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Search found 1933 results on 78 pages for 'genetic algorithms'.

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  • Mutation Problem - Clojure

    - by Silanglaya Valerio
    having trouble changing an element of my function represented as a list. code for random function: (defn makerandomtree-10 [pc maxdepth maxwidth fpx ppx] (if-let [output (if (and (< (rand) fpx) (> maxdepth 0)) (let [head (nth operations (rand-int (count operations))) children (doall (loop[function (list) width maxwidth] (if (pos? width) (recur (concat function (list (makerandomtree-10 pc (dec maxdepth) (+ 2 (rand-int (- maxwidth 1))) fpx ppx))) (dec width)) function)))] (concat (list head) children)) (if (and (< (rand) ppx) (>= pc 0)) (nth parameters (rand-int (count parameters))) (rand-int 100)))] output )) I will provide also a mutation function, which is still not good enough. I need to be able to eval my statement, so the following is still insufficient. (defn mutate-5 "chooses a node changes that" [function pc maxwidth pchange] (if (< (rand) pchange) (let [output (makerandomtree-10 pc 3 maxwidth 0.5 0.6)] (if (seq? output) output (list output))) ;mutate the children of root ;declare an empty accumulator list, with root as its head (let [head (list (first function)) children (loop [acc(list) walker (next function)] (println "----------") (println walker) (println "-----ACC-----") (println acc) (if (not walker) acc (if (or (seq? (first function)) (contains? (set operations) (first function))) (recur (concat acc (mutate-5 walker pc maxwidth pchange)) (next walker)) (if (< (rand) pchange) (if (some (set parameters) walker) (recur (concat acc (list (nth parameters (rand-int (count parameters))))) (if (seq? walker) (next walker) nil)) (recur (concat acc (list (rand-int 100))) (if (seq? walker) (next walker) nil))) (recur acc (if (seq? walker) (next walker) nil)))) ))] (concat head (list children))))) (side note: do you have any links/books for learning clojure?)

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  • How does heap compaction work quickly?

    - by Mason Wheeler
    They say that compacting garbage collectors are faster than traditional memory management because they only have to collect live objects, and by rearranging them in memory so everything's in one contiguous block, you end up with no heap fragmentation. But how can that be done quickly? It seems to me that that's equivalent to the bin-packing problem, which is NP-hard and can't be completed in a reasonable amount of time on a large dataset within the current limits of our knowledge about computation. What am I missing?

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  • Looking for evolutionary music example code

    - by Dan Dyer
    I would like to implement an interactive evolutionary algorithm for generating music (probably just simple melodies to start with). I'd like to use JFugue for this. Its website claims that it is well-suited to evolutionary music, but I can't find any evolutionary examples. I already have a framework to provide the evolutonary machinery. What I am looking for is some simple, working code that demonstrates viable approaches for the musical part (e.g. suitable encodings and evolutionary operators for the evolved tunes). I have some ideas how it might be achieved, but I'm not particularly knowledgeable about music theory, so to start with I'd like to just reimplement something that is known to work. So does anybody have, or know of, any freely available code (any language is fine) that demonstrates one or more approaches to evolutionary music? EDIT: I'm specifically looking for evolutionary code rather than other techniques that could be used for music synthesis.

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  • Find unique vertices from a 'triangle-soup'

    - by sum1stolemyname
    I am building a CAD-file converter on top of two libraries (Opencascade and DWF Toolkit). However, my question is plattform agnostic: Given: I have generated a mesh as a list of triangular faces form a model constructed through my application. Each Triangle is defined through three vertexes, which consist of three floats (x, y & z coordinate). Since the triangles form a mesh, most of the vertices are shared by more then one triangle. Goal: I need to find the list of unique vertices, and to generate an array of faces consisting of tuples of three indices in this list. What i want to do is this: //step 1: build a list of unique vertices for each triangle for each vertex in triangle if not vertex in listOfVertices Add vertex to listOfVertices //step 2: build a list of faces for each triangle for each vertex in triangle Get Vertex Index From listOfvertices AddToMap(vertex Index, triangle) While I do have an implementation which does this, step1 (the generation of the list of unique vertices) is really slow in the order of O(n!), since each vertex is compared to all vertices already in the list. I thought "Hey, lets build a hashmap of my vertices' components using std::map, that ought to speed things up!", only to find that generating a unique key from three floating point values is not a trivial task. Here, the experts of stackoverflow come into play: I need some kind of hash-function which works on 3 floats, or any other function generating a unique value from a 3d-vertex position.

