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• mysql, sqlite database source code

  - by Yang

  hi guys, i know implementing database is a huge topic, but i want to have a basic understanding of how database systems works (e.g. memory management, binary tree, transaction, sql parsing, multi-threading, partitions, etc) by investigating the source code of the database, since there are a few already proven very robust open source databases like mysql, sqlite and so on. however, the code are very complicated and i have no clue where to start. also i find that the old school database textbooks are only explaining the theory, not the implementation details. Can anyone suggest how should i get started and is there any books that emphasis on the technology and techniques of building dbms used in modern database industry? Thank in advance!

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• Determining the hostname/IP address from the MX record in PHP

  - by pmmenneg

  Hi there, have a basic email domain validation script that takes a user's email domain, resolves the IP address from that and then checks that against various published blacklists. Here is how I am determining the IP: $domain = substr(strchr($email, '@'), 1); $ip = gethostbyname($domain); The problem is that some email address domains, such as [email protected], use an MX record rather than an A record, so using gethostbyname('alumni.example.net') will fail to resolve. I know when a user's email is using an MX in the email itself by using the PHP checkdnsrr function, but once at that stage am a little stuck as to how to proceed. In theory, I could parse out the 'root' domain, i.e. 'example.net' and check it, but I've not found reliable regex that can handle this task when the user could easily have an email the format of [email protected]... So, any suggestions on how to best tackle this??

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• Which is faster in Python: x**.5 or math.sqrt(x)?

  - by Casey

  I've been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power? UPDATE This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works? I sent Guido van Rossum an email cause I really wanted to know the differences in these methods. My email: There are at least 3 ways to do a square root in Python: math.sqrt, the '**' operator and pow(x,.5). I'm just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better? His response: pow and ** are equivalent; math.sqrt doesn't work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea...

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• Can I use ido-completing-read instead of completing-read everywhere?

  - by haxney

  I'm a big fan of ido-mode, so much so that I would like to use it for things like describe-function or find-tag and so on, without having to write something like in "Can I get ido-mode-style completion for searching tags in Emacs?" for each one. Both (defalias completing-read ido-completing-read) and (setf 'completing-read 'ido-completing-read) don't work, at least partly because ido-completing-read calls completing-read in its body, so any simple redefinition would result in infinite recursion. In theory, it should be possible, since the first line of the docstring for ido-completing-read is "Ido replacement for the built-in completing-read." I've looked around a bit and can't seem to find anyone else who has attempted or succeeded at it. I realize that Icicles [2] probably provides something like this, and I may end up going with that anyway, but it is a bit more of a plunge than I care to take right now. Thanks for any help.

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• Event based scheduling in excel

  - by andreas

  Hey fellas! Where i am working we have a number of contractor programmers. We handle the requirements and the project management of our products. I have been trying using various project timing and estimations techniques but cant get the hang of it yet. I have read Joel's evidence based scheduling and i was wondering if there's anything out there that can help me apply that theory? not looking for complex software but perhaps something in excel? Any help will be appreciated Andreas

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• Event based PROJECT MANAGEMENT

  - by andreas

  Hey fellas! Where i am working we have a number of contractor programmers. We handle the requirements and the project management of our products. I have been trying using various project timing and estimations techniques but cant get the hang of it yet. I have read Joel's evidence based scheduling and i was wondering if there's anything out there that can help me apply that theory? not looking for complex software but perhaps something in excel? Any help will be appreciated Andreas

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• Interview questions for junior C and C++ developer position

  - by Ondrej Slinták

  What interview questions should people expect as a junior C and C++ developer? Code questions or more of theory? Solutions in pseudo-code or in C code? Maybe I'm misinterpreting the word "junior", but I have no idea what would anyone ask me if I have no C work experiences. I'm bit afraid of tricky questions with pointers, so I'd like to be sure what should I look up before actually going there. I'm a junior PHP developer with 1 year of experiences, if it helps the question. Hope it isn't duplicate as I'm asking particularly about junior developer job.

