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• Static Evaluation Function for Checkers

  - by Kamikaze

  Hi all! I'm trying to write an evaluation function for a game of checkers that I'm developing but I can't find the right documentation. I've read several documents on the web witch describe different techniques for either writing one or letting the computer find it(using genetic algorithms or Bayesian learning) but they're too complicated for a novice like me. All documents pointed a reference to "Some studies in machine learning using the game of checkers" by A.L.Samuel but I couldn't get my hands on it yet :(. I've only read the follow up "Some studies in machine learning using the game of checkers -II" and found some good info there, but it doesn't explain what the eval parameters mean (I think I don't have the whole article). Thanks for your help!

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• Sudoku solver evaluation function

  - by Rich

  Hi, So I'm trying to write a simple genetic algorithm for solving a sudoku (not the most efficient way, I know, but it's just to practice evolutionary algorithms). I'm having some problems coming up with an efficient evaluation function to test if the puzzle is solved or not and how many errors there are. My first instinct would be to check if each row and column of the matrix (doing it in octave, which is similar to matlab) have unique elements by ordering them, checking for duplicates and then putting them back the way they were, which seems long winded. Any thoughts? Sorry if this has been asked before...

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• Is regex too slow? Real life examples where simple non-regex alternative is better

  - by polygenelubricants

  I've seen people here made comments like "regex is too slow!", or "why would you do something so simple using regex!" (and then present a 10+ lines alternative instead), etc. I haven't really used regex in industrial setting, so I'm curious if there are applications where regex is demonstratably just too slow, AND where a simple non-regex alternative exists that performs significantly (maybe even asymptotically!) better. Obviously many highly-specialized string manipulations with sophisticated string algorithms will outperform regex easily, but I'm talking about cases where a simple solution exists and significantly outperforms regex. What counts as simple is subjective, of course, but I think a reasonable standard is that if it uses only String, StringBuilder, etc, then it's probably simple.

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• Handling User Authentication in C#.NET?

  - by Daniel

  I am new to .NET, and don't have much experience in programming. What is the standard way of handling user authentication in .NET in the following situation? 1.In Process A, User inputs ID/Password 2.Process A sends the ID/Password to Process B over a nonsecure public channel. 3.Process B authenticates the user with the recieved ID/Password what are some of the standard cryptographic algorithms I can use in above model? The users(customers that bought my company's software) will be running the software(Process A) locally in their computer(connected to internet). I need to authenticate the users so that only registered users can run the program. Thank You!

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• Graph Algorithm To Find All Paths Between N Arbitrary Vertices

  - by russtbarnacle

  I have an graph with the following attributes: Undirected Not weighted Each vertex has a minimum of 2 and maximum of 6 edges connected to it. Vertex count will be < 100 I'm looking for paths between a random subset of the vertices (at least 2). The paths should simple paths that only go through any vertex once. My end goal is to have a set of routes so that you can start at one of the subset vertices and reach any of the other subset vertices. Its not necessary to pass through all the subset nodes when following a route. All of the algorithms I've found (Dijkstra,Depth first search etc.) seem to be dealing with paths between two vertices and shortest paths. Is there a known algorithm that will give me all the paths (I suppose these are subgraphs) that connect these subset of vertices?

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• Interpolation of scattered data: What could I do?

  - by Simon

  Hi! I need your help. I'm working on a 3D chart in Java using Java 3D. It should be able to display a bunch of measured values. As measured, the data I get is scattered. This means I will have to interpolate the missing points in order to get my surface plotted nicely. I didn't study all that 3D-Geometry stuff yet and I don't know where to start. My idea is to triangulate the points to a surface and then, based on the triangulation, interpolate the missing points. (see this to have a rough idea of what I want to achieve) Does someone have experiences with the interpolation of scattered data? Is my approach the right one? If yes, what kind of data structures and algorithms will I need in order to triangulate my points cloud?

