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• WCF for a shared data access

  - by Audrius

  Hi all, I have a little experience with WCF and would like to get your opinion/suggestion on how the following problem can be solved: A web service needs to be accessible from multiple clients simultaneously and service needs to return a result from a shared data set. The concrete project I'm working on has to store a list of IP addresses/ranges. This list will be queried by a bunch of web servers for a validation purposes and we speak of a couple of thousand or more queries per minute. My initial draft approach was to use Windows service as a WCF host with service contract implementing class that is decorated with ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple) that has a list object and a custom locking for accessing it. So basically I have a WCF service singleton with a list = shared data - multiple clients. What I do not like about it is that data and communication layers are merged into one and performance wise this doesn't feel "right". What I really really (- want is Windows service running an instance of IP list holding container class object, a second service running WCF service contract implementation and a way the latter querying the former in a nice way with a minimal blocking. Using another WCF channel would not really take me far away from the initial draft implementation or would it? What approach would you take? Project is still in a very early stage so complete design re-do is not out of question. All ideas are appreciated. Thanks! UPDATE: The data set will be changed dynamically. Web service will have a separate method to add IP or IP range and on top of that there will be a scheduled task that will trigger data cleanup every 10-15 minutes according to some rules. UPDATE 2: a separate benchmark project will be kicked up that should use MSSQL as a data backend (instead on in-memory list).

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• finding "line-breaks" in textarea that is word-wrapping ARABIC text

  - by Irfan jamal

  I have a string of text that I display in a textarea (right-to-left orientation). The user can resize the textarea dynamically (I use jquery for this) and the text will wrap as necessary. When the user hits submit, I will take that text and create an image using PHP, BUT before submitting I would like to know where the "line-breaks" or rather "word-wraps" occur. Everywhere I have looked so far only shows me how to process line-breaks on the php side. I want to make it clear that there ARE NO LINE-BREAKS. What I have is one LONG string that will be word-wrapped in different ways based on the width of the textarea set by the user. I can't use "columns" or any other standard width representation because I have a very complex arabic font that is actually composed of glyphs (characters) of numerous different widths. If anyone knows of a way of accessing where the word wraps occur (either in a textarea or a div if need-be), I'd really like to know. My only other solution is to actually store (in my DB) the width of every single character (somewhat tedious since there are over 200 characters in 600 different fonts, for a total of...some huge number). My hopes aren't high, but I thought I would ask. Thanks i. jamal

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• x86 opcode alignment references and guidelines

  - by mrjoltcola

  I'm generating some opcodes dynamically in a JIT compiler and I'm looking for guidelines for opcode alignment. 1) I've read comments that briefly "recommend" alignment by adding nops after calls 2) I've also read about using nop for optimizing sequences for parallelism. 3) I've read that alignment of ops is good for "cache" performance Usually these comments don't give any supporting references. Its one thing to read a blog or a comment that says, "its a good idea to do such and such", but its another to actually write a compiler that implements specific op sequences and realize most material online, especially blogs, are not useful for practical application. So I'm a believer in finding things out myself (disassembly, etc. to see what real world apps do). This is one case where I need some outside info. I notice compilers will usually start an odd byte instruction immediately after whatever previous instruction sequence there was. So the compiler is not taking any special care in most cases. I see "nop" here or there, but usually it seems nop is used sparingly, if at all. How critical is opcode alignment? Can you provide references for cases that I can actually use for implementation? Thanks.

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• what's the alternative to readonlycollection when using lazy="extra"?

