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• How to improve Java performance on Informix for Windows

  - by Michal Niklas

  I have problem with performance of Java UDR functions on Informix on Windows. On this server I already have some functions in C and SPL. I chose one function to write it in those 3 languages and I measured performance of this function on test table. Function calculates some kind of checksum so it does not use any db libraries etc. only string and math operations. I observed performance on 30k records with SQL like: select function(txt) from _tmp_perf_test and I changed function to 'function_c, function_spl or function_java. My performance tests showed that C function is the fastest, SPL function is about 5 times slower, where Java is 100 (one hundred!) times slower than C. I checked it few times and 1:100 ratio didn't improve. I changed Java function to simply return length of the string but even this do not help so it looks, that there is general problem with Java function invocation, because there was no difference in time between Java function that calculate checksum and Java function that returns length of the string. I increased JVM_MAX_HEAP_SIZE to 128 and it not helped too. I use IBM Informix Dynamic Server Version 11.50.TC6DE. The same test on Linux server: IBM Informix Dynamic Server Version 11.50.FC6 show more "normal" results, i.e. Java is slower from C and SPL but only 2 to 5 times. What can I do to improve Java performance on Informix server on Windows? More info about Java on servers: c:\Informix\extend\krakatoa\jre\bin>java -version java version "1.5.0" Java(TM) 2 Runtime Environment, Standard Edition (build pwi32dev-20081129a (SR9-0 )) IBM J9 VM (build 2.3, J2RE 1.5.0 IBM J9 2.3 Windows Server 2003 x86-32 j9vmwi3223-20081129 (JIT enabled) J9VM - 20081126_26240_lHdSMr JIT - 20081112_1511ifx1_r8 GC - 200811_07) JCL - 20081129 [root@informix11 bin]# ./java -version java version "1.5.0" Java(TM) 2 Runtime Environment, Standard Edition (build pxa64devifx-20071025 (SR6b)) IBM J9 VM (build 2.3, J2RE 1.5.0 IBM J9 2.3 Linux amd64-64 j9vmxa6423-20071005 (JIT enabled) J9VM - 20071004_14218_LHdSMr JIT - 20070820_1846ifx1_r8 GC - 200708_10) JCL - 20071025

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• Using MinHash to find similiarities between 2 images

  - by Sung Meister

  I am using MinHash algorithm to find similar images between images. I have run across this post, How can I recognize slightly modified images? which pointed me to MinHash algorithm. Being a bit mathematically challenged, I was using a C# implementation from this blog post, Set Similarity and Min Hash. But while trying to use the implementation, I have run into 2 problems. What value should I set universe value to? When passing image byte array to HashSet, it only contains distinct byte values; thus comparing values from 1 ~ 256. What is this universe in MinHash? And what can I do to improve the C# MinHash implementation? Since HashSet<byte> contains values upto 256, similarity value always come out to 1. Here is the source that uses the C# MinHash implementation from Set Similarity and Min Hash: class Program { static void Main(string[] args) { var imageSet1 = GetImageByte(@".\Images\01.JPG"); var imageSet2 = GetImageByte(@".\Images\02.TIF"); //var app = new MinHash(256); var app = new MinHash(Math.Min(imageSet1.Count, imageSet2.Count)); double imageSimilarity = app.Similarity(imageSet1, imageSet2); Console.WriteLine("similarity = {0}", imageSimilarity); } private static HashSet<byte> GetImageByte(string imagePath) { using (var fs = new FileStream(imagePath, FileMode.Open, FileAccess.Read)) using (var br = new BinaryReader(fs)) { //List<int> bytes = br.ReadBytes((int)fs.Length).Cast<int>().ToList(); var bytes = new List<byte>(br.ReadBytes((int) fs.Length).ToArray()); return new HashSet<byte>(bytes); } } }

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• Error while compiling Hello world program for CUDA

