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• Multiple ParticleSystems in cocos2d

  - by Mattias Akerman

  I wonder about what road I should go with ParticleSystem. In this particular case I want to create 1-20 small explosions at the same time but with different positions. Right now I'm creating a new ParticleSystem for each explosion and then release it, but of course this is very punishing to the performance. My question is: Is there a way to create one ParticleSystem with multiple emitting sources. If not should I create an array of ParticleSystem in init and then use a free one when an explosion is needed? Or is there another approach I haven't thought of?

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• Are C++ meta-templates required knowledge for programmers?

  - by Robert Gould

  In my experience Meta-templates are really fun (when your compilers are compliant), and can give good performance boosts, and luckily I'm surrounded by seasoned C++ programmers that also grok meta-templates, however occasionally a new developer arrives and can't make heads or tails of some of the meta-template tricks we use (mostly Andrei Alenxandrescu stuff), for a few weeks until he gets initiated appropriately. So I was wondering what's the situation for other C++ programmers out there? Should meta-template programming be something C++ programmers should be "required" to know (excluding entry level students of course), or not? Edit: Note my question is related to production code and not little samples or prototypes

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• Concatenation Operator

  - by Chaitanya

  This might be a silly question but it struck me, and here i ask. <?php $x="Hi"; $y=" There"; $z = $x.$y; $a = "$x$y"; echo "$z"."<br />"."$a"; ?> $z uses the traditional concatenation operator provided by php and concatenates, conversely $a doesn't, My questions: by not using the concatenation operator, does it effect the performance? If it doesn't why at all have the concatenation operator. Why have 2 modes of implementation when one does the work?

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• Tokenizer for full-text

  - by user72185

  This should be an ideal case of not re-inventing the wheel, but so far my search has been in vain. Instead of writing one myself, I would like to use an existing C++ tokenizer. The tokens are to be used in an index for full text searching. Performance is very important, I will parse many gigabytes of text. Edit: Please note that the tokens are to be used in a search index. Creating such tokens is not an exact science (afaik) and requires some heuristics. This has been done a thousand time before, and probably in a thousand different ways, but I can't even find one of them :) Any good pointers? Thanks!

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• GPU YUV to RGB. Worth the effort?

  - by Jaime Pardos

  Hello, I have to convert several full PAL videos (720x576@25) from YUV 4:2:2 to RGB, in real time, and probably a custom resize for each. I have thought of using the GPU, as I have seen some example that does just this (except that it's 4:4:4 so the bpp is the same in source and destiny)-- http://www.fourcc.org/source/YUV420P-OpenGL-GLSLang.c However, I don't have any experience with using GPU's and I'm not sure of what can be done. The example, as I understand it, just converts the video frame to YUV and displays it in the screen. Is it possible to get the processed frame instead? Would it be worth the effort to send it to the GPU, get it transformed, and sending it again to main memory, or would it kill performance? Being a bit platform-specific, assuming I work on windows, is it possible to get an OpenGL or DirectDraw surface from a window so the GPU can draw directly to it?

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• Python: create a function to modify a list by reference not value

  - by Jonathan

  Hey all- I'm doing some performance-critical Python work and want to create a function that removes a few elements from a list if they meet certain criteria. I'd rather not create any copies of the list because it's filled with a lot of really large objects. Functionality I want to implement: def listCleanup(listOfElements): i = 0 for element in listOfElements: if(element.meetsCriteria()): del(listOfElements[i]) i += 1 return listOfElements myList = range(10000) myList = listCleanup(listOfElements) I'm not familiar with the low-level workings of Python. Is myList being passed by value or by reference? How can I make this faster? Is it possible to somehow extend the list class and implement listCleanup() within that? myList = range(10000) myList.listCleanup() Thanks- Jonathan

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• Java: Netbeans debugging session works faster than normal run

  - by Martijn Courteaux

  Hello, I'm making Braid in Netbeans 6.7.1. Computer Spec: Windows 7 Running processes: 46 Running threads: +/- 650 NVidia GeForce 9200M GS Intel Core 2 Duo CPU P8400 @ 2.26Ghz Game-spec with normal run: Memory: between 80 MB and 110 MB CPU: between 9% and 20% CPU when time rewinding: 90% The same values for the debugging session, except when I rewind the time: CPU: 20%. Is there any reason for? Is there a way to reach the same performance with a normal run. This is my repaint code: @Override public void repaint() { BufferStrategy bs = getBufferStrategy(); // numBuffers: 4 Graphics g = bs.getDrawGraphics(); g.setColor(Color.BLACK); g.fillRect(-1, -1, 2000, 2000); gamePanel.paint(g.create(x, y, gameDim.width, gameDim.height)); bs.show(); g.dispose(); Toolkit.getDefaultToolkit().sync(); update(g); } The game runs in fullscreen (undecorated + frame.size = screensize) Martijn

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• [OpenGL] I'm having an issue to use GLshort for representing Vertex, and Normal.

