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  • What about parallelism across network using multiple PCs?

    - by MainMa
    Parallel computing is used more and more, and new framework features and shortcuts make it easier to use (for example Parallel extensions which are directly available in .NET 4). Now what about the parallelism across network? I mean, an abstraction of everything related to communications, creation of processes on remote machines, etc. Something like, in C#: NetworkParallel.ForEach(myEnumerable, () => { // Computing and/or access to web ressource or local network database here }); I understand that it is very different from the multi-core parallelism. The two most obvious differences would probably be: The fact that such parallel task will be limited to computing, without being able for example to use files stored locally (but why not a database?), or even to use local variables, because it would be rather two distinct applications than two threads of the same application, The very specific implementation, requiring not just a separate thread (which is quite easy), but spanning a process on different machines, then communicating with them over local network. Despite those differences, such parallelism is quite possible, even without speaking about distributed architecture. Do you think it will be implemented in a few years? Do you agree that it enables developers to easily develop extremely powerfull stuff with much less pain? Example: Think about a business application which extracts data from the database, transforms it, and displays statistics. Let's say this application takes ten seconds to load data, twenty seconds to transform data and ten seconds to build charts on a single machine in a company, using all the CPU, whereas ten other machines are used at 5% of CPU most of the time. In a such case, every action may be done in parallel, resulting in probably six to ten seconds for overall process instead of forty.

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  • Any suggestions to improve my PDO connection class?

    - by Scarface
    Hey guys I am pretty new to pdo so I basically just put together a simple connection class using information out of the introductory book I was reading but is this connection efficient? If anyone has any informative suggestions, I would really appreciate it. class PDOConnectionFactory{ public $con = null; // swich database? public $dbType = "mysql"; // connection parameters public $host = "localhost"; public $user = "user"; public $senha = "password"; public $db = "database"; public $persistent = false; // new PDOConnectionFactory( true ) <--- persistent connection // new PDOConnectionFactory() <--- no persistent connection public function PDOConnectionFactory( $persistent=false ){ // it verifies the persistence of the connection if( $persistent != false){ $this->persistent = true; } } public function getConnection(){ try{ $this->con = new PDO($this->dbType.":host=".$this->host.";dbname=".$this->db, $this->user, $this->senha, array( PDO::ATTR_PERSISTENT => $this->persistent ) ); // carried through successfully, it returns connected return $this->con; // in case that an error occurs, it returns the error; }catch ( PDOException $ex ){ echo "We are currently experiencing technical difficulties. We have a bunch of monkies working really hard to fix the problem. Check back soon: ".$ex->getMessage(); } } // close connection public function Close(){ if( $this->con != null ) $this->con = null; } }

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  • What *is* an IPM.DistList?

    - by Jeremy
    I'm trying to get the recipient addresses within an IPM.DistList that is stored in a public folder (of type contacts) in Exchange 2003. The typeName of the object (once I get hold of it) is a Message (with a parent object being a Messages collection) and the messageType is "IPM.DistList". I can find all sorts of things about IPM.DistListItems, which you would think an IPM.DistList would contain, but there apparently isn't any documentation on the DistList (that I can find) and DistListItems documentation lists no parent possibilities in MSDN. I'll state it another way in case I've left you confused: We have an Exchange 2003 info store with Public Folders. Within those Public Folders is a [sub]folder (that holds items of type "Contact") that has a bunch of distribution lists (IPM.DistList's) that have contact entries, members of the list essentially. I need to get the addresses of the members of the lists in the Public Folder sub-folder using any VB language, because the company I work for hired me as a VB guy and expects me to write VB solutions, even though I could do it in C++... alas, I digress. VB is the language I'm supposed to figure this out in. (.net, script, vba, vb6, it doesn't matter which one. Yes, I know vb.net is not really related to those that came before, but they don't know that.) Anyone ran into anything like this? Am I just not finding the IPM.DistList documentation but it does actually exist somewhere? This isn't a Message.MAPIOBJECT (iUnknown) problem is it? Thanks.... Jeremy

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  • If attacker has original data, and encrypted data, can they determine the passphrase?

    - by Brad Cupit
    If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require this extra table. I'm leaning towards the the one-way hash + extra table solution, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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  • SPSS - sum of squares change radically with slight model changes in ANOVA??

    - by Pat
    I have noticed that the sum of squares in my models can change fairly radically with even the slightest adjustment to my models???? Is this normal???? I'm using SPSS 16, and both models presented below used the same data and variables with only one small change - categorizing one of the variables as either a 2 level or 3 level variable. Details - using a 2 x 2 x 6 mixed model ANOVA with the 6 being the repeated measure i get the following in the between group analysis ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 4086.46 | 1 | 4086.46 | 104.93 | .000 X | 224.61 | 1 | 224.61 | 5.77 | .019 Y | 2.60 | 1 | 2.60 | .07 | .80 X by Y | 19.25 | 1 | 19.25 | .49 | .49 Error | 2570.40 | 66 | 38.95 | Then, when I use the exact same data but a slightly different model in which variable Y has 3 levels instead of 2 levels I get the following ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 3603.88 | 1 | 3603.88 | 90.89 | .000 X | 171.89 | 1 | 171.89 | 4.34 | .041 Y | 19.23 | 2 | 9.62 | .24 | .79 X by Y | 17.90 | 2 | 17.90 | .80 | .80 Error | 2537.76 | 64 | 39.65 | I don't understand why variable X would have a different sum of squares simply because variable Y gets devided up into 3 levels instead of 2. This is also the case in the within groups analysis too. Please help me understand :D Thank you in advance Pat

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  • Why does my DIV clip its child DIV when jQuery moves it in IE?

