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• Help me with DB design

  - by eugeneK

  Hi, i'm developing text ads system. Some small clone of Google Ads. Here is diagram with common tables. Basically make it short, advertiser can have up to 10 variant of same campaign with different text variations, can geo-target his ads and unique impressions count only for IP that haven't been on certain site for more than 24 hours. Pretty simple but the question is what i lack in here from your experience because later it would much harder to fix design flaws and some of you probably done something alike also many SQL gurus in here so maybe i did over normalized DB or did not normalized as needed ? Second question is. My end goal is to get ads for user from ie. Germany that haven't seen same ad on same site for 24 hours as long as ads fit country of user. Each impression is count same as each click if there is one. I need to get 5 "random" ads based on IP, Country and higher CPC (pay per click). How can i achieve this with current design or maybe to design database the way it would be easy to get ads and show stats for advirtisers... thanks for any help...

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• How do I match complete XML objects in a string?

  - by cyclotis04

  I'm attempting to find complete XML objects in a string. They have been placed in the string by an XmlSerializer, but may or may not be complete. I've toyed with the idea of using a regular expression, because it seems like the kind of thing they were built for, except for the fact that I'm trying to parse XML. I'm trying to find complete objects in the form: <?xml version="1.0"?> <type> <field>value</field> ... </type> My thought was a regex to find <?xml version="1.0"?><type> and </type>, but if a field has the same name as type, it obviously won't work. There's plenty of documentation on XML parsers, but they seem to all need a complete, fully-formed document to parse. My XML objects can be in a string surrounded by pretty much anything else (including other complete objects). hw<e>reR@lot$0fr@ndm&nchrs%<?xml version="1.0"?><type><field>...</field>...</type>@ndH#r$omOre!!>nuT6erjc?y!<?xml version="1.0"?><type><field>...</field>...</type>ty!=] A regex would be able to match a string while excluding the random characters, but not find a complete XML object. I'd like some way to extract an object, parse it with a serializer, then repeat until the string contains no more valid objects.

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• How to generate a key for a group entity?

  - by user246114

  Hi, I'm trying to make a group entity. Something like: class User { } class UserColor { } ... Key key = new KeyFactory.Builder( User.class.getSimpleName(), username). .addChild(UserColor.class.getSimpleName(), ???).getKey(); I know the unique username up-front to use for the key of the User object. But I just want app engine to generate a random unique value for the key value of the UserColor instance. I think this is described here, but I don't understand their wording: http://code.google.com/appengine/docs/java/datastore/transactions.html To create an object with a system-generated numeric ID and an entity group parent, you must use an entity group parent key field (such as customerKey, above). Assign the key of the parent to the parent key field, then leave the object's key field set to null. When the object is saved, the datastore populates the key field with the complete key, including the entity group parent. and this is their example: @Persistent @Extension(vendorName="datanucleus", key="gae.parent-pk", value="true") private Key customerKey; but I don't understand - should UserColor look like this then?: class UserColor { @Persistent @Extension(vendorName="datanucleus", key="gae.parent-pk", value="true") private Key mKeyParent; @Primary private Key mKey; // leave null } ... Key keyParent = new KeyFactory.Builder( User.class.getSimpleName(), username); UserColor uc = new UserColor(); uc.setKeyParent(keyParent); pm.makePersistent(uc); // now generated for me automatically? is that correct? Using this method, I should be able to use a User and a UserColor object in a transaction together, right? Thanks

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• How can I test that my hash function is good in terms of max-load?

  - by philcolbourn

  I have read through various papers on the 'Balls and Bins' problem and it seems that if a hash function is working right (ie. it is effectively a random distribution) then the following should/must be true if I hash n values into a hash table with n slots (or bins): Probability that a bin is empty, for large n is 1/e. Expected number of empty bins is n/e. Probability that a bin has k collisions is <= 1/k!. Probability that a bin has at least k collisions is <= (e/k)**k. These look easy to check. But the max-load test (the maximum number of collisions with high probability) is usually stated vaguely. Most texts state that the maximum number of collisions in any bin is O( ln(n) / ln(ln(n)) ). Some say it is 3*ln(n) / ln(ln(n)). Other papers mix ln and log - usually without defining them, or state that log is log base e and then use ln elsewhere. Is ln the log to base e or 2 and is this max-load formula right and how big should n be to run a test? This lecture seems to cover it best, but I am no mathematician. http://pages.cs.wisc.edu/~shuchi/courses/787-F07/scribe-notes/lecture07.pdf BTW, with high probability seems to mean 1 - 1/n.

