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• How can I disable keep-alive on ASP.NET Web Service client requests?

  - by Matthew Brindley

  I have a few web servers behind an Amazon EC2 load balancer. I'm using TCP balancing on port 80 (rather than HTTP balancing). I have a client polling a Web Service (running on all web servers) for new items every few seconds. However, the client seems to stay connected to one server and polls that same server each time. I've tried using ServicePointManager to disable KeepAlive, but that didn't change anything. The outgoing connection still had its "connection: keep-alive" HTTP header, and the server kept the TCP connection open. I've also tried adding an override of GetWebRequest to the proxy class created by VS, which inherits from SoapHttpClientProtocol, but I still see the keep-alive header. If I kill the client's process and restart, it'll connect to a new server via the load balancer, but it'll continue polling that new server forever. Is there a way to force it to connect to a random server each time? I want the load from the one client to be spread across all of the web servers. The client is written in C# (as is the server) and uses a Web Reference (not a Service Reference), which points to the load balancer.

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• Java OutOfMemoryError due to Linux RAM disk cache not freed

  - by Markus Jevring

  The process will run fine all day, then, bam, without warning, it will throw this error. Sometimes seemingly in the middle of doing nothing. It will happen at seemingly random times during the day. I checked to see if anything else was running on the machine, like scheduled backups or something, but found nothing. The machine has enough physical memory (2GB, with about 1GB free for a 3-500MB load), and has sufficient -Xmx specified. According to our sysadmin, the problem is that the RAM that the kernel uses as a disk cache (apparently all but 8MB) is not freed when the JVM needs to allocate memory, so the JVM process throws an OutOfMemoryError. This could be because Java asks the kernel if enough memory is available before allocating and finds that it is insufficient, resulting in a crash. I would like to think, however, that Java simply tries to allocate the memory via the kernel, and when the kernel gets such a request, it makes room for the application by throwing our some of the disk cache. Has anyone else run in to the issue, and if so, what was the error, and how did you solve it? We are currently using jdk1.6.0_20 on SLES 10 SP2 Linux 2.6.16.60-0.42.9-smp in VMWare ESX.

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• iPad + OpenGL ES2. Why the Puzzling Virtual Memory Spike During Device Reorientation?

  - by dugla

  I've been spending the afternoon starring at Xcode Instruments memory monitor trying to decipher the following memory issue. I have a fullscreen OpenGL ES2 app running on iPad. I am fanatical about memory issues so my retains/releases are all nicely balanced. I closely monitor memory leaks. My app is basically squeeky clean. Except occassionally when I reorient the device. Portrait to Landscape. Back and forth I rock the device stress testing my discarding and rebuilding of the OpenGL framebuffer. The ambient memory footprint of my app is about 70MB Real Mems and 180MB Virtual Mems. Real memory hardly varies at all during device rotations. However the virtual mems reading sometimes briefly spikes up to 250MB and then recedes back to 180MB. No real pattern. But clearly related discarding/rebuilding the framebuffer. I see random memory warnings in my NSlogs but the app just hums along, no worries. 1) Since iPhone OS devices don't have VM could someone explain to me what the VM reading actually means? 2) My app totally leak free and generally bulletproof dispite the VM spikes. Never crashes. Rock solid. Should I be concerned about this? 3) There is clearly something happening in OpenGL framebuffer land that is causing this but I am using the API in the proper way: paraphrasing: Discarding the framebuffer: glDeleteRenderbuffers(1, &m_colorbuffer); glDeleteFramebuffers(1, &m_framebuffer); Rebuilding the framebuffer: glGenFramebuffers(1, &m_framebuffer); glGenRenderbuffers(1, &m_colorbuffer); Is there some other memory flushing trick I have missed? Thanks for any insight. Cheers, Doug

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• Preventing iframe caching in browser

