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• Java "Pool" of longs or Oracle sequence with reusable values

  - by Anthony Accioly

  Several months ago I implemented a solution to choose unique values from a range between 1 and 65535 (16 bits). This range is used to generate unique Route Targets suffixes, which for this customer massive network (it's a huge ISP) are a very disputed resource, so any free index needs to become immediately available to the end user. To tackle this requirement I used a BitSet. Allocate on the RT index with set and deallocate a suffix with clear. The method nextClearBit() can find the next available index. I handle synchronization / concurrency issues manually. This works pretty well for a small range... The entire index is small (around 10k), it is blazing fast and can be easy serialized into a Blob field. The problem is, some new devices can handle RTs of 32 bits (range 1 / 4294967296). Which can't be managed with a BitSet (it would, by itself, consume around 600Mb, plus be limited to int range). Even with this massive range available, the client still wants to free available Route Targets for the end user, mainly because the lowest ones (up to 65535) - which are compatible with old routers - are being heavily disputed. Before I tell the customer that this is impossible and he will have to conform with my reusable index for lower RTs (up to 65550) and use a database sequence for the other ones (which means that when the user frees a Route Target, it will not become available again). Would anyone shed some light? Maybe some kind soul already implemented a high performance number pool for Java (6 if it matters), or I am missing a killer feature of Oracle database (11R2 if it matters)... Wishful thinking. Thank you very much in advance.

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• The question about the basics of LINQ to SQL working

  - by Alex

  I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer Get all customers from the database ("SELECT * FROM Customers"), move them to the Customers array and then make a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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• Efficiency of manually written loops vs operator overloads (C++)

  - by Sagekilla

  Hi all, in the program I'm working on I have 3-element arrays, which I use as mathematical vectors for all intents and purposes. Through the course of writing my code, I was tempted to just roll my own Vector class with simple +, -, *, /, etc overloads so I can simplify statements like: for (int i = 0; i < 3; i++) r[i] = r1[i] - r2[i]; // becomes: r = r1 - r2; Which should be more or less identical in generated code. But when it comes to more complicated things, could this really impact my performance heavily? One example that I have in my code is this: Manually written version: for (int j = 0; j < 3; j++) { p.vel[j] = p.oldVel[j] + (p.oldAcc[j] + p.acc[j]) * dt2 + (p.oldJerk[j] - p.jerk[j]) * dt12; p.pos[j] = p.oldPos[j] + (p.oldVel[j] + p.vel[j]) * dt2 + (p.oldAcc[j] - p.acc[j]) * dt12; } Using a Vector class with operator overloads: p.vel = p.oldVel + (p.oldAcc + p.acc) * dt2 + (p.oldJerk - p.jerk) * dt12; p.pos = p.oldPos + (p.oldVel + p.vel) * dt2 + (p.oldAcc - p.acc) * dt12; I am compiling my code for maximum possible speed, as it's extremely important that this code runs quickly and calculates accurately. So will me relying on my Vector's for these sorts of things really affect me? For those curious, this is part of some numerical integration code which is not trivial to run in my program. Any insight would be appreciated, as would any idioms or tricks I'm unaware of.

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• Hibernate: fetching multiple bags efficiently

  - by Jens Jansson

  Hi! I'm developing a multilingual application. For this reason many objects have in their name and description fields collections of something I call LocalizedStrings instead of plain strings. Every LocalizedString is basically a pair of a locale and a string localized to that locale. Let's take an example an entity, let's say a book -object. public class Book{ @OneToMany private List<LocalizedString> names; @OneToMany private List<LocalizedString> description; //and so on... } When a user asks for a list of books, it does a query to get all the books, fetches the name and description of every book in the locale the user has selected to run the app in, and displays it back to the user. This works but it is a major performance issue. For the moment hibernate makes one query to fetch all the books, and after that it goes through every single object and asks hibernate for the localized strings for that specific object, resulting in a "n+1 select problem". Fetching a list of 50 entities produces about 6000 rows of sql commands in my server log. I tried making the collections eager but that lead me to the "cannot simultaneously fetch multiple bags"-issue. Then I tried setting the fetch strategy on the collections to subselect, hoping that it would do one query for all books, and after that do one query that fetches all LocalizedStrings for all the books. Subselects didn't work in this case how i would have hoped and it basically just did exactly the same as my first case. I'm starting to run out of ideas on how to optimize this. So in short, what fetching strategy alternatives are there when you are fetching a collection and every element in that collection has one or multiple collections in itself, which has to be fetch simultaneously.

