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• DDD: Client-side script to enforce invariants

  - by Mosh

  Hello, One thing that I'm confused about in regards to DDD is that our domain is supposed to handle all business logic and enforce invariants. I have noticed some people (me included) handle certain invariants in the presentation layer (i.e. WebForms, Views, etc) with javascript. This is mainly done to improve performance so the server is not hit for every request which may be invalid. Even though this approach may be beneficial performance-wise, it violates DDD principles. What if the business rules are changed? This way we don't have a rich domain where all the business rules are captured. In case of a change, we should change the domain as well as the presentation layer. Has anyone come across this situation before? I'd like to know your thoughts on this. Cheers, Mosh

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• Adjacency List Tree Using Recursive WITH (Postgres 8.4) instead of Nested Set

  - by Koobz

  I'm looking for a Django tree library and doing my best to avoid Nested Sets (they're a nightmare to maintain). The cons of the adjacency list model have always been an inability to fetch descendants without resorting to multiple queries. The WITH clause in Postgres seems like a solid solution to this problem. Has anyone seen any performance reports regarding WITH vs. Nested Set? I assume the Nested set will still be faster but as long as they're in the same complexity class, I could swallow a 2x performance discrepancy. Django-Treebeard interests me. Does anyone know if they've implemented the WITH clause when running under Postgres? Has anyone here made the switch away from Nested Sets in light of the WITH clause?

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• Optimizing a large iteration of PHP objects (EAV-based)

  - by Aron Rotteveel

  I am currently working on a project that utilizes the EAV model. This turns out to work quite well, but like many others I am now stumbling upon some performance issues. The data set in this particular case consists of aproximately 2500 entities, each with aprox. 150 attributes. Each entity and each attribute is represented by a PHP-object. Since most parts of the application only iterate through a filtered set of entities, we have not had very large issues yet. Now, however, I am working on an algorithm that requires iteration over the entire dataset, which causes a major impact on performance. This information is perhaps not very much to work with, but since this is an architectural problem, I am hoping for a architectural pattern to help me on the way as well. Each entity, including it's attributes takes up aprox. 500KB of memory.

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• To store images from UIGetScreenImage() in NSMutable Array

  - by sujyanarayan

  Hi, I'm getting images from UIGetScreenImage() and storing directly in mutable array like:- image = [UIImage imageWithScreenContents]; [array addObject:image]; [image release]; I've set this code in timer so I cant use UIImagePNGRepresentation() to store as NSData as it reduces the performance. I want to use this array directly after sometime i.e after capturing 1000 images in 100 seconds. When I use the code below:- UIImage *im = [[UIImage alloc] init]; im = [array objectAtIndex:i]; UIImageWriteToSavedPhotosAlbum(im, nil, nil, nil); the application crashes. And I dont want to use UIImagePNG or JPGRepresentation() in timer as it reduces performance. My problem is how to use this array so that it is converted into image. If anybody has idea related to it please share with me. Thanks in Advance.

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• What Simple Changes Made the Biggest Improvements to Your Delphi Programs

  - by lkessler

  I have a Delphi 2009 program that handles a lot of data and needs to be as fast as possible and not use too much memory. What small simple changes have you made to your Delphi code that had the biggest impact on the performance of you program by noticeably reducing execution time or memory use? Thanks everyone for all your answers. Many great tips. For completeness, I'll post a few important articles on Delphi optimization that I found. Before you start optimizing Delphi code at About.com Speed and Size: Top 10 Tricks also at About.com Code Optimization Fundamentals and Delphi Optimization Guidelines at High Performance Delphi, relating to Delphi 7 but still very pertinent.

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• Schemas and tables versus user-ids in a single table using PostgreSQL

  - by gvkv

  I'm developing a web app and I've come to a fork in the road with respect to database structure and I don't know which direction to take. I have a database with user information that I can structure one of two ways. The first is to create a schema and a set of tables for each user (duplicating the structure for each user) and the second is to create a single set of tables and query information based on user-id. Suppose 100000 users. Here are my questions: Considering security, performance, scalability and administration where does each choice lie? Would the answers change for 1000000 or 10000? Is there a set of best practices that lead to one choice or the other? It seems to me that multiple schemas are more secure since it's trivial to restrict user privileges but what about performance and scalability? Administration seems like a wash since dumping (and restoring) lots of schemas isn't any more difficult than dumping a few.

