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  • NetBeans does not install properly

    - by upapilot
    I'm trying to install NetBeans IDE on my Ubuntu 12.04. However no matter how many time i install/resintall it (from Software Center), it still gives this strange problem: After I complete the installation and try to launch it, Netbeans first displays the initialization window. After it completes, the window disappears and nothing happens. Then after a while Netbeans seemingly restarts and then again shows the initialization window. This goes on in an infinitesimal cycle and I'm ultimately forced to restart my computer and uninstall NetBeans. Why could this be happening? I really need NetBeans as it is a very good IDE.

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  • C++ copy-construct construct-and-assign question

    - by Andy
    Blockquote Here is an extract from item 56 of the book "C++ Gotchas": It's not uncommon to see a simple initialization of a Y object written any of three different ways, as if they were equivalent. Y a( 1066 ); Y b = Y(1066); Y c = 1066; In point of fact, all three of these initializations will probably result in the same object code being generated, but they're not equivalent. The initialization of a is known as a direct initialization, and it does precisely what one might expect. The initialization is accomplished through a direct invocation of Y::Y(int). The initializations of b and c are more complex. In fact, they're too complex. These are both copy initializations. In the case of the initialization of b, we're requesting the creation of an anonymous temporary of type Y, initialized with the value 1066. We then use this anonymous temporary as a parameter to the copy constructor for class Y to initialize b. Finally, we call the destructor for the anonymous temporary. To test this, I did a simple class with a data member (program attached at the end) and the results were surprising. It seems that for the case of b, the object was constructed by the copy constructor rather than as suggested in the book. Does anybody know if the language standard has changed or is this simply an optimisation feature of the compiler? I was using Visual Studio 2008. Code sample: #include <iostream> class Widget { std::string name; public: // Constructor Widget(std::string n) { name=n; std::cout << "Constructing Widget " << this->name << std::endl; } // Copy constructor Widget (const Widget& rhs) { std::cout << "Copy constructing Widget from " << rhs.name << std::endl; } // Assignment operator Widget& operator=(const Widget& rhs) { std::cout << "Assigning Widget from " << rhs.name << " to " << this->name << std::endl; return *this; } }; int main(void) { // construct Widget a("a"); // copy construct Widget b(a); // construct and assign Widget c("c"); c = a; // copy construct! Widget d = a; // construct! Widget e = "e"; // construct and assign Widget f = Widget("f"); return 0; } Output: Constructing Widget a Copy constructing Widget from a Constructing Widget c Assigning Widget from a to c Copy constructing Widget from a Constructing Widget e Constructing Widget f Copy constructing Widget from f I was most surprised by the results of constructing d and e.

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  • New Dell PE R710 - Storage Question

    - by rihatum
    Hi All, Dell PE R710, received from Dell in the following state : Windows Disk 0 1800GB ( Volume C & D ) Windows Disk 1 526 GB (Volume E ) Perc6i Integrated Raid Controller 6 x 500GB Nearline SAS 7200RPM HDDs Raid 5 Configuration with two Virtual Disks I have installed Dell open Manage and it shows the following : Virtual Disk 0 - State : Background Initialization ( 7% ) Virtual Disk 1 - State : Background Initialization ( 25% ) Now when I click on Virtual Disk 0 it shows me all 6 Disks and the same happens when I click on Virtual Disk 1 it displays all 6 disks. But when I click on Storage Perc6i Connector 0 I get 4 Physical disks with the following numbers : Physical Disk 0:0:0 Physical Disk 0:0:1 Physical Disk 0:0:2 Physical Disk 0:0:3 When I click on Storage Perc6i Connector 1 I get 2 Physical Disks Listed in the following way : Physical Disk 1:0:4 Physical Disk 1:0:5 I am a little confused in this description, does this 1:0:4 interprets to Controller1, Disk4. Does this integrated raid card have two controllers coming out of it ? Also, When I first switched on the machine, the boot partition was showing 1GB Available out of 40GB, now its showing 38GB available out of 40GB. Is this because the Virtual Disks are still Initializing ? Any recommendations or suggestions ? Also, this server have 6 x 500GB NearLine SAS Hard drives, what would be a good raid config ? We are planning to use it for Hyper-V with quite a few (7 or 8) virtual servers, your suggestions would be helpful. Also, while the virtual disks are in a initialization state, can I destroy and re-create the raid configuration ? I would have to do it at the BIOS CTRL-M ? Thanks and Regards

