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  • How to implement B+ Tree for file systems ?

    - by user312544
    I have a text file which contains some info on extents about all the files in the file system, like below C:\Program Files\abcd.txt 12345 100 23456 200 C:\Program Files\bcde.txt 56789 50 26746 300 ... Now i have another binary which tries to find out about extents for all the files. Now currently i am using linear search to find extent info for the files in the above mentioned text file. This is a time consuming process. Is there a better way of coding this ? Like Implementing any good data structure like BTree. If B+ Tree is used what is the key, branch factor i need to use ?

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  • Is there a library / tool to query MySQL data files (MyISAM / InnoDB) without the server? (the SQLit

    - by MGW
    Oftentimes I want to query my MySQL data directly without a server running or without having access to the server (but having read / write rights to the files). Is there a tool or maybe even a library around to query MySQL data files like it is possible with SQLite? I'm specifically looking for InnoDB and MyISAM support. Performance is not a factor. I don't have any knowledge about MySQL internals, but I presume it should be possible to do and not too hard to get the specific code out? Thank you for any suggestions!

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  • SVG Animation in Python? - Any options other than Things! 0.4?

    - by ThantiK
    I recently gave my daughter some time on the computer, and she really likes a program called 'BabySmash!', and I also have another program that came with a keyboard attachment called 'Laugh, Smile & Learn' from playschool I think. I'm not a python guru by any stretch of the imagination and I kind of have it in my head that I want to create some sort of program in the spirit of these two, with vector animation and sounds. Thing is, it doesn't look like there are many options for vector animation in python. I found a library called Things! 0.4, but it's lacking in-depth documentation and seems to be more of an experiment in vector animation rather than a full blown solution. Are there any options that I'm not immediately finding? What other animation-libraries do you recommend? Even if the library isn't vector-based, ease of use is probably the strongest factor in my use.

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  • Pattern matching for lambda expressions

    - by alphomega
    21 --Primitive recursion constructor 22 pr :: ([Int] -> Int) -> ([Int] -> Int) -> ([Int] -> Int) 23 pr f g = \xs 0 -> f xs 24 pr f g = \xs (y+1) -> g xs y ((pr f g) xs y) I want the function this function creates to act differently on different inputs, so that it can create a recursive function. As expected, the above code doesn't work. How do I do something like pattern matching, but for the function it creates? Thanks

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  • Getting started with Android code samples - permissions error

    - by StevenX
    New to android. Running Eclipse on Ubuntu 9.10 with Android SDK plugin installed and working. Trying to get some code samples from http://developer.android.com/resources/samples/get.html , and following its procedure to load said samples in Eclipse yields: Parent of resource: /home/user/android-sdk/platforms/android-4/samples/Notepad/.project is marked as read-only. chmod is not recursive, so I entered ~/android-sdk/platforms and "chmod 777 *" ie. all folders in /platforms. Still doesnt work. Appears to be be a bug in Eclipse that wants to create the project in the SDK folder rather than under ~/workspace.

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  • In what circumstances can large pages produce a speedup ?

    - by timday
    Modern x86 CPUs have the ability to support larger page sizes than the legacy 4K (ie 2MB or 4MB), and there are OS facilities (Linux, Windows) to access this functionality. The Microsoft link above states large pages "increase the efficiency of the translation buffer, which can increase performance for frequently accessed memory". Which isn't very helpful in predicting whether large pages will improve any given situation. I'm interested in concrete, preferably quantified, examples of where moving some program logic (or a whole application) to use huge pages has resulted in some performance improvement. Anyone got any success stories ? There's one particular case I know of myself: using huge pages can dramatically reduce the time needed to fork a large process (presumably as the number of TLB records needing copying is reduced by a factor on the order of 1000). I'm interested in whether huge pages can also benefit more mundane applications though.

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  • How to see variable in calling function in visual studio?

    - by carter-boater
    Hi all, Does anyone know how to watch a variable in calling function. For example: C#: void fn a() { int myVar=9; b(); } b() { Throw new Exception(); } How can I watch myVar when I get the exception in function b?? I have a really big recursive function with in a loop and get an exception in one iteration. I don't know which iteration it belongs to$%^&*(. The thing I did was to promote my intersted variable to global so I can watch them anywhere. However, I don't think that's a good idea only for debug. Thanks everyone!

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  • Pre-cache site as user visits

    - by strager
    I am making a static site which is 'forced' to be cached via Cache-control, etc. When a user visits my site, I want the browser to crawl my site, caching pages, so when the user navigates to a page, the load is almost instant. (I do not need a recursive crawl, as that will probably happen as the user navigates between pages. I just need to crawl the links on the current page, and of course not re-caching a page which has already been cached.) (Also, I am not changing pages using Ajax-like techniques. These are essentially normal flat HTML files with normal links.) How can I do this pre-caching using Javascript? (I am using jQuery.)

