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  • Genetic Algorithms applied to Curve Fitting

    - by devoured elysium
    Let's imagine I have an unknown function that I want to approximate via Genetic Algorithms. For this case, I'll assume it is y = 2x. I'd have a DNA composed of 5 elements, one y for each x, from x = 0 to x = 4, in which, after a lot of trials and computation and I'd arrive near something of the form: best_adn = [ 0, 2, 4, 6, 8 ] Keep in mind I don't know beforehand if it is a linear function, a polynomial or something way more ugly, Also, my goal is not to infer from the best_adn what is the type of function, I just want those points, so I can use them later. This was just an example problem. In my case, instead of having only 5 points in the DNA, I have something like 50 or 100. What is the best approach with GA to find the best set of points? Generating a population of 100, discard the worse 20% Recombine the remaining 80%? How? Cutting them at a random point and then putting together the first part of ADN of the father with the second part of ADN of the mother? Mutation, how should I define in this kind of problem mutation? Is it worth using Elitism? Any other simple idea worth using around? Thanks

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  • Scalaz: request for use case

    - by oxbow_lakes
    This question isn't meant as flame-bait! As it might be apparent, I've been looking at Scalaz recently. I'm trying to understand why I need some of the functionality that the library provides. Here's something: import scalaz._ import Scalaz._ type NEL[A] = NonEmptyList[A] val NEL = NonEmptyList I put some println statements in my functions to see what was going on (aside: what would I have done if I was trying to avoid side effects like that?). My functions are: val f: NEL[Int] => String = (l: NEL[Int]) => {println("f: " + l); l.toString |+| "X" } val g: NEL[String] => BigInt = (l: NEL[String]) => {println("g: " + l); BigInt(l.map(_.length).sum) } Then I combine them via a cokleisli and pass in a NEL[Int] val k = cokleisli(f) =>= cokleisli(g) println("RES: " + k( NEL(1, 2, 3) )) What does this print? f: NonEmptyList(1, 2, 3) f: NonEmptyList(2, 3) f: NonEmptyList(3) g: NonEmptyList(NonEmptyList(1, 2, 3)X, NonEmptyList(2, 3)X, NonEmptyList(3)X) RES: 57 The RES value is the character count of the (String) elements in the final NEL. Two things occur to me: How could I have known that my NEL was going to be reduced in this manner from the method signatures involved? (I wasn't expecting the result at all) What is the point of this? Can a reasonably simple and easy-to-follow use case be distilled for me? This question is a thinly-veiled plea for some lovely person like retronym to explain how this powerful library actually works.

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  • Create ntp time stamp from gettimeofday

    - by krunk
    I need to calculate an ntp time stamp using gettimeofday. Below is how I've done it with comments on method. Look good to you guys? (minus error checking). Also, here's a codepad link. #include <unistd.h> #include <sys/time.h> const unsigned long EPOCH = 2208988800UL; // delta between epoch time and ntp time const double NTP_SCALE_FRAC = 4294967295.0; // maximum value of the ntp fractional part int main() { struct timeval tv; uint64_t ntp_time; uint64_t tv_ntp; double tv_usecs; gettimeofday(&tv, NULL); tv_ntp = tv.tv_sec + EPOCH; // convert tv_usec to a fraction of a second // next, we multiply this fraction times the NTP_SCALE_FRAC, which represents // the maximum value of the fraction until it rolls over to one. Thus, // .05 seconds is represented in NTP as (.05 * NTP_SCALE_FRAC) tv_usecs = (tv.tv_usec * 1e-6) * NTP_SCALE_FRAC; // next we take the tv_ntp seconds value and shift it 32 bits to the left. This puts the // seconds in the proper location for NTP time stamps. I recognize this method has an // overflow hazard if used after around the year 2106 // Next we do a bitwise AND with the tv_usecs cast as a uin32_t, dropping the fractional // part ntp_time = ((tv_ntp << 32) & (uint32_t)tv_usecs); }

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  • Using HTMLAgility Pack to Extract Links

    - by Soham
    Hi Folks, Consider this simplest piece of code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using HtmlAgilityPack; namespace WebScraper { class Program { static void Main(string[] args) { HtmlDocument doc = new HtmlDocument(); doc.LoadHtml("http://www.google.com"); foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[@href]")) { } } } } This effectively doesnt do anything at all, and is copied/inspired from various other StackOverflow questions like this. When compiling this, there is a runtime error which says "Object reference not set to an instance of an object." highlighting the foreach line. I can't understand, why the environment has become irritable to this humble,innocent and useless piece of code. I would also like to know, does HTMLAgilityPack accept HTML classes as nodes?

