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  • Caching vector addition over changing collections

    - by DRMacIver
    I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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  • get next available integer using LINQ

    - by Daniel Williams
    Say I have a list of integers: List<int> myInts = new List<int>() {1,2,3,5,8,13,21}; I would like to get the next available integer, ordered by increasing integer. Not the last or highest one, but in this case the next integer that is not in this list. In this case the number is 4. Is there a LINQ statement that would give me this? As in: var nextAvailable = myInts.SomeCoolLinqMethod(); Edit: Crap. I said the answer should be 2 but I meant 4. I apologize for that! For example: Imagine that you are responsible for handing out process IDs. You want to get the list of current process IDs, and issue a next one, but the next one should not just be the highest value plus one. Rather, it should be the next one available from an ordered list of process IDs. You could get the next available starting with the highest, it does not really matter.

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  • SQL left join with multiple rows into one row

    - by beardedd
    Basically, I have two tables, Table A contains the actual items that I care to get out, and Table B is used for language translations. So, for example, Table A contains the actual content. Anytime text is used within the table, instead of storing actual varchar values, ids are stored that relate back to text stored in Table B. This allows me to by adding a languageID column to Table B, have multiple translations for the same row in the database. Example: Table A Title (int) Description (int) Other Data.... Table B TextID (int) - This is the column whose value is stored in other tables LanguageID (int) Text (varchar) My question is more a call for suggestions on how to best handle this. Ideally I want a query that I can use to select from the table, and get the text as opposed to the ids of the text out of the table. Currently when I have two text items in the table this is what I do: SELECT C.ID, C.Title, D.Text AS Description FROM (SELECT A.ID, A.Description, B.Text AS Title FROM TableA A, TranslationsTable B WHERE A.Title = B.TextID AND B.LanguaugeID = 1) C LEFT JOIN TranslationsTable D ON C.Description = D.TextID AND D.LanguaugeID = 1 This query gives me the row from Table A I am looking for (using where statements in the inner select statement) with the actual text based on the language ID used instead of the text ids. This works fine when I am only using one or two text items that need to be translated, but adding a third item or more, it starts to get really messy - essentially another left join on top of the example. Any suggestions on a better query, or at least a good way to handle 3 or more text items in a single row?

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  • How do I make a lock that allows only ONE thread to read from the resource ?

    - by mare
    I have a file that holds an integer ID value. Currently reading the file is protected with ReaderWriterLockSlim as such: public int GetId() { _fileLock.EnterUpgradeableReadLock(); int id = 0; try { if(!File.Exists(_filePath)) CreateIdentityFile(); FileStream readStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read); StreamReader sr = new StreamReader(readStream); string line = sr.ReadLine(); sr.Close(); readStream.Close(); id = int.Parse(line); return int.Parse(line); } finally { SaveNextId(id); // increment the id _fileLock.ExitUpgradeableReadLock(); } } The problem is that subsequent actions after GetId() might fail. As you can see the GetId() method increments the ID every single time, disregarding what happens after it has issued an ID. The issued ID might be left hanging (as said, exceptions might occur). As the ID is incremented, some IDs might be left unused. So I was thinking of moving the SaveNextId(id) out, remove it (the SaveNextId() actually uses the lock too, except that it's EnterWriteLock). And call it manually from outside after all the required methods have executed. That brings out another problem - multiple threads might enter the GetId() method before the SaveNextId() gets executed and they might all receive the same ID. I don't want any solutions where I have to alter the IDs after the operation, correcting them in any way because that's not nice and might lead to more problems. I need a solution where I can somehow callback into the FileIdentityManager (that's the class that handles these IDs) and let the manager know that it can perform the saving of the next ID and then release the read lock on the file containing the ID. Essentialy I want to replicate the relational databases autoincrement behaviour - if anything goes wrong during row insertion, the ID is not used, it is still available for use but it also never happens that the same ID is issued. Hopefully the question is understandable enough for you to provide some solutions..

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  • How can you exclude a large number of records in a cross db query using LINQ2SQL?

    - by tap
    So here is my situation: I have a vendor supplied DB we cannot modify and a custom db that imports data from the vendor app and acts on it. Once records are imported form the vendor app, they cannot appear on the list of records to be imported. Also we only want to display the 250 most recent records that have not been imported. What I originally started with was select the list of ids that have been imported from the custom db, and then query the vendor db, using the list of ids in a .Where(x = !idList.Contains(x.Id)) clause on the remote query. This worked up until we broke 2100 records imported into the custom db, as 2100 is the limit on the number of parameters that can be passed into SQL. After finding out this was the actual problem and not the 'invalid buffer'/'severe error' ADO.Net reported, my solution was to remove the first 2000 ids in the remote query, and then remove the remaining records in the local query. Having to pull back a large number of irrelevant records, just to exclude them, so I can get the correct 250 records seems very inelegant. Is there a better way to do this, short of doing a cross db stored procedure? Thanks in advance.