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• IIS7 dynamic content compression and webservices

  - by vandalo

  I am moving and old asmx webservice to a new server with IIS7. This webservice basically sends a big dataset (10mb+) to a winform application. The old solution was implemented using a custom soap extension which compressed the content before sending the stream to the client. The client, of course, implemented the same custom soap extension, to decompressed the stream in a dataset. Everything has worked pretty well for years. My customer doesn't want to change the code upgrading to WCF. They just want to put the old App on the new server and use the new dynamic content compression features. We're testing things on a test server (win serv 2008) and it seems that it's working pretty well, even if it seems slow: we can't see any difference in performance (speed) between the uncompressed and compressed stream. Here's the question. Where should I put the settings? Most people say I can't put it in my web.config; others say it can be put there. I am a bit confused. Are there any tricks or things I should know? What about mimeTypes? Should I set some parameters, somewhere? ... considering my stream is XML (dataset) ?? Thanks to everyone who would like to help Alberto

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• cython setup.py gives .o instead of .dll

  - by alok1974

  Hi, I am a newbie to cython, so pardon me if I am missing something obvious here. I am trying to build c extensions to be used in python for enhanced performance. I have fc.py module with a bunch of function and trying to generate a .dll through cython using dsutils and running on win64: c:\python26\python c:\cythontest\setup.py build_ext --inplace I have the dsutils.cfg in C:\Python26\Lib\distutils. As required the disutils.cfg has the following config settings: [build] compiler = mingw32 My startup.py looks like this: from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext ext_modules = [Extension('fc', [r'C:\cythonTest\fc.pyx'])] setup( name = 'FC Extensions', cmdclass = {'build_ext': build_ext}, ext_modules = ext_modules ) I have latest version mingw for target/host amdwin64 type builds. I have the latest version of cython for python26 for win64. Cython does give me an fc.c without errors, only a few warning for type conversions, which I will handle once I have it right. Further it produces fc.def an fc.o files Instead of giving a .dll. I get no errors. I find on threads that it will create the .so or .dll automatically as required, which is not happening.

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• How can I tell if a byte array has already been compressed?

  - by MikeG

  Hi, Can I rely on the first few bytes of data compressed using the System.IO.Compression.DeflateStream in .NET always being the same? These bytes seem to always be the 1st bytes: 237, 189, 7, 96, 28, 73, 150, 37, 38, 47 , ... I'm assuming this is some kind of header, I'd like to assume that this header is fixed and isn't going to change. Has anyone got any extra info about this? Background info (The reason I want to know this info is...) I have a load of data in a database table that could do with being made smaller. I've decided I'm going to start compressing the data and not going to bother compressing the existing data. When the data gets into my .NET code the data is a String. I'd like to be able to look at the 1st few bytes of the string and see if it has been compressed, if it has then I need to de-compress it. I was originally thinking I could convert the string to bytes and just try de-compressing the data. Then if an exception happens, I could just assume it wasn't compressed. But I think checking the header bytes would give me much better performance. Many thanks, Mike G

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• Advanced search engine or server for relational database [closed]

  - by Pawel

  In my current project we are storing big volume of data in relational database. One of the recent key requirements is to enrich application by adding some advanced search capabilities. In the Project, performance is one of the important factors due to very large tables (10+ milions of records) with parent-children relations (for example: multi-level parent-child relationship, where I am looking for all parents with specific children). The search engine should also be able to check these references for hits. I have found some potential engines on stack overflow, however it looks like that all of them are dedicated rather for text search than relational db and hosted on linux os: lucene Solr Sphinx As I understand some of them use documents as a source of searching, but is it possible or efficient to create programmaticaly documents based on my relational data? As I am not familiar with all of their features/capabilities can anyone please make some recommendations or propose some different solution? To summarize my requirements: framework/engine to search relational database including decendants. support for Microsoft SQL Server can be used in .NET applications preferably hosted on Windows systems Does any of mentioned above are able to solve my problem? do you know any better solution?