    - by Ben Saufley
    I have two divs, both with position:absolute;, one inside the other. The parent isn't in a place where it can be set as position:relative without an extra layer of complexity (there are a lot of other elements around it that I'd have to account for to put it where it needs to be, which is at the very top of the page, over everything). The child element is made to stick off the bottom of the parent. In Chrome, Safari, Firefox, it all works splendidly. In IE, it works until jQuery moves the parent element - at which point the parent element clips the child, so you can barely see the top of the child. I feel like I've read about this, about IE clipping child elements, but I can't seem to find an answer that applies to my case. It's pretty simple, basically: <div id="parent" style="position:absolute;top:0;left:0;"> [content] <div id="tab" style="position:absolute;bottom:-30px;left:0;width:64px;height:32px;background-image:(...);"></div> </div> <script> $(document).ready( function() { $("#tab").click(function() { $("#parent").animate({"top":"-50px"},300); }); }); </script>

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  • Is it legal to take sealed .NET framework class source and extend it?

    - by Giedrius
    To be short, I'm giving very specific example, but I'm interested in general situation. There is a FtpWebRequest class in .NET framework and it is missing some of new FTP operations, like MFCT. It is ok in a sense that this operation is still in draft mode, but it is not ok in a sense, that FtpWebRequest is sealed and there's no other way (at least I don't see it) to extend it with this new operation. Easiest way to do it would be take FtpWebRequest class source from .NET reference sources and extend it, in such way will be kept all the consistence in naming, implementation, etc. Question is how much legal it is? I won't sell this class as a product, I can publish my changes on web - nothing to hide here. If it is not legal, can I take this class source from mono and include in native .net project? Did you had similar case and how you solved it? Update: as long as extension method is offered, I'm pasting source from .NET framework which should show that extension methods are not the solution. So there's a property Method, where you can pass FTP command: public override string Method { get { return m_MethodInfo.Method; } set { if (String.IsNullOrEmpty(value)) { throw new ArgumentException(SR.GetString(SR.net_ftp_invalid_method_name), "value"); } if (InUse) { throw new InvalidOperationException(SR.GetString(SR.net_reqsubmitted)); } try { m_MethodInfo = FtpMethodInfo.GetMethodInfo(value); } catch (ArgumentException) { throw new ArgumentException(SR.GetString(SR.net_ftp_unsupported_method), "value"); } } } As you can see there FtpMethodInfo.GetMethodInfo(value) call in setter, which basically validates value against internal enum static array. Update 2: Checked mono implementation and it is not exact replica of native code + it does not implement some of the things.

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  • Tool to migrate a repo with only read access?

    - by Corazu
    I have a subversion repository located on our school servers from a project my friends and I worked on the past semester. We want to take the project and polish it and make it more of a portfolio item and I'm not quite sure that the repo will stay intact on the school servers (they usually wipe it after a few semesters). I don't have access to dump the repo, although I've sent an email to see if I can get one - which would be the best solution. I tried svnsync but the school server doesn't support the replay command (probably turned off), so that won't work for me. Now, theoretically, wouldn't it be possible to (manually or programmatically) checkout each revision of the repository and check it in to a new repository on our own server? I think it would work - there's only 3 of us, and there's no working copy conflicts that we'd have to worry about, just want a copy of all the history in the repo in case we need to go back and look at it. That being said, before I go and reinvent a wheel by writing a script to do it - does something like this already exist? I have to figure there's already a tool to do it, or that someone has wrote a script to do it.

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  • Stop NSXMLParser Instance from Causing _NSAutoreleaseNoPool

    - by PF1
    Hi Everyone: In my iPhone application, I have an instance of NSXMLParser that is set to a custom delegate to read the XML. This is then moved into its own thread so it can update the data in the background. However, ever since I have done this, it has been giving me a lot of _NSAutoreleaseNoPool warnings in the console. I have tried to add a NSAutoreleasePool to each of my delegate classes, however, this hasn't seemed to solve the problem. I have included my method of creating the NSXMLParser in case that is at fault. NSURL *url = [[NSURL alloc] initWithString:@"http://www.mywebsite.com/xmlsource.xml"]; NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:url]; CustomXMLParser *parser = [[CustomXMLParser alloc] init]; parser.managedObjectContext = self.managedObjectContext; parser = [parser initXMLParser]; [xmlParser setDelegate:parser]; [NSThread detachNewThreadSelector:@selector(parse) toTarget:xmlParser withObject:nil]; If anyone has any ideas to get rid of this problem, I would really appreciate it. Thanks.