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  • Integration testing - can it be done right?

    - by Max
    I used TDD as a development style on some projects in the past two years, but I always get stuck on the same point: how can I test the integration of the various parts of my program? What I am currently doing is writing a testcase per class (this is my rule of thumb: a "unit" is a class, and each class has one or more testcases). I try to resolve dependencies by using mocks and stubs and this works really well as each class can be tested independently. After some coding, all important classes are tested. I then "wire" them together using an IoC container. And here I am stuck: How to test if the wiring was successfull and the objects interact the way I want? An example: Think of a web application. There is a controller class which takes an array of ids, uses a repository to fetch the records based on these ids and then iterates over the records and writes them as a string to an outfile. To make it simple, there would be three classes: Controller, Repository, OutfileWriter. Each of them is tested in isolation. What I would do in order to test the "real" application: making the http request (either manually or automated) with some ids from the database and then look in the filesystem if the file was written. Of course this process could be automated, but still: doesn´t that duplicate the test-logic? Is this what is called an "integration test"? In a book i recently read about Unit Testing it seemed to me that integration testing was more of an anti-pattern?

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  • SLRequest return nil before block complete

    - by jaytr0n
    I'm having a little trouble thinking through this and deciding if it's a design flaw on my behalf or if I'm missing a piece that could make this work. Basically I'm using the new SLRequest to make a Twitter API call. After the data is returned, I'd like to put it into an object and return that object: -(AUDSlide *) getFollowerSlide { SLRequest *getRequest = [SLRequest requestForServiceType:SLServiceTypeTwitter requestMethod:SLRequestMethodGET URL:[NSURL URLWithString:[NSString stringWithFormat:@"https://api.twitter.com/1.1/followers/ids.json?user_id=%@", [[self.twitterAccount valueForKey:@"properties"] valueForKey:@"user_id"]]] parameters:nil]; getRequest.account = twitterAccount; AUDSlide *slide = [[AUDSlide alloc] init]; [getRequest performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) { if ([urlResponse statusCode] == 200) { NSError *jsonError = nil; NSDictionary *list = [NSJSONSerialization JSONObjectWithData:responseData options:0 error:&jsonError]; NSLog(@"Number of Followers: %u", [[list objectForKey:@"ids"] count]); slide.title = @"Followers"; slide.number = [NSString stringWithFormat:@"%u",[[list objectForKey:@"ids"] count]]; } else{ slide.title = @"Error"; slide.number = [NSString stringWithFormat: @"E%u", [urlResponse statusCode]]; } }]; return slide; } Of course the slide is returned before the call is complete and returns a nil object. So I'm not sure if I should try to force this into a synchronous request (that seems like it could be a bad idea) or rethink the design. Does anyone have any advice?

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  • Get LDAP Information For University Email. For Thunderbird

    - by Dhruvenkumar Shah
    I am a Student at Northeastern University. They use G-Apps for email ids, so whenever I need to email someone, using university Id which ends with husky.neu.edu. I have to go Gmails compose mail, They have some LDAP Setting by which I get all the email ids using AJAX in "To" as soon as I start typing. I want to configure same in Thunderbird, I contacted university but they are not able to help me. Is it possible that on my G-Apps Gmail Settings those LDAP Parameter needed for configuration are presents? Can anyone help me? I want to configure a directory reference in my email client thunderbird, I dont know the parameters to use, it is possible I can get it somehow?

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  • how to protect php app (vbulletin) from hackers

    - by samsmith
    Our vBulletin system is under constant attack, raising cpu load and making the system very slow for legit users. The attack is a script type attack that is attempting to log in and/or create new login ids (mostly it is trying to create login ids in order to spam the site). In vBulletin, we have black listed large ranges of ips, which has helped a lot, but the attacks continue. Is there an automated way to protect the application or web server? ideally, the protection would detect the pages accessed and automatically black list the ip.

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  • Linux (lsusb) not showing String Descriptors of a USB device

    - by tzippy
    I have an embedded device that when plugged to a linux host, shows up with vid and pid that are not in the usb.ids file (proprietary IDs). However I provide String Descriptors that do show up when plugged into a Windows Host. But not on a Linux Host. lsusb -v shows only iManufacturer 3 iProduct 2 iSerial 1 But on the device side, when processing the setup requests, I see that the Strings are actually requested by the Host. By Windows and also the Linux Host. The USB Device Tree Viewwer under Windows shows this output: iManufacturer : 0x01 Language 0x0409 : "My Manufacturer" iProduct : 0x02 Language 0x0409 : "MyProduct" iSerialNumber : 0x03 Language 0x0409 : "My Serial" I feel that lsusb does not show all of the information. Is there a more informative tool?