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  • C++ find method is not const?

    - by Rachel
    I've written a method that I'd like to declare as const, but the compiler complains. I traced through and found that this part of the method was causing the difficulty: bool ClassA::MethodA(int x) { bool y = false; if(find(myList.begin(), myList.end(), x) != myList.end()) { y = true; } return y; } There is more happening in the method than that, but with everything else stripped away, this was the part that didn't allow the method to be const. Why does the stl find algorithm prevent the method from being const? Does it change the list in any way?

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  • Machine Learning Algorithm for Predicting Order of Events?

    - by user213060
    Simple machine learning question. Probably numerous ways to solve this: There is an infinite stream of 4 possible events: 'event_1', 'event_2', 'event_4', 'event_4' The events do not come in in completely random order. We will assume that there are some complex patterns to the order that most events come in, and the rest of the events are just random. We do not know the patterns ahead of time though. After each event is received, I want to predict what the next event will be based on the order that events have come in in the past. The predictor will then be told what the next event actually was: Predictor=new_predictor() prev_event=False while True: event=get_event() if prev_event is not False: Predictor.last_event_was(prev_event) predicted_event=Predictor.predict_next_event(event) The question arises of how long of a history that the predictor should maintain, since maintaining infinite history will not be possible. I'll leave this up to you to answer. The answer can't be infinte though for practicality. So I believe that the predictions will have to be done with some kind of rolling history. Adding a new event and expiring an old event should therefore be rather efficient, and not require rebuilding the entire predictor model, for example. Specific code, instead of research papers, would add for me immense value to your responses. Python or C libraries are nice, but anything will do. Thanks! Update: And what if more than one event can happen simultaneously on each round. Does that change the solution?

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  • Algorithm on trajectory analysis.

    - by Arman
    Hello, I would like to analyse the trajectory data based on given templates. I need to stack the similar trajectories together. The data is a set of coordinates xy,xy,xy and the templates are again the lines defined by the set of control points. I don't know to what direction to go, maybe to Neural Networks or pattern recognition? Could you please advace me page, book or library to start with? kind regards Arman. PS. Is it the right place to ask the question?

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  • "Undefined symbols" linker error with simple template class

    - by intregus
    Been away from C++ for a few years and am getting a linker error from the following code: Gene.h #ifndef GENE_H_INCLUDED #define GENE_H_INCLUDED template <typename T> class Gene { public: T getValue(); void setValue(T value); void setRange(T min, T max); private: T value; T minValue; T maxValue; }; #endif // GENE_H_INCLUDED Gene.cpp #include "Gene.h" template <typename T> T Gene<T>::getValue() { return this->value; } template <typename T> void Gene<T>::setValue(T value) { if(value >= this->minValue && value <= this->minValue) { this->value = value; } } template <typename T> void Gene<T>::setRange(T min, T max) { this->minValue = min; this->maxValue = max; } Using Code::Blocks and GCC if it matters to anyone. Also, clearly porting some GA stuff to C++ for fun and practice.

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  • little oh notation as the limit of n goes to infinity

    - by Tony
    Hi all, I'm just trying to understand how in little o notation this is true: f(n)/g(n) as n goes to infinity = infinity? Can someone explain that to me? I do get the idea that f(n) = o(g(n)) means that f(n) grows no faster then cg(n) for all constants c 0. I just don't get the bit in bold above.