  - by Zarjay

  How do you prevent Firefox and Safari from caching iframe content? I have a simple webpage with an iframe to a page on a different site. Both the outer page and the inner page have HTTP response headers to prevent caching. When I click the "back" button in the browser, the outer page works properly, but no matter what, the browser always retrieves a cache of the iframed page. IE works just fine, but Firefox and Safari are giving me trouble. My webpage looks something like this: <html> <head><!-- stuff --></head> <body> <!-- stuff --> <iframe src="webpage2.html?var=xxx" /> <!-- stuff --> </body> </html> The var variable always changes. Despite the fact that the URL of the iframe has changed (and thus, the browser should be making a new request to that page), the browser just fetches the cached content. I've examined the HTTP requests and responses going back and forth, and I noticed that even if the outer page contains <iframe src="webpage2.html?var=222" />, the browser will still fetch webpage2.html?var=111. Here's what I've tried so far: Changing iframe URL with random var value Adding Expires, Cache-Control, and Pragma headers to outer webpage Adding Expires, Cache-Control, and Pragma headers to inner webpage I'm unable to do any JavaScript tricks because I'm blocked by the same-origin policy. I'm running out of ideas. Does anyone know how to stop the browser from caching the iframed content?

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• jQuery hover DIV- stay active if they hover over the DIV itself

  - by Lock

  I have a DIV that opens up when an image is hovered. When the user leaves the image, the div disappears after a timeout. How can I make it so that the DIV will stay active if the user was to hover over the DIV itself? So the DIV will stay active as long as the user is on the image or the DIV itself? I am using the following: $(document).ready(function() { $(".hover").hover( function(e){ if ( $("#status").is(":hidden")) { var ref = $(this).attr("wsref"); var url = "https://site/_ref/shop/_base/order_status.php?action=getstatus&ref="+ref+"&sid="+Math.random(); $("#status").show(); var height = $(".status").height(); var width = $(".status").width(); leftVal = e.pageX - width -10 + "px"; topVal = e.pageY - height -10 + "px"; $("#status").css({left:leftVal,top:topVal}); $("#status").html("<div id='loading'></div>").load(url); } }, function() { if ( $("#status").is(':visible')) { setTimeout('$("#status").hide()',0); } }); }); HTML <a href="#"><img class="hover" title="Order Received" name="Order Received" src="https://site/_ref/images/cart.png" wsref="002731"/></a>

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• Has the recent version of subversion dealt with "Access Denied" errors from windows services that mo

  - by Eric LaForce

  Does anyone know if this subversion "bug" has been dealt with? https://svn.apache.org/repos/asf/subversion/tags/1.6.9/www/faq.html#windows-access-denied I'm getting occasional "Access Denied" errors on Windows. They seem to happen at random. Why? These appear to be due to the various Windows services that monitor the filesystem for changes (anti-virus software, indexing services, the COM+ Event Notification Service). This is not really a bug in Subversion, which makes it difficult for us to fix. A summary of the current state of the investigation is available here. A workaround that should reduce the incidence rate for most people was implemented in revision 7598; if you have an earlier version, please update to the latest release. Currently I am experiencing this same behavior in version 1.5.6 when I try and do a SVN switch (I have suspected McAfee as the culprit for a while and when I saw this I feel it validates my suspicions). I read through the link given but it seems pretty old, so I didn't know if this FAQ was just outdated and the issue has actually be resolved. Thanks for any help. Configuration: SVN 1.5.6 TortoiseSVN 1.5.9 Build 15518 Windows XP SP3 32-bit

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• Calling web service using javascript error