  - by Xylopia

  As my project gets close to optimization stage, I notice that reducing Vertex Metadata could vastly improve the performance of 3D rendering. Eventually, I've dearly searched around and have found following advices from stackoverflow. Using GL_SHORT instead of GL_FLOAT in an OpenGL ES vertex array How do you represent a normal or texture coordinate using GLshorts? Advice on speeding up OpenGL ES 1.1 on the iPhone Simple experiments show that switching from "FLOAT" to "SHORT" for vertex and normal isn't tough, but what troubles me is when you're to scale back verticies to their original size (with glScalef), normals are multiplied by the reciprocal of the scale. Then how do you use "short" for both vertex and normal at the same time? I've been trying this and that for about a full day, but I could only go for "float vertex w/ byte normal" or "short vertex w/ float normal" so far. Your help would be truly appreciated.

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• Tables with no Primary Key

  - by Matt Hamilton

  I have several tables whose only unique data is a uniqueidentifier (a Guid) column. Because guids are non-sequential (and they're client-side generated so I can't use newsequentialid()), I have made a non-primary, non-clustered index on this ID field rather than giving the tables a clustered primary key. I'm wondering what the performance implications are for this approach. I've seen some people suggest that tables should have an auto-incrementing ("identity") int as a clustered primary key even if it doesn't have any meaning, as it means that the database engine itself can use that value to quickly look up a row instead of having to use a bookmark. My database is merge-replicated across a bunch of servers, so I've shied away from identity int columns as they're a bit hairy to get right in replication. What are your thoughts? Should tables have primary keys? Or is it ok to not have any clustered indexes if there are no sensible columns to index that way?

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• Are we asking too much of transactional memory?

  - by Carl Seleborg

  I've been reading up a lot about transactional memory lately. There is a bit of hype around TM, so a lot of people are enthusiastic about it, and it does provide solutions for painful problems with locking, but you regularly also see complaints: You can't do I/O You have to write your atomic sections so they can run several times (be careful with your local variables!) Software transactional memory offers poor performance [Insert your pet peeve here] I understand these concerns: more often than not, you find articles about STMs that only run on some particular hardware that supports some really nifty atomic operation (like LL/SC), or it has to be supported by some imaginary compiler, or it requires that all accesses to memory be transactional, it introduces type constraints monad-style, etc. And above all: these are real problems. This has lead me to ask myself: what speaks against local use of transactional memory as a replacement for locks? Would this already bring enough value, or must transactional memory be used all over the place if used at all?

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• PHP Initialising strings as boolean first

  - by Anriëtte Myburgh

  I'm in the habit of initialising variables in PHP to false and then applying whatever (string, boolean, float) value to it later. Which would you reckon is better? $name = false; if (condition == true) { $name = $something_else; } if ($name) { …do something… } vs. $name =''; if (condition == true) { $name = $something_else; } if (!empty($name)) { …do something… } Which would you reckon can possibly give better performance? Which method would you use?

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• Need details about applications that are running on Windows Azure

  - by veda

  I have an application which requires large amount of data storage (say some PB) and computing resources. Instead of going for clusters, I am planning to propose to use Windows Azure Cloud for this application. I have gone through white papers of Windows Azure and have collected some details about Azure. But I feel that is not substantial. I need to do some case study about applications that are running on the azure and that uses azure storage efficiently. I looked for several research paper in related to performance of the applications in Windows Azure. But as Azure was quite new, I wasn't able to find any. Now, I am looking for some white papers/details regarding application that uses azure storage to substantiate my proposal. I also need to understand the windows azure storage architecture and virtual machine architecture. Do anyone know some research papers or details or blogs or something related to these topics.

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• Struct in C, are they efficient?

