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  • Is this a correct Interlocked synchronization design?

    - by Dan Bryant
    I have a system that takes Samples. I have multiple client threads in the application that are interested in these Samples, but the actual process of taking a Sample can only occur in one context. It's fast enough that it's okay for it to block the calling process until Sampling is done, but slow enough that I don't want multiple threads piling up requests. I came up with this design (stripped down to minimal details): public class Sample { private static Sample _lastSample; private static int _isSampling; public static Sample TakeSample(AutomationManager automation) { //Only start sampling if not already sampling in some other context if (Interlocked.CompareExchange(ref _isSampling, 0, 1) == 0) { try { Sample sample = new Sample(); sample.PerformSampling(automation); _lastSample = sample; } finally { //We're done sampling _isSampling = 0; } } return _lastSample; } private void PerformSampling(AutomationManager automation) { //Lots of stuff going on that shouldn't be run in more than one context at the same time } } Is this safe for use in the scenario I described?

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  • Memcache failover and consistent hashing

    - by Industrial
    Hi everyone, I am trying to work out a good way to handle offline/down memcached servers in my current web application that are built with PHP. I just found this link that shows an approach on how to do what I want, I think: http://cmunezero.com/2008/08/11/consistent-memcache-hashing-and-failover-with-php/ Anyhow, it gets me confused when I start working with it and reading the PHP documention about failover with memcache. Why is offline memcache servers added to the $realInstance server pool together with the online servers? Reading the memcache documentation confuses me even more: http://www.php.net/manual/en/memcache.addserver.php status Controls if the server should be flagged as online. Setting this parameter to FALSE and retry_interval to -1 allows a failed server to be kept in the pool so as not to affect the key distribution algorithm. Requests for this server will then failover or fail immediately depending on the memcache.allow_failover setting. Default to TRUE, meaning the server should be considered online. Thanks,

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  • Can anyone tell me what the authors mean on this line?

    - by Anirudh Goel
    i was going through this link: FAT16 Basics to Assemble Clusters. I have read the structures involved in defining a directory entry in FAT. Now when giving the example for a FAT16 File, it says the data cluster is 0x03 for the example file MyFile.txt. Which means if we logically compute the Data Cluster we will be able to reach to the first node which happens to be cluster no 3. But what I fail to understand is what the author is trying to say in the next line where it says What we can see in the File Allocation Table at this moment? How suddenly we reach to the File Allocation Table? Weren't we already there when we were going through the information of Myfile.txt? I couldn't find any reason how suddenly the author jumped to an offset location of 00000200 and is identifying the emptiness of the clusters. It will be great if someone can help me understand. Thanks

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  • Alert dialog is gone before the user see anything

    - by Android Developer
    PopIt("Exit Application", "Are you sure you want to exit?"); public void PopIt( String title, String message ){ new AlertDialog.Builder(this) .setTitle( title ) .setMessage( message ) .setPositiveButton("YES", new OnClickListener() { public void onClick(DialogInterface arg0, int arg1) { //do stuff onclick of YES finish(); } }).setNegativeButton("NO", new OnClickListener() { public void onClick(DialogInterface arg0, int arg1) { //do stuff onclick of CANCEL Toast.makeText(getBaseContext(), "You touched CANCEL", Toast.LENGTH_SHORT).show(); } }).show(); } this alert dialog gone so fast as I cant read or click on it !! why is that ?

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  • Fastest way to calculate summary of database field

    - by Jo-wen
    I have a ms-sql table with the following structure: Name nvarchar; Sign nvarchar; Value int example contents: Test1, 'plus', 5 Test1, 'minus', 3 Test2, 'minus', 1 I would like to have totals per "Name". (add when sign = plus, subtract when sign = minus) result: Test1, 2 Test2, -1 I want to show these results (and update them when a new record is added)... and I'm looking for the fastest solution! [sproc? fast-forward cursor? calculate in .net?]

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  • Should a given URI in a RESTful architecture always return the same response?

    - by keithjgrant
    This is kind of a follow-up question to this one. So is having a unique response for any given URI a core tenant of RESTful architecture? A lot of discussion here tends that direction, but I haven't seen it anywhere as a "hard and fast" rule. I understand the value of it (for caching, crawling, passing links, etc), but I also see things like the twitter API violate it (A request to http://api.twitter.com/1/statuses/friends_timeline.xml will vary based on the username given), and I understand there are times when it may be necessary--not to mention that a chronologically paged resource will also change as new elements are added. Should I strive for varied responses from the same URI to be eliminated altogether, or do I just accept that sometimes it isn't practical, and as long as I minimize its occurrence, I'll be in decent shape.

