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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • What is the purpose of this delegate usage?

    - by Kev
    Whilst poking around some code in .NET Reflector in an app I don't have the source code for I found this: if (DeleteDisks) { using (List<XenRef<VDI>>.Enumerator enumerator3 = list.GetEnumerator()) { MethodInvoker invoker2 = null; XenRef<VDI> vdiRef; while (enumerator3.MoveNext()) { vdiRef = enumerator3.Current; if (invoker2 == null) { // // Why do this? // invoker2 = delegate { VDI.destroy(session, vdiRef.opaque_ref); }; } bestEffort(ref caught, invoker2); } } } if (caught != null) { throw caught; } private static void bestEffort(ref Exception caught, MethodInvoker func) { try { func(); } catch (Exception exception) { log.Error(exception, exception); if (caught == null) { caught = exception; } } } Why not call VDI.destroy() directly. Is this just a way of wrapping the same pattern of try { do something } catch { log error } if it's used a lot?

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  • Castle Windsor Weak Typed Factory

    - by JeffN825
    In a very very limited number of scenarios, I need to go from an unknown Type (at compile time) to an instance of the object registered for that type. For the most part, I use typed factories and I know the type I want to resolve at compile time...so I inject a Func<IMyType> into a constructor ...but in these limited number of scenarios, in order to avoid a direct call to the container (and thus having to reference Windsor from the library, which is an anti-pattern I'd like to avoid), I need to inject a Func<Type,object>...which I want to internally container.Resolve(type) for the Type parameter of the Func. Does anyone have some suggestions on the easiest/most straightforward way of setting this up? I tried the following, but with this setup, I end up bypassing the regular TypedFactoryFacility altogether which is definitely not what I want: Kernel.Register(Component.For(typeof (Func<Type, object>)).LifeStyle.Singleton.UsingFactoryMethod( (kernel, componentModel, creationContext) => kernel.Resolve(/* not sure what to put here... */))); Thanks in advance for any assistance.

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  • What is the most efficient functional version of the following imperative code?

    - by justin.r.s.
    I'm learning Scala and I want to know the best way of expressing this imperative pattern using Scala's functional programming capabilities. def f(l: List[Int]): Boolean = { for (e <- l) { if (test(e)) return true } } return false } The best I can come up with is along the lines of: l map { e => test(e) } contains true But this is less efficient since it calls test() on each element, whereas the imperative version stops on the first element that satisfies test(). Is there a more idiomatic functional programming technique I can use to the same effect? The imperative version seems awkward in Scala.

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  • question of sed replace

    - by chun
    hi i have a config file xml <tflow name="CENTRE" inputDTD="/JOBS/cnav/etc/jobReporting/batch/dtd/dtd-ContactCentre.dtd" inputFile="/JOBS/cnav/etc/jobReporting/import/2010.05.02.CONTACTCENTRE.xml" logPath="/JOBS/cnav/etc/jobReporting/logs/" rejectPath="/JOBS/cnav/etc/jobReporting/rejets/"/> <tflow name="SKILL" inputDTD="/JOBS/cnav/etc/jobReporting/batch/dtd/dtd-Skill.dtd" inputFile="/JOBS/cnav/etc/jobReporting/import/2010.05.02.SKILLS.xml" logPath="/JOBS/cnav/etc/jobReporting/logs/" rejectPath="/JOBS/cnav/etc/jobReporting/rejets/"/> my shell is aim to change, by example '2010.05.02.SKILLS.xml' with 'newdate.SKILLS.xml' currently i think of SED, i wrote: sed 's/(import\/)(\d{4}.\d{2}.\d{2})/$1$newdate/g' myfile.xml it doesn't work,i test the pattern with RegExr(a site) which is fine. is it a problem of synthesis of SED? thanks.

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  • c# EnumerateFiles wildcard returning non matches?

    - by Sam Underhill
    As a simplified example I am executing the following IEnumerable<string> files = Directory.EnumerateFiles(path, @"2010*.xml", SearchOption.TopDirectoryOnly).ToList(); In my results set I am getting a few files which do no match the file pattern. According to msdn searchPattern wildcard is "Zero or more characters" and not a reg ex. An example is that I am getting a file name back as "2004_someothername.xml". For information there are in excess of 25,000 files in the folder. Does anyone have any idea what is going on?

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  • How should I synchronize lists in WCF?