  - by politrok

  Hi , I try to call webservice using json , when i call to web service without excepted parameters , its work , but when i'm try to send parameter , ive got an error : This is my code: function GetSynchronousJSONResponse(url, postData) { var xmlhttp = null; if (window.XMLHttpRequest) xmlhttp = new XMLHttpRequest(); else if (window.ActiveXObject) { if (new ActiveXObject("Microsoft.XMLHTTP")) xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); else xmlhttp = new ActiveXObject("Msxml2.XMLHTTP"); } url = url + "?rnd=" + Math.random(); // to be ensure non-cached version xmlhttp.open("POST", url, false); xmlhttp.setRequestHeader("Content-Type", "application/json; charset=utf-8"); xmlhttp.send(postData); var responseText = xmlhttp.responseText; return responseText; } function Test() { var result = GetSynchronousJSONResponse('http://localhost:1517/Mysite/Myservice.asmx/myProc', '{"MyParam":"' + 'test' + '"}'); result = eval('(' + result + ')'); alert(result.d); } This is the error : System.InvalidOperationException: Request format is invalid: application/json; charset=utf-8. at System.Web.Services.Protocols.HttpServerProtocol.ReadParameters() at System.Web.Services.Protocols.WebServiceHandler.CoreProcessRequest What is wrong ? Thanks in advance .

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• mysql error in php

  - by fusion

  i'm trying to run this php code which should display a quote from mysql, but can't figure out where is it going wrong. the result variable is null or empty. can someone help me out. thanks! <?php include 'config.php'; // 'text' is the name of your table that contains // the information you want to pull from $rowcount = mysql_query("select count(*) as rows from quotes"); // Gets the total number of items pulled from database. while ($row = mysql_fetch_assoc($rowcount)) { $max = $row["rows"]; //print_r ($max); } // Selects an item's index at random $rand = rand(1,$max)-1; print_r ($rand); $result = mysql_query("select * from quotes limit $rand, 1") or die ('Error: '.mysql_error()); if (!$result or mysql_num_rows($result)) { echo "Empty"; } else{ while ($row = mysql_fetch_array($result)) { $randomOutput = $row['cQuotes']; echo '<p>' . $randomOutput . '</p>'; } }

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• iPhone: UIImagePickerController Randomly Fails to Take Picture

  - by pion

  I use a UIPickerViewController to take picture. It works 80% but seemingly at random it fails to take a picture. In tracing the code I found out that it occasionally goes to -PinRecordNewTableViewController:viewDidUnload. That is where it fails because it set nil to all ivars. @interface PinRecordNewTableViewController : UITableViewController { } ... @implementation PinRecordNewTableViewController ... - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { ... PinRecordNewPicture *pinRecordNewPicture = [[PinRecordNewPicture alloc] initWithNibName:@"PinRecordNewPicture" bundle:nil]; pinRecordNewPicture.delegate = self; [self.navigationController pushViewController:pinRecordNewPicture animated:YES]; [pinRecordNewPicture release]; ... } @interface PinRecordNewPicture : UIViewController ... @implementation PinRecordNewPicture ... - (void)picturePicker:(UIImagePickerControllerSourceType)theSource { UIImagePickerController *picker = [[UIImagePickerController alloc] init]; picker.delegate = self; picker.sourceType = theSource; picker.allowsEditing = YES; [self presentModalViewController:picker animated:YES]; [picker release]; } - (IBAction) takePicture:(id)sender { UIImagePickerControllerSourceType source = UIImagePickerControllerSourceTypeCamera; if ([UIImagePickerController isSourceTypeAvailable:source]) { [self picturePicker:source]; } What did I do wrong? Did I miss something that causes it to behave "randomly"? Thanks in advance for your help.

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• Bubble Breaker Game Solver better than greedy?

