Search Results

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

Page 56/78 | < Previous Page | 52 53 54 55 56 57 58 59 60 61 62 63  | Next Page >

• Dynamic programming - Coin change decision problem?

  - by Tony

  I'm reviewing some old notes from my algorithms course and the dynamic programming problems are seeming a bit tricky to me. I have a problem where we have an unlimited supply of coins, with some denominations x1, x2, ... xn and we want to make change for some value X. We are trying to design a dynamic program to decide whether change for X can be made or not (not minimizing the number of coins, or returning which coins, just true or false). I've done some thinking about this problem, and I can see a recursive method of doing this where it's something like... MakeChange(X, x[1..n this is the coins]) for (int i = 1; i < n; i++) { if ( (X - x[i] ==0) || MakeChange(X - x[i]) ) return true; } return false; Converting this a dynamic program is not coming so easily to me. How might I approach this?

  Read the article

• Chaining multiple MapReduce jobs in Hadoop.

  - by Niels Basjes

  In many real-life situations where you apply MapReduce, the final algorithms end up being several MapReduce steps. I.e. Map1 , Reduce1 , Map2 , Reduce2 , etc. So you have the output from the last reduce that is needed as the input for the next map. The intermediate data is something you (in general) do not want to keep once the pipeline has been successfully completed. Also because this intermediate data is in general some data structure (like a 'map' or a 'set') you don't want to put too much effort in writing and reading these key-value pairs. What is the recommended way of doing that in Hadoop? Is there a (simple) example that shows how to handle this intermediate data in the correct way, including the cleanup afterward? Thanks.

  Read the article

• Translation of clustering problem to graph theory language

  - by honk

  I have a rectangular planar grid, with each cell assigned some integer weight. I am looking for an algorithm to identify clusters of 3 to 6 adjacent cells with higher-than-average weight. These blobs should have approximately circular shape. For my case the average weight of the cells not containing a cluster is around 6, and that for cells containing a cluster is around 6+4, i.e. there is a "background weight" somewhere around 6. The weights fluctuate with a Poisson statistic. For small background greedy or seeded algorithms perform pretty well, but this breaks down if my cluster cells have weights close to fluctuations in the background. Also, I cannot do a brute-force search looping through all possible setups because my grid is large (something like 1000x1000). I have the impression there might exist ways to tackle this in graph theory. I heard of vertex-covers and cliques, but am not sure how to best translate my problem into their language.

  Read the article

• I need to choose a compression algorithm

  - by chiz

  I need to choose a compression algorithm to compress some data. I don't know the type of data I'll be compressing in advance (think of it as kinda like the WinRAR program). I've heard of the following algorithms but I don't know which one I should use. Can anyone post a short list of pros and cons? For my application the first priority is decompression speed; the second priority is space saved. Compression (not decompression) speed is irrelevant. Deflate Implode Plain Huffman bzip2 lzma

  Read the article

• What topic in computer science is this?

  - by jasonbogd

  Hi, I am trying to figure out what 'topic' this is called, so I can learn more about it. Basically, I'm talking about designing my applications's architecture. I'm not talking about algorithms. More like -- this class should have these methods and these instance variables, and communicate with this class in this way, this class should have these responsibilities etc. Can anybody tell me what the name of this topic is called and how I can get better at doing this? Thanks.

  Read the article

• Big 0 theta notation

  - by niggersak

  Can some pls help with the solution Use big-O notation to classify the traditional grade school algorithms for addition and multiplication. That is, if asked to add two numbers each having N digits, how many individual additions must be performed? If asked to multiply two N-digit numbers, how many individual multiplications are required? Suppose f is a function that returns the result of reversing the string of symbols given as its input, and g is a function that returns the concatenation of the two strings given as its input. If x is the string hrwa, what is returned by g(f(x),x)? Explain your answer - don't just provide the result!

  Read the article

• NLP - Word Alignment

  - by mgj

  Hi..:) I am looking for word alignment tools and algorithms, I am dealing with bilingual English - Hindi text, Currently I am working on DTW(Dynamic Time Warping) algorithm, CLA(Competitive Linking Algorithm) , NATool, Giza++. Could you please suggest me any other alogrithm/tool which is language independent which could achieve Statistical word alignment for parallel English Hindi Corpora and its Evaluation, some tools languages are best for certain languages.. Could one please tell me how true is that and if so could you please give me an example what would suite better for Asian languages like Hindi and what shouldn't I use for such languages. I have heard a bit about uplug word aligner.. could one tell me if I could use it as a tool for my purpose. Thank you.. :)

  Read the article

• How do I determine a best-fit distribution in java?

  - by Eadwacer

  I have a bunch of sets of data (between 50 to 500 points, each of which can take a positive integral value) and need to determine which distribution best describes them. I have done this manually for several of them, but need to automate this going forward. Some of the sets are completely modal (every datum has the value of 15), some are strongly modal or bimodal, some are bell-curves (often skewed and with differing degrees of kertosis/pointiness), some are roughly flat, and there are any number of other possible distributions (possion, power-law, etc.). I need a way to determine which distribution best describes the data and (ideally) also provides me with a fitness metric so that I know how confident I am in the analysis. Existing open-source libraries would be ideal, followed by well documented algorithms that I can implement myself.