  - by Kunjan

  I am trying to use lazy="extra" for the child collection of Trades I have on my Client object. The trades is an Iset<Trade Trades, exposed as ReadOnlyCollection<Trade because I do not want anyone to modify the collection directly. As a result, I have added AddTrade and RemoveTrade methods. Now I have a Client Search page where I need to show the Trade Count. and on the Client details page I have a tab where I need to show all the trades for the Client in paged gridview. What I want to achieve is, for the search when I say on the client object as client.Trades.Count, nHibernate should only fire a select count(*) query. Hence I am using lazy="extra". But because I am using a ReadOnlyCollection, nHibernate fires a count query & a separate query to load the child collection trades completely. Also, I cannot include the Trades in my initial search request as this would disturb the paging because a counterparty can have n trades which would result in n rows, when I am searching clients only. So the child collections have to be loaded lazily. The second problem is that on the client details page -- Trades grid view, I have enabled paging for performance reasons. But by nature nHibernate loads the entire collection of trades as the user goes from one page to another. Ideally I want to control this by getting only trades specific to the page the user is on. How can I achieve this? I came across this very good article. http://stackoverflow.com/questions/876976/implementing-ipagedlistt-on-my-models-using-nhibernate But I am not sure if this will work for me, as lazy=extra currently doesnt work as expected with the ReadOnlyCollection. So, if I went ahead and implemented the solution this way and further enhanced it by making the List/Set Immutable, will lazy=extra give me the same problem as with ReadOnlyCollections?

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• Static method , Abstract method , Interface method comparision ?

  - by programmerist

  When i choose these methods? i can not decide which one i must prefer or when will i use one of them?which one give best performance? First Type Usage public abstract class _AccessorForSQL { public virtual bool Save(string sp, ListDictionary ld, CommandType cmdType); public virtual bool Update(); public virtual bool Delete(); public virtual DataSet Select(); } class GenAccessor : _AccessorForSQL { DataSet ds; DataTable dt; public override bool Save(string sp, ListDictionary ld, CommandType cmdType) { } public override bool Update() { return true; } public override bool Delete() { return true; } public override DataSet Select() { DataSet dst = new DataSet(); return dst; } Second Type Usage Also i can write it below codes: public class GenAccessor { public Static bool Save() { } public Static bool Update() { } public Static bool Delete() { } } Third Type Usage Also i can write it below codes: public interface IAccessorForSQL { bool Delete(); bool Save(string sp, ListDictionary ld, CommandType cmdType); DataSet Select(); bool Update(); } public class _AccessorForSQL : IAccessorForSQL { private DataSet ds; private DataTable dt; public virtual bool Save(string sp, ListDictionary ld, CommandType cmdType) { } } } I can use first one below usage: GenAccessor gen = New GenAccessor(); gen.Save(); I can use second one below usage: GenAccessor.Save(); Which one do you prefer? When will i use them? which time i need override method ? which time i need static method?

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• Did I find a bug in WriteableBitmap when using string literals

  - by liserdarts

  For performance reasons I'm converting a large list of images into a single image. This code does exactly what I want. Private Function FlattenControl(Control As UIElement) As Image Control.Measure(New Size(1000, 1000)) Control.Arrange(New Rect(0, 0, 1000, 1000)) Dim ImgSource As New Imaging.WriteableBitmap(1000, 1000) ImgSource.Render(Control, New TranslateTransform) ImgSource.Invalidate Dim Img As New Image Img.Source = ImgSource Return Img End Function I can add all the images into a canvas pass the canvas to this function and I get back one image. My code to load all the images looks like this. Public Function BuildTextures(Layer As GLEED2D.Layer) As FrameworkElement Dim Container As New Canvas For Each Item In Layer.Items If TypeOf Item Is GLEED2D.TextureItem Then Dim Texture = CType(Item, GLEED2D.TextureItem) Dim Url As New Uri(Texture.texture_filename, UriKind.Relative) Dim Img As New Image Img.Source = New Imaging.BitmapImage(Url) Container.Children.Add(Img) End If Next Return FlattenControl(Container) End Function The GLEED2D.Layer and GLEED2D.TextureItem classes are from the free level editor GLEED2D (http://www.gleed2d.de/). The texture_filename on every TextureItem is "Images/tree_clipart_pine_tree.png" This works just fine, but it's just a proof of concept. What I really need to do (among other things) is have the path to the image hard coded. If I replace Texture.texture_filename in the code above with the string literal "Images/tree_clipart_pine_tree.png" the images do not appear in the final merged image. I can add a breakpoint and see that the WriteableBitmap has all of it's pixels as 0 after the call to Invalidate. I have no idea how this could cause any sort of difference, but it gets stranger. If I remove the call to FlattenControl and just return the Canvas instead, the images are visible. It's only when I use the string literal with the WriableBitmap that the images do not appear. I promise you that the value in the texture_filename property is exactly "Images/tree_clipart_pine_tree.png". I'm using Silverlight 3 and I've also reproduced this in Silverlight 4. Any ideas?