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• Distributed development systems

  - by Nathan Adams

  I am interested in a system that allows for distributed development with an authentication piece. What do I mean by that? Ok so lets take SVN, SVN keeps track of revisions and doesn't care who submits, as long as you have the right to submit you can submit, really, to any part in the repository. Where does my system come into play? Being able to granulate access control and give a stackoverflow like feel to the environment. In the system I am describing we have 4 users Bob, Alice, Dan, Joe. Bob is a project managed, Alice and Dan are programmers under Bob and Joe is a random programmer on the internet who wants to help. Ideally in this system, Bob can commit any changes and won't require approval. Alice and Dan can commit to their branches, or a branch, but a commit to the trunk would need approval by Bob. This is where Joe comes in, wants to help, however, you just don't want to give him the keys to the kingdom just yet so to speak, so in my system you would setup a "low user" account. Any commits that Joe makes would need to be approved by Dan, Alice or both. However, in the system, Joe can build up "Karma" where after so many approved commits it would only need approval by one of the programmers, and then eventually no approval would be necessary. Does that make sense and do you know if a system like that exists? Or am I just crazy to even think such a system/environment would be possible?

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• Flash As3 Mute Button problems

  - by Lee

  Hey guys, I am trying to create a UI movie clip that can be used across different scenes. It uses variables from the root scope to determine states. When i press the mute button is works fine, however when i try to un-mute things go weird. Sometimes it takes 2 clicks to unmute, sometimes more. It seems random. Muting however seems to work first time.. Any ideas? Main Timeline: var mute:Boolean = false; var playerName = "Fred"; function setMute(vol) { var sTransform:SoundTransform = new SoundTransform(1,0); sTransform.volume = vol; SoundMixer.soundTransform = sTransform; } function toggleMuteBtn(event:Event) { if (mute) { // Sound On, Mute Off mute = false; setMute(1); ui_mc.muteCross_mc.visible = false; } else { // Sound Off, Mute On mute = true; setMute(0); ui_mc.muteCross_mc.visible = true; } } ui_mc Action Script: if (MovieClip(parent).mute == false) { muteCross_mc.visible = false; } mute_btn.addEventListener(MouseEvent.CLICK, MovieClip(parent).toggleMuteBtn);

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• How to get raw jpeg data (but no metatags / proprietary markers)

  - by CoolAJ86

  I want to get raw jpeg data - no metadata. I'm very confused looking at the jpeg "standards". How correct is my understanding of the marker "tree"? 0xFFD8 - Identifies the file as an image 0xFFE? - EXIF, JFIF, SPIFF, ICC, etc 0x???? - the length of the tag 0xFFD8 - Start of Image 0xFFE0 - should follow SOI as per spec, but often preceded by comments ??? 0x???? - Matrices, tags, random data ??? There are never other markers in-between these markers? Or these include the matrices and such? 0xFFDA - Start of Stream - This is what I want, yes? 0xXXXX - length of stream 0xFFD9 - End of Stream (EOI) 0x???? - Comment tags, extra exif, jfif info??? 0xFFD9 - End of Image 0xFF00 - escaped 0xFF, not to be confused with a marker This has been my reading material: http://en.wikipedia.org/wiki/JPEG http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html http://www.media.mit.edu/pia/Research/deepview/exif.html http://www.faqs.org/faqs/jpeg-faq/part1/section-15.html

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• Using multiple sockets, is non-blocking or blocking with select better?