    - by mafutrct
    I've got a WCF service that offers multiple lists of items of different types. The lists can be changed on the server. Every change has to be published to all clients to make sure every client has an up-to-date copy of each server list. Currently I'm using this strategy: On login, every client receives the current status of every list. On every change, the added or removed item is sent to all clients. The drawback is that I have to create a callback for every list, since the items are of different types. Is there a pattern I could apply? Or do I really have to duplicate code for each of the lists?

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  • Insert A Line At The Beginnig Of A File

    - by thebourneid
    I'm trying to insert/add a line 'COMMENT DUMMY' at the beginnig of a file as a first row if /PATTERN/ not found. I know how to do this with OPEN CLOSE function. Probably after reading the file it should look something like this: open F, ">", $fn or die "could not open file: $!"; ; print F "COMMENT DUMMY\n", @array; close F; But I have a need to implement this with the use of the Tie::File function and don't know how. use strict; use warnings; use Tie::File; my $fn = 'test.txt'; tie my @lines, 'Tie::File', $fn or die "could not tie file: $!"; untie @lines;

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  • WPF Prism deactivate ?

    - by 2Fast4YouBR
    Hi all, I have an problem and would like to know if it is common problem or jsut with me. I am using Wpf with Prism and Unity, all with the pattern MvvM. I am loading a viewModel that has a reference to a dropdown with few items, my idea is that each time that the user click in some place to open the view that has this dropdown is that the dropdown will be shown with diferent values. The problem is that I see is that after I show the view for the first time and after the first DEACTIVATE, when I try to load it again looks like it is already in the memory (was not deactivated/disposed), so as is already in memory, it not call the constructor again of the modelView and the dropdown is shown with tha same old values. public BranchSelectionViewModel(IUnityContainer unityContainer) { this.unityContainer = unityContainer; User user = this.unityContainer.Resolve<User>(); this.branches = new ObservableCollection<Department>(user.Departments .Where(department => department.DepartmentId != user.SelectedDepartment.DepartmentId)); }

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  • Rails: Best practice to store user settings?

    - by ole_berlin
    Hi, I'm wondering what the best way is to store user settings? For a web 2.0 app I want users to be able to select certain settings. At the moment is it only when to receive email notifications. The easiest way would be to just create a Model "Settings" and have a column for every setting and then have a 1-1 relationship with users. But is there a pattern to solve this better? Is it maybe better to store the info in the user table itself? Or should I use a table with "settings_name" and "settings_value" to be completely open about the type of settings stored there (without having to run any migrations when adding options)? What is your opinion? Thanks

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  • Is it inefficient to access a python class member container in a loop statement?

    - by Dave
    Hi there. I'm trying to adopt some best practices to keep my python code efficient. I've heard that accessing a member variable inside of a loop can incur a dictionary lookup for every iteration of the loop, so I cache these in local variables to use inside the loop. My question is about the loop statement itself... if I have the following class: class A(object): def init(self) self.myList = [ 'a','b','c', 'd', 'e' ] Does the following code in a member function incur one, or one-per-loop-iteration (5) dictionary lookups? for letter in self.myList: print letter IE, should I adopt the following pattern, if I am concerned about efficiency... localList = self.myList for letter in localList: print letter or is that actually LESS efficient due to the local variable assign? Note, I am aware that early optimization is a dangerous pitfall if I'm concerned about the overall efficiency of code development. Here I am specifically asking about the efficiency of the code, not the coding. Thanks in advance! D

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  • The ** idiom in C++ for object construction

    - by bobobobo
    In a lot of C++ API'S (COM-based ones spring to mind) that make something for you, the pointer to the object that is constructed is usually required as a ** pointer (and the function will construct and init it for you) You usually see signatures like: HRESULT createAnObject( int howbig, Object **objectYouWantMeToInitialize ) ; -- but you seldom see the new object being passed as a return value. Besides people wanting to see error codes, what is the reason for this? Is it better to use the ** pattern rather than a returned pointer for simpler operations such as: wchar_t* getUnicode( const char* src ) ; Or would this better be written as: void getUnicode( const char* src, wchar_t** dst ) ; The most important thing I can think of is to remember to free it, and the ** way, for some reason, tends to remind me that I have to deallocate it as well.