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• How to Determine The Module a Particular Exception Class is Defined In

  - by doug

  Note: i edited my Q (in the title) so that it better reflects what i actually want to know. In the original title and in the text of my Q, i referred to the source of the thrown exception; what i meant, and what i should have referred to, as pointed out in one of the high-strung but otherwise helpful response below, is the module that the exception class is defined in. This is evidenced by the fact that, again, as pointed out in one of the answers below the answer to the original Q is that the exceptions were thrown from calls to cursor.execute and cursor.next, respectively--which of course, isn't the information you need to write the try/except block. For instance (the Q has nothing specifically to do with SQLite or the PySQLite module): from pysqlite2 import dbapi2 as SQ try: cursor.execute('CREATE TABLE pname (id INTEGER PRIMARY KEY, name VARCHARS(50)') except SQ.OperationalError: print("{0}, {1}".format("table already exists", "... 'CREATE' ignored")) # cursor.execute('SELECT * FROM pname') while 1: try: print(cursor.next()) except StopIteration: break # i let both snippets error out to see the exception thrown, then coded the try/finally blocks--but that didn't tell me anything about which module the exception class is defined. In my example, there's only a single imported module, but where there are many more, i am interested to know how an experienced pythonista identifies the exception source (search-the-docs-till-i-happen-to-find-it is my current method). [And yes i am aware there's a nearly identical question on SO--but for C# rather than python, plus if you read the author's edited version, you'll see he's got a different problem in mind.]

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• Large number of simultaneous long-running operations in Qt

  - by Hostile Fork

  I have some long-running operations that number in the hundreds. At the moment they are each on their own thread. My main goal in using threads is not to speed these operations up. The more important thing in this case is that they appear to run simultaneously. I'm aware of cooperative multitasking and fibers. However, I'm trying to avoid anything that would require touching the code in the operations, e.g. peppering them with things like yieldToScheduler(). I also don't want to prescribe that these routines be stylized to be coded to emit queues of bite-sized task items...I want to treat them as black boxes. For the moment I can live with these downsides: Maximum # of threads tend to be O(1000) Cost per thread is O(1MB) To address the bad cache performance due to context-switches, I did have the idea of a timer which would juggle the priorities such that only idealThreadCount() threads were ever at Normal priority, with all the rest set to Idle. This would let me widen the timeslices, which would mean fewer context switches and still be okay for my purposes. Question #1: Is that a good idea at all? One certain downside is it won't work on Linux (docs say no QThread::setPriority() there). Question #2: Any other ideas or approaches? Is QtConcurrent thinking about this scenario? (Some related reading: how-many-threads-does-it-take-to-make-them-a-bad-choice, many-threads-or-as-few-threads-as-possible, maximum-number-of-threads-per-process-in-linux)

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• WPF Exposing a calculated property for binding (as DependencyProperty)

  - by kubal5003

  Hello, I have a complex WPF control that for some reasons (ie. performance) is not using dependency properties but simple C# properties (at least at the top level these are exposed as properties). The goal is to make it possible to bind to some of those top level properties - I guess I should declare them as DPs.(right? or is there some other way to achieve this? ) I started reading on MSDN about DependencyProperties and DependencyObjects and found an example: public class MyStateControl : ButtonBase { public MyStateControl() : base() { } public Boolean State { get { return (Boolean)this.GetValue(StateProperty); } set { this.SetValue(StateProperty, value); } } public static readonly DependencyProperty StateProperty = DependencyProperty.Register( "State", typeof(Boolean), typeof(MyStateControl),new PropertyMetadata(false)); } If I'm right - this code enforces the property to be backed up by DependencyProperty which restricts it to be a simple property with a store(from functional point of view, not technically) instead of being able to calculate the property value each time getter is called and setting other properties/fields each time setter is called. What can I do about that? Is there any way I could make those two worlds meet at some point?