  - by pygabriel

  I'm reading some C code like that: double function( int lena,double xa,double ya, double za, double *acoefs, ..., int lenb,double xb,double yb, double zb, double *bcoefs, ..., same for c, same for d ) This function is called in the code mor than 100.000 times so it's performance-critical. I'm trying to extend this code but I want to know if it's efficient or not (and how much this influences the speed) to encapsulate all the parameters in a struct like this struct PGTO { int len; double x,y,z ; double *acoefs } and then access the parameters in the function.

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• Best practices to build a highly configurable software product.

  - by Kabeer

  Hello. I am working on a software product that can substantially change behavior based on the configuration & meta-data supplied. I would like to know best practices to architect / build a highly configurable software product. Considering that there are substantial number of configuration parameters, I'd like to look at something that will not affect the performance before I look at dependency injection. My platform is .Net ... I seek recommendations on architecture / design and implementations fronts.

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• PostgreSQL 8.3 data types: xml vs varchar

  - by Sejanus

  There's xml data type in Postgres, I never used it before so I'd like to hear opinions. Downsides and upsides vs using regular varchar (or Text) column to store xml. The text I'm going to store is xml, well-formed, UTF-8. No need to search by it (I've read searching by xml is slow). This XML actually is data prepared for PDF generation with Apache FOP. XML can be generated dynamically from data found elsewhere (other Postgres tables), it's stored as is only so that I won't need to generate it twice. Kinda backup#2 for already generated PDF documents. Anything else to know? Good practices, performance, maintenance, etc?

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• Why might SQL execute more quickly on SQL Server 2000 when NOT using a stored procedure?

  - by Kofi Sarfo

  I could see nothing wrong with the execution plan. Besides, as I understand it, SQL Server 2000 extended many of the performance benefits of stored procedures to all SQL statements by recognising new T-SQL statements against T-SQL statements of existing execution plans (by retaining execution plans for all SQL statements in the procedure cache, not just stored procedure execution plans) It's a fairly straight forward SELECT statement with sensible table joins, no transactions included or linked servers being referenced within the query and WITH (NOLOCK) table hints applied. The stored procedure was created by dbo and the user has all the necessary permissions. So my question is this: What are the likely reasons for a query to take only a few seconds to run but then take several minutes when identical T-SQL is run via a stored procedure?

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• Concatenation Operator - PHP

  - by Chaitanya

  This might be a silly question but it struck me, and here i ask. <?php $x="Hi"; $y=" There"; $z = $x.$y; $a = "$x$y"; echo "$z"."<br />"."$a"; ?> $z uses the traditional concatenation operator provided by php and concatenates, conversely $a doesn't, My questions: a. by not using the concatenation operator, does it effect the performance? b. If it doesn't why at all have the concatenation operator. c. Why have 2 modes of implementation when one does the work?

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• How can I calculate data for a boxplot (quartiles, median) in a Ralis app on Heroku? ( Heroku uses P

  - by hadees

  I'm trying to calculate the data needed to generate a box plot which means I need to figure out the 1st and 3rd Quartiles along with the median. I have found some solutions for doing it in Postgresql however they seem to depend on either PL/Python or PL/R which it seems like Heroku does not have either enabled for their postgresql databases. In fact I ran "select lanname from pg_language;" and only got back "internal". I also found some code to do it in pure ruby but that seems somewhat inefficient to me. I'm rather new to Box Plots, Postgresql, and Ruby on Rails so I'm open to suggestions on how I should handle this. There is a possibility to have a lot of data which is why I'm concerned with performance however if the solution ends up being too complex I may just do it in ruby and if my application gets big enough to warrant it get my own Postgresql I can host somewhere else. *note: since I was only able to post one link, cause I'm new, I decided to share a pastie with some relevant information

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• Is AsParallel() good practice in a web environment?

  - by Bjorn Bailleul

  I have no doubt that for client applications, AsParallel() will bring some out-of-the-box performance gains. But what if I would use it in a web environment. Let's say I have a widget framework that loops over all widgets to get their data and render output. This would parallelize great no? I do have my doubts on using AsParallel() in this scenario. What if I have a large number of visitors for my site, isn't IIS going to use multiple threads to handle all requests? Aren't there going to be locking issues presented after a while, or threads dying because all processors are in use? It's just a thought, what do you think about this?