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  • How to delete columns?

    - by Joey jie
    Hi all, I have generated the following text file below: fe120b99164f151b28bf86afa6389b22 -rw-r--r-- 1 joey joey 186 2010-03-14 19:26 Descript.txt 41705ea936cfc653f273b5454c1cdde6 -rw-r--r-- 1 joey joey 30 2010-03-14 20:29 listof.txt 0e25cca3222d32fff43563465af03340 -rw-r--r-- 1 joey joey 28 2010-03-14 23:35 sedexample.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test1.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test2.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test3.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test4.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test5.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test6.txt f5c7f1856249d0526be10df5bd5b895a -rw-r--r-- 1 joey joey 26 2010-03-13 14:13 testingfile.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-03-15 00:28 uniquelist.txt Basically I would like to get rid of the access, amount column, user and group columns. In other words, I want rid of columns 3,4,5. I have tried using cut to keep the columns that I do want and having " " as my delimiter however because of the file size figures, it messes up using "space" as a delimiter. Any advice would be much appreciated! Oh just to add, I would like to save the output as another text file. Many thanks!

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  • Web serivce time out errors in delphi

    - by JD
    Hi, I have a client application that makes SOAP requests. I have set the timeout to 20 minutes. However, sometimes I see the timeout error occurring after 10 seconds. I have the following in code: RIO.HTTPWebNode.ReceiveTimeout := 1200000 Do I need to set the ConnectTimeout and SendTimeOut? Currently they are set to the default values of 0. What difference would setting these make? I am using Delphi 2007. Looking further at the error message I see I get "The operation timed out....". So should I be setting my ReceiveTimeOut to zero since I really do not want any timeout at all?

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  • Where did the "Polymorphism" word come from?

    - by Alon
    I've always wondered where did the word "Polymorphism" word come from. I know what is polymorphism and I use it of course, but I just don't understand why this technique called polymorphism. Note that I'm not a native English speaker, and I will thank you if you'll use simple English in your answers. Thank you.

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  • Python equivalent of IDL's stop and .reset

    - by Jamie
    Hi there, I'm relatively new to python but have a bit of experience using IDL. I was wondering if anyone knows if there are equivalent commands in python for IDL's stop and .reset commands. If I'm running some IDL script I wrote that I put a stop command in, essentially what it does is stop the script there and give me access to the command line in the middle of the script. So I have access to all the functions and variables that I defined before the stop command, which I find really useful for debugging. The .reset command I find extremely useful too. What it does is reset the the IDL environment (clears all variables, functions, etc.). It's as if I closed that session and opened a new one, but without having to exit and restart IDL. I find that if I'm trying to debug a script I wrote it's useful sometimes to start from scratch and not have to reset IDL (or python now). It would be useful also in python to be able to un-import any modules I had previously imported. Any help with these issues would be greatly appreciated. Cheers Related Python Drop into REPL Is it possible to go into ipython from code?

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  • Generic Data Structure Description Language

    - by Jon Purdy
    I am wondering whether there exists any declarative language for arbitrarily describing the format and semantics of a data structure, that can be compiled to a specific implementation of that structure in any of a set of target languages. That is, something like a generic data definition language but geared toward describing arbitrary data structures such as vectors, lists, trees, etc., and the semantics of operations on those structures. I ask because I had an idea for a feasible implementation of this concept, and I'm just wondering whether it's worth it, and, consequently, whether it's been done before. Another, slightly more abstract question: is there any real difference between the normative specification of a data structure (what it does) and its implementation (how it does it)?

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  • What's the simplest way to call Http GET url using Delphi?

