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• Are there Adaptive Replacement Cache patent-free alternatives?

  - by aleccolocco

  An open source high-performance project I'm working on needs to keep a cache of parsed/compiled files. A plain LRU or a plain LFU wouldn't fit. Plain LRU wouldn't work as there will be remote batch/spider processes hitting the service regularly. Plain LFU wouldn't work because content will age. ARC seems like the perfect solution but since IBM holds patents to it at least one open source project dropped it. Are there any (good enough) alternatives? EDIT: I'm not looking for exactly the same thing, just something that could handle those two situations. Perhaps some simple strategy with timestamps and sources. There have to be many programmers who faced this situation before. That's why the "good enough" bit.

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• Subtract displaced mask using OpenCV

  - by dario_ramos

  I want to do: masked = image - mask But I want to "displace" mask. That is, move it vertically and horizontally (as long as the intersection between it and image is not empty, this would be valid). I have some hand-coded assembly (which uses MMX instructions) which does this, embedded in a C++ program, but it's unstable when doing vertical displacemente, so I thought of using OpenCV instead. Would it be possible to do this calling only one OpenCV function? Performance is critical; using OpenCV, time should be at least in the same order of magnitude as the assembly code.

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• Tool for response time analysis on JBoss server?

  - by Ariel Vardi

  I am running a pretty high traffic cluster of JBoss servers serving REST requests and I am interested in tools reading the access logs in Tomcat format (with %D parameter) to provide a detailed analysis of the response time on a per-call basis. Ideally this tool would generate a chart showing the progression of the response time throughout the day, hour per hour, then a weekly view with averages on the day, and monthly with average on the weeks (CACTI style). I've looked for such tools and couldn't find anything. Is any of you guys aware of something close to that before I start writing my own? I haven't looked into CACTI extensions yet, but that be an option?

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• Agile - When does it work well, and when doesn't it?

  - by Randy Minder

  Our team is debating whether we want to become Agile or not. None of us are really fluent in Agile. I'd like some thoughts on when Agile works well, and when it doesn't? To give a little background, we are a small group of developers, six in total. We have far more work that we can handle. Our priorities change often. What is a high priority today, may not be tomorrow. We have many applications to create and maintain. If you need more information to answer this, please feel free to ask. Thanks.

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• How to test reliability of my own (small) embedded operating system ?

  - by TridenT

  I've written a small operating system for embedded project running on small to medium target. I added some automated unit test with a high test code coverage (95%), but the scope is only the static part. I got some code metrics as complexity and readability. I'm testing my code with a rule checker with MiSRA support, and of course fixed all warnings. I'm testing the code with a static analyzer and again fixed all warnings. What can I do now to test - and improve - the reliability of my OS ? How about the dynamic part ?

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• Programming language for fast calculations with big integers

  - by sub

  I'm doing Project Euler problems at the moment and I can solve most of them using my own programming language which uses direct C++ integers (so they are bound to 2^32 on my machine). However, at times there are problems which require me to work with very high numbers, I can't do that with native integers. So I implemented a BigInt library in my language which unfortunately gets extremely slow at times. Is there a programming language suitable for very efficient handling of big numbers? I mean that I want to do the things I could do in other programming languages with it (variables, loops, etc.), but in a faster way. If you have got tips for workarounds of the 2^32 limit in my language/C++/other languages, please tell me too!

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• Django admin page dropdowns

  - by zen

  I am building a high school team application using Django. Here is my working models file: class Directory(models.Model): school = models.CharField(max_length=60) website = models.URLField() district = models.SmallIntegerField() conference = models.ForeignKey(Conference) class Conference(models.Model): conference_name = models.CharField(max_length=50) url = models.URLField() class Meta: ordering = ['conference_name'] When I open my admin pages and go to edit a school's conference the drop down looks like this: <select> <option value="1">Conference Object</option> <option value="2">Conference Object</option> <select> How do I replace "Conference Object" with the conference_name?