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• Getting Android SDK WebView and TabWidget to play nice

  - by jdandrea

  I’m taking the HelloTabWidget Android example and trying two things: Moving the tabs to the bottom vs. the top (if that’s even desirable from an Android UI POV) Making each tab show a particular WebView in the space above I’ve got this for a layout (high level): <TabHost> <LinearLayout> <FrameLayout> <WebView/> <WebView/> <WebView/> <WebView/> <WebView/> </FrameLayout> <TabWidget/> </LinearLayout> </TabHost> Everything has a width/height set to fill_parent except for the TabWidget which has its layout_height set to wrap_content (and the layout_gravity set to bottom). First thing I noticed is that WebViews don’t show anything until all the parents have width/height set to fill_parent. However, once I do that, they fill the entire display, obscuring the TabWidget. Is there some other trick to making these two views play nicely together?

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• How should I handle persistence in a Java MUD? OptimisticLockException handling

  - by Chase

  I'm re-implementing a old BBS MUD game in Java with permission from the original developers. Currently I'm using Java EE 6 with EJB Session facades for the game logic and JPA for the persistence. A big reason I picked session beans is JTA. I'm more experienced with web apps in which if you get an OptimisticLockException you just catch it and tell the user their data is stale and they need to re-apply/re-submit. Responding with "try again" all the time in a multi-user game would make for a horrible experience. Given that I'd expect several people to be targeting a single monster during a fight I think the chance of an OptimisticLockException would be high. My view code, the part presenting a telnet CLI, is the EJB client. Should I be catching the PersistenceExceptions and TransactionRolledbackLocalExceptions and just retrying? How do you decide when to stop? Should I switch to pessimistic locking? Is persisting after every user command overkill? Should I be loading the entire world in RAM and dumping the state every couple of minutes? Do I make my session facade a EJB 3.1 singleton which would function as a choke point and therefore eliminating the need to do any type of JPA locking? EJB 3.1 singletons function as a multiple reader/single writer design (you annotate the methods as readers and writers). Basically, what is the best design and java persistence API for highly concurrent data changes in an application where it is not acceptable to present resubmit/retry prompts to the user?

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• Handling mach exceptions in 64bit OS X application

  - by Brad S

  I have been able to register my own mach port to capture mach exceptions in my applications and it works beautifully when I target 32 bit. However when I target 64 bit, my exception handler catch_exception_raise() gets called but the array of exception codes that is passed to the handler are 32 bits wide. This is expected in a 32 bit build but not in 64 bit. In the case where I catch EXC_BAD_ACCESS the first code is the error number and the second code should be the address of the fault. Since the second code is 32 bits wide the high 32 bits of the 64 bit fault address is truncated. I found a flag in <mach/exception_types.h> I can pass in task_set_exception_ports() called MACH_EXCEPTION_CODES which from looking at the Darwin sources appears to control the size of the codes passed to the handler. It looks like it is meant to be ored with the behavior passed in to task_set_exception_ports(). However when I do this and trigger an exception, my mach port gets notified, I call exc_server() but my handler never gets called, and when the reply message is sent back to the kernel I get the default exception behavior. I am targeting the 10.6 SDK. I really wish apple would document this stuff better. Any one have any ideas?