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• Keep the images downloaded in the listview during scrolling

  - by Paveliko

  I'm developing my first app and have been reading a LOT here. I've been trying to find a solution for the following issue for over a week with no luck. I have an Adapter that extends ArrayAdapter to show image and 3 lines of text in each row. Inside the getView I assign relevant information for the TextViews and use ImageLoader class to download image and assign it to the ImageView. Everything works great! I have 4.5 rows visible on my screen (out of total of 20). When I scroll down for the first time the images continue to download and be assigned in right order to the list. BUT when I scroll back the list looses all the images and start redrawing them again (0.5-1 sec per image) in correct order. From what I've been reading it's the standard list performance but I want to change it. I want that, once the image was downloaded, it will be "sticked" to the list for the whole session of the current window. Just like in Contacts list or in the Market. It is only 20 images (6-9kb each). Hope I managed to explain myself.

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• Android opengl releasing textures

  - by user1642418

  I have a bit of a problem. I am developing a game for android + engine and I got stuck. I am getting OpenGL out of memory error and either app crashes or phone hangs after loading a scene multiple times. For example: app launches, shows main menu, 1st level/scene is loaded. Then I go back to main menu, and repeat. It doesnt matter which scene I load, after 4-6 times the error occurs. Some background: Each time when scene is loaded all the resources are released and upon first frame render - needed stuff gets loaded. The performance is more or less ok. Note that I am calling glDeleteTexture method, but I think its not doing its job and releasing memory. Thing is that -when I minimize and open it again - problem doesn't occur, but almost the same things are executed. Problem doesn't occur. This way android releases memory. How do I release/get rid of unused textures properly? This happens on HTC Desire HD ( ice cream sandwich 4.0.4) . Other games works fine, so I bet this is not the problem in ROM.

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• Get the first and last posts in a thread

  - by Grampa

  I am trying to code a forum website and I want to display a list of threads. Each thread should be accompanied by info about the first post (the "head" of the thread) as well as the last. My current database structure is the following: threads table: id - int, PK, not NULL, auto-increment name - varchar(255) posts table: id - int, PK, not NULL, auto-increment thread_id - FK for threads The tables have other fields as well, but they are not relevant for the query. I am interested in querying threads and somehow JOINing with posts so that I obtain both the first and last post for each thread in a single query (with no subqueries). So far I am able to do it using multiple queries, and I have defined the first post as being: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id LIMIT 0, 1 The last post is pretty much the same except for ORDER BY id DESC. Now, I could select multiple threads with their first or last posts, by doing: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id GROUP BY t.id But of course I can't get both at once, since I would need to sort both ASC and DESC at the same time. What is the solution here? Is it even possible to use a single query? Is there any way I could change the structure of my tables to facilitate this? If this is not doable, then what tips could you give me to improve the query performance in this particular situation?

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• I'm annoyed with asp .net mvc action links? Is there something better in MVC3?

  - by Jonathon Kresner

  After almost 3 years with mvc I'm scratching my head. Is it just me, or does the way we specify links in asp .net mvc suck? @Html.ActionLink("Log Off", "LogOff", "Account") In the previews for mvc 1 we had the funky generic action links which gave us intellisense and compile checking, which I LOVED. I know they removed them because of performance issues and because you could not actually guarantee that the route would resolve all the time... However the default way of doing it just doesn't make me feel safe enough in a big application. I've also used T4Mvc with MVC2, to be honest, I didn't really like it. It's not part of the Mvc framework and frustrating to develop with especially with source control in big teams and continuous integration builds. I guess I could also import Mvc Futures and keep using the generic types (it's probably what I'll do). I'm just about to start a very big project and was wondering what other people are thinking? Is anyone else annoyed with the options or has a new solution? It seems like ActionLinks are the most basic & frequently used feature. Shouldn't there be a good out of the box solution, we're just about to hit revision 3 of this framework.

