dda and bresenhems line and circle drawing algorithm. how should i go about implementing these programs through these compilers (not the command line tools). i have a really vague picture of graphics programming.please help.. thanks in advance. please note : i have a nvidia graphics card 1gb.. so i cannot use dos graphics (i think the card is the reason).

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  • djb2 Hash Function

    - by Jainish
    I am using the djb2 algorithm to generate the hash key for a string which is as follows hash(unsigned char *str) { unsigned long hash = 5381; int c; while (c = *str++) hash = ((hash << 5) + hash) + c; /* hash * 33 + c */ return hash; } Now with every loop there is a multiplication with two big numbers, After some time with the 4th of 5th character of the string there is a overflow as the hash value becomes huge What is the correct way to refactor so that the hash value does not overflow and the hashing also happens correctly

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  • Metalanguage like BNF or XML-Schema to validate a tree-instance against a tree-model

    - by Stefan
    Hi! I'm implementing a new machine learning algorithm in Java that extracts a prototype datastructure from a set of structured datasets (tree-structure). As im developing a generic library for that purpose, i kept my design independent from concrete data-representations like XML. My problem now is that I need a way to define a data model, which is basically a ruleset describing valid trees, against which a set of trees is being matched. I thought of using BNF or a similar dialect. Basically I need a way to iterate through the space of all valid TreeNodes defined by the ModelTree (Like a search through the search space for algorithms like A*) so that i can compare my set of concrete trees with the model. I know that I'll have to deal with infinite spaces there but first things first. I know, it's rather tricky (and my sentences are pretty bumpy) but I would appreciate any clues. Thanks in advance, Stefan

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  • Linear Regression and Java Dates

    - by Smithers
    I am trying to find the linear trend line for a set of data. The set contains pairs of dates (x values) and scores (y values). I am using a version of this code as the basis of my algorithm. The results I am getting are off by a few orders of magnitude. I assume that there is some problem with round off error or overflow because I am using Date's getTime method which gives you a huge number of milliseconds. Does anyone have a suggestion on how to minimize the errors and compute the correct results?

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  • CUDA: accumulate data into a large histogram of floats

    - by shoosh
    I'm trying to think of a way to implement the following algorithm using CUDA: Working on a large volume of voxels, for each voxel I calculate an index i and a value c. after the calculation I need to perform histogram[i] += c c is a float value and the histogram can have up to 15,000 bins. I'm looking for a way to implement this efficiently using CUDA. The first obvious problem is that with compute capabilities 1.3 which is what I'm using I can't even do an atomicAdd() of floats so how can I accumulate anything reliably? This example by nVidia does something somewhat simpler. The histograms are saved in the shared memory (which I can't do due to its size) and it only accumulates integers. Can this approach be generalized to my case?

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  • PHP mcrypt usage class?

    - by kavoir.com
    I'm pretty new at this. Tried to make sense of the manual page for mcrypt at PHP.net when I thought a good tutorial would do a better job. So I searched yet without anything substantial. I also tried one of the examples of using mcrypt to perform the encryption and decryption with 2 functions, but it gives a warning of "Size of key is too large for this algorithm". Can anyone please write me a two-way class to do the encryption / decryption using mcrypt so I can make sense of the library? Thanks!

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  • Implementation of ECC in Java

    - by Rookie_22
    While trying to encrypt a given input using Elliptic Curve Cryptography in Java I'm using the following algorithms for generating the cipher and the key: KeyPairGenerator g = KeyPairGenerator.getInstance("ECDSA"); Cipher cipher = Cipher.getInstance("ECIES"); Now as expected, the cipher isn't accepting the keys generated by the ECDSA algorithm. I get the error as - must be passed IE key. I searched for the ciphers being supported by these 2 methods here: http://java.sun.com/javase/6/docs/technotes/guides/security/StandardNames.html#Cipher Unfortunately no else algo is supported for ECC. Has anyone used ECC generated keys to encrypt/decrypt an input? Which algo should I use for both so that they don't clash with each other?