  - by Gregory

  For a mental exercise I decided to try and solve the bubble breaker game found on many cell phones as well as an example here:Bubble Break Game The random (N,M,C) board consists N rows x M columns with C colors The goal is to get the highest score by picking the sequence of bubble groups that ultimately leads to the highest score A bubble group is 2 or more bubbles of the same color that are adjacent to each other in either x or y direction. Diagonals do not count When a group is picked, the bubbles disappear, any holes are filled with bubbles from above first, ie shift down, then any holes are filled by shifting right A bubble group score = n * (n - 1) where n is the number of bubbles in the bubble group The first algorithm is a simple exhaustive recursive algorithm which explores going through the board row by row and column by column picking bubble groups. Once the bubble group is picked, we create a new board and try to solve that board, recursively descending down Some of the ideas I am using include normalized memoization. Once a board is solved we store the board and the best score in a memoization table. I create a prototype in python which shows a (2,15,5) board takes 8859 boards to solve in about 3 seconds. A (3,15,5) board takes 12,384,726 boards in 50 minutes on a server. The solver rate is ~3k-4k boards/sec and gradually decreases as the memoization search takes longer. Memoization table grows to 5,692,482 boards, and hits 6,713,566 times. What other approaches could yield high scores besides the exhaustive search? I don't seen any obvious way to divide and conquer. But trending towards larger and larger bubbles groups seems to be one approach Thanks to David Locke for posting the paper link which talks above a window solver which uses a constant-depth lookahead heuristic.

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• what's the correct way to release a new website?

  - by kk

  so i've been working on a website on and off for about a year now, and i'm finally at a point where it's functional enough to test out in a sort of private beta (not ready for live release). but i never thought about the correct process for doing this and what things i need to take care of. i've never released a public website before. some of the questions/concerns i have in mind: 1) is it against my MSDN license agreement to release a website using the software? 2) how do i protect my "idea"? is it a bad idea to find random people you don't know to test out your site? can you make them digitally sign some sort of NDA? 3) i'm using some open source code - any proper way to release open source code to live production? 4) how much traffic can a place like discountasp.net handle anyway? can hosting sites generally handle large volume of traffic? any comments/suggestions regarding the proper/safe way to release a public website would be appreciated. i've been working on this for a while and never actually sat down to think about the right way to move from a personal side project to a live production website.

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• Versioning friendly, extendible binary file format

  - by Bas Bossink

  In the project I'm currently working on there is a need to save a sizable data structure to disk (edit: think dozens of MB's). Being an optimist, I thought that there must be a standard solution for such a problem; however, up to now I haven't found a solution that satisfies the following requirements: .NET 2.0 support, preferably with a FOSS implementation Version friendly (this should be interpreted as: reading an old version of the format should be relatively simple if the changes in the underlying data structure are simple, say adding/dropping fields) Ability to do some form of random access where part of the data can be extended after initial creation (think of this as extending intermediate results) Space and time efficient (XML has been excluded as option given this requirement) Options considered so far: Protocol Buffers: was turned down by verdict of the documentation about Large Data Sets - since this comment suggested adding another layer on top, this would call for additional complexity which I wish to have handled by the file format itself. HDF5,EXI: do not seem to have .net implementations SQLite/SQL Server Compact edition: the data structure at hand would result in a pretty complex table structure that seems too heavyweight for the intended use BSON: does not appear to support requirement 3. Fast Infoset: only seems to have paid .NET implementations. Any recommendations or pointers are greatly appreciated. Furthermore if you believe any of the information above is not true, please provide pointers/examples to prove me wrong.

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• Concat LPSTR in C++

  - by Cat Man Do

  Trying to use as basic C++ as I can to build a list of numbers from 1-52 in a random order (deck of cards). Unfortauntely, all my attempts to concat the strings and get a result end in failure. Any suggestions? NOTE: This is not homework it's something I'm using to create a game. // Locals char result[200] = ""; // Result int card[52]; // Array of cards srand(time(0)); // Initialize seed "randomly" // Build for (int i=0; i<52; i++) { card[i] = i; // fill the array in order } // Shuffle cards for (int i=0; i<(52-1); i++) { int r = i + (rand() % (52-i)); int temp = card[i]; card[i] = card[r]; card[r] = temp; } // Build result for (int c=0; c<52; c++) { // Build sprintf(result, "%d", card[c]); // Comma? if ( c < 51 ) { sprintf(result, "%s", ","); } } My end result is always garbled text. Thanks for the help.