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• How to ignore/prevent javadoc folder from validation during Eclipse Build?

  - by h2g2java

  In my war is a huge javadoc folder. There is no point in validating it since javadocs are produced by Sun(Oracle) javadoc utility. I have forgotten how I did it the last time. I need to tell Eclipse build not to validate that particular folder. Reasons why I need it: 1. the html produced by Sun javadoc generation utility does not meet the requirement that Eclipse uses - there is a bug report in Eclipse but Eclipse responds that Sun javadoc generator non-compliance is not their fault and that Eclipse intends to stick to their strict compliance. Which results in lots of html errors listed in the problems tab. 2. the javadoc folder is a remote link and high activity on that link is using up my cpu resource, and because it is a link to a remote location, that cpu high activity is sustained for long time until it finishes scanning the whole 35MB javadocs. Thanks - need help.

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• silverlight for .NET / CLR based numerical computing on osx

  - by Jonathan Shore

  I'm interested in using F# for numerical work, but my platforms are not windows based. Mono still has a significant performance penalty for programs that generate a significant amount of short-lived objects (as would be typical for functional languages). Silverlight is available on OSX. I had seen some reference indicating that assemblies compiled in the usual way could not be referenced, but not clear on the details. I'm not interested in UIs, but wondering whether could use the VM bundled with silverlight effectively for execution? I would want to be able to reference a large library of numerical models I already have in java (cross-compiled via IKVM to .NET assemblies) and a new codebase written in F#. My hope would be that the silverlight VM on OSX has good performance and can reference external assemblies and native libraries. Is this doable?

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• Is there anything for Python that is like readability.js?

  - by Emre Sevinç

  Hi, I'm looking for a package / module / function etc. that is approximately the Python equivalent of Arc90's readability.js http://lab.arc90.com/experiments/readability http://lab.arc90.com/experiments/readability/js/readability.js so that I can give it some input.html and the result is cleaned up version of that html page's "main text". I want this so that I can use it on the server-side (unlike the JS version that runs only on browser side). Any ideas? PS: I have tried Rhino + env.js and that combination works but the performance is unacceptable it takes minutes to clean up most of the html content :( (still couldn't find why there is such a big performance difference).

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• What is the best virtual grid for Winforms Csharp

  - by oo

  i am looking for both performance as well as ease of learning curve. thoughts?

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• JW Player - How can I add an event listener for fullscreen toggling?

  - by Charles

  I'm using JW Player 4.5 on my site and I need to add an event listener for when fullscreen is toggled. The reason for this is to switch between a low-def version and high-def version. The default video will be the low-def version and when they switch to a fullscreen display, it will change to the high-def version. According to http://developer.longtailvideo.com/trac/wiki/Player5Events, the ViewEvent.JWPLAYER_VIEW_FULLSCREEN1 event can only be called from Actionscript. I need it to be from Javascript... Is there any way to achieve this? Can you recommend a better solution?

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• Difference between Apache Tapestry and Apache Wicket

  - by Stephan Schmidt

  Apache Wicket ( http://wicket.apache.org/ ) and Apache Tapestry ( http://wicket.apache.org/ ) are both component oriented web frameworks - contrary to action based frameworks like Stripes - by the Apache Foundation. Both allow you to build your application from components in Java. They both look very similar to me. What are the differences between those two frameworks? Has someone experience in both? Specifically: How is their performance, how much can state handling be customized, can they be used stateless? What is the difference in their component model? What would you choose for which applications? How do they integrate with Guice, Spring, JSR 299? Edit: I have read the documentation for both and I have used both. The questions cannot be answered sufficently from reading the documentation, but from the experience from using these for some time, e.g. how to use Wicket in a stateless mode for high performance sites. Thanks.

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• Assert parameters in a table-valued UDF

  - by Clay Lenhart

  Is there a way to create "asserts" on the parameters of a table-valued UDF. I'd like to use a table-valued UDF for performance reasons, however I know that certain parameter combinations (like start and end dates that are more than a month apart) will cause performance issues on the server for all users. End users query the database via Excel using UDFs. UDFs (and table-valued UDFs in particular) are useful when the data is too large for Excel. Users write simple SQL queries that categorizes the data into groups to reduce the number of rows. For example, the user may be interested in weekly aggregates rather than hourly ones. Users write a group by SELECT statement to reduce the rows by 24x7=168 times. I know I can write RAISERROR statements in multistatement UDFs, but table-valued UDFs are integrated in the query optimizer so these queries are more efficient with table-valued UDFs. So, can I define assertions on the parameters passed to a table-valued UDF?