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  • http streaming using java servlet

    - by Shamik
    I have a servlet based web application which produces two sets of data. One set of data in the webpage which is essential and other set which is optional. I would like to render the essential data as fast as possible and then stream the optional data. I was thinking of writing the essential data to the output stream of HttpServletRequest and then call HttpServletRequest.flushBuffer() to commit the response to the client, but do not return from the servlet code, but instead create the optional data , write that to the outputstream again and then return from servlet code. What are the things that could go wrong in this scheme ? Is this a standard practice to achieve this goal?

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  • C# failing LDAP queries

    - by jpkomick
    I'm trying to access an LDAP directory via the SearchRequest object in C#. I can make the same calls via an LDAP library running in and iPhone app, as well as directly via a terminal session. However, the C# queries all seem to fail. var search = new SearchRequest("ou=calendar,dc=ualberta,dc=ca", "term=*,course=094398,class=*", System.DirectoryServices.Protocols.SearchScope.Subtree, attributeLst); This returns a list of terms for the course calendar. However, making the following calls won't return results for specific courses var search = new SearchRequest("ou=calendar,dc=ualberta,dc=ca", "term=1330,course=094398", System.DirectoryServices.Protocols.SearchScope.Subtree, attributeLst); The attributeLst object has proper attribute names included, but the query always returns with zero results. Any suggestions anyone has would be greatly appreciated. Thanks.

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  • hibernate createSQL how to cache it?

    - by cometta
    If i use Criteria statement, i able to use cache easily. but when i using custom CREATESQL, like below, how do i cache it? Query query = getHibernateTemplate().getSessionFactory().getCurrentSession().createSQLQuery( " select company_keysupplier.ddiv as ddiv, company_division.name as DIVISION, company_keysupplier.ddep as ddep,company_department.name as DEPARTMENT"+ " from company_keysupplier "+ " left join company_division on "+ " (company_keysupplier.ddiv= company_division.division_code and company_keysupplier.survey_num=company_division.survey_num) "+ " left join company_department on "+ " (company_keysupplier.ddep= company_department.department_code and company_keysupplier.survey_num=company_department.survey_num) "+ " where company_keysupplier.sdiv = :sdiv and company_keysupplier.sdep = :sdep and company_keysupplier.survey_num= :surveyNum " + " order by company_division.name, company_keysupplier.ddep " ) .addScalar("ddiv") .addScalar("ddep") .addScalar("DIVISION") .addScalar("DEPARTMENT") .setResultTransformer(Transformers.aliasToBean(IssKeysupplier.class)); query.setString("sdiv", sdiv); query.setString("sdep", sdepartment); query.setBigInteger("surveyNum", survey_num); //i tried query.setCachable(true) fail...... List result= (List<IssKeysupplier>)query.list(); return result;

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  • Why does this explicit call of a Scala method allow it to be implicitly resolved?

    - by Matt R
    Why does this code fail to compile, but compiles successfully when I uncomment the indicated line? (I'm using Scala 2.8 nightly). It seems that explicitly calling string2Wrapper allows it to be used implicitly from that point on. class A { import Implicits.string2Wrapper def foo() { //string2Wrapper("A") ==> "B" // <-- uncomment } def bar() { "A" ==> "B" "B" ==> "C" "C" ==> "D" } object Implicits { implicit def string2Wrapper(s: String) = new Wrapper(s) class Wrapper(s: String) { def ==>(s2: String) {} } } }

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  • Parameter Tuning for Perceptron Learning Algorithm

    - by Albert Diego
    Hi, I'm having sort of an issue trying to figure out how to tune the parameters for my perceptron algorithm so that it performs relatively well on unseen data. I've implemented a verified working perceptron algorithm and I'd like to figure out a method by which I can tune the numbers of iterations and the learning rate of the perceptron. These are the two parameters I'm interested in. I know that the learning rate of the perceptron doesn't affect whether or not the algorithm converges and completes. I'm trying to grasp how to change n. Too fast and it'll swing around a lot, and too low and it'll take longer. As for the number of iterations, I'm not entirely sure how to determine an ideal number. In any case, any help would be appreciated. Thanks.