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  • Creating a new object destroys an older object with different name in C++

    - by Mikael
    First question here! So, I am having some problems with pointers in Visual C++ 2008. I'm writing a program which will control six cameras and do some processing on them so to clean things up I have created a Camera Manager class. This class handles all operations which will be carried out on all the cameras. Below this is a Camera class which interacts with each individual camera driver and does some basic image processing. Now, the idea is that when the manager is initialised it creates two cameras and adds them to a vector so that I can access them later. The catch here is that when I create the second camera (camera2) the first camera's destructor is called for some reason, which then disconnects the camera. Normally I'd assume that the problem is somewhere in the Camera class, but in this case everything works perfectly as long as I don't create the camera2 object. What's gone wrong? CameraManager.h: #include "stdafx.h" #include <vector> #include "Camera.h" class CameraManager{ std::vector<Camera> cameras; public: CameraManager(); ~CameraManager(); void CaptureAll(); void ShowAll(); }; CameraManager.cpp: #include "stdafx.h" #include "CameraManager.h" CameraManager::CameraManager() { printf("Camera Manager: Initializing\n"); [...] Camera *camera1 = new Camera(NodeInfo,1, -44,0,0); cameras.push_back(*camera1); // Adding the following two lines causes camera1's destructor to be called. Why? Camera *camera2 = new Camera(NodeInfo,0, 44,0,0); cameras.push_back(*camera2); printf("Camera Manager: Ready\n"); }

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  • Aggregating a list of dates to start and end date

    - by Joe Mako
    I have a list of dates and IDs, and I would like to roll them up into periods of consucitutive dates, within each ID. For a table with the columns "testid" and "pulldate" in a table called "data": | A79 | 2010-06-02 | | A79 | 2010-06-03 | | A79 | 2010-06-04 | | B72 | 2010-04-22 | | B72 | 2010-06-03 | | B72 | 2010-06-04 | | C94 | 2010-04-09 | | C94 | 2010-04-10 | | C94 | 2010-04-11 | | C94 | 2010-04-12 | | C94 | 2010-04-13 | | C94 | 2010-04-14 | | C94 | 2010-06-02 | | C94 | 2010-06-03 | | C94 | 2010-06-04 | I want to generate a table with the columns "testid", "group", "start_date", "end_date": | A79 | 1 | 2010-06-02 | 2010-06-04 | | B72 | 2 | 2010-04-22 | 2010-04-22 | | B72 | 3 | 2010-06-03 | 2010-06-04 | | C94 | 4 | 2010-04-09 | 2010-04-14 | | C94 | 5 | 2010-06-02 | 2010-06-04 | This is the the code I came up with: SELECT t2.testid, t2.group, MIN(t2.pulldate) AS start_date, MAX(t2.pulldate) AS end_date FROM(SELECT t1.pulldate, t1.testid, SUM(t1.check) OVER (ORDER BY t1.testid,t1.pulldate) AS group FROM(SELECT data.pulldate, data.testid, CASE WHEN data.testid=LAG(data.testid,1) OVER (ORDER BY data.testid,data.pulldate) AND data.pulldate=date (LAG(data.pulldate,1) OVER (PARTITION BY data.testid ORDER BY data.pulldate)) + integer '1' THEN 0 ELSE 1 END AS check FROM data ORDER BY data.testid, data.pulldate) AS t1) AS t2 GROUP BY t2.testid,t2.group ORDER BY t2.group; I use the use the LAG windowing function to compare each row to the previous, putting a 1 if I need to increment to start a new group, I then do a running sum of that column, and then aggregate to the combinations of "group" and "testid". Is there a better way to accomplish my goal, or does this operation have a name? I am using PostgreSQL 8.4

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  • GWT Deserialisation of Persistent Entities (JPA)