  Read the article

• Using Nearest Neighbour Algorithm for image pattern recognition

  - by user293895

  So I want to be able to recognise patterns in images (such as a number 4), I have been reading about different algorithms and I would really like to use the Nearest Neighbour algorithm, it looks simple and I do understand it based on this tutorial: http://people.revoledu.com/kardi/tutorial/KNN/KNN_Numerical-example.html Problem is, although I understand how to use it to fill in missing data sets, I don't understand how I could use it as a pattern recognition tool to aim in Image Shape Recognition. Could someone please shed some light as to how this algorithm could work for pattern recognition? I have seen tutorials using OpenCV, however I don't really want to use this library as I have the ability to do the pre-processing myself, and it seems silly that I would implement this library just for what should be a simple nearest neighbour algorithm.

  Read the article

• 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

  Read the article

• 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?

  Read the article

• 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

  Read the article

• 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 !

  Read the article

• Image scaling in C

  - by Ganesh

  Hi, I am designing a jpeg to bmp decoder which scales the image. I have been supplied with the source code for the decoder so my actual work is to design a scaler . I do not know where to begin. I have scouted the internet for the various scaling algorithms but am not sure where to introduce the scaling. So should I do the the scaling after the image is converted into bmp or should I do this during the decoding at the MCU level. am confused :( If you guys have some information to help me out, its appreciated. any material to read, source code to analyse etc....

  Read the article

• How to specify behavior of Java BufferedImage resize: need min for pixel rows instead of averaging

  - by tucuxi

  I would like to resize a Java BufferedImage, making it smaller vertically but without using any type of averaging, so that if a pixel-row is "blank" (white) in the source image, there will be a white pixel-row in the corresponding position of the destination image: the "min" operation. The default algorithms (specified in getScaledInstance) do not allow me a fine-grained enough control. I would like to implement the following logic: for each pixel row in the w-pixels wide destination image, d = pixel[w] find the corresponding j pixel rows of the source image, s[][] = pixel[j][w] write the new line of pixels, so that d[i] = min(s[j][i]) over all j, i I have been reading on RescaleOp, but have not figured out how to implement this functionality -- it is admittedly a weird type of scaling. Can anyone provide me pointers on how to do this? In the worse case, I figure I can just reserve the destination ImageBuffer and copy the pixels following the pseudocode, but I was wondering if there is better way.

  Read the article

• Datamining on a mysql database

  - by sliptix

  Hello, I Begin with textmining. I have two database tables with thousands of data.. a table for "skills" and a table for "skills categories" every "skill" belongs to a skills categorie. a "skill" is , physicaly, a varchar(200) field in the database, where there is some text describing the skill. Here are some skills extracted from the skills table: "PHP (good level), Java (intermediaite), C++" "PHP5" "project management and quality management" "begining Javascript" "water engineering" "dfsdf zerze rzer" "cibling customers" what i want to do is to extract knowledge from those fields, i mean extract only the real skill and ignore the rest of useless text. for the above example i want to get only an array with: "PHP" "Java" "C++" "PHP5" "project management" "quality management" "Javascript" "water engineering" "cibling customers" what should i do to extract the skills from tons of data please ? do you know specific algorithms to do this ? ex : k-means ... ? Thanks in advance.

  Read the article

• Calculating determinant by hand

  - by ldigas

  Okey, this is only half programming, but let's see how you are on terms with manual calculations. I believe many of you did this on your university's while giving "linear systems" ... the problem is it's been so long I can't remember how to do it any more. I know quite a few algorithms for calculating determinants, and they all work fine ... for large systems, where one would never try to do it manually. Unfortunatelly, I'm soon going on an exam, where I do have to calculate it manually, up to the system of 5. So, I have a K(omega) matrix that looks like this: [2-(omega^2)*c -4 2 0 0] [-2 5-(omega^2)*c -4 1 0] [1 -4 6-(omega^2)*c -4 1] [0 1 -4 5-(omega^2)*c -2] [0 0 2 -4 2-(omega^2)*c] and I need all the omegas which satisfy the det[K(omega)]=0 criteria. What would be a good way to calculate it so it can be repeated in a manual process ?

  Read the article

• Java Concurrency: CAS vs Locking

  - by Hugo Walker

  Im currently reading the Book Java Concurrency in Practice. In the Chapter 15 they are speaking about the Nonblocking algorithms and the compare-and-swap (CAS) Method. It is written that the CAS perform much better than the Locking Methods. I want to ask the people which already worked with both of this concepts and would like to hear when you are preferring which of these concept? Is it really so much faster? Personally for me the usage of Locks is much clearer and easier to understand and maybe even better to maintain. (Please correct me if I am wrong). Should we really focus creating our concurrent code related on CAS than Locks to get a better performance boost or is sustainability a higher thing? I know there is maybe not a strict rule, when to use what. But I just would like to hear some opinions, experiences with the new concept of CAS.