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• Functional data structures in C++

  - by drg

  Does anyone know of a C++ data structure library providing functional (a.k.a. immutable, or "persistent" in the FP sense) equivalents of the familiar STL structures? By "functional" I mean that the objects themselves are immutable, while modifications to those objects return new objects sharing the same internals as the parent object where appropriate. Ideally, such a library would resemble STL, and would work well with Boost.Phoenix (caveat- I haven't actually used Phoenix, but as far as I can tell it provides many algorithms but no data structures, unless a lazily-computed change to an existing data structure counts - does it?)

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• Plain-English tutorial on artificial neural networks?

  - by Stuart

  I've Googled, StackOverflowed, everything, and I cannot seem to find a tutorial I can understand. I understand the concept of genetic algorithms, and how to implement them, (Though I haven't tried) but I cannot grasp the concept of neural networks. I know vaguely how they work... And that's about it. Could someone direct me to a tutorial that could help someone who has not even graduated middle school yet? Sure, I'm several years ahead of the majority of people my grade, but I don't understand summation, (which I apparently need if I don't want a simple binary output) vectors, and other things that I apparently should know. Is there a simple, bare-bones tutorial for neural networks? After I learn the basics, I'll proceed to more difficult ones. Preferably, they would be in Java. Thanks!

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• Which OOD approach should I take?

  - by Sorush Rabiee

  According to Niklaus Wirth, Algorithms + Data Structures = Programs. So I use this as a start point to object-oriented modeling and inheritance design: in a way that I separate the 'Objects' from 'Operations'. then look for patterns and inheritance hierarchy. But now after practice I guess it's not a good idea for every modeling problem, because sometimes it's not effective. (I mean there is no possibility of developing (or is very hard to develop) codes of Turing-Completed languages based on this paradigm.) What is your viewpoint for designing an OOD structure as an experienced programmer?

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• Discrete and Continuous Classifier on Sparse Data

  - by Chris S

  I'm trying to classify an example, which contains discrete and continuous features. Also, the example represents sparse data, so even though the system may have been trained on 100 features, the example may only have 12. What would be the best classifier algorithm to use to accomplish this? I've been looking at Bayes, Maxent, Decision Tree, and KNN, but I'm not sure any fit the bill exactly. The biggest sticking point I've found is that most implementations don't support sparse data sets and both discrete and continuous features. Can anyone recommend an algorithm and implementation (preferably in Python) that fits these criteria? Libraries I've looked at so far include: Orange (Mostly academic. Implementations not terribly efficient or practical.) NLTK (Also academic, although has a good Maxent implementation, but doesn't handle continuous features.) Weka (Still researching this. Seems to support a broad range of algorithms, but has poor documentation, so it's unclear what each implementation supports.)

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• Evenly select N elems from array

  - by ninuhadida

  Hi, I need to evenly select n elements from an array. I guess the best way to explain is by example. say I have: array [0,1,2,3,4] and I need to select 3 numbers.. 0,3,4. of course, if the array length <= n, I just need to return the whole array. I'm pretty sure there's a defined algorithm for this, been trying to search, and I took a look at Introduction to algorithms but couldn't find anything that met my needs (probably overlooked it) The problem I'm having is that I can't figure out a way to scale this up to any array [ p..q ], selecting N evenly elements. note: I can't just select the even elements from the example above.. A couple other examples; array[0,1,2,3,4,5,6], 3 elements ; I need to get 0,3,6 array[0,1,2,3,4,5], 3 elements ; I need to get 0, either 2 or 3, and 5

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• What should every programmer know about security ?

  - by M.H

  I am an IT student and I am now in the 3rd year in university,until now we are studing a lot of subjects related to computer in general (Programming,Algorithms,Computer architecture,maths....etc). But there is a whole world called security we are very far from it ,I mean here security in general(Computers Security,Interner Security,Networks Security,hacking,cracking...etc). I am very sure that nobody can learn every thing about security but sure there is a "minimum" knowledge every programmer or IT student should know about it and my question is what is this minimum knowledge ? can you suggest some E-books or courses or any thing can help to start with this road ?

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• Storing old previous year data in Rails?