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  • Is it possible to find the KNN for a node that is *IN* the KD-tree?

    - by Stephen
    Hi there, Trying to create a KNN search using a KD-tree. I can form the KD-tree fine (or at least, I believe I can!). My problem is that I am searching to find the closest 2 neighbours to every point in a list of points. So, is there a method to find the K nearest neighbours to a point using a KD tree even if the point is actually IN the tree, or do I need to construct a seperate KD tree for each point, leaving out the point that I wish to search for? My implementation language is C++, but I am more looking for either an algorithm or general help, thanks! Thanks, Stephen

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  • image focus calculation

    - by Oren Mazor
    Hi folks, I'm trying to develop an image focusing algorithm for some test automation work. I've chosen to use AForge.net, since it seems like a nice mature .net friendly system. Unfortunately, I can't seem to find information on building autofocus algorithms from scratch, so I've given it my best try: take image. apply sobel edge detection filter, which generates a greyscale edge outline. generate a histogram and save the standard dev. move camera one step closer to subject and take another picture. if the standard dev is smaller than previous one, we're getting more in focus. otherwise, we've past the optimal distance to be taking pictures. is there a better way? update: HUGE flaw in this, by the way. as I get past the optimal focus point, my "image in focus" value continues growing. you'd expect a parabolic-ish function looking at distance/focus-value, but in reality you get something that's more logarithmic

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  • Robotics Simulator

    - by Arkapravo
    Which is the best robotics simulator ? Player Project (simulator + control interface) Microsoft Robotics Studio (simulator + control interface) KiKS (in Matlab, only for Khepera) MobotSim (for point like robots ) ROS (I have only heard about it) URBI (also, only heard about it) Any other As of now, I am just looking to get simple simulations of Potential Field method, Bug Algorithms, A* Algorithm etc ! This article gives a number of such softwares etc, however I was looking for a first hand view from fellow stackoverflowers. Anyone who has worked with any other software etc is most welcome to share his/her experience !

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  • async handler deleted by the wrong thread in django

    - by user3480706
    I'm run this algorithm in my django application.when i run several time from my GUI django local server will stopped and i got this error Exception RuntimeError: RuntimeError('main thread is not in main loop',) in ignored Tcl_AsyncDelete: async handler deleted by the wrong thread Aborted (core dumped) code print "Learning the sin function" network =MLP.MLP(2,10,1) samples = np.zeros(2000, dtype=[('x', float, 1), ('y', float, 1)]) samples['x'] = np.linspace(-5,5,2000) samples['y'] = np.sin(samples['x']) #samples['y'] = np.linspace(-4,4,2500) for i in range(100000): n = np.random.randint(samples.size) network.propagate_forward(samples['x'][n]) network.propagate_backward(samples['y'][n]) plt.figure(figsize=(10,5)) # Draw real function x = samples['x'] y = samples['y'] #x=np.linspace(-6.0,7.0,50) plt.plot(x,y,color='b',lw=1) samples1 = np.zeros(2000, dtype=[('x1', float, 1), ('y1', float, 1)]) samples1['x1'] = np.linspace(-4,4,2000) samples1['y1'] = np.sin(samples1['x1']) # Draw network approximated function for i in range(samples1.size): samples1['y1'][i] = network.propagate_forward(samples1['x1'][i]) plt.plot(samples1['x1'],samples1['y1'],color='r',lw=3) plt.axis([-2,2,-2,2]) plt.show() plt.close() return HttpResponseRedirect('/charts/charts') how can i fix this error ?need a quick help

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  • Recompile a x86 code with LLVM to some faster one x86

    - by osgx
    Hello Is it possible to run LLVM compiler with input of x86 32bit code? There is a huge algorithm which I have no source code and I want to make it run faster on the same hardware. Can I translate it from x86 back to x86 with optimizations. This Code runs a long time, so I want to do static recompilation of it. Also, I can do a runtime profile of it and give to LLVM hints, which branches are more probable. The original Code is written for x86, and uses no SSE/MMX/SSE2. After recompilation It has a chances to use x86_64 and/or SSE3. Also, The code will be regenerated in more optimal way to hardware decoder. Thanks.