  - by JPhi1618

  Lets say I have a server program that can accept connections from 10 (or more) different clients. The clients send data at random which is received by the server, but it is certain that at least one client will be sending data every update. The server cannot wait for information to arrive because it has other processing to do. Aside from using asynchronous sockets, I see two options: Make all sockets non-blocking. In a loop, call recv on each socket and allow it to fail with WSAEWOULDBLOCK if there is no data available and if I happen to get some data, then keep it. Leave the sockets as blocking. Add all sockets to a fd_set and call select(). If the return value is non-zero (which it will be most of the time), loop through all the sockets to find the appropriate number of readable sockets with FD_ISSET() and only call recv on the readable sockets. The first option will create a lot more calls to the recv function. The second method is a bigger pain from a programming perspective because of all the FD_SET and FD_ISSET looping. Which method (or another method) is preferred? Is avoiding the overhead on letting recv fail on a non-blocking socket worth the hassle of calling select()? I think I understand both methods and I have tried both with success, but I don't know if one way is considered better or optimal. Only knowledgeable replies please!

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• Tricky file parsing. Inconsistent Delimeters

  - by Ben Truby

  I need to parse a file with the following format. 0000000 ...ISBN.. ..Author.. ..Title.. ..Edit.. ..Year.. ..Pub.. ..Comments.. NrtlExt Nrtl Next Navg NQoH UrtlExt Urtl Uext Uavg UQoH ABS NEB MBS FOL ABE0001 0-679-73378-7 ABE WOMAN IN THE DUNES (INT'L ED) 1st 64 RANDOM 0.00 13.90 0.00 10.43 0 21.00 10.50 6.44 3.22 2 2.00 0.50 2.00 2.00 ABS The ID and ISBN are not a problem, the title is. There is no set length for these fields, and there are no solid delimiters- the space can be used for most of the file. Another issue is that there is not always an entry in the comments field. When there is, there are spaced within the content. So I can get the first two, and the last fourteen. I need some help figuring out how to parse the middle six fields. This file was generated by an older program that I cannot change. I am using php to parse this file.

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• Batch script crashing

  - by TamirGali

  My Batch script keeps crashing with the note: "set was unexpected at this time" which I could only see via video recording and checking frame by frame. here is the script: @echo off color 6f set min=0 set max=25 goto REDIR :REDIR set var=0 goto TOP :TOP cls set /a var=%var%+1 set /a rand%var%=%random% %% (max - min + 1)+ min if %rand2%==%rand1% set var=0&goto TOP if %rand3%==%rand2% set var=1&goto TOP if %rand4%==%rand3% set var=2&goto TOP if %rand5%==%rand4% set var=3&oto TOP if %rand6%==%rand5% set var=4&goto TOP if %rand7%==%rand6% set var=5&goto TOP if %rand8%==%rand7% set var=6&goto TOP if %rand9%==%rand8% set var=7&goto TOP if %rand10%==%rand9% set var=8&goto TOP if %rand11%==%rand10% set var=9&goto TOP if %rand12%==%rand11% set var=10&goto TOP if %rand13%==%rand12% set var=11&goto TOP if %rand14%==%rand13% set var=12&goto TOP if %rand15%==%rand14% set var=13&goto TOP if %rand16%==%rand15% set var=14&goto TOP if %rand17%==%rand16% set var=15&goto TOP if %rand18%==%rand17% set var=16&goto TOP if %rand19%==%rand18% set var=17&goto TOP if %rand20%==%rand19% set var=18&goto TOP if %rand21%==%rand20% set var=19&goto TOP if %rand22%==%rand21% set var=20&goto TOP if %rand23%==%rand22% set var=21&goto TOP if %rand24%==%rand23% set var=22&goto TOP if %rand25%==%rand24% set var=23&goto TOP if %rand26%==%rand25% set var=24&goto TOP if %var%==26 goto SHOW goto TOP :SHOW cls echo A=%rand1% echo B=%rand2% echo C=%rand3% echo D=%rand4% echo E=%rand5% echo F=%rand6% echo G=%rand7% echo H=%rand8% echo I=%rand9% echo J=%rand10% echo K=%rand11% echo L=%rand12% echo M=%rand13% echo N=%rand14% echo O=%rand15% echo P=%rand16% echo Q=%rand17% echo R=%rand18% echo S=%rand19% echo T=%rand20% echo U=%rand21% echo V=%rand22% echo W=%rand23% echo X=%rand24% echo Y=%rand25% echo Z=%rand26% pause goto REDIR