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  • systemd: enabling cherokee service as a `unit file`

    - by Calvin Cheng
    So I am learning how to use systemd to initialize my services automatically on server reboot. So of course, I first make sure I have systemd and some optional systemd related packages installed. pacman -S systemd initscripts-systemd Installation seems to go well and checking, I can see that systemd and its dependency libsystemd are installed. And the optional package initscripts-systemd is also installed:- [root@li280-195 ~]# pacman -Ss systemd extra/libsystemd 44-5 [installed] systemd client libraries extra/systemd 44-5 [installed] system and service manager extra/systemd-sysvcompat 2-2 sysvinit compat symlinks for systemd community/initscripts-systemd 20120412-1 [installed] Arch specific systemd initialization/bootup scripts for systemd community/systemd-arch-units 20120412-2 Arch specific Systemd unit files Next, I ensure that systemd is loaded up when my server reboots, via grub in grub's /boot/grub/menu.lst file like this:- kernel /boot/vmlinuz root=/dev/xvda ro init=/bin/systemd Rebooting my server to check, all loads up well and I can check that systemd is operational via:- systemctl list-unit-files However, I don't see my cherokee initialization script (which is simply created at /etc/rc.d/cherokee when I installed cherokee earlier via pacman -S cherokee) being listed as one of my unit files. So the question is, how do I do that? How do I put my cherokee initialization script under systemd's control?

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  • Why won't sql server express 2008 service restart after I enable TCP/IP Protocol?

    - by John
    Whenever I enable TCP/IP connections on my SQL Server Express 2008 database server running on Windows XP SP3, I cannot restart the service, it simply states "The request failed or did respond in a timely fashion". Any suggestions of what I may have configured incorrectly? [update] Here is the applicable part of the Error Log: MSSQL$SQLEXPRESS Server failed to list on 'any' 3060. Error: 0x2747. To proceed, notify you system administrator. MSSQL$SQLEXPRESS TDSSNIClient initialization failed with error 0x2747, status code 0xa. Reason: Unable to initialize the TCP/IP listener. An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full. MSSQL$SQLEXPRESS TDSSNIClient initialization failed with error 0x2747, status code 0x1. Reason: Initialization failed with an infrastructure error. Check for previous errors. An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full. MSSQL$SQLEXPRESS Could not start the network library because of an internal error in the network library. To determine the cause, review the errors immediately preceding this one in the error log. MSSQL$SQLEXPRESS SQL Server could not spawn FRunCM thread. Check the SQL Server error log and the Windows event logs for information about possible related problems.

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  • Flex: replace all spaces with comma

    - by Treby
    im new with regexp, so can i ask for some assistance Using string.replace function what code that can replace spaces with comma Input:The quick brown fox jumps over the lazy dog. Output:The,quick,brown,fox,jumps,over,the,lazy dog. Thanks

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  • Object declaration in Objective-C

    - by Sahat
    Is there any difference in declaring objects in Objective-C between (1) and (2), besides the style and personal preference? (1) One-line declaration, allocation, initialization. Student *myStudent = [[Student alloc] init]; (2) Multi-line declaration, allocation, initialization. Student *myStudent; myStudent = [Student alloc]; myStudent = [myStudent init];

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  • log4j properties file: how to configure ?