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• LINQ to SQL - Tracking New / Dirty Objects

  - by Joseph Sturtevant

  Is there a way to determine if a LINQ object has not yet been inserted in the database (new) or has been changed since the last update (dirty)? I plan on binding my UI to LINQ objects (using WPF) and need it to behave differently depending whether or not the object is already in the database. MyDataContext context = new MyDataContext(); MyObject obj; if (new Random().NextDouble() > .5) obj = new MyObject(); else obj = context.MyObjects.First(); // How can I distinguish these two cases? The only simple solution I can think of is to set the primary key of new records to a negative value (my PKs are an identity field and will therefore be set to a positive integer on INSERT). This will only work for detecting new records. It also requires identity PKs, and requires control of the code creating the new object. Is there a better way to do this? It seems like LINQ must be internally tracking the status of these objects so that it can know what to do on context.SubmitChanges(). Is there some way to access that "object status"? Clarification Apparently my initial question was confusing. I'm not looking for a way to insert or update records. I'm looking for a way, given any LINQ object, to determine if that object has not been inserted (new) or has been changed since its last update (dirty).

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• Looping through python-dictionary-turned-into-json in javascript.

  - by Phil

  In writing a django app, I am returning the following json on a jQuery ajax call: { "is_owner": "T", "author": "me", "overall": "the surfing lifestyle", "score": "1", "meanings": { "0": "something", "1": "something else", "3": "yet something else", "23": "something random" }, "user vote": "1" } In the javascript/jQuery callback function, I can access the is_owner, author, etc. easily enough. is_owner = json.is_owner; author = json.author; But for meanings, the numbers are different depending on what it pulls from the server. On the server side for the meanings part, right now what I'm doing is constructing a dictionary like so: meanings_dict = {} meanings = requested_tayke.meanings.all() for meaning in meanings: meanings_dict[meaning.location] = meaning.text and then returning a json I create like this: test_json = simplejson.dumps({'is_owner':is_owner, 'overall':overall, 'score':str(score),'user vote':str(user_vote), 'author': author, 'meanings' : meanings_dict }) print test_json return HttpResponse(test_json) My question is this: how do I access the 'meanings' data from my json in javascript? I need to loop through all of it. Maybe I need to be loading it into json differently. I have full control so of both the server and client side so I'm willing to change either to make it work. Also worth noting: I'm not using Django's serialize functionality. I couldn't make it work with my situation.

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• What Is The Proper Location For One-Offs In VCS Repos?

  - by Joe Clark

  I have recently started using Mercurial as our VCS. Over the years, I have used RCS, CVS, and - for the last 5 years - SVN. Back 13 years ago, when I primarily used CVS and RCS, large projects went into CVS and one-offs were edited in place on the specific server and stored in RCS. This worked well as the one-offs were usually specific to the server and the servers were backed up nightly. Jump forward a decade and a lot of the one-off scripts became less centralized - they might be needed on any server at some random time. This was also OK, because now I was a begrudging SVN user. Everything (except for docs) got dumped into one repo. Jump to 2010. Now I am using Mercurial and am putting large projects in their own repo again. But what to do with the one-offs? The options as I see them: A repo for each script. It seems a bit cluttered to create a repo for every one page script that might get ran once a year. RCS Not an option. There are many possible servers that might need a specific script. Continuing to use SVN just for one-offs. No. There no advantage I see over the next option. Create a repo in Mercurial named "one-offs". This seems the most workable. The last option seems the best to me - however; is there a best practice regarding this? You also might be wondering if these scripts are truly one-offs if they will be reused. Some of them may be reused 6 months or a year from now - some, never. However, nearly all of them involve several man-hours of work due to either complex logic or extensive error checking. Simply discarding them is not efficient.