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• How do I find a source code position from an address given by a crash in Window CE

  - by Shane MacLaughlin

  I have a Windows mobile 4.0 application, written using EVC++ 4.0 SP4 with MFC, that is exhibiting a random occasional crash in the field. e.g. Exception ox800000002 at 00112584. It does not happen under various emulators and simulators, hence is very difficult to trace using a debugger. The crash throws up and address and exception type. Given that I have the PDB is there any way to track this address to the source. I can't recompile using VC++ 8 as it doesn't support the mobile 4 SDK. My guess is that without a stack trace I'm not going to have much joy, as the chances are that the exception may not be in my source. Worth a try all the same. Edit As suggested, I have looked at the address in the context of the .MAP file for the program. This reveals the following Address Publics by Value Rva+Base Lib:Object 0001:00000000 ?GetUnduValue@@YANMM@Z 00011000 f 7Par.obj ' ' ' 0001:001124b8 ?OnLButtonUp@CGXGridUserDragSelectRangeImp@@UAAHPAVCGXGridCore@@AAVCPoint@@AAI@Z 001234b8 f gxseldrg.obj 0001:001126d8 ?OnSelDragStart@CGXGridUserDragSelectRangeImp@@UAAHPAVCGXGridCore@@KK@Z 001236d8 f gxseldrg.obj Which suggests the error occured during CGXGridUserDragSelectRangeImp::OnLButtonUp(), which seems a bit odd as I don't think there was a mouse / keyboard / screen button pressed at the time. Could be the stack got fragged before the crash got reported, and I'm wasting my time. I'll recompile with assembler output to try to isolate it to a given line, but don't hold out much hope :( Does the fact that the map file reports segmented addresses e.g. 0001:xxxxxxxxx and the crash report unsegmented addresses mean I have to carry out some computation to get the map address from the crash address?

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• [SOLVED]: Delegate OpenID to Google (NOT Google Apps)

  - by Rio

  OK, I searched this question on SO but no good answer. After spent some time I figured out how to do it. I'm going to answer this myself as a way to share it. Not sure if this is the correct way to use SO, but here it goes: Now it is possible delegate OpenID to your Google account (not Google Apps). No, this is not using the demo OpenID provider using App Engine. This is your REAL Google account! First you need to enable your Google Profiles. Try to view your profile and edit it, there should be an option to set your Profile URL. You have two choices there: either use your Gmail account name (without the @gmail.com part) as your profile id, or a random number assigned to you. It's up to you to decide which one to use. Either way, that id is your profile id below. Now add the following HTML code to your delegating page: <link rel="openid2.provider" href="https://www.google.com/accounts/o8/ud?source=profiles" > <link rel="openid2.local_id" href="http://www.google.com/profiles/[YOUR PROFILE ID]" > And it's done. Now try login SO with your custom url!

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• How To Generate Parameter Set for the Diffie-Hellman Key Agreement Algorithm in Android

  - by sebby_zml

  Hello everyone, I am working on mobile/server security related project. I am now stuck in generating a Diffie-Hellman key agreement part. It works fine in server side program but it is not working in mobile side. Thus, I assume that it is not compactible with Android. I used the following class to get the parameters. It returns a comma-separated string of 3 values. The first number is the prime modulus P. The second number is the base generator G. The third number is bit size of the random exponent L. My question is is there anything wrong with the code or it is not compactible for android?What kind of changes should I do? Your suggestion and guidance would be very much help for me. Thanks a lot in advance. public static String genDhParams() { try { // Create the parameter generator for a 1024-bit DH key pair AlgorithmParameterGenerator paramGen = AlgorithmParameterGenerator.getInstance("DH"); paramGen.init(1024); // Generate the parameters AlgorithmParameters params = paramGen.generateParameters(); DHParameterSpec dhSpec = (DHParameterSpec)params.getParameterSpec(DHParameterSpec.class); // Return the three values in a string return ""+dhSpec.getP()+","+dhSpec.getG()+","+dhSpec.getL(); } catch (NoSuchAlgorithmException e) { } catch (InvalidParameterSpecException e) { } return null; } Regards, Sebby