    - by EugeneP
    Is it right that the procedure of using log4j looks like this: 1) put a .properties file somewhere in a project folder 2) in an initialization method, that runs only once, invoke PropertyConfigurator.configure("path_to_file"); 3) in every method we need to use logger we define a static logger variable and simply invoke getLogger(class) I'm asking you this: what if the initialization module is not defined? Where to put "log4j.properties" file so that we wouldn't need to invoke propertyconfigurator.configure at all, or if it's not possible, is it ok to invoke PropertyConfigurator.configure("path_to_file") in every method that uses a logger?

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  • Purpose of Explicit Default Constructors

    - by Dennis Zickefoose
    I recently noticed a class in C++0x that calls for an explicit default constructor. However, I'm failing to come up with a scenario in which a default constructor can be called implicitly. It seems like a rather pointless specifier. I thought maybe it would disallow Class c; in favor of Class c = Class(); but that does not appear to be the case. Some relevant quotes from the C++0x FCD, since it is easier for me to navigate [similar text exists in C++03, if not in the same places] 12.3.1.3 [class.conv.ctor] A default constructor may be an explicit constructor; such a constructor will be used to perform default-initialization or value initialization (8.5). It goes on to provide an example of an explicit default constructor, but it simply mimics the example I provided above. 8.5.6 [decl.init] To default-initialize an object of type T means: — if T is a (possibly cv-qualified) class type (Clause 9), the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor); 8.5.7 [decl.init] To value-initialize an object of type T means: — if T is a (possibly cv-qualified) class type (Clause 9) with a user-provided constructor (12.1), then the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor); In both cases, the standard calls for the default constructor to be called. But that is what would happen if the default constructor were non-explicit. For completeness sake: 8.5.11 [decl.init] If no initializer is specified for an object, the object is default-initialized; From what I can tell, this just leaves conversion from no data. Which doesn't make sense. The best I can come up with would be the following: void function(Class c); int main() { function(); //implicitly convert from no parameter to a single parameter } But obviously that isn't the way C++ handles default arguments. What else is there that would make explicit Class(); behave differently from Class();? The specific example that generated this question was std::function [20.8.14.2 func.wrap.func]. It requires several converting constructors, none of which are marked explicit, but the default constructor is.

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  • How to search for alphanumeric word before or after a keyword in perl?

    - by aliocee
    I have sentences as shown in the below examples: $sen1 = "The quick brown fox jump KEYWORD over123 the3 lazy dog, fox is quick"; $sen2 = "The quick brown fox jump123 KEYWORD over the lazy dog, fox is quick"; i want to use the keyword 'KEYWORD' as my search string to extract the alphanumeric words before and after the search string using Perl regular expression. sample output: over123 jump123 NB: The word 'the3' is left out because i'm only searching for alphanumeric words exactly before or after the 'KEYWORD'. Thanks

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  • How to disable automatic loading in NHibernate?

    - by Drevak
    This question might be a duplicate of this one: http://stackoverflow.com/questions/217761/nhibernate-disable-automatic-lazy-loading-of-child-records-for-one-to-many-rela I'd like to know if there is any way to tell nhibernate to do not load a child collections (best if it's with fluent Nhibernate) unless i do it manually with a query (keeping all the mappings!). The problem is that even turning off lazy loading the collections get eager-loaded automatically. I'd like that no collections are loaded unless I specify a fetchmode in my query.

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  • Entities equals(), hashCode() and toString(). How to correctly implement them?

    - by spike07
    I'm implementing equals(), hashCode() and toString() of my entities using all the available fields in the bean. I'm getting some Lazy init Exception on the frontend when I try to compare the equality or when I print the obj state. That's because some list in the entity can be lazy initialized. I'm wondering what's the correct way to for implementing equals() and toString() on an entity object.

