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  • Lock-Free, Wait-Free and Wait-freedom algorithms for non-blocking multi-thread synchronization.

    - by GJ
    In multi thread programming we can find different terms for data transfer synchronization between two or more threads/tasks. When exactly we can say that some algorithem is: 1)Lock-Free 2)Wait-Free 3)Wait-Freedom I understand what means Lock-free but when we can say that some synchronization algorithm is Wait-Free or Wait-Freedom? I have made some code (ring buffer) for multi-thread synchronization and it use Lock-Free methods but: 1) Algorithm predicts maximum execution time of this routine. 2) Therad which call this routine at beginning set unique reference, what mean that is inside of this routine. 3) Other threads which are calling the same routine check this reference and if is set than count the CPU tick count (measure time) of first involved thread. If that time is to long interrupt the current work of involved thread and overrides him job. 4) Thread which not finished job because was interrupted from task scheduler (is reposed) at the end check the reference if not belongs to him repeat the job again. So this algorithm is not really Lock-free but there is no memory lock in use, and other involved threads can wait (or not) certain time before overide the job of reposed thread. Added RingBuffer.InsertLeft function: function TgjRingBuffer.InsertLeft(const link: pointer): integer; var AtStartReference: cardinal; CPUTimeStamp : int64; CurrentLeft : pointer; CurrentReference: cardinal; NewLeft : PReferencedPtr; Reference : cardinal; label TryAgain; begin Reference := GetThreadId + 1; //Reference.bit0 := 1 with rbRingBuffer^ do begin TryAgain: //Set Left.Reference with respect to all other cores :) CPUTimeStamp := GetCPUTimeStamp + LoopTicks; AtStartReference := Left.Reference OR 1; //Reference.bit0 := 1 repeat CurrentReference := Left.Reference; until (CurrentReference AND 1 = 0)or (GetCPUTimeStamp - CPUTimeStamp > 0); //No threads present in ring buffer or current thread timeout if ((CurrentReference AND 1 <> 0) and (AtStartReference <> CurrentReference)) or not CAS32(CurrentReference, Reference, Left.Reference) then goto TryAgain; //Calculate RingBuffer NewLeft address CurrentLeft := Left.Link; NewLeft := pointer(cardinal(CurrentLeft) - SizeOf(TReferencedPtr)); if cardinal(NewLeft) < cardinal(@Buffer) then NewLeft := EndBuffer; //Calcolate distance result := integer(Right.Link) - Integer(NewLeft); //Check buffer full if result = 0 then //Clear Reference if task still own reference if CAS32(Reference, 0, Left.Reference) then Exit else goto TryAgain; //Set NewLeft.Reference NewLeft^.Reference := Reference; SFence; //Try to set link and try to exchange NewLeft and clear Reference if task own reference if (Reference <> Left.Reference) or not CAS64(NewLeft^.Link, Reference, link, Reference, NewLeft^) or not CAS64(CurrentLeft, Reference, NewLeft, 0, Left) then goto TryAgain; //Calcolate result if result < 0 then result := Length - integer(cardinal(not Result) div SizeOf(TReferencedPtr)) else result := cardinal(result) div SizeOf(TReferencedPtr); end; //with end; { TgjRingBuffer.InsertLeft } RingBuffer unit you can find here: RingBuffer, CAS functions: FockFreePrimitives, and test program: RingBufferFlowTest Thanks in advance, GJ

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  • Projections.count() and Projections.countDistinct() both result in the same query

    - by Kim L
    EDIT: I've edited this post completely, so that the new description of my problem includes all the details and not only what I previously considered relevant. Maybe this new description will help to solve the problem I'm facing. I have two entity classes, Customer and CustomerGroup. The relation between customer and customer groups is ManyToMany. The customer groups are annotated in the following way in the Customer class. @Entity public class Customer { ... @ManyToMany(mappedBy = "customers", fetch = FetchType.LAZY) public Set<CustomerGroup> getCustomerGroups() { ... } ... public String getUuid() { return uuid; } ... } The customer reference in the customer groups class is annotated in the following way @Entity public class CustomerGroup { ... @ManyToMany public Set<Customer> getCustomers() { ... } ... public String getUuid() { return uuid; } ... } Note that both the CustomerGroup and Customer classes also have an UUID field. The UUID is a unique string (uniqueness is not forced in the datamodel, as you can see, it is handled as any other normal string). What I'm trying to do, is to fetch all customers which do not belong to any customer group OR the customer group is a "valid group". The validity of a customer group is defined with a list of valid UUIDs. I've created the following criteria query Criteria criteria = getSession().createCriteria(Customer.class); criteria.setProjection(Projections.countDistinct("uuid")); criteria = criteria.createCriteria("customerGroups", "groups", Criteria.LEFT_JOIN); List<String> uuids = getValidUUIDs(); Criterion criterion = Restrictions.isNull("groups.uuid"); if (uuids != null && uuids.size() > 0) { criterion = Restrictions.or(criterion, Restrictions.in( "groups.uuid", uuids)); } criteria.add(criterion); When executing the query, it will result in the following SQL query select count(*) as y0_ from Customer this_ left outer join CustomerGroup_Customer customergr3_ on this_.id=customergr3_.customers_id left outer join CustomerGroup groups1_ on customergr3_.customerGroups_id=groups1_.id where groups1_.uuid is null or groups1_.uuid in ( ?, ? ) The query is exactly what I wanted, but with one exception. Since a Customer can belong to multiple CustomerGroups, left joining the CustomerGroup will result in duplicated Customer objects. Hence the count(*) will give a false value, as it only counts how many results there are. I need to get the amount of unique customers and this I expected to achieve by using the Projections.countDistinct("uuid"); -projection. For some reason, as you can see, the projection will still result in a count(*) query instead of the expected count(distinct uuid). Replacing the projection countDistinct with just count("uuid") will result in the exactly same query. Am I doing something wrong or is this a bug? === "Problem" solved. Reason: PEBKAC (Problem Exists Between Keyboard And Chair). I had a branch in my code and didn't realize that the branch was executed. That branch used rowCount() instead of countDistinct().