    - by slartidan
    Hi everyone, I am currently developing Java/GWT-application which is hosted on a weblogic application server. I am using EJB3.0 with EclipseLink as persistence layer. Sadly my GWT has problems to deserialize persistent entities. It might be helpful for you to know, that I have the EclipseLink-Library in my classpath (including javax.persistence.Entity) am not recieving the persistence objects from a database or persistence-manager - I am creating the objects with standard java code use Eclipse IDE for Java EE Developers for development and deploying and I am compiling my GWT code with the GWT-Plugin (GWT 2.1.0) - my source code is split up in several projects am pretty sure, that the problems occures on client side, since the HTTP response of my server is the same in my working and in my not working example tried to patch javax.persistence.Entity and tried to include several libraries which included javax.persistence.Entity but nothing was helping In my server provides a list of instances of class SerialClass; the interface looks like this: public interface GreetingService extends RemoteService { List<SerialClass> greetServer(); } My onModuleLoad()-Method gets those instances and creates a browser-popup with the information: public void onModuleLoad() { GreetingServiceAsync server = (GreetingServiceAsync) GWT.create(GreetingService.class); server.greetServer(new AsyncCallback<List<SerialClass>>() { public void onFailure(Throwable caught) { } public void onSuccess(List<SerialClass> result) { String resultString = ""; try { for (SerialClass serial : result) { if (serial == null) { resultString += "null "; } else { resultString += ">" + serial.id + "< "; } } } catch (Throwable t) { Window.alert("failed to process"); } Window.alert("success:" + resultString); } }); } My server is looking like this: public class GreetingServiceImpl extends RemoteServiceServlet implements GreetingService { public List<SerialClass> greetServer() throws IllegalArgumentException { List<SerialClass> list = new ArrayList<SerialClass>(); for (int i = 0; i < 100; i++) { list.add(new SerialClass()); } return list; } } Case 1 = everything works fine I am using this SerialClass (either without any annotation, or with any annotation other than Entity - for example javax.persistence.PersistenceContext works fine): //@Entity public class SerialClass implements Serializable, IsSerializable { public int id = 4711; } The popup contains (as expected): success:>4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< The data sent over HTTP looks like this: //OK[4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,100,1,["java.util.ArrayList/3821976829","serial.shared.SerialClass/10650133"],0,6] Case 2 = its not working at all I am using this SerialClass: @Entity public class SerialClass implements Serializable, IsSerializable { public int id = 4711; } My popup contains (THIS IS MY PROBLEM): success:>2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null The data sent over HTTP looks like this (exactly the same!): //OK[4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,100,1,["java.util.ArrayList/3821976829","serial.shared.SerialClass/10650133"],0,6] There is no suspicious logging output - neither on server, nor on client. All HTTP-responses have return code 200. My current workaround I am going to try to create transfer objects as a copy of my SerialClass - those transfer objects will look exactly the same, but will not have the @Entity annotation. Alternatively I could try to use the RequestFactory (thanks to @Hilbrand for the hint). I really don't know how to solve that problem and I'm really thankful about any suggestions, hints, tips, links, etc.

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  • Data Warehouse: Modelling a future schedule

    - by Pat
    I'm creating a DW that will contain data on financial securities such as bonds and loans. These securities are associated with payment schedules. For example, a bond could pay quarterly, while a mortage would usually pay monthly (sometimes biweekly). The payment schedule is created when the security is traded and, in the majority of cases, will remain unchanged. However, the design would need to accomodate those cases where it does change. I'm currently attempting to model this data and I'm having difficulty coming up with a workable design. One of the most commonly queried fields is "next payment date". Users often want to know when a security will pay next. Therefore, I want to make it as easy as possible for them to get the next payment date and amount for each security. Also, users often run historical queries in which case they'd want the next payment date and amount as of a specific point in time. For example, they may want to look back at 1/31/09 and query the next payment dates (which would usually be in February 2009 for mortgages). It's also common that they want to query a security's entire payment schedule, which might consist of 360 records (30 year mortgage x 12 payments/year). Since the next payment date and amount would be changing each month or even biweekly, these fields wouldn't seem to fit into a slow-changing dimension very well. It would probably make more sense to use a fact table, but I'm unsure of how to model it. Any ideas would be greatly appreciated.

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  • C++ Templates: Convincing self against code bloat

    - by ArunSaha
    I have heard about code bloats in context of C++ templates. I know that is not the case with modern C++ compilers. But, I want to construct an example and convince myself. Lets say we have a class template< typename T, size_t N > class Array { public: T * data(); private: T elems_[ N }; }; template< typename T, size_t N > T * Array<T>::data() { return elems_; } Further, let's say types.h contains typedef Array< int, 100 > MyArray; x.cpp contains MyArray ArrayX; and y.cpp contains MyArray ArrayY; Now, how can I verify that the code space for MyArray::data() is same for both ArrayX and ArrayY? What else I should know and verify from this (or other similar simple) examples? If there is any g++ specific tips, I am interested for that too. PS: Regarding bloat, I am concerned even for the slightest of bloats, since I come from embedded context.

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  • Standard term for a thread I/O reorder buffer?

    - by Crashworks
    I have a case where many threads all concurrently generate data that is ultimately written to one long, serial file. I need to somehow serialize these writes so that the file gets written in the right order. ie, I have an input queue of 2048 jobs j0..jn, each of which produces a chunk of data oi. The jobs run in parallel on, say, eight threads, but the output blocks have to appear in the file in the same order as the corresponding input blocks — the output file has to be in the order o0o1o2... The solution to this is pretty self evident: I need some kind of buffer that accumulates and writes the output blocks in the correct order, similar to a CPU reorder buffer in Tomasulo's algorithm, or to the way that TCP reassembles out-of-order packets before passing them to the application layer. Before I go code it, I'd like to do a quick literature search to see if there are any papers that have solved this problem in a particularly clever or efficient way, since I have severe realtime and memory constraints. I can't seem to find any papers describing this though; a Scholar search on every permutation of [threads, concurrent, reorder buffer, reassembly, io, serialize] hasn't yielded anything useful. I feel like I must just not be searching the right terms. Is there a common academic name or keyword for this kind of pattern that I can search on?