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• How to exploit Diffie-hellman to perform a man in the middle attack

  - by jfisk

  Im doing a project where Alice and Bob send each other messages using the Diffie-Hellman key-exchange. What is throwing me for a loop is how to incorporate the certificate they are using in this so i can obtain their secret messages. From what I understand about MIM attakcs, the MIM acts as an imposter as seen on this diagram: Below are the details for my project. I understand that they both have g and p agreed upon before communicating, but how would I be able to implement this with they both having a certificate to verify their signatures? Alice prepares ?signA(NA, Bob), pkA, certA? where signA is the digital signature algorithm used by Alice, “Bob” is Bob’s name, pkA is the public-key of Alice which equals gx mod p encoded according to X.509 for a fixed g, p as specified in the Diffie-Hellman key- exchange and certA is the certificate of Alice that contains Alice’s public-key that verifies the signature; Finally, NA is a nonce (random string) that is 8 bytes long. Bob checks Alice's signature, and response with ?signB{NA,NB,Alice},pkB,certB?. Alice gets the message she checks her nonce NA and calculates the joint key based on pkA, pkB according to the Diffie-Hellman key exchange. Then Alice submits the message ?signA{NA,NB,Bob},EK(MA),certA? to Bob and Bobrespondswith?SignB{NA,NB,Alice},EK(MB),certB?. where MA and MB are their corresponding secret messages.

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• Alternative native api for Process.Start

  - by Akash Kava

  Ok this is not duplicate of "http://stackoverflow.com/questions/2065592/alternative-to-process-start" because my question is something different here. I need to run a process and wait till execution of process and get the output of console. There is way to set RedirectStandardOutput and RedirectStandardError to true, however this does not function well on some machines, (where .NET SDK is not installed), only .NET runtime is installed, now it works on some machines and doesnt work on some machines so we dont know where is the problem. I have following code, ProcessStartInfo info = new ProcessStartInfo("myapp.exe", cmd); info.CreateNoWindow = true; info.UseShellExecute = false; info.RedirectStandardError = true; info.RedirectStandardOutput = true; Process p = Process.Start(info); p.WaitForExit(); Trace.WriteLine(p.StandardOutput.ReadToEnd()); Trace.WriteLine(p.StandardError.ReadToEnd()); On some machines, this will hang forever on p.WaitForExit(), and one some machine it works correctly, the behaviour is so random and there is no clue. Now if I can get a real good workaround for this using pinvoke, I will be very happy.

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• Silverlight 4 race condition with DataGrid master details control

  - by Simon_Weaver

  Basically I want a DataGrid (master) and details (textbox), where DataGrid is disabled during edit of details (forcing people to save/cancel)... Here's what I have... I have a DataGrid which serves as my master data. <data:DataGrid IsEnabled="{Binding CanLoad,ElementName=dsReminders}" ItemsSource="{Binding Data, ElementName=dsReminders}" > Its data comes from a DomainDataSource: <riaControls:DomainDataSource Name="dsReminders" AutoLoad="True" ... I have a bound Textbox which is the 'details' (very simple right now). There are buttons (Save/Cancel) which should be enabled when user tries to edit the text. Unfortunately Silverlight doesn't support UpdateSourceTrigger=PropertyChanged so I have to raise an event: <TextBox Text="{Binding SelectedItem.AcknowledgedNote, Mode=TwoWay, UpdateSourceTrigger=Explicit, ElementName=gridReminders}" TextChanged="txtAcknowledgedNote_TextChanged"/> The event to handle this calls BindingExpression.UpdateSource to update the source immediately: private void txtAcknowledgedNote_TextChanged(object sender, TextChangedEventArgs e) { BindingExpression be = txtAcknowledgedNote.GetBindingExpression(TextBox.TextProperty); be.UpdateSource(); } IN other words - typing in the textbox causes CanLoad of the DomainDataSource to become False (because we're editing). This in turn disables the DataGrid (IsEnabled is bound to it) and enables 'Cancel' and 'Save' buttons. However I'm running up against a race condition if I move quickly through rows in the DataGrid (just clicking random rows). The TextChanged presumably is being called on the textbox and confusing the DomainDataSource which then thinks there's been a change. So how should I disable the DataGrid while editing without having the race condition? One obvious solution would be to use KeyDown events to trigger the call to UpdateSource but I always hate having to do that.