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  • NHibernate Many to Many delete all my data in the table

    - by Daoming Yang
    I would love to thank @Stefan Steinegger and @David helped me out yesterday with many-to-many mapping. I have 3 tables which are "News", "Tags" and "News_Tags" with Many-To-Many relationship and the "News_Tags" is the link table. If I delete one of the news records, the following mappings will delete all my news records which have the same tags. One thing I need to notice, I only allowed unique tag stored in the "Tag" table. This mapping make sense for me, it will delete the tag and related News records, but how can I implement a tagging system with NHibernate? Can anyone give me some suggestion? Many thanks. Daoming. News Mapping: <class name="New" table="News" lazy="false"> <id name="NewID"> <generator class="identity" /> </id> <property name="Title" type="String"></property> <property name="Description" type="String"></property> <set name="TagsList" table="New_Tags" lazy="false" inverse="true" cascade="all"> <key column="NewID" /> <many-to-many class="Tag" column="TagID" /> </set> </class> Tag Mapping: <class name="Tag" table="Tags" lazy="false"> <id name="TagID"> <generator class="identity" /> </id> <property name="TagName" type="String"></property> <property name="DateCreated" type="DateTime"></property> <!--inverse="true" has been defined in the "News mapping"--> <set name="NewsList" table="New_Tags" lazy="false" cascade="all"> <key column="TagID" /> <many-to-many class="New" column="NewID" /> </set> </class>

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  • Use Shakespeare-text and external file

    - by Adam
    How can I convert the below example to use an external file instead of the embedded lazy text quasi quotes? {-# LANGUAGE QuasiQuotes, OverloadedStrings #-} import Text.Shakespeare.Text import qualified Data.Text.Lazy.IO as TLIO import Data.Text (Text) import Control.Monad (forM_) data Item = Item { itemName :: Text , itemQty :: Int } items :: [Item] items = [ Item "apples" 5 , Item "bananas" 10 ] main :: IO () main = forM_ items $ \item -> TLIO.putStrLn [lt|You have #{show $ itemQty item} #{itemName item}.|] This is from the yesod online book.

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  • Entities equals() - hashcode() - toString(). How to correctly implement them?

    - by spike07
    I'm implementing equals() - hashcode() - toString() of my Entities using all the available fields in the bean. I'm getting some Lazy init Exception on the frontend when I try to compare the equality or when I print the obj state. That's because some list in the entity can be lazy initialized. I'm wondering what's the correct way to for implementing equals() and toString() on an Entity Obj

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  • Haskell "Source reduction"

    - by Martin
    I'm revising for an upcoming Haskell exam and I don't understand one of the questions on a past paper. Google turns up nothing useful fst(x, y) = x square i = i * i i) Source reduce, using Haskells lazy evaluation, the expression: fst(square(3+4), square 8) ii) Source reduce, using strict evaluation, the same expression iii) State one advantage of lazy evaluation and one advantage of strict evaluation

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  • Adding object to child collection causes entire collection to load in Fluent NHibernate.

    - by Mike C.
    Hello, I have my Parent object, which contains an ICollection of Children objects. The Children are lazy loaded and I do not need them in the context of my scenario. However, when I try to add a new child object to my Children collection, it kicks off the lazy load and loads all 7000 child records. I assume I am making a newbie mistake. Anybody out there know how I can fix this? Thanks!

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  • Where to read the provided height value in an UITableViewCell?

    - by mystify
    I made a UITableViewCell subclass, and now I want that subclass to be "clever". It should align it's contents to the height of the row. But for this, the cell must know what height value was provided for it in this method: - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath However, no matter what value I assign here, my cell's frame is 44 px height at initialization time (default style). Is there any way I can get that value from the cell at initialization time?

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  • What runs before main()?

    - by MikimotoH
    After testing on msvc8, I found: Parse GetCommandLine() to argc and argv Standard C Library initialization C++ Constructor of global variables These three things are called before entering main(). My questions are: Will this execution order be different when I porting my program to different compiler (gcc or armcc), or different platform? What stuff does Standard C Library initialization do? So far I know setlocale() is a must. Is it safe to call standard C functions inside C++ constructor of global variables?