  - by Millisami

  Hi, I'm developing an app which has massive data entries. Its like Campaign which has attrs like rate_per_sq_feet, start_date, end_date. i.e it will have max date of around 30 days. Once the campaign is finished, its done and another starts. Now I'm confused that how to store those campaigns as reports so that its not accessed regurlarly. What I mean is to store in such a way that it will act like report on later years to come? Its something like fiscal year on accounts where the previous year reports are stored with all the calculations done so that when retrieved later, all the algorithms and calculations shouldn't be performed. Something like frozen data??

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• Java - Collections.binarySearch with PriorityQueue?

  - by msr

  Hello, Can I use Collections.binarySearch() method to search elements in a PriorityQueue? Otherwise, how can I apply search algorithms to a PriorityQueue? I have this (class Evento implements Comparable): public class PriorityQueueCAP extends PriorityQueue<Evento>{ // (...) public void removeEventos(Evento evento){ Collections.binarySearch(this, evento); // ERROR! } } And I got this error: "The method binarySearch(List, T) in the type Collections is not applicable for the arguments (PriorityQueueCAP, Evento)" Why? Thanks in advance!

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• Text editing best practices (with tags, etc.)

  - by Ron

  Hi there, I want to create a text field with some text, that is styled with tags. Think of MS Word, some ext is bold, some is a headline, etc. The tags that style the text are not visible to the user, he just sees the text in bold. How do I preserve these tags? I mean when I backspace over the closing bold-tag, for example, how do I preserve that and prevent that the rest of the text is now bold until the end? I guess this is a pretty basic question for experiences programmers. Are there any algorithms or best practices? This problem surely has been solved before, any pointers? (If this is of any concern, I develop for the iPhone OS and the text field will be a UITextView, but my question is more general I guess.) Thanks in advance!

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• FIPS-compliant encryption in .NET 2.0

  - by Odrade

  We have a .NET 2.0 application that uses the RijindaelManaged class to encrypt some sensitive data. This was fine until we ran into some machines that require the use of FIPS-compliant algorithms. We'd like to switch to AesCryptoServiceProvider, but most of our target machines haven't upgraded past .NET 2.0. Requiring an upgrade is out of the question. After all, upgrades are scary! Is there any way we could use AesCryptoServiceProvider in a .NET 2.0 application? Since 3.5 uses the 2.0 CLR, I was hoping there might be a way to build the needed libraries into the app. Failing that, could someone point me to a reference on the native API that's wrapped by AesCryptoServiceProvider?

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• How to perform FST (Finite State Transducer) composition

  - by Tasbeer

  Consider the following FSTs : T1 0 1 a : b 0 2 b : b 2 3 b : b 0 0 a : a 1 3 b : a T2 0 1 b : a 1 2 b : a 1 1 a : d 1 2 a : c How do I perform the composition operation on these two FSTs (i.e. T1 o T2) I saw some algorithms but couldn't understand much. If anyone could explain it in a easy way it would be a major help. Please note that this is NOT a homework. The example is taken from the lecture slides where the solution is given but I couldn't figure out how to get to it.

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• Good "Modelling & Simulation" book recommendations for programmers?

  - by Harry

  I'm a programmer, and have completely forgotten all the advanced engineering Math I studied ~20 years ago at school. I now have an urgent need to learn about Modelling and Simulation. Though the present context is Disease Modelling, I'm not sure if there's such a thing as 'general' modelling and simulation... with concepts / techniques / algorithms that could be used in just about any domain (and not just limited to biology, finance, trade, economic, weather, etc.) Would you have any recommendations that are easy to read by a semi-Math-literate programmer? Basically, I cannot afford to drown myself in too much Math and theory behind M & S, hence this post. Tia...