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• How to get the coordinate of Gridlayout

  - by Jessy

  Hi, I set my JPanel to GridLayout (6,6), with dimension (600,600) Each cell of the grid will display one pictures with different widths and heights. The picture first add to a JLabel, and the JLabel then added to the cells. How can retrieved the coordinate of the pictures in the cells and not the coordinate of cells? So far the out give these coordinate which equal height and width even on screen the pictures showed in different sizes. e.g. java.awt.Rectangle[x=100,y=100,width=100,height=100] java.awt.Rectangle[x=200,y=100,width=100,height=100] java.awt.Rectangle[x=300,y=100,width=100,height=100] The reason why I used GridLayout instead of gridBagLayout is that, I want each pictures to have boundary. If I use GridBagLayout, the grid will expand according to the picture size. I want grid size to be in fix size. JPanel pDraw = new JPanel(new GridLayout(6,6)); pDraw.setPreferredSize(new Dimension(600,600)); for (int i =0; i<(6*6); i++) { //get random number for height and width of the image int x = rand.nextInt(40)+(50); int y = rand.nextInt(40)+(50); ImageIcon icon = createImageIcon("bird.jpg"); //rescale the image according to the size selected Image img = icon.getImage().getScaledInstance(x,y,img.SCALE_SMOOTH); icon.setImage(img ); JLabel label = new JLabel(icon); pDraw.add(label); } for(Component component:components) { //retrieve the coordinate System.out.println(component.getBounds()); }

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• Evolutionary Algorithms: Optimal Repopulation Breakdowns

  - by Brian MacKay

  It's really all in the title, but here's a breakdown for anyone who is interested in Evolutionary Algorithms: In an EA, the basic premise is that you randomly generate a certain number of organisms (which are really just sets of parameters), run them against a problem, and then let the top performers survive. You then repopulate with a combination of crossbreeds of the survivors, mutations of the survivors, and also a certain number of new random organisms. Do that several thousand times, and efficient organisms arise. Some people also do things like introduce multiple "islands" of organisms, which are seperate populations that are allowed to crossbreed once in awhile. So, my question is: what are the optimal repopulation percentages? I have been keeping the top 10% performers, and repopulating with 30% crossbreeds and 30% mutations. The remaining 30% is for new organisms. I have also tried out the multiple island theory, and I'm interested in your results on that as well. It is not lost on me that this is exactly the type of problem an EA could solve. Are you aware of anyone trying that? Thanks in advance!

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• How to draw line inside a scatter plot

  - by ruffy

  I can't believe that this is so complicated but I tried and googled for a while now. I just want to analyse my scatter plot with a few graphical features. For starters, I want to add simply a line. So, I have a few (4) points and like in this plot [1] I want to add a line to it. http://en.wikipedia.org/wiki/File:ROC_space-2.png [1] Now, this won't work. And frankly, the documentation-examples-gallery combo and content of matplotlib is a bad source for information. My code is based upon a simple scatter plot from the gallery: # definitions for the axes left, width = 0.1, 0.85 #0.65 bottom, height = 0.1, 0.85 #0.65 bottom_h = left_h = left+width+0.02 rect_scatter = [left, bottom, width, height] # start with a rectangular Figure fig = plt.figure(1, figsize=(8,8)) axScatter = plt.axes(rect_scatter) # the scatter plot: p1 = axScatter.scatter(x[0], y[0], c='blue', s = 70) p2 = axScatter.scatter(x[1], y[1], c='green', s = 70) p3 = axScatter.scatter(x[2], y[2], c='red', s = 70) p4 = axScatter.scatter(x[3], y[3], c='yellow', s = 70) p5 = axScatter.plot([1,2,3], "r--") plt.legend([p1, p2, p3, p4, p5], [names[0], names[1], names[2], names[3], "Random guess"], loc = 2) # now determine nice limits by hand: binwidth = 0.25 xymax = np.max( [np.max(np.fabs(x)), np.max(np.fabs(y))] ) lim = ( int(xymax/binwidth) + 1) * binwidth axScatter.set_xlim( (-lim, lim) ) axScatter.set_ylim( (-lim, lim) ) xText = axScatter.set_xlabel('FPR / Specificity') yText = axScatter.set_ylabel('TPR / Sensitivity') bins = np.arange(-lim, lim + binwidth, binwidth) plt.show() Everything works, except the p5 which is a line. Now how is this supposed to work? What's good practice here?