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  • c# - can you make a "weak" assembly reference to a strong named assembly

    - by Tim
    hi, for various reasons i would rather not use strong named (signed) assemblies in my project. however, one of the projects is referenced by a sharepoint web part which means it must be signed. is it possible to have this assembly signed but when I reference it from other projects, to do so using a non-strong reference. this would give me the advantages of having a non-signed assembly for the rest of my code but still allow it to be loaded by sharepoint Tim

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  • Separate Query for Count

    - by Anraiki
    Hello, I am trying to get my query to grab multiple rows while returning the maximum count of that query. My query: SELECT *, COUNT(*) as Max FROM tableA LIMIT 0 , 30 However, it is only outputting 1 record. I would like to return multiple record as it was the following query: SELECT * FROM tableA LIMIT 0 , 30 Do I have to use separate queries?

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  • Ninject.Web.PageBase still resulting in null reference to injected dependency

    - by Ted
    I have an ASP.NET 3.5 WebForms application using Ninject 2.0. However, attempting to use the Ninject.Web extension to provide injection into System.Web.UI.Page, I'm getting a null reference to my injected dependency even though if I switch to using a service locator to provide the reference (using Ninject), there's no issue. My configuration (dumbed down for simplicity): public partial class Default : PageBase // which is Ninject.Web.PageBase { [Inject] public IClubRepository Repository { get; set; } protected void Page_Load(object sender, EventArgs e) { var something = Repository.GetById(1); // results in null reference exception. } } ... //global.asax.cs public class Global : Ninject.Web.NinjectHttpApplication { /// <summary> /// Creates a Ninject kernel that will be used to inject objects. /// </summary> /// <returns> /// The created kernel. /// </returns> protected override IKernel CreateKernel() { IKernel kernel = new StandardKernel(new MyModule()); return kernel; } .. ... public class MyModule : NinjectModule { public override void Load() { Bind<IClubRepository>().To<ClubRepository>(); //... } } Getting the IClubRepository concrete instance via a service locator works fine (uses same "MyModule"). I.e. private readonly IClubRepository _repository = Core.Infrastructure.IoC.TypeResolver.Get<IClubRepository>(); What am I missing? [Update] Finally got back to this, and it works in Classic Pipeline mode, but not Integrated. Is the classic pipeline a requirement? [Update 2] Wiring up my OnePerRequestModule was the problem (which had removed in above example for clarity): protected override IKernel CreateKernel() { var module = new OnePerRequestModule(); module.Init(this); IKernel kernel = new StandardKernel(new MyModule()); return kernel; } ...needs to be: protected override IKernel CreateKernel() { IKernel kernel = new StandardKernel(new MyModule()); var module = new OnePerRequestModule(); module.Init(this); return kernel; } Thus explaining why I was getting a null reference exception under integrated pipeline (to a Ninject injected dependency, or just a page load for a page inheriting from Ninject.Web.PageBase - whatever came first).

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  • Relative path reference in WebConfig.ConnectionString

    - by Ngu Soon Hui
    Is it possible to specify a relative path reference in connectionstring, attachDbFileName property in a web.config? For example, In my database is located in the App_data folder, I can easily specify the AttachDBFilename as|DataDirectory|\mydb.mdf and the |Datadirectory| will automatically resolve to the correct path. Now, suppose that web.config file is located in A folder, but the database is located in B\App_data folder, where A and B folder is located in the same folder. Is there anyway to use relative path reference to resolve to the correct path?

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  • preg match count matches

    - by Scarface
    Hey guys quick question, I have a preg match statement, and it checks for matches, but I was wondering how you can count the matches. Any advice appreciated. $message='[tag] [tag]'; preg_match('/\[tag]\b/i',$message); for example a count of this message string should lead to 2 matches

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  • How to display total record count against models in django admin

    - by Rog
    Is there a neat way to make the record/object count for a model appear on the main model list in the admin module? I have found techniques for showing counts of related objects within sets in the list_display page (and I can see the total in the pagination section at the bottom of the same), but haven't come across a neat way to show the record count at the model list level.