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• Scope of Connection Object for a Website using Connection Pooling (Local or Instance)

  - by Danny

  For a web application with connection polling enabled, is it better to work with a locally scoped connection object or instance scoped connection object. I know there is probably not a big performance improvement between the two (because of the pooling) but would you say that one follows a better pattern than the other. Thanks ;) public class MyServlet extends HttpServlet { DataSource ds; public void init() throws ServletException { ds = (DataSource) getServletContext().getAttribute("DBCPool"); } protected void doGet(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException { SomeWork("SELECT * FROM A"); SomeWork("SELECT * FROM B"); } void SomeWork(String sql) { Connection conn = null; try { conn = ds.getConnection(); // execute some sql ..... } finally { if(conn != null) { conn.close(); // return to pool } } } } Or public class MyServlet extends HttpServlet { DataSource ds; Connection conn;* public void init() throws ServletException { ds = (DataSource) getServletContext().getAttribute("DBCPool"); } protected void doGet(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException { try { conn = ds.getConnection(); SomeWork("SELECT * FROM A"); SomeWork("SELECT * FROM B"); } finally { if(conn != null) { conn.close(); // return to pool } } } void SomeWork(String sql) { // execute some sql ..... } }

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• Could CouchDB benefit significantly from the use of BERT instead of JSON?

  - by Victor Rodrigues

  I appreciate a lot CouchDB attempt to use universal web formats in everything it does: RESTFUL HTTP methods in every interaction, JSON objects, javascript code to customize database and documents. CouchDB seems to scale pretty well, but the individual cost to make a request usually makes 'relational' people afraid of. Many small business applications should deal with only one machine and that's all. In this case the scalability talk doesn't say too much, we need more performance per request, or people will not use it. BERT (Binary ERlang Term http://bert-rpc.org/ ) has proven to be a faster and lighter format than JSON and it is native for Erlang, the language in which CouchDB is written. Could we benefit from that, using BERT documents instead of JSON ones? I'm not saying just for retrieving in views, but for everything CouchDB does, including syncing. And, as a consequence of it, use Erlang functions instead of javascript ones. This would modify some original CouchDB principles, because today it is very web oriented. Considering I imagine few people would make their database API public and usually its data is accessed by the users through an application, it would be a good deal to have the ability to configure CouchDB for working faster. HTTP+JSON calls could still be handled by CouchDB, considering an extra cost in these cases because of parsing.

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• DDD: Aggregate Roots

  - by Mosh

  Hello, I need help with finding my aggregate root and boundary. I have 3 Entities: Plan, PlannedRole and PlannedTraining. Each Plan can include many PlannedRoles and PlannedTrainings. Solution 1: At first I thought Plan is the aggregate root because PlannedRole and PlannedTraining do not make sense out of the context of a Plan. They are always within a plan. Also, we have a business rule that says each Plan can have a maximum of 3 PlannedRoles and 5 PlannedTrainings. So I thought by nominating the Plan as the aggregate root, I can enforce this invariant. However, we have a Search page where the user searches for Plans. The results shows a few properties of the Plan itself (and none of its PlannedRoles or PlannedTrainings). I thought if I have to load the entire aggregate, it would have a lot of overhead. There are nearly 3000 plans and each may have a few children. Loading all these objects together and then ignoring PlannedRoles and PlannedTrainings in the search page doesn't make sense to me. Solution 2: I just realized the user wants 2 more search pages where they can search for Planned Roles or Planned Trainings. That made me realize they are trying to access these objects independently and "out of" the context of Plan. So I thought I was wrong about my initial design and that is how I came up with this solution. So, I thought to have 3 aggregates here, 1 for each Entity. This approach enables me to search for each Entity independently and also resolves the performance issue in solution 1. However, using this approach I cannot enforce the invariant I mentioned earlier. There is also another invariant that states a Plan can be changed only if it is of a certain status. So, I shouldn't be able to add any PlannedRoles or PlannedTrainings to a Plan that is not in that status. Again, I can't enforce this invariant with the second approach. Any advice would be greatly appreciated. Cheers, Mosh

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• When is LINQ (to objects) Overused?