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  • Matlab fft function

    - by CTZStef
    The code below is from the Matlab 2011a help about fft function. I think there is a problem here : why do they multiply t(1:50) by Fs, and then say it's time in millisecond ? Certainly, it happens to be true in this very particular case, but change the value of Fs to, say, 2000, and it won't work anymore, obviously because of this factor of 2. Right ? Quite misleading, isn't it ? What do I miss ? Fs = 1000; % Sampling frequency T = 1/Fs; % Sample time L = 1000; % Length of signal t = (0:L-1)*T; % Time vector % Sum of a 50 Hz sinusoid and a 120 Hz sinusoid x = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t); y = x + 2*randn(size(t)); % Sinusoids plus noise plot(Fs*t(1:50),y(1:50)) title('Signal Corrupted with Zero-Mean Random Noise') xlabel('time (milliseconds)') Clearer with this : fs = 2000; % Sampling frequency T = 1 / fs; % Sample time L = 1000; % Length of signal t2 = (0:L-1)*T; % Time vector f = 50; % signal frequency s2 = sin(2*pi*f*t2); figure, plot(fs*t2(1:50),s2(1:50)); % NOT good figure, plot(t2(1:50),s2(1:50)); % good

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  • SQL Group by Minute- Expanded

    - by Barnie
    I am working on something similar to this post here: TS SQL - group by minute However mine is pulling from an message queue, and I need to see an accurate count of the amount of traffic the Message Queue is creating/ sending, and at what time Select * From MessageQueue mq My expanded version of this though is the following: A) User defines a start time and an end time (Easy enough using Declare's @StartTime and @EndTime B) Give the user the option of choosing the "grouping". Will it be broken out by 1 minutes, 5 minutes, 15 minutes, or 30 minutes (Max). (I had thought to do this with a CASE statement, but my test problems fall apart on me.) C) Display the data to accurately show a count of what happened during the interval (Grouping) selected. This is where I am at so far SQL Blob: DECLARE @StartTime datetime DECLARE @EndTime datetime SELECT DATEPART(n, mq.cre_date)/5 as Time --Trying to just sort by 5 minute intervals ,CONVERT(VARCHAR(10),mq.Cre_Date,101) ,COUNT(*) as results FROM dbo.MessageQueue mq WHERE mq.cre_date BETWEEN @StartDate AND @EndDate GROUP BY DATEPART(n, mq.cre_date)/5 --Trying to just sort by 5 minute intervals , eq.Cre_Date This is the output I would like to achieve: [Time] [Date] [Message Count] 1300 06/26/2012 5 1305 06/26/2012 1 1310 06/26/2012 100

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  • Java: Tracking a user login session - Session EJBs vs HTTPSession

    - by bguiz
    If I want to keep track of a conversational state with each client using my web application, which is the better alternative - a Session Bean or a HTTP Session - to use? Using HTTP Session: //request is a variable of the class javax.servlet.http.HttpServletRequest //UserState is a POJO HttpSession session = request.getSession(true); UserState state = (UserState)(session.getAttribute("UserState")); if (state == null) { //create default value .. } String uid = state.getUID(); //now do things with the user id Using Session EJB: In the implementation of ServletContextListener registered as a Web Application Listener in WEB-INF/web.xml: //UserState NOT a POJO this this time, it is //the interface of the UserStateBean Stateful Session EJB @EJB private UserState userStateBean; public void contextInitialized(ServletContextEvent sce) { ServletContext servletContext = sce.getServletContext(); servletContext.setAttribute("UserState", userStateBean); ... In a JSP: public void jspInit() { UserState state = (UserState)(getServletContext().getAttribute("UserState")); ... } Elsewhere in the body of the same JSP: String uid = state.getUID(); //now do things with the user id It seems to me that the they are almost the same, with the main difference being that the UserState instance is being transported in the HttpRequest.HttpSession in the former, and in a ServletContext in the case of the latter. Which of the two methods is more robust, and why?

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  • Android App crashing on Back Button (performResumeActivity)