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  • iPhone Store Kit returning invalid product ID errors

    - by EToreo
    Hello, I am trying to test In App Purchases on my iPhone and running into a problem where the product IDs I request information for end up being returned to me as invalid product IDs in the "didRecieveResponse" method. I have: Created an in store product associated with this app. It's bundle ID matches everything else. It has been cleared for sale and approved by the developer. Made sure my new provisioning profile has in store app purchases enabled and it has the full app name: "com.domain.appname" Made sure this is the provisioning profile being used to sign the app to my iPhone. Made sure that "com.domain.appname" is the app ID used to build the provisioning profile. Made sure that "com.domain.appname" is used in my plist file as the bundle identifier. Everything seems to be in place, however I still get my products returned to me as invalid IDs. This is the code I am using: - (void)requestProductData { SKProductRequest *request = [[SKProductsRequest alloc] initWithProductIdentifiers: [NSSet setWithObject: @"com.domain.appname.productid"]]; request.delegate = self; [request start]; } - (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response { NSArray *myProducts = response.products; NSArray *myInvalidProducts = response.invalidProductIdentifiers; for(int i = 1; i < myInvalidProducts.count; ++i) { std::cout <<"invalid product id = " << [[myInvalidProducts objectAtIndex:i] UTF8String] << std::endl; } for(int i = 0; i < myProducts.count; ++i) { SKProduct * myProduct = [myProducts objectAtIndex:i]; std::cout << "Product Info:" << std::endl; std::cout << "\tlocalizedTitle = " << [[myProduct localizedTitle] UTF8String] << std::endl; std::cout << "\tlocalizedDescription = " << [[myProduct localizedDescription] UTF8String] << std::endl; std::cout << "\tproductIdentifier = " << [[myProduct productIdentifier] UTF8String] << std::endl; std::cout << "\tprice = " << [[myProduct price] doubleValue] << std::endl; std::cout << "\tpriceLocale = " << [myProduct priceLocale] << std::endl; } [request autorelease]; } All my product IDs show up in the invalid printouts and none of them show up in the "Product Info:" printouts. Any suggestions would be greatly appreciated... P.S. Yes, this is built as Objective-c/c++.

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  • Passing integer lists in a sql query, best practices

    - by Artiom Chilaru
    I'm currently looking at ways to pass lists of integers in a SQL query, and try to decide which of them is best in which situation, what are the benefots of each, and what are the pitfalls, what should be avoided :) Right now I know of 3 ways that we currently use in our application. 1) Table valued parameter: Create a new Table Valued Parameter in sql server: CREATE TYPE [dbo].[TVP_INT] AS TABLE( [ID] [int] NOT NULL ) Then run the query against it: using (var conn = new SqlConnection(DataContext.GetDefaultConnectionString)) { var comm = conn.CreateCommand(); comm.CommandType = CommandType.Text; comm.CommandText = @" UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN @values IDs ON DA.ID = IDs.ID"; comm.Parameters.Add(new SqlParameter("values", downloadResults.Select(d => d.ID).ToDataTable()) { TypeName = "TVP_INT" }); conn.Open(); comm.ExecuteScalar(); } The major disadvantages of this method is the fact that Linq doesn't support table valued params (if you create an SP with a TVP param, linq won't be able to run it) :( 2) Convert the list to Binary and use it in Linq! This is a bit better.. Create an SP, and you can run it within linq :) To do this, the SP will have an IMAGE parameter, and we'll be using a user defined function (udf) to convert this to a table.. We currently have implementations of this function written in C++ and in assembly, both have pretty much the same performance :) Basically, each integer is represented by 4 bytes, and passed to the SP. In .NET we have an extension method that convers an IEnumerable to a byte array The extension method: public static Byte[] ToBinary(this IEnumerable intList) { return ToBinaryEnum(intList).ToArray(); } private static IEnumerable<Byte> ToBinaryEnum(IEnumerable<Int32> intList) { IEnumerator<Int32> marker = intList.GetEnumerator(); while (marker.MoveNext()) { Byte[] result = BitConverter.GetBytes(marker.Current); Array.Reverse(result); foreach (byte b in result) yield return b; } } The SP: CREATE PROCEDURE [Accounts-UpdateImportAttempts] @values IMAGE AS BEGIN UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN dbo.udfIntegerArray(@values, 4) IDs ON DA.ID = IDs.Value4 END And we can use it by running the SP directly, or in any linq query we need using (var db = new DataContext()) { db.Accounts_UpdateImportAttempts(downloadResults.Select(d => d.ID).ToBinary()); // or var accounts = db.Accounts .Where(a => db.udfIntegerArray(downloadResults.Select(d => d.ID).ToBinary(), 4) .Select(i => i.Value4) .Contains(a.ID)); } This method has the benefit of using compiled queries in linq (which will have the same sql definition, and query plan, so will also be cached), and can be used in SPs as well. Both these methods are theoretically unlimited, so you can pass millions of ints at a time :) 3) The simple linq .Contains() It's a more simple approach, and is perfect in simple scenarios. But is of course limited by this. using (var db = new DataContext()) { var accounts = db.Accounts .Where(a => downloadResults.Select(d => d.ID).Contains(a.ID)); } The biggest drawback of this method is that each integer in the downloadResults variable will be passed as a separate int.. In this case, the query is limited by sql (max allowed parameters in a sql query, which is a couple of thousand, if I remember right). So I'd like to ask.. What do you think is the best of these, and what other methods and approaches have I missed?