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  • C#/.NET Little Wonders: Interlocked CompareExchange()

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Two posts ago, I discussed the Interlocked Add(), Increment(), and Decrement() methods (here) for adding and subtracting values in a thread-safe, lightweight manner.  Then, last post I talked about the Interlocked Read() and Exchange() methods (here) for safely and efficiently reading and setting 32 or 64 bit values (or references).  This week, we’ll round out the discussion by talking about the Interlocked CompareExchange() method and how it can be put to use to exchange a value if the current value is what you expected it to be. Dirty reads can lead to bad results Many of the uses of Interlocked that we’ve explored so far have centered around either reading, setting, or adding values.  But what happens if you want to do something more complex such as setting a value based on the previous value in some manner? Perhaps you were creating an application that reads a current balance, applies a deposit, and then saves the new modified balance, where of course you’d want that to happen atomically.  If you read the balance, then go to save the new balance and between that time the previous balance has already changed, you’ll have an issue!  Think about it, if we read the current balance as $400, and we are applying a new deposit of $50.75, but meanwhile someone else deposits $200 and sets the total to $600, but then we write a total of $450.75 we’ve lost $200! Now, certainly for int and long values we can use Interlocked.Add() to handles these cases, and it works well for that.  But what if we want to work with doubles, for example?  Let’s say we wanted to add the numbers from 0 to 99,999 in parallel.  We could do this by spawning several parallel tasks to continuously add to a total: 1: double total = 0; 2:  3: Parallel.For(0, 10000, next => 4: { 5: total += next; 6: }); Were this run on one thread using a standard for loop, we’d expect an answer of 4,999,950,000 (the sum of all numbers from 0 to 99,999).  But when we run this in parallel as written above, we’ll likely get something far off.  The result of one of my runs, for example, was 1,281,880,740.  That is way off!  If this were banking software we’d be in big trouble with our clients.  So what happened?  The += operator is not atomic, it will read in the current value, add the result, then store it back into the total.  At any point in all of this another thread could read a “dirty” current total and accidentally “skip” our add.   So, to clean this up, we could use a lock to guarantee concurrency: 1: double total = 0.0; 2: object locker = new object(); 3:  4: Parallel.For(0, count, next => 5: { 6: lock (locker) 7: { 8: total += next; 9: } 10: }); Which will give us the correct result of 4,999,950,000.  One thing to note is that locking can be heavy, especially if the operation being locked over is trivial, or the life of the lock is a high percentage of the work being performed concurrently.  In the case above, the lock consumes pretty much all of the time of each parallel task – and the task being locked on is relatively trivial. Now, let me put in a disclaimer here before we go further: For most uses, lock is more than sufficient for your needs, and is often the simplest solution!    So, if lock is sufficient for most needs, why would we ever consider another solution?  The problem with locking is that it can suspend execution of your thread while it waits for the signal that the lock is free.  Moreover, if the operation being locked over is trivial, the lock can add a very high level of overhead.  This is why things like Interlocked.Increment() perform so well, instead of locking just to perform an increment, we perform the increment with an atomic, lockless method. As with all things performance related, it’s important to profile before jumping to the conclusion that you should optimize everything in your path.  If your profiling shows that locking is causing a high level of waiting in your application, then it’s time to consider lighter alternatives such as Interlocked. CompareExchange() – Exchange existing value if equal some value So let’s look at how we could use CompareExchange() to solve our problem above.  