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  • Bind any version of MySql.Data using the app.config

    - by Martin Kirsche
    How do I bind any version or a range of versions of an assembly by using the app.config? I'm currently binding the MySql.Data assembly like this: <runtime> <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1" applies-to="v2.0.50727"> <qualifyAssembly partialName="MySql.Data" fullName="MySql.Data, Version=6.2.2.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d, processorArchitecture=MSIL"/> </assemblyBinding> </runtime> Any version of MySql.Data other than 6.2.2.0 is not working this way. The versions of this assembly are changing fast so I either want to bind any or all versions beginning with 6.2 to my application without changing the app.config each time.

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  • Pitfalls to avoid when starting a software company.

    - by Imagist
    It's been my goal to start my own software company basically since I started programming HyperCard on System 6 back in elementary school. Recent changes in my job situation have convinced me that I should be pursuing this goal more actively. My question is, what are some pitfalls that I should avoid when starting a software company? A lot of companies fail and I'm sure there are a lot of reasons. As a side-request, it would be particularly helpful if you could tell me a little about your own experience with starting a software company or being a part of a startup, so I know how you know what you know.

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  • Is it safe to catch an access violation in this scenario?

    - by Eloff
    I've read a lot, including here on SO that suggests this is a very bad idea in general and that the only thing you can do safely is exit the program. I'm not sure that this is true. This is for a pooling memory allocator that hands off large allocations to malloc. During pool_free() a pointer needs to be checked it it belongs to a pool or was allocated with malloc. By rounding the address down to the nearest 1MB boundary, I get a pointer to the beginning of a block of memory in the pool, or undefined if malloc was used. In the first case I can easily verify that the block of memory belongs to the pool, but, if it does not I will either fail this verification, or I will get an access violation (note that this is a read-only process). Could I not catch this with SEH (Windows) or handle the signal (POSIX) and simply treat it as a failed verification? (i.e. this is only possible if malloc was used, so pass the ptr to free())

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  • Fastest way to display a full calendar

    - by Aurélien Ribon
    Hello, I need to display a complete calendar (12 months, 31~ days/month) on screen. Currently, I'm using a 12-column grid, with each column filled with a "months" stackpanel. Each "month" stackpanel is filled with 31 (or less) day representations. Each day representation is composed of a DockPanel embedding three controls : a textblock to display the day letter a textblock to display the day number a textblock to display a short message Of course, performances are crushed down when I try to resize the window. Is there a useful trick to allow a fast display of many textblocks ?

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  • how to search files of particular extension in the entire device ?

    - by KayKay
    In my application, i am trying to find all files of particular extension (like .pdf, .txt, etc) that are stored in the whole device (not only in Home Directory) and want to list them in table View. Is it possible to do so and if it is then can i associate file of specific extension to get it open in supporting application (any third party plug-ins).I went through numerous documentation but couldn't find the solution. Also how can i index files of these extension for fast search. Any help is appreciated. Thanks.

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  • jQuery Toggle Cookie Support

    - by hell0w0rld
    I'm trying to implement the jQuery Cookie plugin into my slide toggle script, but so far haven't been successful. Here's my code (without any cookie implementation): jQuery: $(document).ready(function() { $('a.toggle').click(function() { var id = $(this).attr('name'); $('#module' + id).slideToggle('fast'); $('a.toggle[name='+id+']').toggle(); return false; }); }); HTML: <a class="toggle" name="1" href="#">- Hide</a> <a class="toggle hidden" name="1" href="#">+ Show</a> <div id="module1"><p>Hello World</p></div> Anyone know if it's easy enough to implement the jQuery Cookie plugin into my existing code so it remembers the open/closed state? Thank you.

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  • how change nginx temp & log folder or disable logging completely

    - by Ehsan Khodarahmi
    I'm running nginx 1.3.5 under windows seven, I need to execute nginx directly from a read-only media (CD or DVD), but when I want to run it, it fails with this error: nginx: [alert] could not open error log file: CreateFile() "logs/error.log" fail ed (5: Access is denied) 2012/08/28 13:52:46 [emerg] 5604#2864: CreateDirectory() "J:\nginx-1.3.5/temp/client_body_temp" failed (5: Access is denied) where J is my CD-ROM drive letter. I've changed nginx.conf to disable logging completely, but seems anyway it still tries to build a file named 'error.log' in '/logs' folder & some extra temporary contents in '/temp' folder at the startup, so I want to change 'logs' & 'temp' directory path to windows temp folder (%temp%), but I dont have any idea that how can I do it. Also I want to know why nginx still creates 'logs/error.log' after disableing error logging ?

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  • How do I convert the below PHP code to VB.NET?