    - by Rutger
    My App consists of 2 Activities at the moment. . the MAIN activity with a Gallery View . a FriendsListActivity with a ListView When the user moves away from the FriendsListActivity with the back button, and returns to the MAIN activity the following error keeps popping up in debug mode. DalvikVM[localhost:8676] Thread [<1 main] (Suspended (exception RuntimeException)) ActivityThread.performResumeActivity(IBinder, boolean) line: 2095 ActivityThread.handleResumeActivity(IBinder, boolean, boolean) line: 2110 BinderProxy(ActivityThread$H).handleMessage(Message) line: 954 ActivityThread$H(Handler).dispatchMessage(Message) line: 99 Looper.loop() line: 123 ActivityThread.main(String[]) line: 3647 Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method] Method.invoke(Object, Object...) line: 507 ZygoteInit$MethodAndArgsCaller.run() line: 839 ZygoteInit.main(String[]) line: 597 NativeStart.main(String[]) line: not available [native method] Thread [<8 Binder Thread #2] (Running) Thread [<7 Binder Thread #1] (Running) With the LogCat 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): FATAL EXCEPTION: main 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): java.lang.RuntimeException: Unable to resume activity {com.package.MAIN/com.package.MAIN.MAIN}: java.lang.NullPointerException 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2095) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2110) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:954) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.os.Handler.dispatchMessage(Handler.java:99) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.os.Looper.loop(Looper.java:123) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.main(ActivityThread.java:3647) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at java.lang.reflect.Method.invokeNative(Native Method) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at java.lang.reflect.Method.invoke(Method.java:507) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at dalvik.system.NativeStart.main(Native Method) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): Caused by: java.lang.NullPointerException 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at com.package.MAIN.MAIN.onResume(MAIN.java:91) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1149) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.Activity.performResume(Activity.java:3833) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2085) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): ... 10 more Further info in the Variables panel states: this: ActivityThread e: NullPointerException cause: NullPointerException detailMessage: null stackTrace: null r: ActivityThread$ActivityClientRecord activity: MAIN detailMessage after one Eclipse Resume: Unable to resume activity (MAIN) The code from the FriendsListActivity looks like this public class FriendsListActivity extends ListActivity { // =========================================================== // Fields // =========================================================== private ArrayList<Friend> friends = new ArrayList<Friend>(); private FriendsArrayAdapter friendsArrayAdapter; private ListView listView; // =========================================================== // onCreate // =========================================================== @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.friends_list); registerForContextMenu(getListView()); setButtonNewFriendClickListener(); } public void generateFriendsList() { FriendsService fs = new FriendsService(this); friends = fs.getFriendsList(); listView = (ListView) findViewById(android.R.id.list); friendsArrayAdapter = new FriendsArrayAdapter( this, R.layout.friend_list_item, friends); listView.setAdapter(friendsArrayAdapter); } @Override public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { super.onCreateContextMenu(menu, v, menuInfo); MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.friends_context_menu, menu); } @Override public boolean onContextItemSelected(MenuItem item) { AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo(); FriendsService fs = new FriendsService(this); Friend f = new Friend(); f = friends.get(info.position); switch (item.getItemId()) { case R.id.edit: Intent i = new Intent(this, FriendEditActivity.class); i.putExtra("userid", f.userId); startActivity(i); return true; case R.id.delete: fs.deleteFriend(f.userId); generateFriendsList(); return true; default: return super.onContextItemSelected(item); } } // =========================================================== // onPause // =========================================================== protected void onPause() { super.onPause(); finish(); } // =========================================================== // onResume // =========================================================== protected void onResume() { super.onResume(); generateFriendsList(); } // =========================================================== // onStop // =========================================================== protected void onStop() { super.onStop(); } // =========================================================== // onDestroy // =========================================================== @Override protected void onDestroy() { super.onDestroy(); } // =========================================================== // Activity methods // =========================================================== private void setButtonNewFriendClickListener() { Button clickButton = (Button)findViewById(R.id.button_add_friend); clickButton.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Intent i = new Intent(v.getContext(), FriendNewActivity.class); startActivity(i); } }); } The AndroidManifest looks like this <manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.package.mypackage"> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name="com.package.mypackage.mypackage" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name=".FriendsListActivity"></activity> <activity android:name=".FriendEditActivity"></activity> <activity android:name=".FriendNewActivity"></activity> <activity android:name=".TakePictureActivity"></activity> <activity android:name=".FriendsService"></activity> <activity android:name=".MyService"></activity> </application> <uses-sdk android:minSdkVersion="9" /> The MAIN activity looks like this: package com.package.mypackage; import java.util.ArrayList; import com.package.domain.Domain; import com.package.service.MyService; import com.package.viewadapter.myImageAdapter; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.view.Window; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.AdapterView.OnItemLongClickListener; import android.widget.Button; import android.widget.Gallery; import android.widget.Toast; public class myActivity extends Activity { // =========================================================== // Fields // =========================================================== private MyImageAdapter myImageAdapter; private ArrayList<Domain> domain = new ArrayList<Domain>(); // =========================================================== // onCreate // =========================================================== @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.main); /* Set Buttons to listen for any click event. */ setButtonFriendsClickListener(); setButtonCameraClickListener(); setButtonPreferencesClickListener(); } // =========================================================== // onStart // =========================================================== @Override public void onStart() { super.onStart(); /* Find the gallery defined in the main.xml */ Gallery g = (Gallery) findViewById(R.id.gallery); /* Show a Toast message when image is clicked */ g.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View v, int position, long id) { MyImageAdapter image_ID = new MyImageAdapter(myActivity.this, position, null); if (image_ID.getItemId(position) == 0) { Toast test_toast = Toast.makeText(myActivity.this, "This is the New Image click", Toast.LENGTH_SHORT); test_toast.show(); } else { Toast test_toast = Toast.makeText(myActivity.this, "The clicked image has image number " + image_ID.getItemId(position) + " in the imageadapter.", Toast.LENGTH_SHORT); test_toast.show(); } } }); g.setOnItemLongClickListener(new OnItemLongClickListener() { @Override public boolean onItemLongClick(AdapterView<?> parent, View v, int position, long id) { MyImageAdapter image_ID = new MyImageAdapter(myActivity.this, position, null); Toast test_toast = Toast.makeText(myActivity.this, "The long clicked image has image number " + image_ID.getItemId(position) + " in the imageadapter.", Toast.LENGTH_SHORT); test_toast.show(); return true; } }); } // =========================================================== // onPause // =========================================================== protected void onPause() { super.onPause(); } // =========================================================== // onResume // =========================================================== protected void onResume() { super.onResume(); generateMyGallery(); } // =========================================================== // onStop // =========================================================== protected void onStop() { super.onStop(); } // =========================================================== // onDestroy // Is also called when user changes from horizontal // to vertical orientation and back // =========================================================== @Override protected void onDestroy() { super.onDestroy(); } // =========================================================== // Save and Restore UI states // =========================================================== @Override protected void onRestoreInstanceState(Bundle savedInstanceState) { super.onRestoreInstanceState(savedInstanceState); } protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); } // =========================================================== // Main Activity methods // =========================================================== public void generateMyGallery() { MyService cs = new MyService(this); domain = cs.getDomainList(); // Add the new_image drawable to the ArrayList Domain d = new Domain(); d.photoLocation = "drawable"; d.photoName = "new_image"; d.extra1 = "no_text"; d.extra2 = "no_text"; domain.add(0, d); myImageAdapter = new MyImageAdapter(this, R.layout.text_overlay_image_view, domain); /* Find the gallery defined in the main.xml */ Gallery g = (Gallery) findViewById(R.id.gallery); g.setSpacing(10); /* Apply a new (custom) ImageAdapter to it. */ g.setAdapter(myImageAdapter); g.setSelection(1); } private void setButtonFriendsClickListener() { Button clickButton = (Button)findViewById(R.id.button_friends_list); clickButton.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { setContentView(R.layout.friends_list); Intent myIntent = new Intent(v.getContext(), FriendsListActivity.class); startActivity(myIntent); } }); } private void setButtonCameraClickListener() { Button clickButton = (Button)findViewById(R.id.button_take_picture); clickButton.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { setContentView(R.layout.take_picture); Intent myIntent = new Intent(v.getContext(), TakePictureActivity.class); startActivity(myIntent); } }); } private void setButtonPreferencesClickListener() { Button clickButton = (Button)findViewById(R.id.button_preferences); clickButton.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Intent myIntent = new Intent(v.getContext(), MyPreferencesActivity.class); startActivity(myIntent); } }); } }; Anyone has an idea why the App crashes. Any help is much appreciated. I did find out that, when I finish() the MAIN activity when I start the FriendListActivity and restart the MAIN activity when closing the FriendListActivity, that the crash does not occur. However, this basically restarts the App and that is not the intention. Thanks all, I got the problem solved. This is what I did. . When moving all gallery related actions to the onCreate, the creash didn't happen anymore. But then after returning to the MAIN activity, the activity wasn't shown. . I then moved all the onCreate (except the super), the generateGallery, and the onStart() to the onResume. Now it works fine!