The general syntax of CompareExchange() is: T CompareExchange<T>(ref T location, T newValue, T expectedValue) If the value in location == expectedValue, then newValue is exchanged.  Either way, the value in location (before exchange) is returned. Actually, CompareExchange() is not one method, but a family of overloaded methods that can take int, long, float, double, pointers, or references.  It cannot take other value types (that is, can’t CompareExchange() two DateTime instances directly).  Also keep in mind that the version that takes any reference type (the generic overload) only checks for reference equality, it does not call any overridden Equals(). So how does this help us?  Well, we can grab the current total, and exchange the new value if total hasn’t changed.  This would look like this: 1: // grab the snapshot 2: double current = total; 3:  4: // if the total hasn’t changed since I grabbed the snapshot, then 5: // set it to the new total 6: Interlocked.CompareExchange(ref total, current + next, current); So what the code above says is: if the amount in total (1st arg) is the same as the amount in current (3rd arg), then set total to current + next (2nd arg).  This check and exchange pair is atomic (and thus thread-safe). This works if total is the same as our snapshot in current, but the problem, is what happens if they aren’t the same?  Well, we know that in either case we will get the previous value of total (before the exchange), back as a result.  Thus, we can test this against our snapshot to see if it was the value we expected: 1: // if the value returned is != current, then our snapshot must be out of date 2: // which means we didn't (and shouldn't) apply current + next 3: if (Interlocked.CompareExchange(ref total, current + next, current) != current) 4: { 5: // ooops, total was not equal to our snapshot in current, what should we do??? 6: } So what do we do if we fail?  That’s up to you and the problem you are trying to solve.  It’s possible you would decide to abort the whole transaction, or perhaps do a lightweight spin and try again.  Let’s try that: 1: double current = total; 2:  3: // make first attempt... 4: if (Interlocked.CompareExchange(ref total, current + i, current) != current) 5: { 6: // if we fail, go into a spin wait, spin, and try again until succeed 7: var spinner = new SpinWait(); 8:  9: do 10: { 11: spinner.SpinOnce(); 12: current = total; 13: } 14: while (Interlocked.CompareExchange(ref total, current + i, current) != current); 15: } 16:  This is not trivial code, but it illustrates a possible use of CompareExchange().  What we are doing is first checking to see if we succeed on the first try, and if so great!  If not, we create a SpinWait and then repeat the process of SpinOnce(), grab a fresh snapshot, and repeat until CompareExchnage() succeeds.  You may wonder why not a simple do-while here, and the reason it’s more efficient to only create the SpinWait until we absolutely know we need one, for optimal efficiency. Though not as simple (or maintainable) as a simple lock, this will perform better in many situations.  Comparing an unlocked (and wrong) version, a version using lock, and the Interlocked of the code, we get the following average times for multiple iterations of adding the sum of 100,000 numbers: 1: Unlocked money average time: 2.1 ms 2: Locked money average time: 5.1 ms 3: Interlocked money average time: 3 ms So the Interlocked.CompareExchange(), while heavier to code, came in lighter than the lock, offering a good compromise of safety and performance when we need to reduce contention. CompareExchange() - it’s not just for adding stuff… So that was one simple use of CompareExchange() in the context of adding double values -- which meant we couldn’t have used the simpler Interlocked.Add() -- but it has other uses as well. If you think about it, this really works anytime you want to create something new based on a current value without using a full lock.  For example, you could use it to create a simple lazy instantiation implementation.  