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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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• Why should I use an N-Tier Approach When using an SqlDatasource is ALOT EASIER ?

  - by The_AlienCoder

  When it comes to web development I have always tried to work SMART not HARD. So for along time My Aproach to interacting with databases in my AspNet projects has been this : 1) Create my stored procedures 2) Drag an SQLDatasource control on my aspx page 3) Bind a DataList Control to my SQLDatasource 4) Insert, Update & Delete by using my Datalist or programmatically using built in SQLDatasource methods e.g MySqlDataSource.InsertParameters["author"].DefaultValue = TextBox1.Text; MySqlDataSource.Insert(); Recently however I got a relatively easy web project. So I decided to employ a 3-tier Model...But I got exhausted halfway and just didnt seem worth it ! It seemed like I was working too HARD for a project that could have been easily accomplished by a couple of SqlDataSource Controls. So Why Is the N-Tier Model better than my Approach? Has it anything to do with performance? What are the advantages of the ObjectDataSource control over the SqlDataSource Control?

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• Are you using Virtual Machine as your primary development enviroment?

  - by Click Ok

  Recently I have purchased a notebook that cames with Windows Home Basic (that don't have with ASP.Net/IIS. I thought in upgrade the Windows version to one with ASP.Net/IIS, but I thought in another possibility: I have an Hard Disk Case with a 360Gb HD. I thought in create a virtual machine with Windows Ultimate (installing too ASP.Net, IIS and Visual Studio 2008) in this HD Case, then I can access my "development enviroment" in any computer that I will work on (my desktop machine and my notebook). But I was worried about the performance. I don't have experience working in Virtual Machines (I use it just to quick compatibility tests)... Are you using Virtual Machine as your primary development enviroment? What your finds? ==================== Thanks for your answers! It really did help me! I would like to know too about portability ie.: the virtual machine that I created in my laptop will work in the desktop? I will need re-activate Windows?

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• How can I measure TForm deserialization time in Delphi?

  - by mjustin

  For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": before the beginning of the deserialization process after the completion of deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions.

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• How can a Delphi TPersistent object calculate its own deserialization time?

  - by mjustin

  For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": start of the deserialization process after the deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event So the log for TMyForm.Create(nil) could look like: - 00.000 instance created - 00.010 before deserialization - 01.823 after deserialization - 02.340 before OnFormCreate Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions.

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• RewriteRule in htaccess in subdirectory

  - by Jay

  Windows server, running Apache. In my Apache conf, I have AllowOverride None for the root of a site and then I have a subdirectory set to AllowOverride All: <Directory /> AllowOverride None </Directory> <Directory "/safe/"> AllowOverride All </Directory> However, when I try to set up a rewrite rule in the subdirectory's htaccess file, nothing happens, I just get a 404 page not found error. Example: RewriteEngine On RewriteRule (.*) /blah?test=$1 [R=302,NC,NE,L] Rwewriting URLs are working fine from the root via the Apache conf. I don't understand why the rule is ignored. I don't want to do the URL re-writing within the conf because for this case I may need to be changing the redirects constantly and don't want to reload the server every time a change is made. I also don't want to affect server performance by enabling htaccess files site-wide, just in the subdirectory I need it.

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• Should we use a CSS frame work ? Are they worth it ?

  - by Gaurav M

  CSS frameworks have nice styles inbuilt and ask you to focuses on the grids but still there is a bit of dependency and lack of freedom it provide.. If I need to generate a webpage by looking on a PSD based mockup screen ..either i will use the classes provided by the framework but if that actual measurements does not exist I need to again specify my own rules that will add upto my CSS filesize and if performance is a constraint as always it is...you need not a big size file..though its in kb but every drop counts. Any comments and suggestions to use the framework in a best possible way.

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• MySQL: Get unique values across multiple columns in alphabetical order

  - by RuCh

  Hey everyone, If my table looks like this: id | colA | colB | colC =========================== 1 | red | blue | yellow 2 | orange | red | red 3 | orange | blue | cyan What SELECT query do I run such that the results returned are: blue, cyan, orange, red, yellow Basically, I want to extract a collective list of distinct values across multiple columns and return them in alphabetical order. I am not concerned with performance optimization, because the results are being parsed to an XML file that will serve as a cache (database is hardly updated). So even a dirty solution would be fine. Thanks for any help!

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• Count of memory copies in *nix systems between packet at NIC and user application?

  - by Michael_73

  Hi there, This is just a general question relating to some high-performance computing I've been wondering about. A certain low-latency messaging vendor speaks in its supporting documentation about using raw sockets to transfer the data directly from the network device to the user application and in so doing it speaks about reducing the messaging latency even further than it does anyway (in other admittedly carefully thought-out design decisions). My question is therefore to those that grok the networking stacks on Unix or Unix-like systems. How much difference are they likely to be able to realise using this method? Feel free to answer in terms of memory copies, numbers of whales rescued or areas the size of Wales ;) Their messaging is UDP-based, as I understand it, so there's no problem with establishing TCP connections etc. Any other points of interest on this topic would be gratefully thought about! Best wishes, Mike

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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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• Best way to daemonize Java application on Linux

  - by SyBer

  Hi. While I found this question being answered here on SW several times, I didn't find a concluding answer what is the best approach. I'm not looking to use any external wrapper, as I found them launching the java process under a nice level lower then themselves which potentially lowers the performance, so it seems only the shell methods are left. I so far found 3 different shell methods: start-stop-daemon RedHat daemon init.d function nohup on start / disown after start What you people are using, and can recommend as the most reliable method? Thanks.

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• What are block expressions actually good for?