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  • c# STILL returning wrong number of cores

    - by Justin
    Ok, so I posted in In C# GetEnvironmentVariable("NUMBER_OF_PROCESSORS") returns the wrong number asking about how to get the correct number of cores in C#. Some helpful people directed me to a couple of questions where similar questions were asked but I have already tried those solutions. My question was then closed as being the same as another question, which is true, it is, but the solution given there didn't work. So I'm opening another one hoping that someone may be able to help realising that the other solutions DID NOT work. That question was How to find the Number of CPU Cores via .NET/C#? which used WMI to try to get the correct number of cores. Well, here's the output from the code given there: Number Of Cores: 32 Number Of Logical Processors: 32 Number Of Physical Processors: 4 As per my last question, the machine is a 64 core AMD Opteron 6276 (4x16 cores) running Windows Server 2008 R2 HPC edition. Regardless of what I do Windows always seems to return 32 cores even though 64 are available. I have confirmed the machine is only using 32 and if I hardcode 64 cores, then the machine uses all of them. I'm wondering if there might be an issue with the way the AMD CPUs are detected. FYI, in case you haven't read the last question, if I type echo %NUMBER_OF_PROCESSORS" at the command line, it returns 64. It just won't do it in a programming environment. Thanks, Justin UPDATE: Outputting PROCESSOR_ARCHITECTURE returns AMD64 from the command line, but x86 from the program. The program is 32-bit running on 64-bit hardware. I was asked to compile it to 64-bit but it still shows 32 cores.