In this case, we want to set the lazy instance only if the previous value was null: 1: public static class Lazy<T> where T : class, new() 2: { 3: private static T _instance; 4:  5: public static T Instance 6: { 7: get 8: { 9: // if current is null, we need to create new instance 10: if (_instance == null) 11: { 12: // attempt create, it will only set if previous was null 13: Interlocked.CompareExchange(ref _instance, new T(), (T)null); 14: } 15:  16: return _instance; 17: } 18: } 19: } So, if _instance == null, this will create a new T() and attempt to exchange it with _instance.  If _instance is not null, then it does nothing and we discard the new T() we created. This is a way to create lazy instances of a type where we are more concerned about locking overhead than creating an accidental duplicate which is not used.  In fact, the BCL implementation of Lazy<T> offers a similar thread-safety choice for Publication thread safety, where it will not guarantee only one instance was created, but it will guarantee that all readers get the same instance.  Another possible use would be in concurrent collections.  Let’s say, for example, that you are creating your own brand new super stack that uses a linked list paradigm and is “lock free”.  We could use Interlocked.CompareExchange() to be able to do a lockless Push() which could be more efficient in multi-threaded applications where several threads are pushing and popping on the stack concurrently. Yes, there are already concurrent collections in the BCL (in .NET 4.0 as part of the TPL), but it’s a fun exercise!  So let’s assume we have a node like this: 1: public sealed class Node<T> 2: { 3: // the data for this node 4: public T Data { get; set; } 5:  6: // the link to the next instance 7: internal Node<T> Next { get; set; } 8: } Then, perhaps, our stack’s Push() operation might look something like: 1: public sealed class SuperStack<T> 2: { 3: private volatile T _head; 4:  5: public void Push(T value) 6: { 7: var newNode = new Node<int> { Data = value, Next = _head }; 8:  9: if (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next) 10: { 11: var spinner = new SpinWait(); 12:  13: do 14: { 15: spinner.SpinOnce(); 16: newNode.Next = _head; 17: } 18: while (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next); 19: } 20: } 21:  22: // ... 23: } Notice a similar paradigm here as with adding our doubles before.  What we are doing is creating the new Node with the data to push, and with a Next value being the original node referenced by _head.  This will create our stack behavior (LIFO – Last In, First Out).  Now, we have to set _head to now refer to the newNode, but we must first make sure it hasn’t changed! So we check to see if _head has the same value we saved in our snapshot as newNode.Next, and if so, we set _head to newNode.  This is all done atomically, and the result is _head’s original value, as long as the original value was what we assumed it was with newNode.Next, then we are good and we set it without a lock!  If not, we SpinWait and try again. Once again, this is much lighter than locking in highly parallelized code with lots of contention.  If I compare the method above with a similar class using lock, I get the following results for pushing 100,000 items: 1: Locked SuperStack average time: 6 ms 2: Interlocked SuperStack average time: 4.5 ms So, once again, we can get more efficient than a lock, though there is the cost of added code complexity.  Fortunately for you, most of the concurrent collection you’d ever need are already created for you in the System.Collections.Concurrent (here) namespace – for more information, see my Little Wonders – The Concurent Collections Part 1 (here), Part 2 (here), and Part 3 (here). Summary We’ve seen before how the Interlocked class can be used to safely and efficiently add, increment, decrement, read, and exchange values in a multi-threaded environment.  In addition to these, Interlocked CompareExchange() can be used to perform more complex logic without the need of a lock when lock contention is a concern. The added efficiency, though, comes at the cost of more complex code.  As such, the standard lock is often sufficient for most thread-safety needs.  But if profiling indicates you spend a lot of time waiting for locks, or if you just need a lock for something simple such as an increment, decrement, read, exchange, etc., then consider using the Interlocked class’s methods to reduce wait. Technorati Tags: C#,CSharp,.NET,Little Wonders,Interlocked,CompareExchange,threading,concurrency