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• Small web-framework like Sinatra, Ramaze etc in .NET

  - by Christian W

  Are there any similar frameworks like Sinatra, Ramaze etc in .NET? I'm in theory after a framework that let's me create an entire webapp with just one classfile (conceptually) like Sinatra. I'm going to use it for something work-internal, where ASP.NET MVC is too "big" (and I get confused by it's usage) and I have WebForms up to my ears right now (doing a big webforms based project, currently hating it ;) ) Any suggestions? Oh, and I need to be able to host it in IIS. I would go for IronRuby with Sinatra, but I can't find a step-by-step tut for setting it up in IIS ;)

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• Good implementations of reinforced learning?

  - by Paperino

  For an ai-class project I need to implement a reinforcement learning algorithm which beats a simple game of tetris. The game is written in Java and we have the source code. I know the basics of reinforcement learning theory but was wondering if anyone in the SO community had hands on experience with this type of thing. What would your recommended readings be for an implementation of reinforced learning in a tetris game? Are there any good open source projects that accomplish similar things that would be worth checking out? Thanks in advanced Edit: The more specific the better, but general resources about the subject are welcomed. Follow up: Thought it would be nice if I posted a followup. Here's the solution (code and writeup) I ended up with for any future students :). Paper / Code

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• 2d terrain generation in real time

  - by Skoder

  Hey, I'm trying to create a game similar to this (Note:When you click 'play', there are SFX in the game which you can't seem to turn off, so you may want to check volume). In particular, I'm interested in knowing how the 'infinite' landscape is generated. Are there any tutorials/articles describing this? I came across procedural generation, but I'm not quite sure what topics I should be looking for (or if it's even procedural generation). (I'm using C#, but I don't mind the language as I assume the theory behind it remains the same) Thanks for any suggestions

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• WPF UC in Winforms occasionally has an odd border to the left / visually corrupted

  - by Ryan ONeill

  I have a WPF user control I created that is used to show the state of tasks in my UI. I get the odd report back that the control sometimes has a nasty looking border to the left and I cannot reproduce it. The control looks like this (when working) (grey tick=not run, green=OK,red cross=fail,hourglass=running); It looks like this when the problem occurs; It may have something to do with the layering of those icons, when the state changes the others are made invisible and the relevant icon is made visible. The four icons are all stacked on top of each other. It could also be the background in theory, which I'll look at next. Problem is reported on both flat panel and CRT displays. Any guidance greatly appreciated. Update: 1) SnapsToDevicePixels does not affect the issue. 2) Grid is not used, only a canvas.

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• Are these AVAudioSettings right?

  - by Dyldo42

  self.recordSettings = [NSMutableDictionary dictionary]; [recordSettings setValue:[NSNumber numberWithInt:kAudioFormatAppleIMA4] forKey:AVFormatIDKey]; [recordSettings setValue:[NSNumber numberWithFloat:44100.0] forKey:AVSampleRateKey]; [recordSettings setValue:[NSNumber numberWithInt:1] forKey:AVNumberOfChannelsKey]; recordSettings is declared in my view's header file and initialised in its viewDidLoad method. For some reason, everything is working in the simulator, but on a device, the [recorder record] method is returning NO. The only theory I have is that something in the recordSettings isn't compatible with an actual device. Any ideas?