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  • Pagination number elements do not work - jquery

    - by ClarkSKent
    Hello, I am trying to get my pagination links to work. It seems when I click any of the pagination number links to go the next page, the new content does not load. literally nothing happens and when looking at the console in Firebug, nothing is sent or loaded. I have on the main page 3 links to filter the content and display it. When any of these links are clicked the results are loaded and displayed along with the associated pagination numbers for that specific content. Here is the main page so you can see what the structure looks like for the jquery: <?php include_once('generate_pagination.php'); ?> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"></script> <script type="text/javascript" src="jquery_pagination.js"></script> <div id="loading" ></div> <div id="content" data-page="1"></div> <ul id="pagination"> <?php generate_pagination($sql) ?> </ul> <br /> <br /> <a href="#" class="category" id="marketing">Marketing</a> <a href="#" class="category" id="automotive">Automotive</a> <a href="#" class="category" id="sports">Sports</a> The jquery below is pretty simple and I don't think I need to explain what it does. I believe the problem may be with the $("#pagination li").click(function(){ since the li elements are the numbers that do not work when clicked. Even when I try to fadeOut or hide the content on click nothing happens. I'm pretty new to the jquery structure so I do not fully understand where the real problem is occurring, this is just from my observation. The jquery file looks like this: $(document).ready(function(){ //Display Loading Image function Display_Load() { $("#loading").fadeIn(900,0); $("#loading").html("<img src='bigLoader.gif' />"); } //Hide Loading Image function Hide_Load() { $("#loading").fadeOut('slow'); }; //Default Starting Page Results $("#pagination li:first").css({'color' : '#FF0084'}).css({'border' : 'none'}); Display_Load(); $("#content").load("pagination_data.php?page=1", Hide_Load()); //Pagination Click $("#pagination li").click(function(){ Display_Load(); //CSS Styles $("#pagination li") .css({'border' : 'solid #dddddd 1px'}) .css({'color' : '#0063DC'}); $(this) .css({'color' : '#FF0084'}) .css({'border' : 'none'}); //Loading Data var pageNum = this.id; $("#content").load("pagination_data.php?page=" + pageNum, function(){ $(this).attr('data-page', pageNum); Hide_Load(); }); }); // Editing below. // Sort content Marketing $("a.category").click(function() { Display_Load(); var this_id = $(this).attr('id'); $.get("pagination.php", { category: this.id }, function(data){ //Load your results into the page var pageNum = $('#content').attr('data-page'); $("#pagination").load('generate_pagination.php?category=' + pageNum +'&ids='+ this_id ); $("#content").load("filter_marketing.php?page=" + pageNum +'&id='+ this_id, Hide_Load()); }); }); }); If anyone could help me on this that would be great, Thanks. EDIT: Here are the innards of <ul id="pagination">: <?php function generate_pagination($sql) { include_once('config.php'); $per_page = 3; //Calculating no of pages $result = mysql_query($sql); $count = mysql_fetch_row($result); $pages = ceil($count[0]/$per_page); //Pagination Numbers for($i=1; $i<=$pages; $i++) { echo '<li class="page_numbers" id="'.$i.'">'.$i.'</li>'; } } $ids=$_GET['ids']; generate_pagination("SELECT COUNT(*) FROM explore WHERE category='$ids'"); ?>

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  • Pagination links do not work properly - incorrect PHP function??