  - by footy

  I am using Ubuntu 12.10 and have sucessfully installed CUDA 5.0 and its sample kits too. I have also run sudo apt-get install nvidia-cuda-toolkit Below is my hello world program for CUDA: #include <stdio.h> /* Core input/output operations */ #include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */ #include <math.h> /* Common mathematical functions */ #include <time.h> /* Converting between various date/time formats */ #include <cuda.h> /* CUDA related stuff */ __global__ void kernel(void) { } /* MAIN PROGRAM BEGINS */ int main(void) { /* Dg = 1; Db = 1; Ns = 0; S = 0 */ kernel<<<1,1>>>(); /* PRINT 'HELLO, WORLD!' TO THE SCREEN */ printf("\n Hello, World!\n\n"); /* INDICATE THE TERMINATION OF THE PROGRAM */ return 0; } /* MAIN PROGRAM ENDS */ The following error occurs when I compile it with nvcc -g hello_world_cuda.cu -o hello_world_cuda.x /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `main': /home/adarshakb/Documents/hello_world_cuda.cu:16: undefined reference to `cudaConfigureCall' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__cudaUnregisterBinaryUtil': /usr/include/crt/host_runtime.h:172: undefined reference to `__cudaUnregisterFatBinary' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__sti____cudaRegisterAll_51_tmpxft_000033f1_00000000_4_hello_world_cuda_cpp1_ii_b81a68a1': /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFatBinary' /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFunction' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `cudaError cudaLaunch<char>(char*)': /usr/lib/nvidia-cuda-toolkit/include/cuda_runtime.h:958: undefined reference to `cudaLaunch' collect2: ld returned 1 exit status I am also making sure that I use gcc and g++ version 4.4 ( As 4.7 there is some problem with CUDA)

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• Code Explanation (MPICH)

  - by user243680

  #include "mpi.h" #include <stdio.h> #include <math.h> double f(double a) { return (4.0 / (1.0 + a*a)); } void main(int argc, char *argv[]) { int done = 0, n, myid, numprocs,i; double PI25DT = 3.141592653589793238462643; double mypi, pi, h, sum, x; double startwtime, endwtime; int namelen; char processor_name[MPI_MAX_PROCESSOR_NAME]; MPI_Init(&argc,&argv); MPI_Comm_size(MPI_COMM_WORLD,&numprocs); MPI_Comm_rank(MPI_COMM_WORLD,&myid); MPI_Get_processor_name(processor_name,&namelen); fprintf(stderr,"Process %d on %s\n", myid, processor_name); fflush(stderr); n = 0; while (!done) { if (myid == 0) { printf("Enter the number of intervals: (0 quits) ");fflush(stdout); scanf("%d",&n); startwtime = MPI_Wtime(); } MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD); if (n == 0) done = 1; else { h = 1.0 / (double) n; sum = 0.0; for (i = myid + 1; i <= n; i += numprocs) { x = h * ((double)i - 0.5); sum += f(x); } mypi = h * sum; MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD); if (myid == 0) { printf("pi is approximately %.16f, Error is %.16f\n", pi, fabs(pi - PI25DT)); endwtime = MPI_Wtime(); printf("wall clock time = %f\n", endwtime-startwtime); } } } MPI_Finalize(); } Can anyone explain me the above code what it does??I am in lab and my miss has asked me to explain and i dont know what it is.please help

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• Can you tell me why this generates time limit exceeded in spoj(Prime Number Generator)

  - by magiix

  #include<iostream> #include<string.h> #include<math.h> using namespace std; bool prime[1000000500]; void generate(long long end) { memset(prime,true,sizeof(prime)); prime[0]=false; prime[1]=false; for(long long i=0;i<=sqrt(end);i++) { if(prime[i]==true) { for(long long y=i*i;y<=end;y+=i) { prime[y]=false; } } } } int main() { int n; long long b,e; scanf("%d",&n); while(n--) { cin>>b>>e; generate(e); for(int i=b;i<e;i++) { if(prime[i]) printf("%d\n",i); } } return 0; } That's my code for spoj prime generator. Altought it generates the same output as another accepted code ..

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• Random String Generator creates same string on multiple calls

  - by rockinthesixstring

  Hi there. I've build a random string generator but I'm having a problem whereby if I call the function multiple times say in a Page_Load method, the function returns the same string twice. here's the code ''' <summary>' ''' Generates a Random String' ''' </summary>' ''' <param name="n">number of characters the method should generate</param>' ''' <param name="UseSpecial">should the method include special characters? IE: # ,$, !, etc.</param>' ''' <param name="SpecialOnly">should the method include only the special characters and excludes alpha numeric</param>' ''' <returns>a random string n characters long</returns>' Public Function GenerateRandom(ByVal n As Integer, Optional ByVal UseSpecial As Boolean = True, Optional ByVal SpecialOnly As Boolean = False) As String Dim chars As String() ' a character array to use when generating a random string' Dim ichars As Integer = 74 'number of characters to use out of the chars string' Dim schars As Integer = 0 ' number of characters to skip out of the characters string' chars = { _ "A", "B", "C", "D", "E", "F", _ "G", "H", "I", "J", "K", "L", _ "M", "N", "O", "P", "Q", "R", _ "S", "T", "U", "V", "W", "X", _ "Y", "Z", "0", "1", "2", "3", _ "4", "5", "6", "7", "8", "9", _ "a", "b", "c", "d", "e", "f", _ "g", "h", "i", "j", "k", "l", _ "m", "n", "o", "p", "q", "r", _ "s", "t", "u", "v", "w", "x", _ "y", "z", "!", "@", "#", "$", _ "%", "^", "&", "*", "(", ")", _ "-", "+"} If Not UseSpecial Then ichars = 62 ' only use the alpha numeric characters out of "char"' If SpecialOnly Then schars = 62 : ichars = 74 ' skip the alpha numeric characters out of "char"' Dim rnd As New Random() Dim random As String = String.Empty Dim i As Integer = 0 While i < n random += chars(rnd.[Next](schars, ichars)) System.Math.Max(System.Threading.Interlocked.Increment(i), i - 1) End While rnd = Nothing Return random End Function but if I call something like this Dim str1 As String = GenerateRandom(5) Dim str2 As String = GenerateRandom(5) the response will be something like this g*3Jq g*3Jq and the second time I call it, it will be 3QM0$ 3QM0$ What am I missing? I'd like every random string to be generated as unique.