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  • C++ Loop - Need variable to accumulate sum

    - by user1780064
    I'm writing a program to ask the user to enter a value between 5 and 21 (inclusive). If the number entered is not in this range, it prints, "Please try again". If the number is within the range, I need to take that number, and print the sum of all the numbers from 1 to the value entered. So if the user entered "7", the sum would be "28". I successfully wrote the first loop, in the case of the number not being within the range, but cannot figure out how to run the second loop- whether to use a while, do-while, or for loop. Please advise. #include <iostream> int main () { int uservalue; int count; int sum; //Prompt user for input do { cout << "Enter a value from 5 to 21: "; cin >> uservalue; if (uservalue < 5 || uservalue > 21) cout << "Value out of range. Try again..." << endl; } while (uservalue < 5 || uservalue > 21); cout << endl; //Loop to accumulate sum for (count = 1, count < uservalue, count++;) { sum = uservalue + count; if (uservalue <= 5 || uservalue <= 21) cout << the sum is " << sum << endl; } return 0; }

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  • Convert enumeration to string

    - by emptyheaded
    I am trying to build a function that converts an item from an enum to its corresponding string. The enums I use are fairly long, so I didn't want to use a switch-case. I found a method using boost::unordered_map very convenient, but I don't know how to make a default return (when there is no item matching the enum). const boost::unordered_map<enum_type, const std::string> enumToString = boost::assign::map_list_of (data_1, "data_1") (data_2, "data_2"); I tried to create an additional function: std::string convert(enum_type entry) { if (enumToString.find(entry)) // not sure what test to place here, return enumToString.at(entry); //because the find method returns an iter else return "invalid_value"; } I even tried something exceedingly wrong: std::string convert(enum_type entry) { try{ return enumToString.at(entry); } catch(...){ return "invalid_value"; } } Result: evil "Debug" runtime error. Can somebody give me a suggestion on how to either 1) find an easier method to convert enum to a string with the same name as the enum item 2) find a way to use already built boost methods to get a default value from a hash map (best option) 3) find what to place in the test to use a function that returns either the pair of the key-value, or a different string if the key is not found in the map. Thank you very much.

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  • How to write a custom predicate for multi_index_containder with composite_key?

    - by Titan
    I googled and searched in the boost's man, but didn't find any examples. May be it's a stupid question...anyway. So we have the famous phonebook from the man: typedef multi_index_container< phonebook_entry, indexed_by< ordered_non_unique< composite_key< phonebook_entry, member<phonebook_entry,std::string,&phonebook_entry::family_name>, member<phonebook_entry,std::string,&phonebook_entry::given_name> >, composite_key_compare< std::less<std::string>, // family names sorted as by default std::greater<std::string> // given names reversed > >, ordered_unique< member<phonebook_entry,std::string,&phonebook_entry::phone_number> > > > phonebook; phonebook pb; ... // look for all Whites std::pair<phonebook::iterator,phonebook::iterator> p= pb.equal_range(boost::make_tuple("White"), my_custom_comp()); How should my_custom_comp() look like? I mean it's clear for me then it takes boost::multi_index::composite_key_result<CompositeKey> as an argumen (due to compilation errors :) ), but what is CompositeKey in that particular case? struct my_custom_comp { bool operator()( ?? boost::multi_index::composite_key_result<CompositeKey> ?? ) const { return blah_blah_blah; } }; Thanks in advance.

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  • C++ STL Map vs Vector speed

    - by sub
    In the interpreter for my experimental programming language I have a symbol table. Each symbol consists of a name and a value (the value can be e.g.: of type string, int, function, etc.). At first I represented the table with a vector and iterated through the symbols checking if the given symbol name fitted. Then I though using a map, in my case map<string,symbol>, would be better than iterating through the vector all the time but: It's a bit hard to explain this part but I'll try. If a variable is retrieved the first time in a program in my language, of course its position in the symbol table has to be found (using vector now). If I would iterate through the vector every time the line gets executed (think of a loop), it would be terribly slow (as it currently is, nearly as slow as microsoft's batch). So I could use a map to retrieve the variable: SymbolTable[ myVar.Name ] But think of the following: If the variable, still using vector, is found the first time, I can store its exact integer position in the vector with it. That means: The next time it is needed, my interpreter knows that it has been "cached" and doesn't search the symbol table for it but does something like SymbolTable.at( myVar.CachedPosition ). Now my (rather hard?) question: Should I use a vector for the symbol table together with caching the position of the variable in the vector? Should I rather use a map? Why? How fast is the [] operator? Should I use something completely different?

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  • MySQL Update query with left join and group by

    - by Rob
    I am trying to create an update query and making little progress in getting the right syntax. The following query is working: SELECT t.Index1, t.Index2, COUNT( m.EventType ) FROM Table t LEFT JOIN MEvents m ON (m.Index1 = t.Index1 AND m.Index2 = t.Index2 AND (m.EventType = 'A' OR m.EventType = 'B') ) WHERE (t.SpecialEventCount IS NULL) GROUP BY t.Index1, t.Index2 It creates a list of triplets Index1,Index2,EventCounts. It only does this for case where t.SpecialEventCount is NULL. The update query I am trying to write should set this SpecialEventCount to that count, i.e. COUNT(m.EventType) in the query above. This number could be 0 or any positive number (hence the left join). Index1 and Index2 together are unique in Table t and they are used to identify events in MEvent. How do I have to modify the select query to become an update query? I.e. something like UPDATE Table SET SpecialEventCount=COUNT(m.EventType)..... but I am confused what to put where and have failed with numerous different guesses.

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