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• What are the best blogs for staying up to date on C#, ASP.NET, LINQ, SQL, C++, Ruby, Java, Python?

  - by Arj

  Apologies if this repeats another - but I couldn't fine one like it. My day to day programming spans a fair number of technologies: C#, ASP.NET, LINQ / SQL, C++, Ruby, Java, Python in approximately that order. It's a struggle to keep up to date on any of best practices, new ideas, innovation and improvements, let alone all. Therefore, what would your top 1 blog be in each of these technologies and which technology do you find easiest to stay up to date with? I'd have a bias towards blogs with broad and high level rather than narrow and detailed content / solutions / examples.

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• How to: Inline assembler in C++ (under Visual Studio 2010)

  - by toxic shock

  I'm writing a performance-critical, number-crunching C++ project where 70% of the time is used by the 200 line core module. I'd like to optimize the core using inline assembly, but I'm completely new to this. I do, however, know some x86 assembly languages including the one used by GCC and NASM. All I know: I have to put the assembler instructions in _asm{} where I want them to be. Problem: I have no clue where to start. What is in which register at the moment my inline assembly comes into play?

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• Mouse Wheel Scroll - How can I capture the time interval between start and stop of scrolling?

  - by Rahat

  Is there any way to capture the time interval between mouse wheel scroll start and stop? Actually I want to capture the interval between the scrolling start and stop when I very quickly scroll the mouse wheel. I have already looked at MouseWheel event but it don't fulfill my requirement. In senes that it always gives a value of Delta 120 or -120 but i want to call a function depending on the speed of the mouse scroll for example when i scroll the mouse normally i want to perform function 1 and when i scrolled the mouse very quickly i want to perform the function 2. In other words is there any way to distinguish between the mouse scroll high and normal speed. Any advice will be appreciated.

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• Has Object in VB 2010 received the same optimalization as dynamic in C# 4.0?

  - by Abel

  Some people have argued that the C# 4.0 feature introduced with the dynamic keyword is the same as the "everything is an Object" feature of VB. However, any call on a dynamic variable will be translated into a delegate once and from then on, the delegate will be called. In VB, when using Object, no caching is applied and each call on a non-typed method involves a whole lot of under-the-hood reflection, sometimes totaling a whopping 400-fold performance penalty. Have the dynamic type delegate-optimization and caching also been added to the VB untyped method calls, or is VB's untyped Object still so slow?

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• ExtJS Grid slow with 3000+ records

  - by Oliver Watkins

  I am using ExtJS Grid and its getting pretty slow with 3000+ records. Sorting takes about 4 seconds. Compared to other more Javascript tables, this is pretty slow. I am thinking maybe to use pagination in my table. However after reading the documentation, I am still a bit unsure about how pagination works in extjs. Does this pull data from the server each time u turn a page? I would prefer that wasn't the case. I would prefer the 3000 records are saved in the browser and then what is rendered is just a portion of those rows. Also I am using Extjs version 4.2.1. If I upgrade to version 5. will I get some performance improvements?

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• Why cant I specify the width and height of a cell in an html table?

  - by Phil

  I am using CSS but for the sake of quick testing i am just using a style tag. This is the code I am trying to implement: echo "<td style='height=10px; width=10px;'>"; it makes sure that the max width of the cell is 10px however the height overflows with the text so becomes very large (high). what I am trying to achieve is any information that is in that cell more than 30 charcters I want to hide so you cant see it. (I know 30 charaters is more than 10px but I am just playing to see if it worked!) Thanks guys.