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• Converting timestamp to time ago in php e.g 1 day ago, 2 days ago...

  - by cosmicbdog

  hi everyone, i am trying to convert a timestamp of the format: 2009-09-12 20:57:19 and turn it into something like '3 minutes ago' with php. I found a useful script to do this, but I think its looking for a different format to be used as the time variable. The script I'm wanting to modify to work with this format is: function _ago($tm,$rcs = 0) { $cur_tm = time(); $dif = $cur_tm-$tm; $pds = array('second','minute','hour','day','week','month','year','decade'); $lngh = array(1,60,3600,86400,604800,2630880,31570560,315705600); for($v = sizeof($lngh)-1; ($v >= 0)&&(($no = $dif/$lngh[$v])<=1); $v--); if($v < 0) $v = 0; $_tm = $cur_tm-($dif%$lngh[$v]); $no = floor($no); if($no <> 1) $pds[$v] .='s'; $x=sprintf("%d %s ",$no,$pds[$v]); if(($rcs == 1)&&($v >= 1)&&(($cur_tm-$_tm) > 0)) $x .= time_ago($_tm); return $x; } I think on those first few lines its trying to do something that looks like this (different date format math): $dif = 1252809479 - 2009-09-12 20:57:19; How would I go about converting my timestamp into that (unix?) format?

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• event flow in action script 3

  - by Shay

  i try to dispatch a custom event from some component on the stage and i register other component to listen to it but the other component doesn't get the event here is my code what do i miss public class Main extends MovieClip //main document class { var compSource:Game; var compMenu:Menu; public function Main() { compSource = new Game; compMenu = new Menu(); var mc:MovieClip = new MovieClip(); addChild(mc); mc.addChild(compSource); // the source of the event - event dispatch when clicked btn mc.addChild(compMenu); //in init of that Movie clip it add listener to the compSource events } } public class Game extends MovieClip { public function Game() { btn.addEventListener(MouseEvent.CLICK, onFinishGame); } private function onFinishGame(e:MouseEvent):void { var score:Number = Math.random() * 100 + 1; dispatchEvent(new ScoreChanged(score)); } } public class Menu extends MovieClip { //TextField score public function Menu() { addEventListener(Event.ADDED_TO_STAGE, init); } private function init(e:Event):void { removeEventListener(Event.ADDED_TO_STAGE, init); //on init add listener to event ScoreChanged addEventListener(ScoreChanged.SCORE_GAIN, updateScore); } public function updateScore(e:ScoreChanged):void { //it never gets here! tScore.text = String(e._score); } } public class ScoreChanged extends Event { public static const SCORE_GAIN:String = "SCORE_GAIN"; public var _score:Number; public function ScoreChanged( score:Number ) { trace("new score"); super( SCORE_GAIN, true); _score = score; } } I don't want to write in Main compSource.addEventListener(ScoreChanged.SCORE_GAIN, compMenu.updateScore); cause i dont want the the compSource will need to know about compMenu its compMenu responsibility to know to what events it needs to listen.... any suggestions? Thanks!