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• Throughput measurements

  - by dotsid

  I wrote simple load testing tool for testing performance of Java modules. One problem I faced is algorithm of throughput measurements. Tests are executed in several thread (client configure how much times test should be repeated), and execution time is logged. So, when tests are finished we have following history: 4 test executions 2 threads 36ms overall time - idle * test execution 5ms 9ms 4ms 13ms T1 |-*****-*********-****-*************-| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-----| <-----------------36ms---------------> For the moment I calculate throughput (per second) in a following way: 1000 / overallTime * threadCount. But there is problem. What if one thread will complete it's own tests more quickly (for whatever reason): 3ms 3ms 3ms 3ms T1 |-***-***-***-***----------------| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-| <--------------32ms--------------> In this case actual throughput is much better because of measured throughput is bounded by the most slow thread. So, my question is how should I measure throughput of code execution in multithreaded environment.

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• Using different languages in one project

  - by Tarbal

  I recently heard about the use of several different languages in a (big) project, I also read about famous services such as Twitter using Rails as frontend, mixed with some other languages, and Scala I think it was as backend. Is this common practice? Who does that? I'm sure there are disadvantages to this. I think that you will have problems with the different interpreters/compilers and seamlessly connecting the different languages. Is this true? Why is this actually done? For performance?

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• A web framework where AJAX was not an after thought

  - by Pirate for Profit

  AJAX is a pain in the ass because it essentially means you'll have to write two sets of similarish code: one for browsers with JavaScript enabled and those without. Not only this, but you have to connect JavaScript events to hook into your models and display the results. And if all that weren't bad enough, you need to send an address change with the request, otherwise the user won't be able to "click back" correctly (if confused look at what happens to the address bar when you click links in GMail). We're searching for something that had the foresight and design goals with all these concerns in mind. Performance and security are also obvious major concerns. We love config-based systems as well, where you don't have to write a lot of code you just drop it into an easily read config format. It's like asking for the holy grail right?

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• IIS7 Modules - managed or native?

  - by Simon Linder

  Hi all, as the old ISAPI filters are going to die sooner or later, I want to rewrite an old ISAPI filter that was used in IIS 6 into a module for use in IIS 7. The module will be used globally, meaning it will be used within each site, on a Windows Server 2008 R2 with IIS 7.5 installed, that will host several thousand web sites and managing about 50 application pools. My question now is if I should write that module in managed or unmanaged code? One of my concerns regarding managed code is the massive memory consumption due to the .NET framework overhead. I don't know how this would effect the server's performance. I already wrote modules in managed as well as in unmanaged code. So this is not the bothering my decision. But I would prefer to write the module in C# if there are no huge drawbacks. Any suggestions about that issue?

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• Clustering and DB Replication in virtualized (and cloud) environments

  - by devdude

  Both replication and clustering are terms for servers setups with physical (real) servers, usually implemented on a DB or AS level. Now the question: In a virtualized environment with "easy" scalable servers (touching clustering) and a higher availability (DB replication) through the means of high availability of the virtual server by the cloudserver provider, do we really need replication and clustering (as in covering the problems of traditional servers) ? Question is asked from a soultion/application provider viewpoint. Please exclude the need of replication with a business requirement background, eg. the need to replicate a DB at 2 different geographical locations to ensure performance and data. Thanks for your insights !

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• setting up/installing/configuring nginx LEMP stack on fresh VPS server

  - by grant tailor

  I need some help in settingup/installing and configuring nginx LEMP stack on a fresh new VPS i have. The specs of the CentOS 5.7 VPS are 2GB DDR3 ECC RAM(4GB burst), 1 core 1.5Ghz(3Ghz burst) and 100GB RAID 10 storage, unmetered bandwidth @ 100Mpbs all for a whopping $25/month(unbeatable, yeah i know :) Anyways i have followed this LEMP(will also need MySQL and PHP) stack guide on linode http://library.linode.com/lemp-guides/centos-5 but basically what i want is to be able to host multiple website on this webserver after everything is setup. I am used to using DirectAdmin control panel on other server and want to have things setup so i can host multiple websites...mostly wordpress and drupal themes. Lets say 10 websites on this nginx web server. So can someone please help me on what i need to do to take "full" advantage of nginx power and performance, while been able to easily manage these multiple websites (wordpress and drupal themes)? Thanks.

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