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  • Parsing xml containing character reference

    - by Shefali Dubey
    The XML im trying to parse contains a control character 0x2 inside CDATA. I tried to replace it with character reference which led to CDATA looking like: CDATA section----charcter reference----CDATA section Now if i try to parse it i get an error message saying: org.xml.sax.SAXParseException: Content is not allowed in prolog.

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  • Count checked CheckedListBox items

    - by comii
    Hi! I have CheckedListBox and four item in it! Now I want to count number of checked item. For this I use: countnumber=CheckedListBox1.CheckedItems.Count But countnumber is always 0 even if I checked CheckedListBox items or not! What I am doing wrong?

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  • Friend WCF Web Service Reference

    - by Bram
    Is it possible to make a WCF reference in a Silverlight DLL private? The option is greyed out and when you edit the Reference.vb file manaully, when running, it complains about not being able to serialize because it is not public. I don't want the service to be exposed outside of the DLL. Is this possible?

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  • Sphinx: cross-reference indexed item

    - by Unbeknown
    How can I cross-reference an indexed item inside a reStructuredText document? For example, how can I cross-reference SectionB: .. index:: pair: SectionA; SectionB SectionB -------- SectionB description. I tried using :ref:'SectionB' and :index:'SectionB' but they don't work. Thanks.

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  • What is the minimum interface that has the Count property in .Net

    - by SoMoS
    Hello, I need to change a method that has one parameter that takes a serie of objects. I need to find the lowest Interface (in inheritance tree) that has the Count property. Until now I was using the IEnumerable but as this has not Count I need to change it to the wider interface possible so the method can work with the biggest number of types of series (collections, lists, arrays, etc). Thanks in advance.

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  • Wordpress - Total User Count who only have posts

    - by knightrider
    I want to display total number of user who only have posts at Wordpress. I can get all users by this query <?php $user_count = $wpdb->get_var("SELECT COUNT(*) FROM $wpdb->users;"); echo $user_count ?> But for the user count only with posts, i think i might need to join another table, does anyone have snippets ? Thanks.

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  • Count words like Microsoft Word does

    - by Maarten
    I need to count words in a string using PHP or Javascript (preferably PHP). The problem is that the counting needs to be the same as it works in Microsoft Word, because that is where the people assemble their original texts in so that is their reference frame. PHP has a word counting function (http://php.net/manual/en/function.str-word-count.php) but that is not 100% the same as far as I know. Any pointers?

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  • Business layer: Looking for a complete reference ?

    - by odiseh
    hi I'm studying business layer and need a complete reference which covers issues about "how to manage dependency between business layer and other layers", "how many ways are there to send data between layers" and most important for me "how to group business logic and make business component". do you know any reference?

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  • What's the best way to reference a .DLL - as a normal reference or as a web service?

    - by dotnetdev
    Hi, What is the best way to reference an existing .NET dll (Class library)? Is there any benefit to expose web services from the class library and reference these as opposed to referencing the actual .dll (Although one benefit of the web service approach is the granularity and thus surface area exposed is up to you at coding time)? I am thinking with loose coupling in mind, as a criteria. Thanks

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  • count and fetch rows in php

    - by Mac Taylor
    hey guys i have a table in my mysql database named (names) now everyone can save their real names now i want to query this table and find out how many times these names used forexample the output should be : Jakob (20) Jenny (17) now this is my own code : list($usernames) =mysql_fetch_row(mysql_query('SELECT name FROM table_user GROUP BY name ORDER BY COUNT(name) DESC LIMIT 50 ')); list($c) =mysql_num_rows(mysql_query('SELECT COUNT(name) FROM table_user GROUP BY name ')); print $usernames.'('.$c.')' is this a correct approach ?!

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  • How to count no of elements ?

    - by rajesh
    hi suppose i have what i want is inside maindiv i want to count no of elements(may be div input tags)present. there may be use of getElementByTagName(). But the problem is that how to count element. Thanks

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  • Javascript reference external script file - security implications

    - by rkrauter
    Hi, If I have a reference to an external third party JavaScript file on my website, what are the security implications? Can the JavaScript file be used to steal cookies? One example of this is the Google Analytics JavaScript reference file. Could the third party technically steal cookies or any other sensitive information from my logged on users (XSS)? The whole cross domain scripting has me confused sometimes. Thanks!

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  • Django: get count of ForeignKey item in template?

    - by AP257
    Straightforward question - apologies if it is a duplicate, but I can't find the answer if so. I have a User model and a Submission model, like this: class Submission(models.Model): uploaded_by = models.ForeignKey('User') class User(models.Model): name = models.CharField(max_length=250 ) How can I show the number of Submissions made by each user in the template? I've tried {{ user.submission.count }}, like this: for user in users: {{ user.name }} ({{ user.submission.count }} submissions) but no luck...

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