  Read the article

• How to generate a unique hash for a URL ?

  - by Jacques René Mesrine

  Given these two images from twitter. http://a3.twimg.com/profile_images/130500759/lowres_profilepic.jpg http://a1.twimg.com/profile_images/58079916/lowres_profilepic.jpg I want to download them to local filesystem & store them in a single directory. How shall I overcome name conflicts ? In the example above, I cannot store them as *lowres_profilepic.jpg*. My design idea is treat the URLs as opaque strings except for the last segment. What algorithms (implemented as f) can I use to hash the prefixes into unique strings. f( "http://a3.twimg.com/profile_images/130500759/" ) = 6tgjsdjfjdhgf f( "http://a1.twimg.com/profile_images/58079916/" ) = iuhd87ysdfhdk That way, I can save the files as:- 6tgjsdjfjdhgf_lowres_profilepic.jpg iuhd87ysdfhdk_lowres_profilepic.jpg I don't want a cryptographic algorithm as it this needs to be a performant operation.

  Read the article

• Storing and comparing biometric information

  - by Chathuranga Chandrasekara

  I am not sure whether this is the best place to post this. But this is strongly related with programming so decided to put this here. In general we use biometrics in computer applications say for authentication. Lets get 2 examples finger prints and facial recognition. In those cases how we keep the information for comparison. As an example we can't keep a image and process it every time. So what are the methodologies we use to store/determine the similarity in such cases? Are there any special algorithms that designed for that purposes.? (Ex : To return a approximately equal value for a finger print of a certain person every time)

  Read the article

• which is best algorithm?

  - by Lopa

  Consider two algorithms A and B which solve the same problem, and have time complexities (in terms of the number of elementary operations they perform) given respectively by a(n) = 9n+6 b(n) = 2(n^2)+1 (i) Which algorithm is the best asymptotically? (ii) Which is the best for small input sizes n, and for what values of n is this the case? (You may assume where necessary that n0.) i think its 9n+6. guys could you please help me with whether its right or wrong?? and whats the answer for part b. what exactly do they want?

  Read the article

• Efficient algorithm for finding largest eigenpair of small general complex matrix

  - by mklassen

  I am looking for an efficient algorithm to find the largest eigenpair of a small, general (non-square, non-sparse, non-symmetric), complex matrix, A, of size m x n. By small I mean m and n is typically between 4 and 64 and usually around 16, but with m not equal to n. This problem is straight forward to solve with the general LAPACK SVD algorithms, i.e. gesvd or gesdd. However, as I am solving millions of these problems and only require the largest eigenpair, I am looking for a more efficient algorithm. Additionally, in my application the eigenvectors will generally be similar for all cases. This lead me to investigate Arnoldi iteration based methods, but I have neither found a good library nor algorithm that applies to my small general complex matrix. Is there an appropriate algorithm and/or library?

  Read the article

• Resources to learn sh scripting 'just like a normal programming language'

  - by Homer J. Simpson

  Hi, what is the best resource (book would be nice) to learn sh scripting (the "standard" shell on Unix systems) just like when i would learn a "normal" programming/scripting language ? There are lots of tutorials on certain aspects of shell scripting, they mostly deal with shells in general and unix commands and so on, but i would rather like to find a more general approach - meaning a quick syntactic overview and an outlook on how to do things you normally do when programming, like implementing small algorithms and so on. Doing actual scripting, not just a structured batch file. And rather 100-liners than 1-to-3-liners. Can you recommend a good standard book on the topic ?

  Read the article

• Fuzzy Regular Expressions

  - by Thomas Ahle

  In my work I have with great results used approximate string matching algorithms such as Damerau–Levenshtein distance to make my code less vulnerable to spelling mistakes. Now I have a need to match strings against simple regular expressions such TV Schedule for \d\d (Jan|Feb|Mar|...). This means that the string TV Schedule for 10 Jan should return 0 while T Schedule for 10. Jan should return 2. This could be done by generating all strings in the regex (in this case 100x12) and find the best match, but that doesn't seam practical. Do you have any ideas how to do this effectively?

  Read the article

• Red-Black trees - Erasing a node with two non-leaf children

  - by SalamiArmi

  Hi all, I've been implementing my own version of a red-black tree, mostly basing my algorithms from Wikipedia (http://en.wikipedia.org/wiki/Red-black_tree). Its fairly concise for the most part, but there's one part that I would like clarification on. When erasing a node from the tree that has 2 non-leaf (non-NULL) children, it says to move either side's children into the deletable node, and remove that child. I'm a little confused as to which side to remove from, based on that. Do I pick the side randomly, do I alternate betweek sides, or do I stick to the same side for every future deletion?

  Read the article

< Previous Page | 52 53 54 55 56 57 58 59 60 61 62 63  | Next Page >