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• How to test my programming experience

  - by Oden

  Hey guys, I'm very excited about how experienced I am in programming. The first, working program that I have written, was in 2004 with C. Since this I have tried many programming languages, now got stuck with php. Currently I'm working as a web-developer, and everyones pleased with the work I do. Except me :) Thats the reason why i want to know, how high my experience and my knowledge is. Could you tell me, some tips, tricks, test, or anything, on what I can see how much I need to learn and practice to get a mastermind in programming? (at first place in php)

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• Multiple Producers Single Consumer Queue

  - by Talguy

  I am new to multithreading and have designed a program that receives data from two microcontroller measuring various temperatures (Ambient and Water) and draws the data to the screen. Right now the program is singly threaded and its performance SUCKS A BIG ONE. I get basic design approaches with multithreading but not well enough to create a thread to do a task but what I don't get is how to get threads to perform seperate task and place the data into a shared data pool. I figured that I need to make a queue that has one consumer and multiple producers (would like to use std::queue). I have seen some code on the gtkmm threading docs that show a single Con/Pro queue and they would lock the queue object produce data and signal the sleeping thread that it is finished then the producer would sleep. For what I need would I need to sleep a thread, would there be data conflicts if i didn't sleep any of the threads, and would sleeping a thread cause a data signifcant data delay (I need realtime data to be drawn 30 frames a sec) How would I go about coding such a queue using the gtkmm/glibmm library.

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• Why and when should one call _fpreset( )?

  - by STingRaySC

  The only documentation I can find (on MSDN or otherwise) is that a call to _fpreset() "resets the floating-point package." What is the "floating point package?" Does this also clear the FPU status word? I see documentation that says to call _fpreset() when recovering from a SIGFPE, but doesn't _clearfp() do this as well? Do I need to call both? I am working on an application that unmasks some FP exceptions (using _controlfp()). When I want to reset the FPU to the default state (say, when calling to .NET code), should I just call _clearfp(), _fpreset(), or both. This is performance critical code, so I don't want to call both if I don't have to...

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• Is the web hosting location important these days?

  - by kristof

  I was recently looking at some web hosting solutions and some of the providers offered various hosting locations e.g. US or UK based servers. My question is: does it really make a difference from the performance point of view? Lets say that I am expecting most of the traffic coming from continental Europe? Would the fact that the servers are based in UK make bigger difference if the traffic was coming from the UK. Any pros and cons of having a website hosted in the same county as the most of the expected traffic?

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• MySQL Many to Many with Unique keys and Update/Select if Exists otherwise Insert

  - by Jayrox

  In my goal to have a Many-to-Many relationship in my MySQL database I have arrived at another bridge to build. Current Tables: Users (id, name) Tags (id, name) User_Tags (user_id, tag_id) Here is the goal: I would like to have the ability to take a tag i.e: #fb and insert it into my Tags database which has a unique constraint on name and if the tag exists I would like to return it's id I would like to insert the tag.id and the current user's user.id into User_Tags. I do not have any unique constraints on the User_Tags table because I would like to be able to track the user's most commonly used tags and present them in a list ordered by frequency of use. I am currently developing this project in PHP using prepared statements. Additionally, performance is not currently an issue as my user count is still fairly small, but it is steadily growing and may be an issue in the future.

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• Retrieving data from database. Retrieve only when needed or get everything?

  - by RHaguiuda

  I have a simple application to store Contacts. This application uses a simple relational database to store Contact information, like Name, Address and other data fields. While designing it, I question came to my mind: When designing programs that uses databases, should I retrieve all database records and store them in objects in my program, so I have a very fast performance or I should always gather data only when required? Of course, retrieving all data can only be done if it`s not too many, but do you use this approach when you make sure that the database will be small (< 300 records for example)? I have designed once a similar application that fetches data only when needed, but that was slow (using a Access database). Thanks for all help.

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• How can I configure different worker pools using celery?

  - by Chris R

  I need to deploy a queued execution service with (generally) the following three classes of worker: A periodic, low-priority job class that takes a long time and can be processed serially; these jobs should only use 0..2 workers in the system at most. A periodic, deadline-sensitive job class that take a short to medium amount of time (say, topping out at 5 minutes) An ad-hoc job class, that is higher priority than #1, but can interleave with #2. Any workers from class #2 that are inactive when this type of job comes in should handle it, without ever starving the pool of workers for #2 All three job classes are the same task, the only difference between them is how they're requested; they'll take the same input and generate the same output, but each one has different performance guarantees. How can I implement this using celery?