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• Autologin for web application

  - by Maulin

  We want to AutoLogin feature to allow user directly login using link into our Web Application. What is the best way achieve this? We have following approches in our mind. 1) Store user credentials(username/password) in cookie. Send cookie for authentication. e.g. http: //www.mysite.com/AutoLogin (here username/password will be passed in cookie) OR Pass user credentials in link URL. http: //www.mysite.com/AutoLogin?userid=<&password=< 2) Generate randon token and store user random token and user IP on server side database. When user login using link, validate token and user IP on server. e.g. http: //www.mysite.com/AutoLogin?token=< The problem with 1st approach is if hacker copies link/cookie from user machine to another machine he can login. The problem with 2nd approach is the user ip will be same for all users of same organization behind proxy. Which one is better from above from security perspective? If there is better solution which is other than mentioned above, please let us know.

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• Flash as3 smooth threshold

  - by arkzai

  hello, I'm building a flash app that pulls images from flickr and removes the white background I'm dong this using threshold and i get a really ragged outcome is there any way to get a better and smoother color key? thanks photoNumber = Math.floor(Math.random() * (photos.length)); loader.load(new URLRequest(photos[photoNumber].path)); loader.contentLoaderInfo.addEventListener(Event.COMPLETE,draw); trace ( "trying to load photo " + photoNumber ); function draw(e:Event) { trace ("show photo " + photoNumber) var W:int=e.target.content.width; var H:int=e.target.content.height; bitmapdata=new BitmapData(W,H); bitmap=new Bitmap(bitmapdata); bitmapdata.draw(e.target.content); var threshold:uint = 0xF9F8F800; var color:uint = 0x00000000; var maskColor:uint = 0x00FF0000; bitmapdata.threshold(bitmapdata,new Rectangle(0,0,W,H),new Point(0,0),">", threshold, color, maskColor, true); bitmap.smoothing = true; //bitmap.scaleX = bitmap.scaleY = 0.99; // <---- imgHolder.addChild(bitmap); } }

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• Matching Regular Expression in Javascript and PHP problem...

  - by Frankie

  I can't figure out how to get the same result from my Javscript as I do from my PHP. In particular, Javascript always leaves out the backslashes. Please ignore the random forward and backslashes; I put them there so that I can cover my basis on a windows system or any other system. Output: Input String: "/root\wp-cont ent\@*%'i@$@%$&^(@#@''mage6.jpg:" /root\wp-content\image6.jpg (PHP Output) /rootwp-contentimage6.jpg (Javscript Output) I would appreciate any help! PHP: <?php $path ="/root\wp-cont ent\@*%'i@$@%$&^(@#@''mage6.jpg:"; $path = preg_replace("/[^a-zA-Z0-9\\\\\/\.-]/", "", $path); echo $path; ?> Javascript: <script type="text/javascript"> var path = "/root\wp-cont ent\@*%'i@$@%$&^(@#@''mage6.jpg:"; //exact same string as PHP var regx = /[^a-zA-Z0-9\.\/-]/g; path = path.replace(regx,""); document.write("<br>"+path); </script>

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• ASP.NET MVC intermittent slow response

  - by arehman

  Problem In our production environment, system occasionally delays the page response of an ASP.NET MVC application up to 30 seconds or so, even though same page renders in 2-3 seconds most of the times. This happens randomly with any arbitrary page, and GET or POST type requests. For example, log files indicates, system took 15 seconds to complete a request for jquery script file or for other small css file it took 10 secs. Similar Problems: Random Slow Downs Production Environment: Windows Server 2008 - Standard (32-bit) - App Pool running in integrated mode. ASP.NET MVC 1.0 We have tried followings/observations: Moved the application to a stand alone web server, but, it didn't help. We didn't ever notice same issue on the server for any 'ASP.NET' application. App Pool settings are fine. No abrupt recycles/shutdowns. No cpu spikes or memory problems. No delays due to SQL queries or so. It seems as something causing delay along HTTP Pipeline or worker processor seeing the request late. Looking for other suggestions. -- Thanks