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• Saving tags into a database table in CakePHP

  - by Cameron

  I have the following setup for my CakePHP app: Posts id title content Topics id title Topic_Posts id topic_id post_id So basically I have a table of Topics (tags) that are all unique and have an id. And then they can be attached to post using the Topic_Posts join table. When a user creates a new post they will fill in the topics by typing them in to a textarea separated by a comma which will then save these into the Topics table if they do not already exist and then save the references into the Topic_posts table. I have the models set up like so: Post model: class Post extends AppModel { public $name = 'Post'; public $hasAndBelongsToMany = array( 'Topic' => array('with' => 'TopicPost') ); } Topic model: class Topic extends AppModel { public $hasMany = array( 'TopicPost' ); } TopicPost model: class TopicPost extends AppModel { public $belongsTo = array( 'Topic', 'Post' ); } And for the New post method I have this so far: public function add() { if ($this->request->is('post')) { //$this->Post->create(); if ($this->Post->saveAll($this->request->data)) { // Redirect the user to the newly created post (pass the slug for performance) $this->redirect(array('controller'=>'posts','action'=>'view','id'=>$this->Post->id)); } else { $this->Session->setFlash('Server broke!'); } } } As you can see I have used saveAll but how do I go about dealing with the Topic data?

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• Slow query. Wrong database structure?

  - by Tin

  I have a database with table that contains tasks. Tasks have a lifecycle. The status of the task's lifecycle can change. These state transitions are stored in a separate table tasktransitions. Now I wrote a query to find all open/reopened tasks and recently changed tasks but I already see with a rather small number of tasks (<1000) that execution time has becoming very long (0.5s). Tasks +-------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+---------+------+-----+---------+----------------+ | taskid | int(11) | NO | PRI | NULL | auto_increment | | description | text | NO | | NULL | | +-------------+---------+------+-----+---------+----------------+ Tasktransitions +------------------+-----------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+-----------+------+-----+-------------------+----------------+ | tasktransitionid | int(11) | NO | PRI | NULL | auto_increment | | taskid | int(11) | NO | MUL | NULL | | | status | int(11) | NO | MUL | NULL | | | description | text | NO | | NULL | | | userid | int(11) | NO | | NULL | | | transitiondate | timestamp | NO | | CURRENT_TIMESTAMP | | +------------------+-----------+------+-----+-------------------+----------------+ Query SELECT tasks.taskid,tasks.description,tasklaststatus.status FROM tasks LEFT OUTER JOIN ( SELECT tasktransitions.taskid,tasktransitions.transitiondate,tasktransitions.status FROM tasktransitions INNER JOIN ( SELECT taskid,MAX(transitiondate) AS lasttransitiondate FROM tasktransitions GROUP BY taskid ) AS tasklasttransition ON tasklasttransition.lasttransitiondate=tasktransitions.transitiondate AND tasklasttransition.taskid=tasktransitions.taskid ) AS tasklaststatus ON tasklaststatus.taskid=tasks.taskid WHERE tasklaststatus.status IS NULL OR tasklaststatus.status=0 or tasklaststatus.transitiondate>'2013-09-01'; I'm wondering if the database structure is best choice performance wise. Could adding indexes help? I already tried to add some but I don't see great improvements. +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | tasktransitions | 0 | PRIMARY | 1 | tasktransitionid | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | taskid_date_ix | 1 | taskid | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | taskid_date_ix | 2 | transitiondate | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | status_ix | 1 | status | A | 3 | NULL | NULL | | BTREE | | | +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ Any other suggestions?

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• Database layout for an application with geocoding features using geokit

  - by vooD

  I'm developing a real estate web catalogue and want to geocode every ad using geokit gem. My question is what would be the best database layout from the performance point if i want to make search by country, city of the selected country, administrative area or nearest metro station of the selected city. Available countries, cities, administrative areas and metro sations should be defined by the administrator of catalogue and must be validated by geocoding. I came up with single table: create_table "geo_locations", :force => true do |t| t.integer "geo_location_id" #parent geo location (ex. country is parent geo location of city t.string "country", :null => false #necessary for any geo location t.string "city", #not null for city geo location and it's children t.string "administrative_area" #not null for administrative_area geo location and it's children t.string "thoroughfare_name" #not null for metro station or street name geo location and it's children t.string "premise_number" #house number t.float "lng", :null => false t.float "lat", :null => false t.float "bound_sw_lat", :null => false t.float "bound_sw_lng", :null => false t.float "bound_ne_lat", :null => false t.float "bound_ne_lng", :null => false t.integer "mappable_id" t.string "mappable_type" t.string "type" #country, city, administrative area, metro station or address end Final geo location is address it contains all neccessary information to put marker of the real estate ad on the map. But i'm still stuck on search functionality. Any help would be highly appreciated.