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• How to detect hidden field tampering?

  - by Myron

  On a form of my web app, I've got a hidden field that I need to protect from tampering for security reasons. I'm trying to come up with a solution whereby I can detect if the value of the hidden field has been changed, and react appropriately (i.e. with a generic "Something went wrong, please try again" error message). The solution should be secure enough that brute force attacks are infeasible. I've got a basic solution that I think will work, but I'm not security expert and I may be totally missing something here. My idea is to render two hidden inputs: one named "important_value", containing the value I need to protect, and one named "important_value_hash" containing the SHA hash of the important value concatenated with a constant long random string (i.e. the same string will be used every time). When the form is submitted, the server will re-compute the SHA hash, and compare against the submitted value of important_value_hash. If they are not the same, the important_value has been tampered with. I could also concatenate additional values with the SHA's input string (maybe the user's IP address?), but I don't know if that really gains me anything. Will this be secure? Anyone have any insight into how it might be broken, and what could/should be done to improve it? Thanks!

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• Securely store a password in program code?

  - by Nick

  My application makes use of the RijndaelManaged class to encrypt data. As a part of this encryption, I use a SecureString object loaded with a password which get's get converted to a byte array and loaded into the RajindaelManaged object's Key at runtime. The question I have is the storage of this SecureString. A user entered password can be entered at run-time, and that can be "securely" loaded into a SecureString object, but if no user entered password is given, then I need to default to something. So ultimately the quesiton comes down to: If I have to have some known string or byte array to load into a SecureString object each time my application runs, how do I do that? The "encrypted" data ultimately gets decrypted by another application, so even if no user entered password is specified, I still need the data to be encrypted while it goes from one app to another. This means I can't have the default password be random, because the other app wouldn't be able to properly decrypt it. One possible solution I'm thinking is to create a dll which only spits out a single passphrase, then I use that passphrase and run it through a couple of different hashing/reorganizing functions at runtime before I ultimately feed it into the secureString object. Would this be secure enough?

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• Learning AES: the KeyBytes

  - by Tom Brito

  I got the following example from here: import java.security.Security; import javax.crypto.Cipher; import javax.crypto.spec.SecretKeySpec; public class MainClass { public static void main(String[] args) throws Exception { Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider()); byte[] input = "www.java2s.com".getBytes(); byte[] keyBytes = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 }; SecretKeySpec key = new SecretKeySpec(keyBytes, "AES"); Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC"); System.out.println(new String(input)); // encryption pass cipher.init(Cipher.ENCRYPT_MODE, key); byte[] cipherText = new byte[cipher.getOutputSize(input.length)]; int ctLength = cipher.update(input, 0, input.length, cipherText, 0); ctLength += cipher.doFinal(cipherText, ctLength); System.out.println(new String(cipherText)); System.out.println(ctLength); // decryption pass cipher.init(Cipher.DECRYPT_MODE, key); byte[] plainText = new byte[cipher.getOutputSize(ctLength)]; int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0); ptLength += cipher.doFinal(plainText, ptLength); System.out.println(new String(plainText)); System.out.println(ptLength); } } I imagine that the byte[] keyBytes should be random generated, so I gone to test the max size before do it. When adding one more byte 0x18 to the array, the exception raised: InvalidKeyException: Key length not 128/192/256 bits. But the original 18 bytes (from 0 to 17) are not multiple of nither 128, 192 or 256. I would like to understand the math here.. can anyone explain me? Thanks!

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