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• Any good interview Questions to ask a sybase dba.

  - by scot

  Hi, I am a java developer and i will be interviewing sybase dbas along with my boss. I know some basic stuff about sybase. Iam looking for good interview questions that i can ask for a sybase dba. they will be having a min of 4 years of experience. I am looking for them to have really good knowledge in performance and tuning related areas like how to measure database performance and suggest ways to improve database design or sybase configuration etc. Help much appreciated. BR

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• Using SqlCacheDependency to get real time updates? - ASP.NET

  - by user102533

  I would like to display real time updates on a web page (based on a status field in a database table that is altered by an external process). Based on my research, there are several ways of doing this. Long Polling (Comet) - This seems to be complex to implement Regular Polling - I can have an AJAX method trigger a database hit every 5seconds to get the current status. But I fear this will have performance issues. Then I read about using SqlCacheDependency - basically the cache gets invalidated based on a field in the table. I am assuming I can use the event trigerred when the cache is invalidated to show the new update to the user? What's an easy solution that will not have performance issues? anyone?

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• What are some best practises and "rules of thumb" for creating database indexes?

  - by Ash

  I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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• Why Tokyo Tyrant so slow

  - by Tantra

  I have follow situation tyrant server lunched on freebsd host, like this: ttserver -uas -log /data/tyrant/1.log -sid 1 -thnum 8 -tout 5 /data/tyrant/data/1.tct And i try to communicate this server on windows from python and pyrant-0.3.5: like this: import pyrant; import time; t = pyrant.Tyrant(host="192.168.0.220", port=1978); tbegin = time.time(); for i in xrange(4000000): if i and ((i % 10000) == 0): print time.time() - tbegin; tbegin = time.time(); t[i] = {"text": "ruslan text", "value": i}; and have i think very slow performance about 5-6 per 10,000 records. But if i start this code on the same machine like server(ttserver). Performance are good - about 0.5 sec per 10,000 records What i must do to workaround this problem?

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• Popularity Algorithm - SQL / Django

  - by RadiantHex

  Hi folks, I've been looking into popularity algorithms used on sites such as Reddit, Digg and even Stackoverflow. Reddit algorithm: t = (time of entry post) - (Dec 8, 2005) x = upvotes - downvotes y = {1 if x > 0, 0 if x = 0, -1 if x < 0) z = {1 if x < 0, otherwise x} log(z) + (y * t)/45000 I have always performed simple ordering within SQL, I'm wondering how I should deal with such ordering. Should it be used to define a table, or could I build an SQL with the ordering within the formula (without hindering performance)? I am also wondering, if it is possible to use multiple ordering algorithms in different occasions, without incurring into performance problems. I'm using Django and PostgreSQL. Help would be much appreciated! ^^

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• pyopengl: Could it replace c++ ?

  - by Tom

  Hi everyone. I'm starting a computer graphics course, and I have to choose a language. Choices are between C++ and Python. I have no problem with C++, python is a work in progress. So i was thinking to go down the python road, using pyopengl for graphics part. I have heard though, that performance is an issue. Is python / pyopengl mature enough to challenge C++ on performance? I realize its a long shot, but I'd like to hear your thoughts, experiences on uses of pyopengl. Thanks in advance.

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• Push data to flex client

  - by KensoDev

  Howday, I want to push data to flex clients. I am talking about anywhere between 5000-15000 concurrent users, need to get data every time a currency is changed so that means lots of changes for lots of users. I have been looking into WebOrb.net, but the performance seem very poor (100 users concurrent) for a product so pricy (we purchased a license). So, I have to look into alternatives, I know there's fluorineFx but it seems no one is really using it for products and it lacks in examples and documentation. My question is: what products can answer my needs (.net backend) and what are the performance I can expect out of these products? Thanks