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• MySQl Error #1064

  - by 01010011

  Hi, I keep getting this error: MySQL said: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO books.book(isbn10,isbn13,title,edition,author_f_name,author_m_na' at line 15 with this query: USE books; DROP TABLE IF EXISTS book; CREATE TABLE `books`.`book`( `book_id` INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, `isbn10` VARCHAR(15) NOT NULL, `isbn13` VARCHAR(15) NOT NULL, `title` VARCHAR(50) NOT NULL, `edition` VARCHAR(50) NOT NULL, `author_f_name` VARCHAR(50) NOT NULL, `author_m_name` VARCHAR(50) NOT NULL, `author_l_name` VARCHAR(50) NOT NULL, `cond` ENUM('as new','very good','good','fair','poor') NOT NULL, `price` DECIMAL(8,2) NOT NULL, `genre` VARCHAR(50) NOT NULL, `quantity` INT NOT NULL) INSERT INTO books.book(isbn10,isbn13,title,edition,author_f_name,author_m_name,author_l_name,cond,price,genre,quantity)** VALUES ('0136061699','978-0136061694','Software Engineering: Theory and Practice','4','Shari','Lawrence','Pfleeger','very good','50','Computing','2'); Any idea what the problem is?

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• SSD and programming

  - by Simon Johnson

  I'm trying to put together a business case for getting every developer in our company an Intel SSD drive. The main codebase contains roughly 400,000 lines of code. My theory is that since the code is scattered about in maybe 1500 files, an SSD drive would be substantially faster for compiles. The logic being that many small reads really punishes the seak-time bottle-neck of a traditional hard-drive. Am I right? Is SSD worth the money in productivity gains by reducing the edit/compile cycle time?

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• Slow SQLite access on iPhone

  - by georgij

  I have a quite slow data retrieval from a sqlite database on my iPhone and perhaps someone have an alternative idea to explain this. From what I tracked down so far sqlite3_step(statement) is sometimes unusually slow. While retrieving e.g. 50 rows from the database to execute this step takes normally some milliseconds but sometimes it takes several seconds. My database is not small (80MB) and my theory is that the reason is paging. But can someone else think of an other reason for this?

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• How would I / could I obtain an reasonably comprehensive list of domain names?

  - by Simon

  I know that domain names are constantly changing, and I know there are a lot of them, but there is clearly a region of the domain name space which is stable. How would I go about getting a list, even a very big one? Such a thing must logically exist, even if it is in a distributed form, because the web's DNS servers resolve names to IP addresses. So in theory if I could poll all the DNS servers in the world at a moment in time I would have the complete list of mapped names. Is there a practical way of doing that? As an aside, does anyone have any good estimates of how many domain names exist at the moment?

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• Master's in Software Engineering vs. Master's in Computer Science: which degree is preferred by empl

  - by dbarker

  I've been building software professionally for 7 years and am considering a master's degree. I understand the difference between these two degrees as simply: MSCS is the theory while MSE is the practice. I'm equally interested in both and would be happy with either, although I'm curious how these degrees rank in the eyes of a potential employer. I could see two views that a hiring manager could possibly take: a MSCS is loftier and has an implied knowledge of Software Engineering an MSE is more practical and has an implied knowledge of Computer Science In my own experience I've seen both MSCS degree holders than cannot program at all while others are among the best programmers I've met, so of course actual ability will depend on the individual. My question is about the "on paper" value of these two degrees when seeking a job. All things considered, is one degree more hirable, higher-paying than the other?

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• Broadcast-style Bluetooth using Sockets on the iPhone?

  - by Kyle

  Is there any way to open a broadcast bluetooth socket, take a listen and send replies? I want a proper peer to peer system where I broadcast and listen for broadcasts in an area. That way, variable clients can mingle. Is this possible? My theory is this: If GameKit can sit around wasting 25 seconds of the users time whilst having access to a broadcast socket, can't I? Or, must I be in kernel mode for such access? I'm not really sure where the proper bluetooth headers are as well. Thanks for reading!

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• Is it possible for competing file access to cause deadlock in Java?

  - by BlairHippo

  I'm chasing a production bug that's intermittent enough to be a real bastich to diagnose properly but frequent enough to be a legitimate nuisance for our customers. While I'm waiting for it to happen again on a machine set to spam the logfile with trace output, I'm trying to come up with a theory on what it could be. Is there any way for competing file read/writes to create what amounts to a deadlock condition? For instance, let's say I have Thread A that occasionally writes to config.xml, and Thread B that occasionally reads from it. Is there a set of circumstances that would cause Thread B to prevent Thread A from proceeding? My thanks in advance to anybody who helps with this theoretical fishing expedition. Edit: To answer Pyrolistical's questions: the code isn't using Filelock, and is running on a WinXP machine.