    - by Mohammed Nasman
    There's a web services I want to call in my application, I can use it with importing the WSDL or by just use "HTTP GET" with the URL and parameters, so I prefer the later because it's simple thing. I know I can use indy idhttp.get, to do the job, but this is very simple thing and I don't want to add complex indy code to my application. UPDATE: sorry if I was not clear, I meant by "not to add complex indy code", that I don't want add indy components for just this simple task, and prefer more lighter way for that.

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  • ansi-c fscanf problem

    - by mongoose
    hi i read the file as follows fscanf(fp,"%f %f %f",&*(p1+i), &*(p2+i), &*(p3+i)); my file's lines consists of three floating point numbers... the problem i have is that in the file let's say i have some floating points with let's say maximum of two digits after the dot. but when i ask c to print those values using different formatting, for example %lf,%.2lf,%.4lf... it starts to play with the digits... my only concern is this, if i have let's say 1343.23 in the file, then will c use this value exactly as it is in computations or it will play with the digits after the dot. if it will play, then how is it possible to make it so that it uses floating point numbers exactly as they are? for example in last case even if i ask it to print that value using %.10lf i would expect it to print only 1343.2300000000.? thanks a lot!

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  • Any PICK programmers on stack?

    - by Coov
    I work in a shop that is divided into two types of programmers. Programmers that code in .net & sql and programmers that code in pick. Actually, a few of the programmers are writing code in both pick and .net. I was curious if there are any pick programmers out there using StackOverflow? I'd like to get the pick programmers involved in the stack community.

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  • How to send raw data over a network?

    - by youllknow
    Hi everyone! I've same data stored in a byte-array. The data contains a IPv4 packet (which contains a udp-packet). I want to send these array raw over the network using C# (preferred) or C++. I don't want to use C#'s udp-client for example. Does anyone know how to perform this? Sorry for my bad English and thanks for your help in advance!!!

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  • How to reuse socket in .NET?

    - by Hermann
    I am trying to reconnect to a socket that I have disconnected from but it won't allow it for some reason even though I called the Disconnect method with the argument "reuseSocket" set to true. _socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); _socket.Connect(ipAddress, port); //...receive data _socket.Disconnect(true); //reuseSocket = true //...wait _socket.Connect(ipAddress, port); //throws an InvalidOperationException: Once the socket has been disconnected, you can only reconnect again asynchronously, and only to a different EndPoint. BeginConnect must be called on a thread that won't exit until the operation has been completed. What am I doing wrong?

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  • Multithreading or task parallel library

    - by Bruce Adams
    I have an application which performs 30 independent tasks simultaneously using multithreading, each task retrieves data over http, performs a calculation and returns a result to the ui thread. Can I use tpl to perform the same tasks? Does tpl create 30 new threads and spread them over all the available cores, or does it just split the tasks over the available cores and use one thread per core? Will there be a performance boost using tpl over multithreading in this case?

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  • iPhone to iPhone communication

    - by Dan
    Hi, I have been looking into communication methods between two iPhone devices and as I understand it there are two main methods to do this: Bluetooth and WiFi. However I wanted to know if anyone knows of any other way of sharing information between two iPhones? If I were in an area with no WiFi or mobile signal, and couldn't use Bluetooth for whatever reason, is there anything that could be done to broadcast data from one iPhone to another? I'm sure its a bit of a silly question, but if you don't ask, you don't get; and if someone knows of anything I might be able to look into with regards to this, I would be very appreciative. Thanks, Dan

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  • Bash Shell; read command; using Cygwin on Windows 7

    - by user312397
    Okay so I am having this problem. I write up a script to be run in cygwin on Windows. I've tried a bunch of basic example scripts in case it was my scripts problem. So I tried this: #!/bin/bash echo -e "Enter your name and press [ENTER]: \c" read var_name echo "Your name is: $var_name" Then I will run it and I enter a name for var_name. I get this: $ ./project1.sh Enter your name and press [ENTER]: Jake ': not a valid identifierad: `var_name Your name is: So as far as I understand it I am having a problem with read. I am trying to work on a project for my class, but I can't seem to figure out why it won't read it. I followed the book with no triumph then resorted to these examples on the web that do not seem to work for me either. Does anyone have any idea if it is my setup or if I am missing something, thanks.

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