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• Creating collaborative whiteboard drawing application

  - by Steven Sproat

  I have my own drawing program in place, with a variety of "drawing tools" such as Pen, Eraser, Rectangle, Circle, Select, Text etc. It's made with Python and wxPython. Each tool mentioned above is a class, which all have polymorphic methods, such as left_down(), mouse_motion(), hit_test() etc. The program manages a list of all drawn shapes -- when a user has drawn a shape, it's added to the list. This is used to manage undo/redo operations too. So, I have a decent codebase that I can hook collaborative drawing into. Each shape could be changed to know its owner -- the user who drew it, and to only allow delete/move/rescale operations to be performed on shapes owned by one person. I'm just wondering the best way to develop this. One person in the "session" will have to act as the server, I have no money to offer free central servers. Somehow users will need a way to connect to servers, meaning some kind of "discover servers" browser...or something. How do I broadcast changes made to the application? Drawing in realtime and broadcasting a message on each mouse motion event would be costly in terms of performance and things get worse the more users there are at a given time. Any ideas are welcome, I'm not too sure where to begin with developing this (or even how to test it)

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• Best way of showing more results with javascript/css

  - by Ricardo Neves

  I'm developing a website and i'm having troubles showing the search results to the user the way I want. Basically, after the user search, the page makes a couple of ajax requests and as soon as a response arrive it appends the info to a specific element on my page. Each results is shown as a line... The problem is that in most case there are going to be more than 1000 results and this would make the page have a large scroll. My idea was to show only the first 15 results and when the user clicks "show more" the element would expand and show the next 15 results and so on... This would be easier to do if the website wasn't responsive, but because it is I can't find the proper way of implementing what I want without lowering the website perfomance. I have "2 ideas": The first is by using something like #element .div:nth-child(-n+15) on my css and figure a way of changing the "15" to how much results I want to show... I don't know if this can be done. Is it possible to call css rules with parameters? Maybe with less css? The second option is probably a bad option if i don't want to lower the website performance. Using javascript I would check if there is a specific css class(like .show-15 .show30 .show45) and add that class to my element and if it don't exist, create it somehow.. Any help would be appreciated.

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• Developing a 2D Game for Windows Phone 8

  - by Vaccano

  I would like to develop a 2D game for Windows Phone 8. I am a professional Application Developer by day and this seems like a fun hobby. But I have been disapointed trying to get going. It seems that 2D games (far and away the majority of games) do not have any real support. It seems the Windows Phone makers did not include support for Direct2D. So unless you are planning to make a fully 3D app, you are out of luck. So, if you just wanted to make a nice 2D app, these are your choices: Write your game using Xaml and C# (Performance Issues?) Write your game using Direct3D and but only draw on one plane. Use the DirectX Took Kit found on codeplex. It allows you to use the dying XNA framework's API for development. Number 3 seems the best for my game. But I hate to waste my time learning the XNA api when Microsoft has clearly stated that it is not going to be supported going forward. Number 2 would work, but 3D development is really hard. I would rather not have to do all that to get the 2D effect. (Assuming Direct2D is easier. I have yet to look into that.) Number 1 seems the easiest, but I worry that my app will not run well if it is based off of xaml rendering rather than DirectX. What is the suggested method from Microsoft? And who decided that 2D games were going to get shortchanged?