  - by Mystagogue

  My career started as a hard-core functional-paradigm developer (LISP), and now I'm a hard-care .net/C# developer. Of course I'm enamored with LINQ. However, I also believe in (1) using the right tool for the job and (2) preserving the KISS principle: of the 60+ engineers I work with, perhaps only 20% have hours of LINQ / functional paradigm experience, and 5% have 6 to 12 months of such experience. In short, I feel compelled to stay away from LINQ unless I'm hampered in achieving a goal without it (wherein replacing 3 lines of O-O code with one line of LINQ is not a "goal"). But now one of the engineers, having 12 months LINQ / functional-paradigm experience, is using LINQ to objects, or at least lambda expressions anyway, in every conceivable location in production code. My various appeals to the KISS principle have not yielded any results. Therefore... What published studies can I next appeal to? What "coding standard" guideline have others concocted with some success? Are there published LINQ performance issues I could point out? In short, I'm trying to achieve my first goal - KISS - by indirect persuasion. Of course this problem could be extended to countless other areas (such as overuse of extension methods). Perhaps there is an "uber" guide, highly regarded (e.g. published studies, etc), that takes a broader swing at this. Anything?

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• Java EE suitablity for a social network using Cassandra datastore ??

  - by Marcos

  We are in the process of making some important technology decisions for a social networking application. We're planning to have Cassandra(a NoSQL database to support efficient data storage). We would be using Hector(a Java client) to interact with Cassandra. 1.) Would Java EE be a good choice over PHP for a social networking application in terms of performance, scalabilty & complexities? 2.) Another possible implementation strategy, Is it suitable to have backend alone in Java and rest in PHP? 3.) What differences(as compared to PHP) it makes in terms of costs at various stages of application development, deployment and maintenance ? 4.) What are the things to keep in mind as we move along with Java development& deployment(as we are relatively new to the Java background) ? 5.) If you could list some major production deployments of similar type(social network) applications in Java. Thank you!

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• AutoMapper How To Map Object A To Object B Differently Depending On Context

  - by IanT8

  Calling all AutoMapper gurus! I'd like to be able to map object A to object B differently depending on context at runtime. In particular, I'd like to ignore certain properties in one mapping case, and have all properties mapped in another case. What I'm experiencing is that Mapper.CreateMap can be called successfully in the different mapping cases however, once CreateMap is called, the map for a particular pair of types is set and is not subsequently changed by succeeding CreateMap calls which might describe the mapping differently. I found a blog post which advocates Mapper.Reset() to get round the problem, however, the static nature of the Mapper class means that it is only a matter of time before a collision and crash occur. Is there a way to do this? What I think I need is to call Mapper.CreateMap once per appdomain, and later, be able to call Mapper.Map with hints about which properties should be included / excluded. Right now, I'm thinking about changing the source code by writing a non-static mapping class that holds the mapping config instance based. Poor performance, but thread safe. What are my options. What can be done? Automapper seems so promising.

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• Crosstab/Cube/Pivot Components for Delphi

  - by Anagoge

  I'm looking for a Delphi VCL crosstab/cube/pivotcube/olap grid component for Delphi 2009, 2010, or XE. I'm willing to sacrifice advanced features to get something open/free (or very cheap if I must) to make it easier to collaborate with any future developers without anyone having to purchase more components than I already use, since this will just be used in one screen. If there isn't anything appropriate out there, I may try to implement something simple on my own. I can live with some fairly basic features: drag and drop to configure dimensions, sort by a column, allow totals/min/max for a column, and (optionally) expand/collapse or drill down to sub-categories. Blazing performance and enterprise scalability are not required, since there should be less than 2000 source rows. There appear to be several decent options in the commercial space (ExpressPivotCube, FastCube, HierCube), but they are all a few hundred dollars. This project already uses existing installations of Excel 2007 and SQL Server 2005/2008, so I might consider leveraging those, though I'd prefer a native Delphi component, if possible. There are also the very old Decision Cube components included in Delphi's Source\xtab directory, but they apparently no longer support unicode compilers (Delphi 2009+), since I got dozens of unicode-related compilation errors while test compiling that source in Delphi XE. Those components also still link to the long-deprecated BDE! Has anyone modified Decision Cube to support unicode/pure-TDataSet? The online tutorials I found were incomplete and silent on the dozens of BDE/unicode compilation errors I see, so I might have to tackle that on my own. Does anyone have suggestions where to start for a free/cheap basic crosstab/pivot grid component?