    - by Greg
    How do I convert the below PHP code to VB.NET? <?php $X_HOST ="foo.com"; $X_URL = "/index.php"; $X_PORT ="8080"; $X_USERNAME = "foo"; $X_PASSWORD = "bar"; $s_POST_DATA = "Channel=UK.VODAFONE"; // Channel $s_POST_DATA .= "&Shortcode=12345"; // Shortcode $s_POST_DATA .= "&SourceReference=3456"; // Source Reference $s_POST_DATA .= "&MSISDN=447811111111"; // Phone $s_POST_DATA .= "&Content=test"; // Content $s_POST_DATA .= "&DataType=0"; // Data Type $s_POST_DATA .= "&Premium=1"; // Premium $s_POST_DATA .= "&CampaignID=4321"; // CampaignID $s_Request = "POST ".$X_URL." HTTP/1.0\r\n"; $s_Request .="Host: ".$X_HOST.":".$X_PORT."\r\n"; $s_Request .="Authorization: Basic ".base64_encode($X_USERNAME.":".$X_PASSWORD)."\r\n"; $s_Request .="Content-Type: application/x-www-form-urlencoded\r\n"; $s_Request .="Content-Length: ".strlen($s_POST_DATA)."\r\n"; $s_Request .="\r\n".$s_POST_DATA; //Sends out the request to the server. $fp = fsockopen ($X_HOST, $X_PORT, $errno, $errstr, 30) or die("Error!!!"); fputs ($fp, $s_Request); while (!feof($fp)) { $s_GatewayResponse .= fgets ($fp, 128); } fclose ($fp); //Array of official response codes. $a_Responses = array( "100" => "Server has returned an unspecified error.", "101" => "Server successfully received the request.", "102" => "Server has returned an database error", "103" => "Server has returned an syntax error." ); echo "<HTML>\n<BODY>\n\n"; //Checks for an official response code. foreach ($a_Responses as $s_ResponseCode => $s_ResponseDescription) { if (stristr($s_GatewayResponse, "\n$s_ResponseCode\n")) { echo "A response code of $s_ResponseCode was returned – "; echo $s_ResponseDescription"; $b_CodeReturned = true; } } //Checks for an authorization failure where an official response code has //not been recognized. if (!$b_CodeReturned) { if (stristr($s_GatewayResponse, "HTTP/1.1 401")) { echo "The server rejected your username/password (HTTP 401)."; } else { echo "No recognised response code was returned by the server."; } } echo "\n\n</BODY>\n</HTML>"; ?> and <?php $s_ref = $HTTP_POST_VARS["Reference"]; // Reference $s_trg = $HTTP_POST_VARS["Trigger"]; // trigger $s_shc = $HTTP_POST_VARS["Shortcode"]; // shortcode $s_pho = $HTTP_POST_VARS["MSISDN"]; // MSISDN $s_con = $HTTP_POST_VARS["Content"]; // Content $s_chn = $HTTP_POST_VARS["Channel"]; // Channel $s_pay = $HTTP_POST_VARS["DataType"]; // Data Type $s_dat = $HTTP_POST_VARS["DateReceived"]; // Date Received $s_cam = $HTTP_POST_VARS["CampaignID"]; // CampaignID $b_IsValid = getValidateRequest($s_ref, $s_trg, $s_shc, $s_pho, $s_con, $s_cam, $s_chn, $s_pay, $s_dat); if ($b_IsValid) { $s_ResponseCode = "success"; } else { $s_ResponseCode = "fail"; } exit($s_ResponseCode); /*******************************************************************************/ function getValidateRequest ($s_req_ref, $s_req_trg, $s_req_shc, $s_req_pho, $s_req_con, $s_req_cam, $s_req_chn, $s_req_pay, $s_req_dat) { /* * Stub function to be replaced with whatever process is needed to * process/validate request from server by specific client requirements. */ return(true); } ?> lastly <?php $s_ref = $HTTP_POST_VARS["Reference"]; // Reference $s_sta = $HTTP_POST_VARS["Status"]; // Status $s_dat = $HTTP_POST_VARS["DateDelivered"]; // Date Delivered $b_IsValid = getValidateReceipt($s_ref, $s_sta, $s_dat); if ($b_IsValid) { $s_ResponseCode = "success"; } else { $s_ResponseCode = "fail"; } exit($s_ResponseCode); /*******************************************************************************/ function getValidateReceipt ($s_req_ref, $s_req_sta, $s_req_dat) { /* * Stub function to be replaced with whatever process is needed to * process/validate receipts from server by specific client requirements. */ return(true); } ?> Thank you very much in advance Regards Greg

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  • C# BinarySearch breaks when inheriting from something that implements IComparable<T>?