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• "image contains error", trying to create and display images using google app engine

  - by bert

  Hello all the general idea is to create a galaxy-like map. I run into problems when I try to display a generated image. I used Python Image library to create the image and store it in the datastore. when i try to load the image i get no error on the log console and no image on the browser. when i copy/paste the image link (including datastore key) i get a black screen and the following message: The image “view-source:/localhost:8080/img?img_id=ag5kZXZ-c3BhY2VzaW0xMnINCxIHTWFpbk1hcBgeDA” cannot be displayed because it contains errors. the firefox error console: Error: Image corrupt or truncated: /localhost:8080/img?img_id=ag5kZXZ-c3BhY2VzaW0xMnINCxIHTWFpbk1hcBgeDA import cgi import datetime import urllib import webapp2 import jinja2 import os import math import sys from google.appengine.ext import db from google.appengine.api import users from PIL import Image #SNIP #class to define the map entity class MainMap(db.Model): defaultmap = db.BlobProperty(default=None) #SNIP class Generator(webapp2.RequestHandler): def post(self): #SNIP test = Image.new("RGBA",(100, 100)) dMap=MainMap() dMap.defaultmap = db.Blob(str(test)) dMap.put() #SNIP result = db.GqlQuery("SELECT * FROM MainMap LIMIT 1").fetch(1) if result: print"item found<br>" #debug info if result[0].defaultmap: print"defaultmap found<br>" #debug info string = "<div><img src='/img?img_id=" + str(result[0].key()) + "' width='100' height='100'></img>" print string else: print"nothing found<br>" else: self.redirect('/?=error') self.redirect('/') class Image_load(webapp2.RequestHandler): def get(self): self.response.out.write("started Image load") defaultmap = db.get(self.request.get("img_id")) if defaultmap.defaultmap: try: self.response.headers['Content-Type'] = "image/png" self.response.out.write(defaultmap.defaultmap) self.response.out.write("Image found") except: print "Unexpected error:", sys.exc_info()[0] else: self.response.out.write("No image") #SNIP app = webapp2.WSGIApplication([('/', MainPage), ('/generator', Generator), ('/img', Image_load)], debug=True) the browser shows the "item found" and "defaultmap found" strings and a broken imagelink the exception handling does not catch any errors Thanks for your help Regards Bert

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• Facebook and retrieving a users "wall"

  - by Neurofluxation

  I have been given the dubious task of working with the Facebook API. I have managed to get quite far with all the little bits and pieces (bringing in "fan pages" and "friend lists"). However, I cannot seem to import a users wall into my App using SOLELY Javascript. I have this code to bring in the users friends: var widget_div = document.getElementById("profile_pics"); FB.ensureInit(function () { FB.Facebook.get_sessionState().waitUntilReady(function() { FB.Facebook.apiClient.friends_get(null, function(result) { var markup = ""; var num_friends = result ? Math.min(100, result.length) : 0; if (num_friends > 0) { for (var i=0; i<num_friends; i++) { markup += "<div align='left' class='commented' style='background-color: #fffbcd; border: 1px solid #9d9b80; padding: 0px 10px 0px 0px; margin-bottom: 5px; width: 75%; height: 50px; font-size: 16px;'><fb:profile-pic size='square' uid='"+result[i]+"' facebook-logo='true'></fb:profile-pic><div style='float: right; padding-top: 15px;'><fb:name uid='"+result[i]+"'></fb:name></div></div>"; } } widget_div.innerHTML = markup; FB.XFBML.Host.parseDomElement(widget_div); }); }); }); /*******YOUR FRIENDS******/ FB.XFBML.Host.parseDomTree(); Any idea whether I can change this to retrieve the Walls? Thanks in advance you great people! ^_^

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• Compile and optimize for different target architectures

  - by Peter Smit

  Summary: I want to take advantage of compiler optimizations and processor instruction sets, but still have a portable application (running on different processors). Normally I could indeed compile 5 times and let the user choose the right one to run. My question is: how can I can automate this, so that the processor is detected at runtime and the right executable is executed without the user having to chose it? I have an application with a lot of low level math calculations. These calculations will typically run for a long time. I would like to take advantage of as much optimization as possible, preferably also of (not always supported) instruction sets. On the other hand I would like my application to be portable and easy to use (so I would not like to compile 5 different versions and let the user choose). Is there a possibility to compile 5 different versions of my code and run dynamically the most optimized version that's possible at execution time? With 5 different versions I mean with different instruction sets and different optimizations for processors. I don't care about the size of the application. At this moment I'm using gcc on Linux (my code is in C++), but I'm also interested in this for the Intel compiler and for the MinGW compiler for compilation to Windows. The executable doesn't have to be able to run on different OS'es, but ideally there would be something possible with automatically selecting 32 bit and 64 bit as well. Edit: Please give clear pointers how to do it, preferably with small code examples or links to explanations. From my point of view I need a super generic solution, which is applicable on any random C++ project I have later. Edit I assigned the bounty to ShuggyCoUk, he had a great number of pointers to look out for. I would have liked to split it between multiple answers but that is not possible. I'm not having this implemented yet, so the question is still 'open'! Please, still add and/or improve answers, even though there is no bounty to be given anymore. Thanks everybody!