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  • What is the relaxation condition in graph theory

    - by windopal
    Hi, I'm trying to understand the main concepts of graph theory and the algorithms within it. Most algorithms seem to contain a "Relaxation Condition" I'm unsure about what this is. Could some one explain it to me please. An example of this is dijkstras algorithm, here is the pseudo-code. 1 function Dijkstra(Graph, source): 2 for each vertex v in Graph: // Initializations 3 dist[v] := infinity // Unknown distance function from source to v 4 previous[v] := undefined // Previous node in optimal path from source 5 dist[source] := 0 // Distance from source to source 6 Q := the set of all nodes in Graph // All nodes in the graph are unoptimized - thus are in Q 7 while Q is not empty: // The main loop 8 u := vertex in Q with smallest dist[] 9 if dist[u] = infinity: 10 break // all remaining vertices are inaccessible from source 11 remove u from Q 12 for each neighbor v of u: // where v has not yet been removed from Q. 13 alt := dist[u] + dist_between(u, v) 14 if alt < dist[v]: // Relax (u,v,a) 15 dist[v] := alt 16 previous[v] := u 17 return dist[] Thanks

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  • retrieve cobol s9(2) COMP onto C variable

    - by Pablo Cazallas
    Hi, I need to retrieve data from a COBOL variable of the type: "PIC S9(2) COMP" onto a C variable of the type "int". It's stored using two bytes of a string, so I receive it as a couple of chars. I know COBOL stores decimal data onto a "S9(2) COMP" in binary format, so It would be a great help letting me know any algorithm or way to convert it safely. Any kind of help & suggestion will be welcome. Thanks in advance and regards, Pablo.

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  • For a primary key of an integral type, why is it important to avoid gaps ?

    - by Jacques René Mesrine
    I am generating a surrogate key for a table & due to my hi/lo algorithm, everytime you reboot/restart the machine, gaps may appear. T1: current hi = 10000000 (sequence being dished out .. 1 to 100) Assume that current sequence is 10000050 T2: restart system. T3: System gives out the next_hi as 10000100 (sequence being dished out now ranges from 101 to 200) T4: Next request for a key returns 100001001 From a primary key or indexing internals perspective, why is it important that there be no gaps in the sequences ? I'm asking this for a deeper understanding of mysql specifically. Thanks

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  • Distance by sea calculator, intermediate coordinates?

    - by Lucian2k
    How do I calculate distance between 2 coordinates by sea? I also want to be able to draw a route between the two coordinates. Only solution I found so far is to split a map into pixels, identify each pixel as LAND or SEA and then try to find the path using A* algorithm. Then transform pixels to relative coordinates. There are some software packages I could buy but none have online extensions. A service that calculates distances between sea ports and plots the path on a map is searates.com

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  • Java - sorted stack

    - by msr
    Hello, I need a sorted stack. I mean, the element removed from the stack must be the one with great priority. Stack dimension varies a lot (becomes bigger very fast). I need also to search elements in that stack. Does Java give some good implementation for this? What class or algorithm do you suggest for this? I'm using a PriorityQueue right now which I consider reasonable except for searching, so Im wondering if I can use something better. Thanks in advance!

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  • Using a priority queue in Java

    - by Bharat
    Forgive me if this is a tried question, but I'm having a little difficulty figuring it out. I currently have a class Node, and each 'node' is a square in a maze. I'm trying to implement the A* algorithm, so each of these nodes will have an f-cost (int) data member inside of it. I was wondering if there's a way that I can create a priority queue of these nodes, and set up the f-cost variable as the comparator? I've looked at examples online, but all I can find are String priority queues. Can I implement Comparator for the Node class? Would this allow me to access the data member stored inside it? Many Thanks!