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• Iterator performance contract (and use on non-collections)

  - by polygenelubricants

  If all that you're doing is a simple one-pass iteration (i.e. only hasNext() and next(), no remove()), are you guaranteed linear time performance and/or amortized constant cost per operation? Is this specified in the Iterator contract anywhere? Are there data structures/Java Collection which cannot be iterated in linear time? java.util.Scanner implements Iterator<String>. A Scanner is hardly a data structure (e.g. remove() makes absolutely no sense). Is this considered a design blunder? Is something like PrimeGenerator implements Iterator<Integer> considered bad design, or is this exactly what Iterator is for? (hasNext() always returns true, next() computes the next number on demand, remove() makes no sense). Similarly, would it have made sense for java.util.Random implements Iterator<Double>? Should a type really implement Iterator if it's effectively only using one-third of its API? (i.e. no remove(), always hasNext())

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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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• Java Performance measurement

  - by portoalet

  Hi, I am doing some Java performance comparison between my classes, and wondering if there is some sort of Java Performance Framework to make writing performance measurement code easier? I.e, what I am doing now is trying to measure what effect does it have having a method as "synchronized" as in PseudoRandomUsingSynch.nextInt() compared to using an AtomicInteger as my "synchronizer". So I am trying to measure how long it takes to generate random integers using 3 threads accessing a synchronized method looping for say 10000 times. I am sure there is a much better way doing this. Can you please enlighten me? :) public static void main( String [] args ) throws InterruptedException, ExecutionException { PseudoRandomUsingSynch rand1 = new PseudoRandomUsingSynch((int)System.currentTimeMillis()); int n = 3; ExecutorService execService = Executors.newFixedThreadPool(n); long timeBefore = System.currentTimeMillis(); for(int idx=0; idx<100000; ++idx) { Future<Integer> future = execService.submit(rand1); Future<Integer> future1 = execService.submit(rand1); Future<Integer> future2 = execService.submit(rand1); int random1 = future.get(); int random2 = future1.get(); int random3 = future2.get(); } long timeAfter = System.currentTimeMillis(); long elapsed = timeAfter - timeBefore; out.println("elapsed:" + elapsed); } the class public class PseudoRandomUsingSynch implements Callable<Integer> { private int seed; public PseudoRandomUsingSynch(int s) { seed = s; } public synchronized int nextInt(int n) { byte [] s = DonsUtil.intToByteArray(seed); SecureRandom secureRandom = new SecureRandom(s); return ( secureRandom.nextInt() % n ); } @Override public Integer call() throws Exception { return nextInt((int)System.currentTimeMillis()); } } Regards

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• Graph-structured databases and Php

  - by stagas

  I want to use a graph database using php. Can you point out some resources on where to get started? Is there any example code / tutorial out there? Or are there any other methods of storing data that relate to each other in totally random/abstract situations? - Very abstract example of the relations needed: John relates to Mary, both relate to School, John is Tall, Mary is Short, John has Blue Eyes, Mary has Green Eyes, query I want is which people are related to 'Short people that have Green Eyes and go to School' - answer John - Another example: TrackA -> ArtistA -> ArtistB -> AlbumA -----> [ label ] -> AlbumB -----> [ A ] -> TrackA:Remix -> Genre:House -> [ Album ] -----> [ label ] TrackB -> [ C ] [ B ] Example queries: Which Genre is TrackB closer to? answer: House - because it's related to Album C, which is related to TrackA and is related to Genre:House Get all Genre:House related albums of Label A : result: AlbumA, AlbumB - because they both have TrackA which is related to Genre:House - It is possible in MySQL but it would require a fixed set of attributes/columns for each item and a complex non-flexible query, instead I need every attribute to be an item by itself and instead of 'belonging' to something, to be 'related' to something.