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• RSA example that do not use NoPadding

  - by Tom Brito

  Where can I find a RSA encrypt example that does not use "NoPadding"? --update Better: how to make this code run correctly without throw the "too much data for RSA block" exception? import java.math.BigInteger; import java.security.KeyFactory; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import java.security.spec.RSAPrivateKeySpec; import java.security.spec.RSAPublicKeySpec; import javax.crypto.Cipher; /** * Basic RSA example. */ public class TestRSA { public static void main(String[] args) throws Exception { byte[] input = new byte[100]; Cipher cipher = Cipher.getInstance("RSA/None/NoPadding", "BC"); KeyFactory keyFactory = KeyFactory.getInstance("RSA", "BC"); // create the keys RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger("d46f473a2d746537de2056ae3092c451", 16), new BigInteger("11", 16)); RSAPrivateKeySpec privKeySpec = new RSAPrivateKeySpec(new BigInteger( "d46f473a2d746537de2056ae3092c451", 16), new BigInteger("57791d5430d593164082036ad8b29fb1", 16)); RSAPublicKey pubKey = (RSAPublicKey) keyFactory.generatePublic(pubKeySpec); RSAPrivateKey privKey = (RSAPrivateKey) keyFactory.generatePrivate(privKeySpec); // encryption step cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] cipherText = cipher.doFinal(input); // decryption step cipher.init(Cipher.DECRYPT_MODE, privKey); byte[] plainText = cipher.doFinal(cipherText); } }

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• Unexpected end of file while searching for ']' to end attribute selector.

  - by zurna

  I dont understand what would be the problem with the following code. It needs to copy image's id value to another textbox but instead I get an error. Unexpected end of file while searching for ']' to end attribute selector. <script> $(function() { $(".floatLeft").click(function() { var id = $(this).attr("id").replace(/\D/g, ""); $("input[name='photo[" + id + "]'").val(Math.abs($("input[name='photo[" + id + "]'").val() - 1)); }); }); </script> <ul class="thumbs"> <li> <img src="/FLPM/media/news/images/2M9Y1I2K_sm.jpg" alt="Garden" id="28" class="floatLeft" /> <input type="text" name="photo28" value="0" /> <br /> <a href="?Process=&IMAGEID=28" class="thumb"><span class="floatLeft">DELETE</span></a> </li> <li> <img src="/FLPM/media/news/images/2A9L1V2X_sm.jpg" alt="Frangipani Flowers" id="27" class="floatLeft" /> <input type="text" name="photo27" value="0" /> <br /> <a href="?Process=&IMAGEID=27" class="thumb"><span class="floatLeft">DELETE</span></a> </li> </ul>

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• Java process is not terminating after starting an external process

  - by tangens

  On Windows I've started a program "async.cmd" with a ProcessBuilder like this: ProcessBuilder processBuilder = new ProcessBuilder( "async.cmd" ); processBuilder.redirectErrorStream( true ); processBuilder.start(); Then I read the output of the process in a separate thread like this: byte[] buffer = new byte[ 8192 ]; while( !interrupted() ) { int available = m_inputStream.available(); if( available == 0 ) { Thread.sleep( 100 ); continue; } int len = Math.min( buffer.length, available ); len = m_inputStream.read( buffer, 0, len ); if( len == -1 ) { throw new CX_InternalError(); } String outString = new String( buffer, 0, len ); m_output.append( outString ); } Now it happened that the content of the file "async.cmd" was this: REM start a command window start cmd /k The process that started this extenal program terminated (process.waitFor() returned the exit value). Then I sent an readerThread.interrupt() to the reader thread and the thread terminated, too. But there was still a thread running that wasn't terminating. This thread kept my java application running even if it exited its main method. With the debugger (eclipse) I wasn't able to suspend this thread. After I quit the opened command window, my java program exited, too. Question How can I quit my java program while the command window stays open?