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• Lightweight HTTP application/server for static content

  - by PartlyCloudy

  Hi, I am in need of a scalable and performant HTTP application/server that will be used for static file serving/uploading. So I only need support for GET and PUT operations. However, there are a few extra features that I need: Custom authentication: I need to check credentials against a database for each request. Thus I must be able to integrate propietary database interaction. Support for signed access keys: The access to resources via PUT should be signed using a key like http://uri/?key=foo The key then contains information about the request like md5(user + path + secret) which allows me to block unwanted requests. The application/server should allow me to check for this. Performance: I'd like to avoid piping content as much as possible. Otherwise the whole application could be implemented in Perl/etc. in a few lines as CGI. Perlbal (in webserver mode) looks nice, however the single-threaded model does not fit with my database lookup and it does also not support query strings. Lighttp/Nginx/… have some modules for these tasks, however it is not feasible putting everything together without ending up writing own extensions/modules. So how would you solve this? Are there other leightweight webservers available for this? Should I implement an application inside of a webserver (i.e. CGI). How can I avoid/speed up piping content between the webserver and my application. Thanks in advance!

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• Fastest way to clamp a real (fixed/floating point) value?

  - by Niklas

  Hi, Is there a more efficient way to clamp real numbers than using if statements or ternary operators? I want to do this both for doubles and for a 32-bit fixpoint implementation (16.16). I'm not asking for code that can handle both cases; they will be handled in separate functions. Obviously, I can do something like: double clampedA; double a = calculate(); clampedA = a > MY_MAX ? MY_MAX : a; clampedA = a < MY_MIN ? MY_MIN : a; or double a = calculate(); double clampedA = a; if(clampedA > MY_MAX) clampedA = MY_MAX; else if(clampedA < MY_MIN) clampedA = MY_MIN; The fixpoint version would use functions/macros for comparisons. This is done in a performance-critical part of the code, so I'm looking for an as efficient way to do it as possible (which I suspect would involve bit-manipulation) EDIT: It has to be standard/portable C, platform-specific functionality is not of any interest here. Also, MY_MIN and MY_MAX are the same type as the value I want clamped (doubles in the examples above).

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• PHP modifying and combining array

  - by Industrial

  Hi everyone, I have a bit of an array headache going on. The function does what I want, but since I am not yet to well acquainted with PHP:s array/looping functions, so thereby my question is if there's any part of this function that could be improved from a performance-wise perspective? I tried to be as complete as possible in my descriptions in each stage of the functions which shortly described prefixes all keys in an array, fill up eventual empty/non-valid keys with '' and removes the prefixes before returning the array: $var = myFunction ( array('key1', 'key2', 'key3', '111') ); function myFunction ($keys) { $prefix = 'prefix_'; $keyCount = count($keys); // Prefix each key and remove old keys for($i=0;$i<$keyCount; $i++){ $keys[] = $prefix.$keys[$i]; unset($keys[$i]); } // output: array('prefix_key1', 'prefix_key2', 'prefix_key3', '111) // Get all keys from memcached. Only returns valid keys $items = $this->memcache->get($keys); // output: array('prefix_key1' => 'value1', 'prefix_key2' => 'value2', 'prefix_key3'=>'value3) // note: key 111 was not found in memcache. // Fill upp eventual keys that are not valid/empty from memcache $return = $items + array_fill_keys($keys, ''); // output: array('prefix_key1' => 'value1', 'prefix_key2' => 'value2', 'prefix_key3'=>'value3, 'prefix_111' => '') // Remove the prefixes for each result before returning array to application foreach ($return as $k => $v) { $expl = explode($prefix, $k); $return[$expl[1]] = $v; unset($return[$k]); } // output: array('key1' => 'value1', 'key2' => 'value2', 'key3'=>'value3, '111' => '') return $return; } Thanks a lot!

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• How to model in J2EE / JEE?

  - by Harry

  Let's say, I have decided to go with J(2)EE stack for my enterprise application. Now, for domain modelling (or: for designing the M of MVC), which APIs can I safely assume and use, and which I should stay away from... say, via a layer of abstraction? For example, Should I go ahead and litter my Model with calls to Hibernate/JPA API? Or, should I build an abstraction... a persistence layer of my own to avoid hard-coding against these two specific persistence APIs? Why I ask this: Few years ago, there was this Kodo API which got superseded by Hibernate. If one had designed a persistence layer and coded the rest of the model against this layer (instead of littering the Model with calls to specific vendor API), it would have allowed one to (relatively) easily switch from Kodo to Hibernate to xyz. Is it recommended to make aggressive use of the *QL provided by your persistence vendor in your domain model? I'm not aware of any real-world issues (like performance, scalability, portability, etc) arising out of a heavy use of an HQL-like language. Why I ask this: I would like to avoid, as much as possible, writing custom code when the same could be accomplished via query language that is more portable than SQL. Sorry, but I'm a complete newbie to this area. Where could I find more info on this topic? Many thanks in advance. /HS