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  • Provable planarity of flowcharts

    - by Nikolaos Kavvadias
    Hi all I have a question: is there any reference (e.g. paper) with a proof of the planarity of flowchart layouts? Can anyone suggest an algorithm for generating flowchart (planar) layouts? I know that there are some code-to-flowchart tools out there, but i'm unaware of their internals. Thanks in advance -kavi

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  • What is the name of this geometrical function?

    - by Spike
    In a two dimentional integer space, you have two points, A and B. This function returns an enumeration of the points in the quadrilateral subset bounded by A and B. A = {1,1} B = {2,3} Fn(A,B) = {{1,1},{1,2},{1,3},{2,1},{2,2},{2,3}} I can implement it in a few lines of LINQ. private void UnknownFunction(Point to, Point from, List<Point> list) { var vectorX = Enumerable.Range(Math.Min(to.X, from.X), Math.Abs(to.X - from.Y) + 1); var vectorY = Enumerable.Range(Math.Min(to.Y, from.Y), Math.Abs(to.Y - from.Y) + 1); foreach (var x in vectorX) foreach (var y in vectorY) list.Add(new Point(x, y)); } I'm fairly sure that this is a standard mathematical operation, but I can't think what it is. Feel free to tell me that it's one line of code in your language of choice. Or to give me a cunning implementation with lambdas or some such. But mostly I just want to know what it's called. It's driving me nuts. It feels a little like a convolution, but it's been too long since I was at school for me to be sure.

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  • binary search and trio

    - by user121196
    given a large list of alphabetically sorted words in a file,I need to write a program that, given a word x, determines if x is in the list. priorties: 1. speed. 2. memory I already know I can use (n is number of words, m is average length of the words) 1. a tri, time is O(log(n)), space(best case) is O(log(n*m)), space(worst case) is O(n*m). 2. load the complete list into memory, then binary search, time is O(log(n)), space is O(n*m) I'm not sure about the complexity on tri, please correct me if they are wrong. Also are there other good approaches?

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  • Merge overlapping triangles into a polygon

    - by nornagon
    I've got a bunch of overlapping triangles from a 3D model projected into a 2D plane. I need to merge each island of touching triangles into a closed, non-convex polygon. The resultant polygons shouldn't have any holes in them (since the source data doesn't). Many of the source triangles share (floating point identical) edges with other triangles in the source data. What's the easiest way to do this? Performance isn't particularly important, since this will be done at design time.

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  • Combinatorial optimisation of a distance metric

    - by Jose
    I have a set of trajectories, made up of points along the trajectory, and with the coordinates associated with each point. I store these in a 3d array ( trajectory, point, param). I want to find the set of r trajectories that have the maximum accumulated distance between the possible pairwise combinations of these trajectories. My first attempt, which I think is working looks like this: max_dist = 0 for h in itertools.combinations ( xrange(num_traj), r): for (m,l) in itertools.combinations (h, 2): accum = 0. for ( i, j ) in itertools.izip ( range(k), range(k) ): A = [ (my_mat[m, i, z] - my_mat[l, j, z])**2 \ for z in xrange(k) ] A = numpy.array( numpy.sqrt (A) ).sum() accum += A if max_dist < accum: selected_trajectories = h This takes forever, as num_traj can be around 500-1000, and r can be around 5-20. k is arbitrary, but can typically be up to 50. Trying to be super-clever, I have put everything into two nested list comprehensions, making heavy use of itertools: chunk = [[ numpy.sqrt((my_mat[m, i, :] - my_mat[l, j, :])**2).sum() \ for ((m,l),i,j) in \ itertools.product ( itertools.combinations(h,2), range(k), range(k)) ]\ for h in itertools.combinations(range(num_traj), r) ] Apart from being quite unreadable (!!!), it is also taking a long time. Can anyone suggest any ways to improve on this?