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• NSOutlineView/NSTreeController - calculate sum of column

  - by matei

  I have a NSOutlineView bound to a NSTreeController. My data items are a custom class , let's call them "Row", and suppose a Row contains a "name" and a numeric field called "number" . All these "Rows" are found in let's say a "RowContainer" which has a "rows" mutable array holding the parent (level 0) rows. Each row also has a "children" NSMutableArray member which holds it's children. I have this working, and I want to display under the outlineview a textfield with the sum of all the "number" values of the rows. I bound this textfield to a "total" property of the "RowContainer". Now the problem is how or from where to trigger the recalculation of the "total" property, since this involves a recursive walk on the tree of rows, and I always get a "Collection was mutated while being enumerated" error. I've tried making a method "recalculateTotal", and calling it from the "setNumber" method of the "Row" class , but same error occurs. If I put the recalculation logic in the "total" getter, I can't trigger it to do the math. I'm sure the solution is simple but I can't see it

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• Java operator overloading

  - by nimcap

  Not using operators makes my code obscure. (aNumber / aNother) * count is better than aNumber.divideBy(aNother).times(count) After 6 months of not writing a single comment I had to write a comment to the simple operation above. Usually I refactor until I don't need comment. And this made me realize that it is easier to read and perceive math symbols and numbers than their written forms. For example TWENTY_THOUSAND_THIRTEEN.plus(FORTY_TWO.times(TWO_HUNDERED_SIXTY_ONE)) is more obscure than 20013 + 42*261 So do you know a way to get rid of obscurity while not using operator overloading in Java? Update: I did not think my exaggeration on comments would cause such trouble to me. I am admitting that I needed to write comment a couple of times in 6 months. But not more than 10 lines in total. Sorry for that. Update 2: Another example: budget.plus(bonusCoefficient.times(points)) is more obscure than budget + bonusCoefficient * points I have to stop and think on the first one, at first sight it looks like clutter of words, on the other hand, I get the meaning at first look for the second one, it is very clear and neat. I know this cannot be achieved in Java but I wanted to hear some ideas about my alternatives.

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• What is causing my HTTP server to fail with "exit status -1073741819"?

  - by Keeblebrox

  As an exercise I created a small HTTP server that generates random game mechanics, similar to this one. I wrote it on a Windows 7 (32-bit) system and it works flawlessly. However, when I run it on my home machine, Windows 7 (64-bit), it always fails with the same message: exit status -1073741819. I haven't managed to find anything on the web which references that status code, so I don't know how important it is. Here's code for the server, with redundancy abridged: package main import ( "fmt" "math/rand" "time" "net/http" "html/template" ) // Info about a game mechanic type MechanicInfo struct { Name, Desc string } // Print a mechanic as a string func (m MechanicInfo) String() string { return fmt.Sprintf("%s: %s", m.Name, m.Desc) } // A possible game mechanic var ( UnkillableObjects = &MechanicInfo{"Avoiding Unkillable Objects", "There are objects that the player cannot touch. These are different from normal enemies because they cannot be destroyed or moved."} //... Race = &MechanicInfo{"Race", "The player must reach a place before the opponent does. Like \"Timed\" except the enemy as a \"timer\" can be slowed down by the player's actions, or there may be multiple enemies being raced against."} ) // Slice containing all game mechanics var GameMechanics []*MechanicInfo // Pseudorandom number generator var prng *rand.Rand // Get a random mechanic func RandMechanic() *MechanicInfo { i := prng.Intn(len(GameMechanics)) return GameMechanics[i] } // Initialize the package func init() { prng = rand.New(rand.NewSource(time.Now().Unix())) GameMechanics = make([]*MechanicInfo, 34) GameMechanics[0] = UnkillableObjects //... GameMechanics[33] = Race } // serving var index = template.Must(template.ParseFiles( "templates/_base.html", "templates/index.html", )) func randMechHandler(w http.ResponseWriter, req *http.Request) { mechanics := [3]*MechanicInfo{RandMechanic(), RandMechanic(), RandMechanic()} if err := index.Execute(w, mechanics); err != nil { http.Error(w, err.Error(), http.StatusInternalServerError) } } func main() { http.HandleFunc("/", randMechHandler) if err := http.ListenAndServe(":80", nil); err != nil { panic(err) } } In addition, the unabridged code, the _base.html template, and the index.html template. What could be causing this issue? Is there a process for debugging a cryptic exit status like this?

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• Help Needed With AJAX Script