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• Supporting different locale regions using Rails i18n

  - by Olly

  I'm using the standard Rails I18n API to localise some of our views. This is working really well, but we now have a few use cases for regional changes to the en locale. The API guide mentions that this isn't supported directly, and other plugins should be used. However, I'm wondering whether there's a simpler way to do this. I already have en.yml, so in theory I could just create en-AU.yml and en-US.yml which are effectively clones of en.yml but with a few regional changes applied. I could then add additional English - American and English - Australian options to our configuration which would map to the new region-specific locales and allow users to use a region-specific locale. The only problem I can think of with this is that it isn't DRY -- I would have duplicate translations for all common English words. I can't see a way around this. Are there any other disadvantages to this approach, or should I just bite the bullet and dive into one of the plug-ins such as Globalize2 instead?

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• QT: Scroll widget that renders directly to the DC

  - by shoosh

  I'm trying to create a widget which paints directly to the windows Device Context by calling getDC() and painting an HBITMAP to it. The widget I'm painting resides inside a scroll widget. I've implemented the paintEvent() and it does seem to paint but immediatly after painting the widget gets painted over again with a blank gray color. I've tried setting WA_PaintOnScreen and Qt::WA_NoSystemBackground but none of those help. In theory this should be possible since this is basically how the GLWidget works. What am I missing?

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• Is there a 3 way merger tool that “understands” common refactoring?

  - by Ian Ringrose

  When a simple refactoring like “rename field” has been done on one branch it can be very hard to merge the changes into the other branches. (Extract method is much harder as the merge tools don’t seem to match the unchanged blocks well) Now in my dreams, I am thinking of a tool that can record (or work out) what well defined refactoring operations have been done on one branch and then “replay” them on the other branch, rather than trying to merge every line the refactoring has affected. see also "Is there an intelligent 3rd merge tool that understands VB.NET" for the other half of my pain! Also has anyone try something like MolhadoRef (blog article about MolhadoRef and Refactoring-aware SCM), This is, in theory, refactoring-aware source control.

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• Good "Modelling & Simulation" book recommendations for programmers?

  - by Harry

  I'm a programmer, and have completely forgotten all the advanced engineering Math I studied ~20 years ago at school. I now have an urgent need to learn about Modelling and Simulation. Though the present context is Disease Modelling, I'm not sure if there's such a thing as 'general' modelling and simulation... with concepts / techniques / algorithms that could be used in just about any domain (and not just limited to biology, finance, trade, economic, weather, etc.) Would you have any recommendations that are easy to read by a semi-Math-literate programmer? Basically, I cannot afford to drown myself in too much Math and theory behind M & S, hence this post. Tia...

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• Should I typecast in PHP when defining my vars?

  - by Borislav

  I am sorry if this is more of a theory question then a real life problem but it is a real life situation for me. We were commenting on the way PHP works with vars and how memory heavy it is on the server due to its "mixed vars" and something occured to me - why not typecast right from the start? So I guess my quesion is: Whould it make any difference for the server load if all you PHP vars were"pre-casted"? Example: protected $_id; VS protected (int) $_id;

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• Inverted index in a search engine

  - by Ayman

  Hello there, I'm trying to write some code to make a small application for searching text from files. Files should be crawled, and I need to put an inverted index to boost searches. My problem is that I kind of have ideas about how the parser would be, I'm willing to implement the AND, NOT, OR in the query. Whereas, I couldn't figure out how my index should be... I have never created an inverted index so if any body could suggest a feasable way to do it I would be very grateful... I do know in theory how it works but my problem is I absolutely have no idea to make happen in MySql I need to give keywords being indexed a weight too... Thank you so much.

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