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• Number Algorithm

  - by James

  I've been struggling to wrap my head around this for some reason. I have 15 bits that represent a number. The bits must match a pattern. The pattern is defined in the way the bits start out: they are in the most flush-right representation of that pattern. So say the pattern is 1 4 1. The bits will be: 000000010111101 So the general rule is, take each number in the pattern, create that many bits (1, 4 or 1 in this case) and then have at least one space separating them. So if it's 1 2 6 1 (it will be random): 001011011111101 Starting with the flush-right version, I want to generate every single possible number that meets that pattern. The # of bits will be stored in a variable. So for a simple case, assume it's 5 bits and the initial bit pattern is: 00101. I want to generate: 00101 01001 01010 10001 10010 10100 I'm trying to do this in Objective-C, but anything resembling C would be fine. I just can't seem to come up with a good recursive algorithm for this. It makes sense in the above example, but when I start getting into 12431 and having to keep track of everything it breaks down.

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• Adding a font for use in ReportLab

  - by Jimmy McCarthy

  I'm trying to add a font to the python ReportLab so that I can use it for a function. The function is using canvas.Canvas to draw a bunch of text in a PDF, nothing complicated, but I need to add a fixed width font for layout issues. When I tried to register a font using what little info I could find, that seemed to work. But when I tried to call .addFont('fontname') from my Canvas object I keep getting "PDFDocument instance has no attribute 'addFont'" Is the function just not implemented? How do I get access to fonts other than the 10 or so default ones that are listed in .getAvailableFonts? Thanks. Some example code of what I'm trying to make happen: from reportlab.pdfgen import canvas c = canvas.Canvas('label.pdf') c.addFont('TestFont') #This throws the error listed above, regardless of what argument I use (whether it refers to a font or not). c.drawString(1,1,'test data here') c.showPage() c.save() To register the font, I tried from reportlab.lib.fonts import addMapping from reportlab.pdfbase import pdfmetrics pdfmetrics.registerFont(TTFont('TestFont', 'ghettomarquee.ttf')) addMapping('TestFont', 0, 0, 'TestFont') where 'ghettomarquee.ttf' was just a random font I had lying around.

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• Binary search in a sorted (memory-mapped ?) file in Java

  - by sds

  I am struggling to port a Perl program to Java, and learning Java as I go. A central component of the original program is a Perl module that does string prefix lookups in a +500 GB sorted text file using binary search (essentially, "seek" to a byte offset in the middle of the file, backtrack to nearest newline, compare line prefix with the search string, "seek" to half/double that byte offset, repeat until found...) I have experimented with several database solutions but found that nothing beats this in sheer lookup speed with data sets of this size. Do you know of any existing Java library that implements such functionality? Failing that, could you point me to some idiomatic example code that does random access reads in text files? Alternatively, I am not familiar with the new (?) Java I/O libraries but would it be an option to memory-map the 500 GB text file (I'm on a 64-bit machine with memory to spare) and do binary search on the memory-mapped byte array? I would be very interested to hear any experiences you have to share about this and similar problems.

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• Finding a picture in a picture with java?

  - by tarrasch

  what i want to to is analyse input from screen in form of pictures. I want to be able to identify a part of an image in a bigger image and get its coordinates within the bigger picture. Example: would have to be located in And the result would be the upper right corner of the picture in the big picture and the lower left of the part in the big picture. As you can see, the white part of the picture is irrelevant, what i basically need is just the green frame. Is there a library that can do something like this for me? Runtime is not really an issue. What i want to do with this is just generating a few random pixel coordinates and recognize the color in the big picture at that position, to recognize the green box fast later. And how would it decrease performance, if the white box in the middle is transparent? The question has been asked several times on SO as it seems without a single answer. I found i found a solution at http://werner.yellowcouch.org/Papers/subimg/index.html . Unfortunately its in C++ and i do not understand a thing. Would be nice to have a Java implementation on SO.

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