  - by Brian

  Hello All I am working on an AJAX script but am having difficulties. First, here is the script: var xmlHttp; function GetXmlHttpObject(){ var objXMLHttp=null if (window.XMLHttpRequest){ objXMLHttp=new XMLHttpRequest() } else if (window.ActiveXObject){ objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP") } return objXMLHttp } function retrieveData(){ var jBossServer = new Array(); jBossServer[0] = "d01"; jBossServer[1] = "d02"; jBossServer[2] = "p01"; jBossServer[3] = "p02"; for(var i=0; i<jBossServer.length; i++){ xmlHttp = GetXmlHttpObject(); if (xmlHttp == null){ alert ("Something weird happened ..."); return; } var url="./retrieveData.php"; url = url + "?jBossID=" + jBossServer[i]; url = url + "&sid=" + Math.random(); xmlHttp.open("GET",url,true); xmlHttp.onreadystatechange = updateMemory; xmlHttp.send(null); } } function updateMemory(){ if (xmlHttp.readyState == 4 || xmlHttp.readyState == "complete"){ aggregateArray = new Array(); aggregateArray = xmlHttp.responseText.split(','); for(var i=0; i<aggregateArray.length; i++){ alert(aggregateArray[i]); } return; } } The "retrieveData.php" page will return data that looks like this: d01,1 MB,2 MB,3 MB They relate to my 4 servers d01, d02, p01, and p02 (dev and prod). What I am doing is scraping the memory information from http://127.0.0.1:8080/web-console/ServerInfo.jsp I want to save code so I attempted to put the AJAX xmlHttp call into a loop, but I don't think it is working. All I ever get back is the information for "p02" four times. Am I able to do what I want or do I need four different functions for each server (i.e., xmlHttpServer01, xmlHttpServer02, xmlHttpServer03, xmlHttpServer04)? Thank you all for reading, have a good day. :)

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• When is a>a true ?

  - by Cricri

  Right, I think I really am living a dream. I have the following piece of code which I compile and run on an AIX machine: AIX 3 5 PowerPC_POWER5 processor type IBM XL C/C++ for AIX, V10.1 Version: 10.01.0000.0003 #include <stdio.h> #include <math.h> #define RADIAN(x) ((x) * acos(0.0) / 90.0) double nearest_distance(double radius,double lon1, double lat1, double lon2, double lat2){ double rlat1=RADIAN(lat1); double rlat2=RADIAN(lat2); double rlon1=lon1; double rlon2=lon2; double a=0,b=0,c=0; a = sin(rlat1)*sin(rlat2)+ cos(rlat1)*cos(rlat2)*cos(rlon2-rlon1); printf("%lf\n",a); if (a > 1) { printf("aaaaaaaaaaaaaaaa\n"); } b = acos(a); c = radius * b; return radius*(acos(sin(rlat1)*sin(rlat2)+ cos(rlat1)*cos(rlat2)*cos(rlon2-rlon1))); } int main(int argc, char** argv) { nearest_distance(6367.47,10,64,10,64); return 0; } Now, the value of 'a' after the calculation is reported as being '1'. And, on this AIX machine, it looks like 1 1 is true as my 'if' is entered !!! And my acos of what I think is '1' returns NanQ since 1 is bigger than 1. May I ask how that is even possible ? I do not know what to think anymore ! The code works just fine on other architectures where 'a' really takes the value of what I think is 1 and acos(a) is 0.

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• Convert pre-IEEE-574 C++ floating-point numbers to/from C#

  - by Richard Kucia

  Before .Net, before math coprocessors, before IEEE-574, Microsoft defined a bit pattern for floating-point numbers. Old versions of the C++ compiler happily used that definition. I am writing a C# app that needs to read/write such floating-point numbers in a file. How can I do the conversions between the 2 bit formats? I need conversion methods in both directions. This app is going to run in a PocketPC/WinCE environment. Changing the structure of the file is out-of-scope for this project. Is there a C++ compiler option that instructs it to use the old FP format? That would be ideal. I could then exchange data between the C# code and C++ code by using a null-terminated text string, and the C++ methods would be simple wrappers around sprintf and atof functions. At the very least, I'm hoping someone can reply with the bit definitions for the old FP format, so I can put together a low-level bit manipulation algorithm if necessary. Thanks.

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• Something is wrong with my C++ compilers [on hold]

  - by Karol Turbiarz

  WARNING!!! IT IS C++ but it uses domath ant rootBase LIBRARY, SOE I CAN MAKE SQARE ROOTS, AND OTHEr STUFF LIKE SIN, COS!!!!!! #include <iostream> #include <cstdio> #include <h.2> #include <time> #include <math> #include <domath> #include <rootBase> Then my code doesn't have any error (by the way I'm doing scientific calculator with squared root, line graphing, sin, cos, etc..) but then ... My debbuger finds problem here: if(math1 !== math2); MathCouldNotReadVoid2(); Which goes to void: void MathCouldNotReadVoid2(); { if(math1 ==! (math3 - math2)) { float decimalpoint(); using namespace std; using namespace fc; SquaredRoot(); float SquaredRootExponents(0.07839947388); float SquaredRootExponentFormForRootFormula((SquaredRootExponents *==)+ PiV); float SqRootFormulaStepOnePISHORTCUT(>=3.14'>DoMath<'<=7.2 * FgYt2 + 7.1107); } else main(); } That's the only one of my couple steps, for SquaredRoot, but it doesn't define the "=3.14'DoMath<'<=7.2*FgYt2+7.1107" step. I know some people may not know this type of "command" from the 'rootBase' library, but maybe some of you may know... Please help...Thanks.