    - by ClarkSKent
    Hi everyone, I am still trying to figure out how to fix my pagination script to work properly. the problem I am having is when I click any of the pagination number links to go the next page, the new content does not load. literally nothing happens and when looking at the console in Firebug, nothing is sent or loaded. I have on the main page 3 links to filter the content and display it. When any of these links are clicked the results are loaded and displayed along with the associated pagination numbers for that specific content. I believe the problem is coming from the function(generate_pagination.php (seen below)). Here is the main page so you can how I am including and starting the function(I'm new to php): <?php include_once('generate_pagination.php'); ?> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"></script> <script type="text/javascript" src="jquery_pagination.js"></script> <div id="loading" ></div> <div id="content" data-page="1"></div> <ul id="pagination"> <?php generate_pagination($sql) ?> </ul> <br /> <br /> <a href="#" class="category" id="marketing">Marketing</a> <a href="#" class="category" id="automotive">Automotive</a> <a href="#" class="category" id="sports">Sports</a> This is as mentioned above, where i think the problem persists since I know nothing of the function formats and how to properly incorporate them: <?php function generate_pagination($sql) { include_once('config.php'); $per_page = 3; //Calculating no of pages $result = mysql_query($sql); $count = mysql_fetch_row($result); $pages = ceil($count[0]/$per_page); //Pagination Numbers for($i=1; $i<=$pages; $i++) { echo '<li class="page_numbers" id="'.$i.'">'.$i.'</li>'; } } $ids=$_GET['ids']; generate_pagination("SELECT COUNT(*) FROM explore WHERE category='$ids'"); ?> I thought I might as well through in the jquery if someone wants to see: $(document).ready(function(){ //Display Loading Image function Display_Load() { $("#loading").fadeIn(900,0); $("#loading").html("<img src='bigLoader.gif' />"); } //Hide Loading Image function Hide_Load() { $("#loading").fadeOut('slow'); }; //Default Starting Page Results $("#pagination li:first").css({'color' : '#FF0084'}).css({'border' : 'none'}); Display_Load(); $("#content").load("pagination_data.php?page=1", Hide_Load()); //Pagination Click $("#pagination li").click(function(){ Display_Load(); //CSS Styles $("#pagination li") .css({'border' : 'solid #dddddd 1px'}) .css({'color' : '#0063DC'}); $(this) .css({'color' : '#FF0084'}) .css({'border' : 'none'}); //Loading Data var pageNum = this.id; $("#content").load("pagination_data.php?page=" + pageNum, function(){ $(this).attr('data-page', pageNum); Hide_Load(); }); }); // Editing below. // Sort content Marketing $("a.category").click(function() { Display_Load(); var this_id = $(this).attr('id'); $.get("pagination.php", { category: this.id }, function(data){ //Load your results into the page var pageNum = $('#content').attr('data-page'); $("#pagination").load('generate_pagination.php?category=' + pageNum +'&ids='+ this_id ); $("#content").load("filter_marketing.php?page=" + pageNum +'&id='+ this_id, Hide_Load()); }); }); }); Any help would be appreciated on getting the function to work properly. Thank you.

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  • Filtering GridViewComboBoxColumn in RadGridView for WPF

    The GridViewComboBox column is used to display lookup data in user friendly manner. For our demo we bind RadGridView for WPF to a collection of custom Location objects. As you may notice – each location has a selectable Country field.  Here is the underlying ‘data model’: public class Location {  public int CountryID { get; set; }  public string CityName { get; set; } } public class Country {  public int ID { get; set; }  public string Name { get; set; } }   The location object contains the integer CountryID. Each CountryID corresponds to a certain country and with the help of GridViewComboBoxColumn we see some human readable country names instead of the underlying numeric IDs. Now The Problem: Unfortunately the filter control does not know that our Country IDs are associated with Country objects, so it displays the ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Rails and Mongoid best way to implement sharing system

    - by Matteo Pagliazzi
    I have to model User and Board in rails using mongoid as ODM. Each board is referenced to an user through a foreign key user_id and now I want to add the ability to share a board with other users. Following CRUD I'd create a new Model called something like Share and it's releated Controller with the ability to create/edit/delete a Share but I have some doubts: First, where to save informations about Shares? I think I may create a field in the Board's collection called shared_with including an array of user ids. in a MySQL I'd created a new table with the ids of who share, the resource shared and the user the resources is shared with but I don't think that's necessary using MongoDB. Every user a Board is shared with should be able to edit the Board (but not to delete it) so the Board should have two relations one with the owner and another with the users the board is shared with, right? For permission (the owner should be able to delete a board but the users it is shared with shouldn't) what to use? I'm using Devise for authentication but I think something like CanCan would fit better. but how to implement it? What do you think about this way? Do you find any problems or have better solutions?