    - by Ender
    In .NET the BinarySearch algorithm (in Lists, Arrays, etc.) appears to fail if the items you are trying to search inherit from an IComparable instead of implementing it directly: List<B> foo = new List<B>(); // B inherits from A, which implements IComparable<A> foo.Add(new B()); foo.BinarySearch(new B()); // InvalidOperationException, "Failed to compare two elements in the array." Where: public abstract class A : IComparable<A> { public int x; public int CompareTo(A other) { return x.CompareTo(other.x); } } public class B : A {} Is there a way around this? Implementing CompareTo(B other) in class B doesn't seem to work.

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  • Casting DataTypes with DirectCast, CType, TryCast

    - by Alex Essilfie
    Ever since I moved from VB6 to VB.NET somewhere in 2005, I've been using CType to do casting from one data type to another. I do this because it is simply faster, used to exist in VB6 and I do not know why I have to be using DirectCast if there is apparently no difference between them. I use TryCast once in a while because I understand that sometimes casting can fail. I however cannot get the difference between CType and DirectCast. Can anyone tell me the difference in plain simple English what the difference the two (CType and DirectCast)? Adding examples of where to use what as well would be helpful. Thanks.

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  • Efficient data structure design

    - by Sway
    Hi there, I need to match a series of user inputed words against a large dictionary of words (to ensure the entered value exists). So if the user entered: "orange" it should match an entry "orange' in the dictionary. Now the catch is that the user can also enter a wildcard or series of wildcard characters like say "or__ge" which would also match "orange" The key requirements are: * this should be as fast as possible. * use the smallest amount of memory to achieve it. If the size of the word list was small I could use a string containing all the words and use regular expressions. however given that the word list could contain potentially hundreds of thousands of enteries I'm assuming this wouldn't work. So is some sort of 'tree' be the way to go for this...? Any thoughts or suggestions on this would be totally appreciated! Thanks in advance, Matt

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  • RMI java doesn't create skeleton class

    - by pavithra
    I wrote a remote service MyremoteImpl.java and used following command after compiled it. rmic MyRemoteImpl I learned that this method suppose to create stub class and a skeleton class but I can only see the stub class, why is that? The other problem I faced after run rmiregistry I started the service but it gives following error, I doubt I get this error as I'm missing skeleton class? java.net.MalformedURLException: invalid URL String: Remote Hello at java.rmi.Naming.parseURL(Unknown Source) at java.rmi.Naming.rebind(Unknown Source) at RMIservice.MyRemoteImpl.main(MyRemoteImpl.java:22) Caused by: java.net.URISyntaxException: Illegal character in path at index 6: Remote Hello at java.net.URI$Parser.fail(Unknown Source) at java.net.URI$Parser.checkChars(Unknown Source) at java.net.URI$Parser.parseHierarchical(Unknown Source) at java.net.URI$Parser.parse(Unknown Source) at java.net.URI.<init>(Unknown Source) at java.rmi.Naming.intParseURL(Unknown Source) ... 3 more Please help me to solve this, Thanx in advance!!!

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  • Load Balancing and Failover for Read-Only PostgreSQL Database

    - by Eric J.
    Scenario Multiple application servers host web services written in Java, running in SpringSource dm Server. To implement a new requirement, they will need to query a read-only PostgreSQL database. Issue To support redundancy, at least two PostgreSQL instances will be running. Access to PostgreSQL must be load balanced and must auto-fail over to currently running instances if an instance should go down. Auto-discovery of newly running instances is desirable but not required. Research I have reviewed the official PostgreSQL documentation on this issue. However, that focuses on the more general case of read/write access to the database. Top google results tend to lead to older newsgroup messages or dead projects such as Sequoia or DB Balancer, as well as one active project PG Pool II Question What are your real-world experiences with PG Pool II? What other simple and reliable alternatives are available?

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  • NTFS-compressing Virtual PC disks (on host and/or guest)

    - by nlawalker
    I'm hoping someone here can answer these definitively: Does putting a VHD file in an NTFS-compressed folder on the host improve performance of the virtual machine, diminish performance, or neither? What about using NTFS compression within the guest? Does using compresssion on either the host or the guest lead to any problems like read or write errors? If I were to put a VHD in a compressed folder on the host, would I benefit from compacting it? I've seen references to using NTFS compression on quite a few VPC "tips and tricks" blog posts, and it seems like half of them say to never do it and the other half say that not only does it save disk space but it actually can improve performance if you have a fast CPU and your primary performance bottleneck is the disk.

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