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• Is there any better IDOMImplementation other than MSXML?

  - by Chau Chee Yang

  There are 3 IDOMImplementation available in Delphi: MSXML Xerces XML ADOM XML v4 MSXML is the default IDOMImplementation. My test is count the time need to load a 10MB xml file. I use a Delphi unit generated from a XSD using XML data binding to load the xml file. This unit has 3 common function: function Getmenubar(Doc: IXMLDocument): IXMLMenubarType; function Loadmenubar(const FileName: WideString): IXMLMenubarType; function Newmenubar: IXMLMenubarType; I learn from the web that some comment that MSXML's overhead is high that it doesn't perform if compare to other XML parser. However, my study shows that MSXML is the best among others. Xerces XML 2nd and ADOM XML v4 the worst: MSXML - 0.6410 seconds Xerces XML - 2.4220 seconds ADOM XML v4 - 67.50 seconds I also come across with OmniXML that claim to have much better performance compare to MSXML but I never success using it with the unit generated by XML data binding. Is there any other vendor that implement IDOMImplementation of Delphi that work much better than MSXML? I am using Delphi 2010 and Windows 7.

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• Google App Engine application instance recycling and response times...

  - by Konrad

  Hi, I posted this on GAE for Java group, but I hope to get some answers here quicker :) I decided to do some long-run performance tests on my application. I created some small client hitting app every 5-30 minutes and I run 3-5 of threads with such client. I noticed huge differenced in response times and started to investigate issue. I found reason very quick. I am experiencing same issues as described in following topics: Uneven response time between connection to server to first byte sent Application instances seem to be too aggressively recycled Getting 'Request was aborted after waiting too long to attempt to service your request.' after application idle I am using Springframework, it tkes around 18-20s to start app instance, which is causing response times to take from 1s (when requests hits running app - very rare) to 22s when fresh application is created. Is there any solution for this? I was thinking about creating most basic servlet performing critical tasks (serving API call) and leave UI as is. But then I would loose all benefits of Springframework. Is there any solution for this? After solving (hacking) numerous constrains of App Engine which I hit while developing my app that is the one I think will make me move out of App Engine... that's simply to much to all the time think how to win with GAE problems than how to solve my application problems... Any help? Regards Konrad

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• Plot in GNU PLOT

  - by guddi

  I have to plot many lines in GNU PLOT.No problem with the X axis. The problem that I am facing is that most of the plotted lines are at yscale [0-0.05] ,few at range 60-70 and rest at 600-700. These numbers correspond to the y axis scale values. But after I plot I can see only 3 sets of lines all messed up. There is no clearity between the lines. Line at 0 and the line at 0.003 look like one single line. If I set yrange[0:0.05], the lines between this range are clearly vissible. But I want all the lines in the same graph. I have heard of breaking axis's and multi plotting..Can they be useful? how to implement them. Anyone pls help me. Below is the sript set terminal png size 1300,1200 enhanced font 'Verdana,20 set output ' output .png’ set key font 'Verdana,16' set key bottom outside set yrange[500:1000] set xtics("25k" 25000,"50k" 50000,"75k" 75000,"100k" 100000) set grid set title 'Performance Metrics' set ylabel 'Metrices' set xlabel 'FES' plot ' input ' using 1:2 title ' A' with linespoints linewidth 4, ' input ' using 1:3 title B'with linespoints linewidth 4, 'input ' using 1:4 title ' c' with linespoints linewidth 4, 'input ' using 1:5 title 'D' with linespoints linewidth 4, ' input ' using 1:6 title 'E' with linespoints linewidth 4, ' input ' using 1:7 title 'F' with linespoints linewidth 4, ' input ' using 1:8 title 'G' with linespoints linewidth 4, ' input ' using 1:9 title ' H ' with linespoints linewidth 4, ' input ' using 1:10 title ' I' Metric ' with linespoints linewidth 4 set output set terminal windows input.dat is something like this: 25 0.002 0.05 899 455 444 0.08 0.00004 900 700 0.003 This way i have other rows. I have shown only the first one