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  • Extracting pure content / text from HTML Pages by excluding navigation and chrome content

    - by Ankur Gupta
    Hi, I am crawling news websites and want to extract News Title, News Abstract (First Paragraph), etc I plugged into the webkit parser code to easily navigate webpage as a tree. To eliminate navigation and other non news content I take the text version of the article (minus the html tags, webkit provides api for the same). Then I run the diff algorithm comparing various article's text from same website this results in similar text being eliminated. This gives me content minus the common navigation content etc. Despite the above approach I am still getting quite some junk in my final text. This results in incorrect News Abstract being extracted. The error rate is 5 in 10 article i.e. 50%. Error as in Can you Suggest an alternative strategy for extraction of pure content, Would/Can learning Natural Language rocessing help in extracting correct abstract from these articles ? How would you approach the above problem ?. Are these any research papers on the same ?. Regards Ankur Gupta

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  • Java Generics Type Safety warning with recursive Hashmap

    - by GC
    Hi, I'm using a recursive tree of hashmaps, specifically Hashmap map where Object is a reference to another Hashmap and so on. This will be passed around a recursive algorithm: foo(String filename, Hashmap<String, Object> map) { //some stuff here for (Entry<String, Object> entry : map.entrySet()) { //type warning that must be suppressed foo(entry.getKey(), (HashMap<String, Object>)entry.getValue()); } } I know for sure Object is of type Hashmap<String, Object> but am irritated that I have to suppress the warning using @SuppressWarnings("unchecked"). I'll be satisfied with a solution that does either a assert(/*entry.getValue() is of type HashMap<String, Object>*/) or throws an exception when it isn't. I went down the Generics route for compile type safety and if I suppress the warning then it defeats the purpose. Thank you for your comments, ksb

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  • Compute average distance from point to line segment and line segment to line segment

    - by Fred
    Hi everyone, I'm searching for an algorithm to calculate the average distance between a point and a line segment in 3D. So given two points A(x1, y1, z1) and B(x2, y2, z2) that represent line segment AB, and a third point C(x3, y3, z3), what is the average distance between each point on AB to point C? I'm also interested in the average distance between two line segments. So given segment AB and CD, what is the average distance from each point on AB to the closest point on CD? I haven't had any luck with the web searches I've tried, so any suggestions would be appreciated. Thanks.

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  • Flash to PHP base64 encode/decode

    - by Gus
    I'm using AS3 to base64 encode a JPG and pass it to Javascript. I'm attempting to use AJAX to pass that base64 encoded string to PHP and have PHP decode it. (I know I could send it back to Flash and Flash could decode it and send it to PHP, but I'm trying to eliminate the need for Flash on the decoding end). It appears that AS3's encodeToBase64String() function and and PHP's base64_decode() function do not use the same algorithm, as PHP evaluates it as a base64 encoded object, but does not seem to output it properly. Is there a way to rectify this problem? Note: Please no posts about not needing Javascript. Javascript is a necessary step for reasons not detailed here.

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  • what is the best way to generate fake data for classification problem ?

    - by Berkay
    i'm working on a project and i have a subset of user's key-stroke time data.This means that the user makes n attempts and i will use these recorded attempt time data in various kinds of classification algorithms for future user attempts to verify that the login process is done by the user or some another person. (Simply i can say that this is biometrics) I have 3 different times of the user login attempt process, ofcourse this is subset of the infinite data. until now it is an easy classification problem, i decided to use WEKA but as far as i understand i have to create some fake data to feed the classification algorithm. can i use some optimization algorithms ? or is there any way to create this fake data to get min false positives ? Thanks

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  • Limit a program's execution time in C (Monte Carlo technique)

    - by rrs90
    I am working on a project which has no determined algorithm to solve using C language. I am Using Monte Carlo technique for solving that problem. And the number of random guesses I want to limit to the execution time specified by the user. This means I want to make full use of the execution time limit defined by the user (as a command line argument) to make as many random iterations as possible. Can I check the execution time elapsed so far for a loop condition. Eg: for(trials=0;execution_time P.S. I am using code blocks 10.05 for coding and GNU compiler.