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  • What are solutions and tradeoffs to maintain search result consistency in a web application

    - by iammichael
    Consider a web application with a custom search function that must display the results in a paged manner (twenty per page with up to hundreds of thousands of total results) and the ability to drill down to individual results that maintain next/previous links to navigate through the results. Re-executing the search on each page request to get the appropriate results for that page of data can be too expensive (up to 15s per search). Also, since the underlying data can change frequently (e.g. addition of new results), re-executing could cause the next/previous functionality to result in inconsistent behavior (e.g. the same results reappearing on a later page after having been viewed on an earlier page). What options exist to ensure the search results can be viewed across multiple pages in a consistent manner, and what tradeoffs does each option have in terms of network, CPU, memory, and storage requirements? EDIT: I thought caching the query search results was an obvious necessity. The question is really asking about where to cache the result set and what tradeoffs might exist to each. For example, storing the ids of the entities in the result set on the client, or storing the IDs of the entities themselves in the users session on the web server, or in a temporary table in the database. I'm not looking specifically for a single solution as different scenarios may result in different approaches (and such a question would be more suited for stackoverflow.com rather than here), but more of a design comparison between the possible approaches.

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  • Form development optimization

    - by Juan
    Like many web developers I do forms all the time. I found myself doing the same all the time: placing input fields, assigning a name to each, ajax the form, then create the PHP which involves to assign a PHP var to each $_REQUEST['var'], escape and validate data, build the html and emailing the results. So I found that 70% of the work is duplicated but I just can't duplicate a page and change the fields. I end up wasting more time reformatting, deleting and adding different fields than creating from scratch. I started planing to program a "list of IDs to html+php" converter in which I'd input all the IDs and this would output the basic html and php. Then I thought: there's got to be thousands of developers that go through this, I'd be reinventing the wheel. So this is my question, I'm trying to find that wheel that somebody must have invented already. I found this: http://www.trirand.com/blog/jqform/ which does more or less what I'm looking for but it's an expensive solution and it has too much functionality for what I'd be using it. Which tools do you use to optimize repetitive task about HTML and PHP?

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  • Best way to store a large amount of game objects and update the ones onscreen

    - by user3002473
    Good afternoon guys! I'm a young beginner game developer working on my first large scale game project and I've run into a situation where I'm not quite sure what the best solution may be (if there is a lone solution). The question may be vague (if anyone can think of a better title after having read the question, please edit it) or broad but I'm not quite sure what to do and I thought it would help just to discuss the problem with people more educated in the field. Before we get started, here are some of the questions I've looked at for help in the past: Best way to keep track of game objects Elegant way to simulate large amounts of entities within a game world What is the most efficient container to store dynamic game objects in? I've also read articles about different data structures commonly used in games to store game objects such as this one about slot maps, but none of them are really what I'm looking for. Also, if it helps at all I'm using Python 3 to design the game. It has to be Python 3, if I could I would use C++ or Unityscript or something else, but I'm restricted to having to use Python 3. My game will be a form of side scroller shooter game. In said game the player will traverse large rooms with large amounts of enemies and other game objects to update (think some of the larger areas in Cave Story or Iji). The player obviously can't see the entire room all at once, so there is a viewport that follows the player around and renders only a selection of the room and the game objects that it contains. This is not a foreign concept. The part that's getting me confused has to do with how certain game objects are updated. Some of them are to be updated constantly, regardless of whether or not they can be seen. Other objects however are only to be updated when they are onscreen (for example, an enemy would only be updated to react to the player when it is onscreen or when it is in a certain range of the screen). Another problem is that game objects have to be easily referable by other game objects; something that happens in the player's update() method may affect another object in the world. Collision detection in games is always a serious problem. I need a way of containing the game objects such that it minimizes the number of cases when testing for collisions against one another. The final problem is that of creating and destroying game objects. I think this problem is pretty self explanatory. To store the game objects then I've considered a number of different methods. The original method I had was to simply store all the objects in a hash table by an id. This method was simple, and decently fast as it allows all the objects to be looked up in O(1) complexity, and also allows them to be deleted fairly easily. Hash collisions would not be a major problem; I wasn't originally planning on using computer generated ids to store the game objects I was going to rely on them all using ids given to them by the game designer (such names would be strings like 'Player' or 'EnemyWeapon4'), and even if I did use computer generated ids, if I used a decent hashing algorithm then the chances of collisions would be around 1 in 4 billion. The problem with using a hash table however is that it is inefficient in checking to see what objects are in range of the viewport. Considering the fact that certain game objects move (as well as the viewport itself), the only solution I could think of in order to only update objects that are in the viewport would be to iterate through every object in the hash table and check if it is in the viewport or not, updating only the ones that are in the valid area. This would be incredibly slow in scenarios where the amount of game objects exceeds 500, or even 200. The second solution was to store everything in a 2-d list. The world is partitioned up into cells (a tilemap essentially), where each cell or tile is the same size and is square. Each cell would contain a list of the game objects that are currently occupying it (each game object would be inserted into a cell depending on the center of the object's collision mask). A 2-d list would allow me to take the top-left and bottom-right corners of the viewport and easily grab a rectangular area of the grid containing only the cells containing entities that are in valid range to be updated. This method also solves the problem of collision detection; when I take an entity I can find the cell that it is currently in, then check only against entities in it's cell and the 8 cells around it. One problem with this system however is that it prohibits easy lookup of game objects. One solution I had would be to simultaneously keep a hash table that would contain all the positions of the objects in the 2-d list indexed by the id of said object. The major problem with a 2-d list is that it would need to be rebuilt every single game frame (along with the hash table of object positions), which may be a serious detriment to game speed. Both systems have ups and downs and seem to solve some of each other's problems, however using them both together doesn't seem like the best solution either. If anyone has any thoughts, ideas, suggestions, comments, opinions or solutions on new data structures or better implementations of the existing data structures I have in mind, please post, any and all criticism and help is welcome. Thanks in advance! EDIT: Please don't close the question because it has a bad title, I'm just bad with names!