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• C# File IO with Streams - Best Memory Buffer Size

  - by AJ

  Hi, I am writing a small IO library to assist with a larger (hobby) project. A part of this library performs various functions on a file, which is read / written via the FileStream object. On each StreamReader.Read(...) pass, I fire off an event which will be used in the main app to display progress information. The processing that goes on in the loop is vaired, but is not too time consuming (it could just be a simple file copy, for example, or may involve encryption...). My main question is: What is the best memory buffer size to use? Thinking about physical disk layouts, I could pick 2k, which would cover a CD sector size and is a nice multiple of a 512 byte hard disk sector. Higher up the abstraction tree, you could go for a larger buffer which could read an entire FAT cluster at a time. I realise with today's PC's, I could go for a more memory hungry option (a couple of MiB, for example), but then I increase the time between UI updates and the user perceives a less responsive app. As an aside, I'm eventually hoping to provide a similar interface to files hosted on FTP / HTTP servers (over a local network / fastish DSL). What would be the best memory buffer size for those (again, a "best-case" tradeoff between perceived responsiveness vs. performance). Thanks in advance for any ideas, Adam

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• Advice for Future Programmers?

  - by Nate Zaugg

  I have a buddy that is going to be giving some presentations to high-schoolers. Specifically he asked: What would you be looking for if they approached you about work? Perhaps you are in that age group right now. What do you want to know? Perhaps you are just a few years into the workforce. What do you wish someone had told you but never did? Perhaps you have children, relatives or friends in or soon to be in that age group. What are you worried they don't know about? I'm sure there are other perspectives and questions I'm not even thinking about. I'd like to hear what you have to say about it. Here was my list: Don't be afraid to try! Don't let the perception that something is too difficult stop you from experimenting. Curiosity may have killed the cat, but an un-inquisitive person is mostly useless. Stolen from Einstein: You don't really understand something until you can explain it to your grandmother. It's never enough to be smart, you also have to work well with others. Before you can be really smart, you must learn how to learn. There will always be someone smarter than you are -- Become their buddy! Get to know great minds and learn all you can. Some knowledge can only be expressed this way. Communication, Communication, Communication! Projects rarely fail because of technical reasons and the difference between good programmers and outstanding programmers is how well they communicate. A good work ethic never goes unnoticed. Know when to ask for help and when to figure something out for yourself.

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• Missing ideas in programming language design

  - by meyka

  I wanted to try something new and so I designed some programming languages and wrote interpreters for them: A rather low-level, not very expressive language. (I didn't want to parse complex expressions right at the beginning) It featured: Variables (yay) Subroutines, with a call stack Basic arithmetic functions, basic string manipulation, ... Code in the language looks like this: set i 0 inc i print i Very, very basic you see. A more high-level language I decided to make it structured and so it featured things like if-else, while, functions, and so on. The stuff most programming languages have. Ended up like a unworthy Python clone, I hated that. A code-golf language Which ended up similar to J, golfcode, APL, etc. Nothing special As you can see: I don't lack the skills but the ideas. I can't figure out anything new, not even bad, unneccessary things, for my languages. - Do you know of some weird things I could implement in my languages, which don't try to make programming harder (like most esoteric languages) but funnier or more different from other languages? It can't be possible that every weird thing has been tried out so far, or?

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