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  • Polynomial division overloading operator

    - by Vlad
    Ok. here's the operations i successfully code so far thank's to your help: Adittion: polinom operator+(const polinom& P) const { polinom Result; constIter i = poly.begin(), j = P.poly.begin(); while (i != poly.end() && j != P.poly.end()) { //logic while both iterators are valid if (i->pow > j->pow) { //if the current term's degree of the first polynomial is bigger Result.insert(i->coef, i->pow); i++; } else if (j->pow > i->pow) { // if the other polynomial's term degree is bigger Result.insert(j->coef, j->pow); j++; } else { // if both are equal Result.insert(i->coef + j->coef, i->pow); i++; j++; } } //handle the remaining items in each list //note: at least one will be equal to end(), but that loop will simply be skipped while (i != poly.end()) { Result.insert(i->coef, i->pow); ++i; } while (j != P.poly.end()) { Result.insert(j->coef, j->pow); ++j; } return Result; } Subtraction: polinom operator-(const polinom& P) const //fixed prototype re. const-correctness { polinom Result; constIter i = poly.begin(), j = P.poly.begin(); while (i != poly.end() && j != P.poly.end()) { //logic while both iterators are valid if (i->pow > j->pow) { //if the current term's degree of the first polynomial is bigger Result.insert(-(i->coef), i->pow); i++; } else if (j->pow > i->pow) { // if the other polynomial's term degree is bigger Result.insert(-(j->coef), j->pow); j++; } else { // if both are equal Result.insert(i->coef - j->coef, i->pow); i++; j++; } } //handle the remaining items in each list //note: at least one will be equal to end(), but that loop will simply be skipped while (i != poly.end()) { Result.insert(i->coef, i->pow); ++i; } while (j != P.poly.end()) { Result.insert(j->coef, j->pow); ++j; } return Result; } Multiplication: polinom operator*(const polinom& P) const { polinom Result; constIter i, j, lastItem = Result.poly.end(); Iter it1, it2, first, last; 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); } Result.poly.sort(SortDescending()); lastItem--; while (true) { nr_matches = 0; for (it1 = Result.poly.begin(); it1 != lastItem; it1++) { first = it1; last = it1; first++; for (it2 = first; it2 != Result.poly.end(); it2++) { if (it2->pow == it1->pow) { it1->coef += it2->coef; nr_matches++; } } nr_matches++; do { last++; nr_matches--; } while (nr_matches != 0); Result.poly.erase(first, last); } if (nr_matches == 0) break; } return Result; } Division(Edited): polinom operator/(const polinom& P) { polinom Result, temp; Iter i = poly.begin(); constIter j = P.poly.begin(); if (poly.size() < 2) { if (i->pow >= j->pow) { Result.insert(i->coef, i->pow - j->pow); *this = *this - Result; } } else { while (true) { if (i->pow >= j->pow) { Result.insert(i->coef, i->pow - j->pow); temp = Result * P; *this = *this - temp; } else break; } } return Result; } The first three are working correctly but division doesn't as it seems the program is in a infinite loop. Update Because no one seems to understand how i thought the algorithm, i'll explain: If the dividend contains only one term, we simply insert the quotient in Result, then we multiply it with the divisor ans subtract it from the first polynomial which stores the remainder. If the polynomial we do this until the second polynomial( P in this case) becomes bigger. I think this algorithm is called long division, isn't it? So based on these, can anyone help me with overloading the / operator correctly for my class? Thanks!

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