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  • delete item from array

    - by davit-datuashvili
    hello can anybody tell me what is wrong here? i want delete item from array but it shows me error ArrayIndexOutBound exception public class delete{ public static void main(String[]args){ int i; //delete item from array int k[]=new int[]{77,99,44,11,00,55,66,33,10}; //delete 55 int searchkey=55; int nums=k.length; for ( i=0;i<nums;i++) if (k[i]==searchkey) break; for (int t=i;t<nums;t++) k[t]=k[t+1]; nums--; for (int m=0;m<nums;m++){ System.out.println(k[m]); } } }

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  • An Efficient data structure for Sorted List

    - by holydiver
    I want to save my objects according to a key in the attributes of my object in a sorted fashion. Later on I'll access these objects sequentially from max key to min key. I'll do some search tasks as well. I consider to use either AVL tree or RB Tree. As far as i know they are nearly equivalent in theory(Both have O(logn)). But in practice which one might be better in performance in my situation. And is there a better alternative than those, considering that I'll mostly do insert and sequentially access to the ds.

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  • Python: Get items at depth? (set library?)

    - by Mark
    I have a nested list something like this: PLACES = ( ('CA', 'Canada', ( ('AB', 'Alberta'), ('BC', 'British Columbia' ( ('van', 'Vancouver'), ), ... )), ('US', 'United States', ( ('AL', 'Alabama'), ('AK', 'Alaska'), ... I need to retrieve some data out of it. If depth is 0 I need to retrieve all the countries (and their codes), if depth == 1, I need to retrieve all the states/provinces, if depth == 2 I need to retrieve all the cities... and so forth. Is there some set library for doing stuff like this? Or can someone point me in the right direction? I started coding up a solution only to realize it wouldn't work for levels deeper than 1 because you have to go in and out of each list...

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  • When can a freely moving sphere escape from a ‘cage’ defined by a set of impassible coordinates?

    - by RGrey
    Hopefully there are some computational geometry folks here who can help me out with the following problem - Please imagine that I take a freely moving ball in 3-space and create a 'cage' around it by defining a set of impassible coordinates, Sc (i.e. points in 3-space that no part of the diffusing ball is allowed to overlap). These points reside within the volume, V(cage), of some larger sphere, where V(cage) V(ball). Provided the set of impassible coordinates, Sc, is there a computationally efficient and/or nice way to determine if the ball can ever escape the cage?

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  • Detect winning game in nought and crosses

    - by Dennis
    I need to know the best way to detect a winning move in a game of noughts and crosses. Source code doesn't matter, I just need a example or something I can start with. The only thing I can come up with is to use loops and test every direction for every move a player makes, to search for e.g five in a row. Is there a faster and more efficient way?

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  • Reverse Bredth First Search in C#

    - by Ngu Soon Hui
    Anyone has a ready implementation of the Reverse Bredth First Search algorithm in C#? By Reverse Bredth First Search, I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node. Let's see the below figure, this is the output of a Bredth First Search: In my reverse bredth first search, 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found. Any ideas or pointers?

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  • Replacing multiple patterns in a block of data

    - by VikrantY
    Hi All, I need to find the most efficient way of matching multiple regular expressions on a single block of text. To give an example of what I need, consider a block of text: "Hello World what a beautiful day" I want to replace Hello with "Bye" and "World" with Universe. I can always do this in a loop ofcourse, using something like String.replace functions availiable in various languages. However, I could have a huge block of text with multiple string patterns, that I need to match and replace. I was wondering if I can use Regular Expressions to do this efficiently or do I have to use a Parser like LALR. I need to do this in JavaScript, so if anyone knows tools that can get it done, it would be appreciated.

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  • Reverse Breath First Search in C#

    - by Ngu Soon Hui
    Anyone has a ready implementation of the Reverse Breath First Search algorithm in C#? By Reverse Breath First Search, I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node. Let's see the below figure, this is the output of a Breath First Search: In my reverse breath first search, 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found. Any ideas or pointers?

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