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  • The Unintended Consequences of Sound Security Policy

    - by Tanu Sood
    v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} Author: Kevin Moulton, CISSP, CISM Meet the Author: Kevin Moulton, Senior Sales Consulting Manager, Oracle Kevin Moulton, CISSP, CISM, has been in the security space for more than 25 years, and with Oracle for 7 years. He manages the East Enterprise Security Sales Consulting Team. He is also a Distinguished Toastmaster. Follow Kevin on Twitter at twitter.com/kevin_moulton, where he sometimes tweets about security, but might also tweet about running, beer, food, baseball, football, good books, or whatever else grabs his attention. Kevin will be a regular contributor to this blog so stay tuned for more posts from him. When I speak to a room of IT administrators, I like to begin by asking them if they have implemented a complex password policy. Generally, they all nod their heads enthusiastically. I ask them if that password policy requires long passwords. More nodding. I ask if that policy requires upper and lower case letters – faster nodding – numbers – even faster – special characters – enthusiastic nodding all around! I then ask them if their policy also includes a requirement for users to regularly change their passwords. Now we have smiles with the nodding! I ask them if the users have different IDs and passwords on the many systems that they have access to. Of course! I then ask them if, when they walk around the building, they see something like this: Thanks to Jake Ludington for the nice example. Can these administrators be faulted for their policies? Probably not but, in the end, end-users will find a way to get their job done efficiently. Post-It Notes to the rescue! I was visiting a business in New York City one day which was a perfect example of this problem. First I walked up to the security desk and told them where I was headed. They asked me if they should call upstairs to have someone escort me. Is that my call? Is that policy? I said that I knew where I was going, so they let me go. Having the conference room number handy, I wandered around the place in a search of my destination. As I walked around, unescorted, I noticed the post-it note problem in abundance. Had I been so inclined, I could have logged in on almost any machine and into any number of systems. When I reached my intended conference room, I mentioned my post-it note observation to the two gentlemen with whom I was meeting. One of them said, “You mean like this,” and he produced a post it note full of login IDs and passwords from his breast pocket! I gave him kudos for not hanging the list on his monitor. We then talked for the rest of the meeting about the difficulties faced by the employees due to the security policies. These policies, although well-intended, made life very difficult for the end-users. Most users had access to 8 to 12 systems, and the passwords for each expired at a different times. The post-it note solution was understandable. Who could remember even half of them? What could this customer have done differently? I am a fan of using a provisioning system, such as Oracle Identity Manager, to manage all of the target systems. With OIM, and email could be automatically sent to all users when it was time to change their password. The end-users would follow a link to change their password on a web page, and then OIM would propagate that password out to all of the systems that the user had access to, even if the login IDs were different. Another option would be an Enterprise Single-Sign On Solution. With Oracle eSSO, all of a user’s credentials would be stored in a central, encrypted credential store. The end-user would only have to login to their machine each morning and then, as they moved to each new system, Oracle eSSO would supply the credentials. Good-bye post-it notes! 3M may be disappointed, but your end users will thank you. I hear people say that this post-it note problem is not a big deal, because the only people who would see the passwords are fellow employees. Do you really know who is walking around your building? What are the password policies in your business? How do the end-users respond?

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  • Android: How to bind spinner to custom object list?