  - by Helper Method

  I just solved the first problem from Project Euler in JavaFX for the fun of it and wondered what block expressions are actually good for? Why are they superior to functions? Is it the because of the narrowed scope? Less to write? Performance? Here's the Euler example. I used a block here but I don't know if it actually makes sense // sums up all number from low to high exclusive which are divisible by a or b function sumDivisibleBy(a: Integer, b: Integer, high: Integer) { def low = if (a <= b) a else b; def sum = { var result = 0; for (i in [low .. <high] where i mod 3 == 0 or i mod 5 == 0) { result += i } result } } Does a block makes sense here?

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• How to implement a mailing system with Rails that sends emails in the background

  - by Tam

  I want to implement a reliable mailing system with Ruby on Rails that sends emails in the background as sending email sometimes takes like 10 seconds or more so I don't want the user to wait. Some ideas I thought of: 1- Write to a table in DB a have a background process that go over and send email (concern: potential many reads/writes to DB slows down my application) 2- Messaging Queue background process / Rake task (concern: if server crashes queued mails will be lost also might eat up a lot of memory if many emails) I was wondering if you a know of a good solution that provides a balance between reliability and performance.

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• C++ Urban Myths

  - by Neil Butterworth

  I'm starting to write an article on what I'm calling "C++ Urban Myths" - that is, ideas and conceptions about C++ that are common but have no actual roots in reality. Some that I've come up with so far are: TR1 is part of standard C++ TR1 (technical Report #1) proposed a whole bunch of changes to C++. Unfortunately, it was never accepted. It is faster to use iterators to access a vector than operator[] Or vice versa. All tests I've carried out indicate the two are nearly identical in performance. The C++ Standard contains something called the STL It doesn't - neither "STL" nor "Standard Template Library" appear in the Standard. I'm wondering if the SO C++ community can come up with any better ones? Ideally, they should be expressible in a single sentence, and not involve any code. Edit: I guess I didn't make it clear enough that I was interested in myths believed by C++ developers, not misconceptions held by non-C++users. Oh well...

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• Seeking tutorial: introduction to ODBC with Delphi

  - by mawg

  I have a lot of embedded C/C++/Ada experience and an outdated smattering of Delphi plus some database stuff. Now I have to implement an app in Delphi which can manipulate MySql, Oracle, maybe MS Access. In short, I need ODBC. I need to programmatically created a database, define its structure and populate its contents, then later query its existence and programmatically search. I would prefer not to use 3rd party components, unless there is a compelling reason to do so (performance ought not to be an issue for the app, it won't have much data or be run often, at least not in v1.0) . Can anyone point me at a tutorial which can get me up to speed? Thanks

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• How do I use compiler intrinsic __fmul_?

  - by Eric Thoma

  I am writing a massively parallel GPU application. I have been optimizing it by hand. I received a 20% performance increase with _fdividef(x, y), and according to The Cuda C Programming Guide (section C.2.1), using similar functions for multiplication and adding is also beneficial. The function is stated as this: "_fmulrn,rz,ru,rd". __fdividef(x,y) was not stated with the arguments in brackets. I was wondering, what are those brackets? If I run the simple code: int t = __fmul_(5,4); I a compiler error about how _fmul is undefined. I have the CUDA runtime included, so I don't think it is a setup thing; rather it is something to do with those square brackets. How do I correctly use this function? Thank you.

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• BDD-testing using a UI driver (e.g. Selenium for a web-application)

  - by jonathanconway

  Can BDD (Behavior Driven Design) tests be implemented using a UI driver? For example, given a web application, instead of: Writing tests for the back-end, and then more tests in Javascript for the front-end Should I: Write the tests as Selenium macros, which simulate mouse-clicks, etc in the actual browser? The advantages I see in doing it this way are: The tests are written in one language, rather than several They're focussed on the UI, which gets developers thinking outside-in They run in the real execution environment (the browser), which allows us to Test different browsers Test different servers Get insight into real-world performance Thoughts?

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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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• 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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• Aggregate functions in ANSI SQL

  - by morpheous

  I want to use multiple aggregate functions in a query. All the examples i have seem on aggregate functions however, are trivial. Typically, they are of the form: SELECT field1,agg_func1, agg_func2 GROUP BY SOME_COLUMNS HAVING agg_func1 OP SOME_SCALAR Where: OP: is a boolean operator (e.g. <, = etc) SOME_SCALAR: is a scalar (i.e. a constant number) What I want to know is if it is possible to write (IN ANSI SQL) queries like: SELECT field1,agg_func1, agg_func2, agg_func3 GROUP BY SOME_COLUMNS HAVING (agg_func1 OP1 agg_func2) OP2 (agg_func2 OP3 agg_func3) Where: OP[N] are boolean operators or ANSI SQL clause operators like 'BETWEEN', 'LIKE', 'IN' etc. Also, assuming this is possible (I have not seen any documentation saying otherwise) are there any efficiency/performance considerations (i.e. penalties) when the HAVING clause consists of a boolean expression combining the output of the aggregate functions - instead of the normal comparison of the output of the aggregate with a constant number (e.g. min('salary') 100 ) - which is often used in the most banal examples involving aggregate functions?

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• Database indexes - what should they be

  - by WebweaverD

  Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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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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• 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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• Implications of Fulltext Search over many columns

  - by Alex

  Hello, I have a really wide table which includes separate columns for billing address, shipping address, primary address, names, aliases etc. (I can't normalize this table further, and that's not the question here anyways). I'm implementing SQL Server fulltext search, and I'm wondering whether I should limit the search ability to just the primary fields (primary address and names for example), or if I can extend the search ability across all columns without occurring too much of a performance or memory penalty. I've done some basic testing with 10,000 sample rows and it's quite fast but I don't have much experience with fulltext indexing, especially its dictionary internals, so I don't know if the index is going to grow over time, or if there is anything else to consider. Thoughts?

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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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