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• Ways to gain a deeper understanding of programming concepts?

  - by MrPlow

  I'm a marketer and have been messing around in PHP/MySQL for years. Recently (the last several months) I've been making my own scripts/programs in Python and I've really enjoyed the whole problem solving process. I've read(skimmed) some books and understand the basics of OOP, polymorphism, etc.. I have a general interest in AI and Natural Language in particular but it seems these things require a masters in Computer Science. My knowledge of math is poor. The last class I took was calculus, and I've forgotten the majority of it. Basically I'm looking for things to learn that will help me think in a more analytic way, and maybe see solutions where I didn't before. Improving my ability to program in Python would be nice too. I don't need to learn a specific language or something for employment, just enjoyment. Although my work often involves web development so some utility would be nice. I don't like learning concepts by just reading them. I need to apply them, even if the examples are contrived. A recommendation of a couple good books or other resources would be nice. :) Apologies if this is too vague/misplaced...

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• How should I start playing with 3D

  - by MarceloRamires

  I'm a developer for just about 6 months now, and since I enjoy programming I make a couple of little programs. I've started making encripters, calculators, tools, stuff to play with DropBox (hehe), stuff that play with bitmaps, drawing graphics, and even a program to update the MSN display image according to the artwork of the music you're listening yo on iTunes. Now I kind of ran off ideas of programs to deal with information, and I've had an idea: play around with 3d! so I've read a little about it and figured I'd have to have good notions on position and math on point spacial position (which I do, from my 3d modelling experience), but I don't know how to use API's for it, so I've 'simulated' simple 3d with a simple program I've made (it's just a spinning cube, please, first one to open it, comment here stating that it's safe, i've got no reason to harm anyone's pc.) One of my other hobbies is 3d modelling (completly amateur) and I'd like to mix these hobbies together! Here are some questions: 1) What would be a nice 3d development tool for a .NET programmer like me? 2) Is there a way of using 3d models made in 3DS Max ? (I intend on modelling characters) 3) What knowledges should I have in order to render it, and move it areound ? 4) Which API should I use ? NOTE: Not a dupe, I'm asking for directions specific for .NET development possibly using 3ds MAX, and there are no questions about it!

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• Unexpected performance curve from CPython merge sort

  - by vkazanov

  I have implemented a naive merge sorting algorithm in Python. Algorithm and test code is below: import time import random import matplotlib.pyplot as plt import math from collections import deque def sort(unsorted): if len(unsorted) <= 1: return unsorted to_merge = deque(deque([elem]) for elem in unsorted) while len(to_merge) > 1: left = to_merge.popleft() right = to_merge.popleft() to_merge.append(merge(left, right)) return to_merge.pop() def merge(left, right): result = deque() while left or right: if left and right: elem = left.popleft() if left[0] > right[0] else right.popleft() elif not left and right: elem = right.popleft() elif not right and left: elem = left.popleft() result.append(elem) return result LOOP_COUNT = 100 START_N = 1 END_N = 1000 def test(fun, test_data): start = time.clock() for _ in xrange(LOOP_COUNT): fun(test_data) return time.clock() - start def run_test(): timings, elem_nums = [], [] test_data = random.sample(xrange(100000), END_N) for i in xrange(START_N, END_N): loop_test_data = test_data[:i] elapsed = test(sort, loop_test_data) timings.append(elapsed) elem_nums.append(len(loop_test_data)) print "%f s --- %d elems" % (elapsed, len(loop_test_data)) plt.plot(elem_nums, timings) plt.show() run_test() As much as I can see everything is OK and I should get a nice N*logN curve as a result. But the picture differs a bit: Things I've tried to investigate the issue: PyPy. The curve is ok. Disabled the GC using the gc module. Wrong guess. Debug output showed that it doesn't even run until the end of the test. Memory profiling using meliae - nothing special or suspicious. ` I had another implementation (a recursive one using the same merge function), it acts the similar way. The more full test cycles I create - the more "jumps" there are in the curve. So how can this behaviour be explained and - hopefully - fixed? UPD: changed lists to collections.deque UPD2: added the full test code UPD3: I use Python 2.7.1 on a Ubuntu 11.04 OS, using a quad-core 2Hz notebook. I tried to turn of most of all other processes: the number of spikes went down but at least one of them was still there.

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• Why does autoboxing in Java allow me to have 3 possible values for a boolean?

  - by John

  Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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