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• Start with remoting or with WCF

  - by Sheldon

  Hi. I'm just starting with distributed application development. I need to create (all by myself) an enterprise application for document management. That application will run on an intranet (within the firewall, no internet access is required now, BUT is probably that will be later). The application needs to manage images that will be stored within MySQL Server (as blobs) and those images will be then recovered by the app and eventually one or more of them will be converted to PDF. Performance is the most important non-functional requirement. I have a couple of doubts. What do you suggest to use, .NET Remoting or WCF over TCP-IP (I think second one is the best for the moment I need to expose the business logic over internet, changing the protocol). Where do you suggest to make the transformation of the images to pdf files, I'm using iText. (I have thought to have the business logic stored within the IIS and exposed via WCF, and that business logic to be responsible of getting the images and transforming them to PDF, that because the IIS and the MySQL Server are the same physical machine). I ask about where to do the transformation because the app must be accessible from multiple devices, and for example, for mobile devices, the pdf maybe is not necessary. Thank you very much in advance.

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• The correct usage of nested #pragma omp for directives

  - by GoldenLee

  The following code runs like a charm before OpenMP parallelization was applied. In fact, the following code was in a state of endless loop! I'm sure that's result from my incorrect use to the OpenMP directives. Would you please show me the correct way? Thank you very much. #pragma omp parallel for for (int nY = nYTop; nY <= nYBottom; nY++) { for (int nX = nXLeft; nX <= nXRight; nX++) { // Use look-up table for performance dLon = theApp.m_LonLatLUT.LonGrid()[nY][nX] + m_FavoriteSVISSRParams.m_dNadirLon; dLat = theApp.m_LonLatLUT.LatGrid()[nY][nX]; // If you don't want to use longitude/latitude look-up table, uncomment the following line //NOMGeoLocate.XYToGEO(dLon, dLat, nX, nY); if (dLon > 180 || dLat > 180) { continue; } if (Navigation.GeoToXY(dX, dY, dLon, dLat, 0) > 0) { continue; } // Skip void data scanline dY = dY - nScanlineOffset; // Compute coefficients as well as its four neighboring points' values nX1 = int(dX); nX2 = nX1 + 1; nY1 = int(dY); nY2 = nY1 + 1; dCx = dX - nX1; dCy = dY - nY1; dP1 = pIRChannelData->operator [](nY1)[nX1]; dP2 = pIRChannelData->operator [](nY1)[nX2]; dP3 = pIRChannelData->operator [](nY2)[nX1]; dP4 = pIRChannelData->operator [](nY2)[nX2]; // Bilinear interpolation usNomDataBlock[nY][nX] = (unsigned short)BilinearInterpolation(dCx, dCy, dP1, dP2, dP3, dP4); } }

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• Updating UI objects in windows forms

  - by P a u l

  Pre .net I was using MFC, ON_UPDATE_COMMAND_UI, and the CCmdUI class to update the state of my windows UI. From the older MFC/Win32 reference: Typically, menu items and toolbar buttons have more than one state. For example, a menu item is grayed (dimmed) if it is unavailable in the present context. Menu items can also be checked or unchecked. A toolbar button can also be disabled if unavailable, or it can be checked. Who updates the state of these items as program conditions change? Logically, if a menu item generates a command that is handled by, say, a document, it makes sense to have the document update the menu item. The document probably contains the information on which the update is based. If a command has multiple user-interface objects (perhaps a menu item and a toolbar button), both are routed to the same handler function. This encapsulates your user-interface update code for all of the equivalent user-interface objects in a single place. The framework provides a convenient interface for automatically updating user-interface objects. You can choose to do the updating in some other way, but the interface provided is efficient and easy to use. What is the guidance for .net Windows Forms? I am using an Application.Idle handler in the main form but am not sure this is the best way to do this. About the time I put all my UI updates in the Idle event handler my app started to show some performance problems, and I don't have the metrics to track this down yet. Not sure if it's related.

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