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  • Dependency Injection with Spring/Junit/JPA

    - by Steve
    I'm trying to create JUnit tests for my JPA DAO classes, using Spring 2.5.6 and JUnit 4.8.1. My test case looks like this: @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations={"classpath:config/jpaDaoTestsConfig.xml"} ) public class MenuItem_Junit4_JPATest extends BaseJPATestCase { private ApplicationContext context; private InputStream dataInputStream; private IDataSet dataSet; @Resource private IMenuItemDao menuItemDao; @Test public void testFindAll() throws Exception { assertEquals(272, menuItemDao.findAll().size()); } ... Other test methods ommitted for brevity ... } I have the following in my jpaDaoTestsConfig.xml: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd"> <!-- uses the persistence unit defined in the META-INF/persistence.xml JPA configuration file --> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean"> <property name="persistenceUnitName" value="CONOPS_PU" /> </bean> <bean id="groupDao" class="mil.navy.ndms.conops.common.dao.impl.jpa.GroupDao" lazy-init="true" /> <bean id="permissionDao" class="mil.navy.ndms.conops.common.dao.impl.jpa.PermissionDao" lazy-init="true" /> <bean id="applicationUserDao" class="mil.navy.ndms.conops.common.dao.impl.jpa.ApplicationUserDao" lazy-init="true" /> <bean id="conopsUserDao" class="mil.navy.ndms.conops.common.dao.impl.jpa.ConopsUserDao" lazy-init="true" /> <bean id="menuItemDao" class="mil.navy.ndms.conops.common.dao.impl.jpa.MenuItemDao" lazy-init="true" /> <!-- enables interpretation of the @Required annotation to ensure that dependency injection actually occures --> <bean class="org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor"/> <!-- enables interpretation of the @PersistenceUnit/@PersistenceContext annotations providing convenient access to EntityManagerFactory/EntityManager --> <bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor"/> <!-- transaction manager for use with a single JPA EntityManagerFactory for transactional data access to a single datasource --> <bean id="jpaTransactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory"/> </bean> <!-- enables interpretation of the @Transactional annotation for declerative transaction managment using the specified JpaTransactionManager --> <tx:annotation-driven transaction-manager="jpaTransactionManager" proxy-target-class="false"/> </beans> Now, when I try to run this, I get the following: SEVERE: Caught exception while allowing TestExecutionListener [org.springframework.test.context.support.DependencyInjectionTestExecutionListener@fa60fa6] to prepare test instance [null(mil.navy.ndms.conops.common.dao.impl.MenuItem_Junit4_JPATest)] org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mil.navy.ndms.conops.common.dao.impl.MenuItem_Junit4_JPATest': Injection of resource fields failed; nested exception is java.lang.IllegalStateException: Specified field type [interface javax.persistence.EntityManagerFactory] is incompatible with resource type [javax.persistence.EntityManager] at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessAfterInstantiation(CommonAnnotationBeanPostProcessor.java:292) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:959) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireBeanProperties(AbstractAutowireCapableBeanFactory.java:329) at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:110) at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75) at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:255) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:93) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.invokeTestMethod(SpringJUnit4ClassRunner.java:130) at org.junit.internal.runners.JUnit4ClassRunner.runMethods(JUnit4ClassRunner.java:61) at org.junit.internal.runners.JUnit4ClassRunner$1.run(JUnit4ClassRunner.java:54) at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34) at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44) at org.junit.internal.runners.JUnit4ClassRunner.run(JUnit4ClassRunner.java:52) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196) Caused by: java.lang.IllegalStateException: Specified field type [interface javax.persistence.EntityManagerFactory] is incompatible with resource type [javax.persistence.EntityManager] at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.checkResourceType(InjectionMetadata.java:159) at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor$PersistenceElement.(PersistenceAnnotationBeanPostProcessor.java:559) at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor$1.doWith(PersistenceAnnotationBeanPostProcessor.java:359) at org.springframework.util.ReflectionUtils.doWithFields(ReflectionUtils.java:492) at org.springframework.util.ReflectionUtils.doWithFields(ReflectionUtils.java:469) at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.findPersistenceMetadata(PersistenceAnnotationBeanPostProcessor.java:351) at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.postProcessMergedBeanDefinition(PersistenceAnnotationBeanPostProcessor.java:296) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyMergedBeanDefinitionPostProcessors(AbstractAutowireCapableBeanFactory.java:745) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:448) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(AccessController.java:219) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:221) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:168) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:435) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:409) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:537) at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:180) at org.springframework.beans.factory.annotation.InjectionMetadata.injectFields(InjectionMetadata.java:105) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessAfterInstantiation(CommonAnnotationBeanPostProcessor.java:289) ... 18 more It seems to be telling me that its attempting to store an EntityManager object into an EntityManagerFactory field, but I don't understand how or why. My DAO classes accept both an EntityManager and EntityManagerFactory via the @PersistenceContext attribute, and they work find if I load them up and run them without the @ContextConfiguration attribute (i.e. if I just use the XmlApplcationContext to load the DAO and the EntityManagerFactory directly in setUp ()). Any insights would be appreciated. Thanks. --Steve

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