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• Weaknesses of Hibernate

  - by Sinuhe

  I would like to know which are the weak points of Hibernate 3. This is not pretended to be a thread against Hibernate. I think it will be a very useful knowledge for decide if Hibernate is the best option for a project or for estimating its time. A weakness can be: A bug Where JDBC or PLSQL are better Performance issues ... Also, can be useful to know some solutions for that problems, better ORM or techniques, or it will be corrected in Hibernate 4. For example, AFAIK, Hibernate will have a very bad performance updating 10000 rows comparing to JDBC in this query: update A set state=3 where state=2

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• Visual Artifacts in Visual Studio 2010

  - by Simon Chadwick

  I'm using VS 2010 on Windows Server 2003, running on a Dell Inspiron 9400 laptop. VS 2010 runs fine, except for persistent and random screen re-drawing issues. Samples of these are here. These artifacts occur as the mouse moves over items that highlight on a mouse-over event, while scrolling, and when switching tabs. VS 2008 has non of these issues, so I assume that it is related to VS 2010's use of WPF. Could it be that my video card or driver is not up to the task of rendering WPF? Some other WPF applications (not Silverlight) also have some of these screen repainting problems. I have tried a variety of settings in System Properties--Advanced--Performance Options--Visual Effects, and in the related "Advanced" tab, Processor Scheduling is adjusted for best performance of programs. Many thanks for any suggestions!

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• How to set that compiler flag?

  - by mystify

  Shark told me this: This instruction is the start of a loop that is not aligned to a 16-byte address boundary. For optimal performance, you should align the start of a hot loop using a compiler directive. With gcc 3.3 or later, use the -falign-loops=16 compiler flag. for (int i=0; i < 4; i++) { // line with the info //...code } How would I set that flag, and does it really improve performance?

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• How to delete multiple files with msbuild/web deployment project?

  - by Alex

  I have an odd issue with how msbuild is behaving with a VS2008 Web Deployment Project and would like to know why it seems to randomly misbehave. I need to remove a number of files from a deployment folder that should only exist in my development environment. The files have been generated by the web application during dev/testing and are not included in my Visual Studio project/solution. The configuration I am using is as follows: <!-- Partial extract from Microsoft Visual Studio 2008 Web Deployment Project --> <ItemGroup> <DeleteAfterBuild Include="$(OutputPath)data\errors\*.xml" /> <!-- Folder 1: 36 files --> <DeleteAfterBuild Include="$(OutputPath)data\logos\*.*" /> <!-- Folder 2: 2 files --> <DeleteAfterBuild Include="$(OutputPath)banners\*.*" /> <!-- Folder 3: 1 file --> </ItemGroup> <Target Name="AfterBuild"> <Message Text="------ AfterBuild process starting ------" Importance="high" /> <Delete Files="@(DeleteAfterBuild)"> <Output TaskParameter="DeletedFiles" PropertyName="deleted" /> </Delete> <Message Text="DELETED FILES: $(deleted)" Importance="high" /> <Message Text="------ AfterBuild process complete ------" Importance="high" /> </Target> The problem I have is that when I do a build/rebuild of the Web Deployment Project it "sometimes" removes all the files but other times it will not remove anything! Or it will remove only one or two of the three folders in the DeleteAfterBuild item group. There seems to be no consistency in when the build process decides to remove the files or not. When I've edited the configuration to include only Folder 1 (for example), it removes all the files correctly. Then adding Folder 2 and 3, it starts removing all the files as I want. Then, seeming at random times, I'll rebuild the project and it won't remove any of the files! I have tried moving these items to the ExcludeFromBuild item group (which is probably where it should be) but it gives me the same unpredictable result. Has anyone experienced this? Am I doing something wrong? Why does this happen?

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• Bitbanging a PIO on Coldfire/ucLinux

  - by G Forty

  Here's the problem: I need to program some hardware via 2 pins of the PIO (1 clock, 1 data). Timing constraints are tight - 10ms clock cycle time. All this, of course, whilst I maintain very high level services (CAN bus, TCP/IP). The downstream unit also ACKS by asserting a PIO pin, configured as an input, high. So this loop has to both read and write. I need to send 16 bits in the serial stream. Is there an established way to do this sort of thing or should I simply get the hardware guys to add a PIC or somesuch. I'd much prefer to avoid exotics like RTAI extensions at this stage. I did once see a reference to user-mode IO which implied a possible interrupt driven driver but lost track of it. Any pointers welcomed.

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