    - by niko
    Hi, In the user interface there has to be a spinner which contains some names (the names are visible) and each name has its own ID (the IDs are not equal to display sequence). When the user selects the name from the list the variable currentID has to be changed. The application contains the ArrayList Where User is an object with ID and name: public class User{ public int ID; public String name; } What I don't know is how to create a spinner which displays the list of user's names and bind spinner items to IDs so when the spinner item is selected/changed the variable currentID is set to appropriate value. I would appreciate if anyone could show the solution of the described problem or provide any link useful to solve the problem. Thanks!

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  • asp.net mvc making ajax call jason

    - by mazhar kaunain baig
    Controller: public ActionResult EditOrganizationMeta(int id) { } [HttpPost] [ValidateInput(false)] public ActionResult EditOrganizationMeta(FormCollection collection) { } View: function DoAjaxCall() { var url = '<%= Url.Action("EditOrganizationMeta", "Organization") %>'; //url = url + '/' + dd; $.post(url, null, function(data) { alert(data); }); } <input type="button" name="something" value="Save" onclick="DoAjaxCall()" /> how would i make the ajax call , i have basically two functions with the same name EditOrganizationMeta,Do the form collection will be passed automatically.Basic confusion is regarding the method call Ok i made a call by ajax but after that My This code is not running anymore [HttpPost] [ValidateInput(false)] public ActionResult EditOrganizationMeta(FormCollection collection) { int OrganizationId = 11; string OrganizationName = "Ministry of Interior"; try { string ids = Request.Params // **getting error here some sequence is not there** .Cast<string>() .Where(p => p.StartsWith("button")) .Select(p => p.Substring("button".Length)) .First(); String RealValueOfThatControl = collection[ids]; } } catch { } return RedirectToAction("EditOrganizationMeta", new { id = OrganizationId }); } I think that there is no post

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  • Reliable way of generating unique hardware ID

    - by mr.b
    Question: what's the best way to accomplish following. I have to come up with unique ID for each networked client, such that: it (ID) should persist once client software is installed on target computer, and should continue to persist if software is re-installed on same computer and same OS installment, it should not change if hardware configuration is modified in most ways (except changing the motherboard) When hard drive with client software installed is cloned to another computer with identical hardware configuration (or, as similar as possible), client software should be aware of that change. A little bit of explanation and some back-story: This question is basically age old question that also touches topic of software copy-protection, as some of mechanisms used in that area are mentioned here. I should be clear at this point that I'm not looking for a copy-protection scheme. Please, read on. :) I'm working on a client-server software that is supposed to work in local network. One of problems I have to solve is to identify each unique client in network (not so much of a problem), so that I can apply certain attributes to every specific client, retain and enforce those attributes during deployment lifetime of a specific client. While I was looking for a solution, I was aware of following: Windows activation system uses some kind of heavy fingerprinting mechanism, that is extremely sensitive to hardware modifications, Disk imaging software copies along all Volume IDs (tied to each partition when formatted), and custom, uniquely generated IDs during installation process, during first run, or in any other way, that is strictly software in its nature, and stored in registry or on hard drive, so it's very easy to confuse two Obvious choice for this kind of problem would be to find out BIOS identifiers (not 100% sure if this is unique through identical motherboard models, though), as that's the only thing I can rely on, that isn't duplicated, transferred by cloning, and that can't be changed (at least not by using some user-space program). Everything else fails as either being not reliable (MAC cloning, anyone?), or too demanding (in terms that it's too sensitive to configuration changes). Am I missing something obvious here? Sub-question that I'd like to ask is, am I doing it correctly, architecture-wise? Perhaps there is a better tool for task that I have to accomplish... Another approach I had in mind is something similar to handshake mechanism, where server maintains internal lookup table of connected client IDs (which can be even completely software-based and non-unique at any given moment), and tells client to come up with different ID during handshake, if duplicate ID is provided upon connection. That approach, unfortunately, doesn't play nicely with one of requirements to tie attributes to specific client during lifetime.

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  • Charater string buffer too small

    - by Ruslan
    I have select: select v.accs, v.currency,v.amount,v.drcr_ind, count(*) qua,wm_concat(ids) npx_IDS, wm_concat(px_dtct) npx_DTCT from table v group by accs, currency, amount, drcr_ind but i get error ORA-06502: PL/SQL: : character string buffer too small if i'll remove one string, because sometimes (when v.accs= 3570) count(*) = 215 but when i try to skip using wm_concat for v.accs= 3570 for example this way: select v.accs, v.currency,v.amount,v.drcr_ind, count(*) qua,wm_concat(ids) npx_IDS, (case when v.accs = 3570 then wm_concat(px_dtct) else 'too many' end) npx_DTCT from table v group by accs, currency, amount, drcr_ind i still have the same error message. But why? How can i fix it? Thanx

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