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  • Irregular layout ItemsControl

    - by firoso
    I have a strange layout for an ItemsControl. I have a 4x6 grid with the following pattern: 1 2 3 4 13 14 15 16 5 6 7 8 17 18 19 20 9 10 11 12 21 22 23 24 Is there an easy way to do this? should I be using 6 Items Controls and take "sections" of my list? is there a good way to do this? What about notification? It's important to note that I may, or may not, have all 24 entries present, but the layout needs to be maintained (think of it like filled slots on a bingo card or something)

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  • Is this the correct why of speaking to a "Content Manager" Class?

    - by DeanMc
    I am creating a silverlight site. I am currently breaking out my ideas into pieces of functionality. One of the idea's I have is the concept of a content manager. This is essentially a UI control with 4 regions. Top, Bottom, Right & Left. I also have a collection of objects that are considered "Menu Items". These are controls that function as a way to navigate around, similar to links. The idea I have is to implement an IMenuItem interface. Among the standard pieces of information (Text, PageReference, etc) I was also going to hold a reference to the content manager. My idea behind this thinking is that I can pass the PageReference to a property on the ContentManager and then call a method which knows how to update the content manager accordingly. Is this the best way of implementing this or is their some sort of pattern for it?

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  • Div horizontal aligning, one fixed, one adaptive

    - by Dorian McHensie
    Hello everyone. I would like to create a vertical splitted site structure using two divs: My intention is to have d2 next to d1 in a horizontal align structure (same line). What i get is not this. In fact using that code, d2 does not take the remaining space, but collapses to the min width. if I use WRONG because d2 goes down and takes all the space (but both divs are in different lines). HOW TO REACH MY OBJECTIVE? Is there a design pattern for this problem???? Thanks.

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  • Allow a new line anywhere in the regex?

    - by Scott Chamberlain
    I am having a find a replace in a bunch of RTF documents, The basic pattern I need is \{(?:\\\*)?\\field\\fldlock\{\\\*\\fldinst ?MERGEFIELD ?((?:\\.*?)?[\w\[\]]+?)(?:\\.*?)?\}(?:\{\\fldrslt\})?\} However I then found out there could potentialy be a newline before each slash, so it turned in to this. \{(?:\s*\\\*)?\s*\\field\s*\\fldlock\s*\{\s*\\\*\s*\\fldinst\s*MERGEFIELD\s*((?:\\.*?)?[\w\[\]]+?(?:\s*\\.*?)?)?\s*\}(?:\s*\{\s*\\fldrslt\s*\})?\s*\} But then I hit this it fails fees totaling $\protect {\field\fldlock{\*\fldinst MERGEFIELD ENTEROUTSTANDINGVETERINARYF EES}}\plain\f0\fs24\prot Is there way have to have it match a new line anywhere in the search too without adding (?:\r?\n)? everywhere? EDIT To clear up confusion on the new lines. I need to keep the newlines in the document, I only want to remove the newlines if they are inside my match, so in the final example I posted it should replace fees totaling $\protect {\field\fldlock{\*\fldinst MERGEFIELD ENTEROUTSTANDINGVETERINARYF EES}}\plain\f0\fs24\prot with fees totaling $\protect ENTEROUTSTANDINGVETERINARYFEES\plain\f0\fs24\prot

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  • Regex for Date DD-MM-YYYY

    - by Josh M
    I have the following expression which will be used as date validation in the HTML5 "pattern" attribute. ?:0[1-9]|1[0-9]|2[0-9])|(?:(?!02)(?:0[1-9]|1[0-2])-(?:30))|(?:(?:0[13578]|1[02])-31))-(?:(?:0[1-9]|1[0-2])-(?:19|20)[0-9]{2} I want it to allow only valid dates, using "-" as a separator. This means up to 29th in February if it's a leap year, and 30/31 for other months respectively. Currently, it only allows years starting with 2 (2012) and months up to 12 (December). But it limits the day to 29 regardless of which month. Can anybody help me fix it?

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  • iPhone UIImage number recognition

    - by Skeep
    Hi All, I have a small UIImage (jpg) with a single typed number. I want to be able to read the number with some kind of pattern recognition. I'm really not sure where to start, so any help would be appreciated. my initial idea was to compare this image with other images. For instance compare the image with that of a 1,2,3, etc until a match was found. That just seems slow and cumbersome and wondered if there was a better way to do it? Thanks

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  • Customer provider Password Reset client.