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• How do I view how many concurrent long polling requests there are on my server?

  - by Pascal

  My host is Joyent. My host says I have 15 process limit and prstat -J shows those processes but that doesn't tell me how many long polling requests are currently being served. I could record it myself but that would add alot of performance overhead. I need to know when the server is at its long polling limits. I know this limit occurs far before the memory or CPU is used up. From experimentation, I've already verified that the number of long polls open is NOT equivalant to the number of processes running, probably because each process has multiple threads, each serving a request. thanks.

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• Can a Javascript bookmarklet overlay an image on a web page?

  - by songdogtech

  Can a bookmarklet be used to overlay an image on a web page? Not as a pop-up, but as a image positioned by CSS and with a high z-index to display on top of other elements. And without a mask i.e., Shadowbox or similar jQuery effect. Just an image from a URL and positioned in the bottom left hand corner of the browser window. This is what I have so far, but it may be the wrong direction to be going: javascript:(function(){document.write("body {background-image:url(http://mydomain.com/image.png); position: absolute; left:50px; top:300px; z-index:9999;}");})() I have a JS function that works as a bookmarklet to change the case of text on the page, and now I'd like to be able to show an image when the bookmarklet is used.

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• Merge two lists of objects which hold different data

  - by C.McAtackney

  I have an object "Project" which has a number of fields, one of which is "Name". I have one spreadsheet of projects which contains some of these fields, and another which contains the rest. However, Both spreadsheets have the "Name" field. I've read them in and populated two List, only populating the available fields from that particular source. E.g. a Project from List 1 looks like; {Name="MyProj", Type="Form", Priority=NULL}, whereas a Project from List 2 {Name="MyProj", Type=NULL, Priority="High"}. Now, I want to merge these two lists into one in which each Project object has all of its fields populated, with the Name field being used to match the elements. How can I achieve this? Are there any nice ways of doing this concisely? Thanks

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• Is it possible to serve an ASPX page without it setting a cookie on your browser?

  - by Django Reinhardt

  Hi, we're in the process of trying to speed up the performance of our website by serving static content from a cookieless domain. That seems to be going well, but I have a new question: I know that it's "static content" that we're talking about when serving it from a cookieless domain, but we also have static content being served by ASPX pages, specifically images. For example: domain.com/resizeImages.aspx?src=images/image123.jpg&width=400&height=400 Pretty standard stuff, and although it's being served by managed code, it's still a static image. So my question is: Is it ok to serve the resizeImages.aspx image from our cookieless/static domain? And if so, how do I go about stopping ASP.NET from setting a ANONYMOUSASPX cookie every time I try? Thanks for any help!

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• Optimising (My)SQL Query

  - by Simon

  I usually use ORM instead of SQL and I am slightly out of touch on the different JOINs... SELECT `order_invoice`.*, `client`.*, `order_product`.*, SUM(product.cost) as net FROM `order_invoice` LEFT JOIN `client` ON order_invoice.client_id = client.client_id LEFT JOIN `order_product` ON order_invoice.invoice_id = order_product.invoice_id LEFT JOIN `product` ON order_product.product_id = product.product_id WHERE (order_invoice.date_created >= '2009-01-01') AND (order_invoice.date_created <= '2009-02-01') GROUP BY `order_invoice`.`invoice_id` The tables/ columns are logically names... it's an shop type application... the query works... it's just very very slow... I use the Zend Framework and would usually use Zend_Db_Table_Row::find(Parent|Dependent)Row(set)('TableClass') but I have to make lots of joins and I thought it'll improve performance by doing it all in one query instead of hundreds... Can I improve the above query by using more appropriate JOINs or a different implementation? Many thanks.

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