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• Math: How to sum each row of a matrix

  - by macek

  I have a 1x8 matrix of students where each student is a 4x1 matrix of scores. Something like: SCORES S [62, 91, 74, 14] T [59, 7 , 59, 21] U [44, 9 , 69, 6 ] D [4 , 32, 28, 53] E [78, 99, 53, 83] N [48, 86, 89, 60] T [56, 71, 15, 80] S [47, 67, 79, 40] Main question: Using sigma notation, or some other mathematical function, how can I get a 1x8 matrix where each student's scores are summed? # expected result TOTAL OF SCORES S [241] T [146] U [128] D [117] E [313] N [283] T [222] S [233] Sub question. To get the average, I will multiply the matrix by 1/4. Would there be a quicker way to get the final result? AVERAGE SCORE S [60.25] T [36.50] U [32.00] D [29.25] E [78.25] N [70.75] T [55.50] S [58.25] Note: I'm not looking for programming-related algorithms here. I want to know if it is possible to represent this with pure mathematical functions alone.

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• big O notation algorithm

  - by niggersak

  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!

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• Boost graph libraries: setting edge weight values

  - by AndyUK

  I am investigating the use of the boost graph libraries in order to apply them to various network problems I have in mind. In the examples I have been looking at the graph edge values ("weights") are always initialized as integers, such as in these Bellman-Ford and Kruskal algorithms eg: int weights[] = { 1, 1, 2, 7, 3, 1, 1, 1 }; My problem is if I try and change the weights to double, I get a heap of warning messages about conversions etc, which so far I have not been able to figure out how to overcome. Does anyone see a way around this?

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• Comparison of music data

  - by Christian P.

  Hey I am looking for theory, algorithms and similar for how to compare music. More specifically, I am looking into how to dupecheck music tracks that have different bitrates or perhaps slightly different variations (radio vs album version), but otherwise sound the same. Use cases for this include services such as Grooveshark, Youtube, etc. where they get a lot of duplicate tracks. I am also interested in text comparisons (Britney Spers vs Britney Spears, how far they deviate, etc.) although this is secondary and I already have some sources to go on in this area. I am mostly interested in codec-agnostic comparison techniques and algoritms (assuming a "raw" stream), but codec-specific resources are appreciated. I am aware of projects such as musicbrainz.org, but have not investigated it further, and would be interested if such projects could be of help in this endeavor.

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• Is it a good idea to create an STL iterator which is noncopyable?

  - by BillyONeal

  Most of the time, STL iterators are CopyConstructable, because several STL algorithms require this to improve performance, such as std::sort. However, I've been working on a pet project to wrap the FindXFile API (previously asked about), but the problem is it's impossible to implement a copyable iterator around this API. A find handle cannot be duplicated by any means -- DuplicateHandle specifically forbids passing handles to it. And if you just maintain a reference count to the find handle, then a single increment by any copy results in an increment of all copies -- clearly that is not what a copy constructed iterator is supposed to do. Since I can't satisfy the traditional copy constructible requirement for iterators here, is it even worth trying to create an "STL style" iterator? On one hand, creating some other enumeration method is going to not fall into normal STL conventions, but on the other, following STL conventions are going to confuse users of this iterator if they try to CopyConstruct it later. Which is the lesser of two evils?

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• C++: building iterator from bits

  - by gruszczy

  I have a bitmap and would like to return an iterator of positions of set bits. Right now I just walk the whole bitmap and if bit is set, then I provide next position. I believe this could be done more effectively: for example build statically array for each combination of bits in single byte and return vector of positions. This can't be done for a whole int, because array would be too big. But maybe there are some better solutions? Do you know any smart algorithms for this?

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• Java Memory Management

  - by Tara Singh

  I am designing a client-server chat application in Java. This is a secure application where the messages are exchanged using cryptographic algorithms. I have one server and it can support many clients. My problem is that when one client logs on the server it works fine, but when another user logs into the system, the server starts giving me bad padding exceptions for the encrypted text. I am not able to figure out the problem, according to my logic, when new connection request to server is made, the server creates a thread for listening to the client. Is it possible that once the instance of thread class is created, it does all the processing correctly for the first client, but not for the second client because the variables in server listener thread class already have some previous value, and thus the encrypted text is not decrypted properly? Please advise how I can make this process more robust so that the number of clients does not affect how well the server functions.

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