    - by ProfK
    I'm looking for guidence on writing a custom password reset UI, but it must fit the Provider 'Pattern', or degrade silently to built-in defaults. E.g. my Reset Control must collect extra information, and perform differently to the standard Password Recovery Control. It must close as possible use the standard MembershipProvider interface for standard functions, and only use an extended interface for the non-standard stuff. I'd like some reading on issues such as, what must I ask the Membership Provider for, and what must I do myself. What must I tell the provider (service?) about what I do? Etc.

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  • Should I always release self for failed init methods?

    - by leo
    Should I always release self when there is a failure inside init, or should I only do so if I have initialized instance variables first? To put it another way, is this pattern valid? Is there a time when I shouldn't release self inside an init method, or should I assume that if the control flow enters init, self has at least a retain count of 1? - (id)init { if ((self = [super init]) == nil) { [self release]; return nil; } //do some init stuff if (somethingFailed) { [self release]; return nil; } return self; }

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  • Help me understand the code snippet in c#

    - by Benny
    I am reading this blog: Pipes and filters pattern I am confused by this code snippet: public class Pipeline<T> { private readonly List<IOperation<T>> operations = new List<IOperation<T>>(); public Pipeline<T> Register(IOperation<T> operation) { operations.Add(operation); return this; } public void Execute() { IEnumerable<T> current = new List<T>(); foreach (IOperation<T> operation in operations) { current = operation.Execute(current); } IEnumerator<T> enumerator = current.GetEnumerator(); while (enumerator.MoveNext()); } } what is the purpose of this statement: while (enumerator.MoveNext());? seems this code is a noop.

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  • How to map inheritance with property returned other inheritance?

    - by dario-g
    Hi I have abstract class Vehicle and two classes that derive from: Car and ForkLift. public abstract class Vehicle { public EngineBase Engine { get; set; } } public class Car : Vehicle { public GasEngine Engine { get; set; } } public class ForkLift : Vehicle { public ElectricEngine Engine { get; set; } } and Engine clasess: public abstract class Engine { } public class GasEngine : Engine { } public class ElectricEngine : Engine { } Engines are mapped with "table per class hierarchy". With Vehicles I want to use the same pattern. How to map Engine class and derived with that Engine property?

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  • Extract dates from filename

    - by Newbie
    I have a situation where I need to extract dates from the file names whose general pattern is [filename_]YYYYMMDD[.fileExtension] e.g. "xxx_20100326.xls" or x2v_20100326.csv The below program does the work //Number of charecter in the substring is set to 8 //since the length of YYYYMMDD is 8 public static string ExtractDatesFromFileNames(string fileName) { return fileName.Substring(fileName.IndexOf("_") + 1, 8); } Is there any better option of achieving the same? I am basically looking for standard practice. I am using C#3.0 and dotnet framework 3.5 Edit: I have like the solution and the way of answerig of LC. I have used his program like string regExPattern = "^(?:.*_)?([0-9]{4})([0-9]{2})([0-9]{2})(?:\\..*)?$"; string result = Regex.Match(fileName, @regExPattern).Groups[1].Value; The input to the function is : "x2v_20100326.csv" But the output is: 2010 instead of 20100326(which is the expected one). Can anyone please help.

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  • Automating builds from subversion tags

    - by Ajaxx
    I'm trying to automate the build process for engineering group. As part of that automation, I'm trying to get to a point where the act of applying a specific tag that adheres to a pattern will kick off an automated process that will do the following: Check out source code Create a build script from a template Build the project I'm pretty certain I could do this with a post-hook in subversion, but I'm trying to figure out a way to do this with something other than a subversion hook. Would it make sense to monitor the tags directory in the subversion repository to kick off my workflow? Are there any decent tools that help with this (.NET would be great if possible). Am I better off just writing an engine to do this? My preferences: Existing product that does all or part of this If development work needs to occur, .NET is preferable Works with Windows (we've got a Linux based repo, but builds all occur on windows)

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  • What elegant method callback design should be used ?

    - by ereOn
    Hi, I'm surprised this question wasn't asked before on SO (well, at least I couldn't find it). Have you ever designed a method-callback pattern (something like a "pointer" to a class method) in C++ and, if so, how did you do it ? I know a method is just a regular function with some hidden this parameter to serve as a context and I have a pretty simple design in mind. However, since things are often more complex than they seem to, I wonder how our C++ gurus would implement this, preferably in an elegant and standard way. All suggestions are welcome !

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