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  • Refactoring multiple if statements for user authentication with subdomains

    - by go minimal
    I'm building a typical web app where once a user signs up they access the app through their own subdomain (company.myapp.com). The "checking what kind of user if any is logged in" piece is starting to get very hairy and it obviously needs to be well-written because its run so often so I was wondering how you guys would re-factor this stuff. Here are the different states: A user must be logged in, the user must not have a company name, and the sub-domain must be blank A user must be logged in, the user must have a company name, that company name must match the current sub-domain A user must be logged in, the user must have a company name, that company name must match the current sub-domain, and the user's is_admin boolean is true if !session[:user_id].nil? @user = User.find(session[:user_id]) if @user.company.nil? && request.subdomains.first.nil? return "state1" elsif [email protected]? if @user.company.downcase == request.subdomains.first.downcase && [email protected]_admin return "state2" elsif @user.company.downcase == request.subdomains.first.downcase && @user.is_admin return "state3" end end end

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  • How to hash and check for equality of objects with circular references

    - by mfya
    I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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  • MS Access vs SQL Server and others ? Is it worth taking a db server when less than 2 Gb and only 20

    - by asksuperuser
    After my experiment with MSAccess vs MySQL which shows MS Access hugely overperforming Mysql odbc insert by a factor 1000% before I would do the same experiment with SQL Server I searched for some other's people and found this one: http://blog.nkadesign.com/2009/access-vs-sql-server-some-stats-part-1/ which says "As a side note, in this particular test, Access offers much better raw performance than SQL Server. In more complex scenarios it’s very likely that Access’ performance would degrade more than SQL Server, but it’s nice to see that Access isn’t a sloth." So is worth bother with some db server when data is less than 2 Gb and users are about 20 (knowing that MS Access theorically supports up to 255 concurrent users though practically it's around a dozen concurrent users only). Are there any real world studies that really compare MS Access with other db in these specific use case ? Because professionaly speaking I keep hearing people systematically recommend DB server from people who have never used Access just because they think DB Server can only perform better in every case which I used to think myself I confess.

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  • ggplot add percentage labels based on x-axis variables

    - by eugeneyan
    I've a ggplot that shows the counts of tweets for some brands as well as a label for the overall percentage. This was done with much help from this link: ggplot: showing % instead of counts in charts of categorical variables # plot ggplot of brands ggplot(data = test, aes(x = brand, fill = brand)) + geom_bar() + stat_bin(aes(label = sprintf("%.02f %%", ..count../sum(..count..)*100)), geom = 'text', vjust = -0.3) Next, I would like to plot it based on brand and sentiment, with the labels for the bars of each brand totalling up to 100%. However, I have difficulty amending my code to do this. Would you be able to help please? Also, would it be possible to change the colours for neu to blue and pos to green? # plot ggplot of brands and sentiment ggplot(data = test, aes(x = brand, fill = factor(sentiment))) + geom_bar(position = 'dodge') + stat_bin(aes(label = sprintf("%.02f %%", ..count../sum(..count..)*100)), geom = 'text', position = position_dodge(width = 0.9), vjust=-0.3)

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  • How can I convert SQL comments with -- to # using Perl?

    - by NJTechie
    I have various SQL files with '--' comments and we migrated to the latest version of MySQL and it hates these comments. I want to replace -- with #. I am looking for a recursive, inplace replace one-liner. This is what I have: perl -p -i -e 's/--/# /g'` ``fgrep -- -- * A sample .sql file: use myDB; --did you get an error I get the following error: Unrecognized switch: --did (-h will show valid options). p.s : fgrep skipping 2 dashes was just discussed here if you are interested. Any help is appreciated.

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  • Perl: Fastest way to get directory (and subdirs) size on unix - using stat() at the moment

    - by ivicas
    I am using Perl stat() function to get the size of directory and it's subdirectories. I have a list of about 20 parent directories which have few thousand recursive subdirs and every subdir has few hundred records. Main computing part of script looks like this: sub getDirSize { my $dirSize = 0; my @dirContent = <*>; my $sizeOfFilesInDir = 0; foreach my $dirContent (@dirContent) { if (-f $dirContent) { my $size = (stat($dirContent))[7]; $dirSize += $size; } elsif (-d $dirContent) { $dirSize += getDirSize($dirContent); } } return $dirSize; } The script is executing for more than one hour and I want to make it faster. I was trying with the shell du command, but the output of du (transfered to bytes) is not accurate. And it is also quite time consuming. I am working on HP-UNIX 11i v1.

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  • Storing expression template functors

    - by UncaughtException
    Hello guys, at the moment I'm really interested in expression templates and want to code a library for writing and differentiating mathematical functions with a lambda-style syntax. At the moment, I'm able to write (_x * _x)(2); and get the correct result 4. But I would really like to do something like MathFunction f = _x * _x; f(2);, but I don't have any ideas on how to cope with the recursive expression templates on the right side. Is it possible to achieve this without using the 'auto'-Keyword instead of MathFunction or having to make the operator() virtual? Thanks for your help!

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  • What are some practical uses of generating all permutations of a list, such as ['a', 'b', 'c'] ?

    - by Jian Lin
    I was asked by somebody in an interview for web front end job, to write a function that generates all permutation of a string, such as "abc" (or consider it ['a', 'b', 'c']). so the expected result from the function, when given ['a', 'b', 'c'], is abc acb bac bca cab cba Actually in my past 20 years of career, I have never needed to do something like that, especially when doing front end work for web programming. What are some practical use of this problem nowadays, in web programming, front end or back end, I wonder? As a side note, I kind of feel that expecting a result in 3 minutes might be "either he gets it or he doesn't", especially I was thinking of doing it by a procedural, non-recursive way at first. After the interview, I spent another 10 minutes and thought of how to do it using recursion, but expecting it to be solved within 3 minutes... may not be a good test of how qualified he is, especially for front end work.

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  • Ideas for band site, which technology to use?

    - by brux
    I am attempting to design and build a website for my friends band. There is minimal content to be included such as bio,news,enbemdded Audio/Visual material. My web dev expertise is average. I'm basicaly looking for inspiration, I was edging towards embedding a silverlight deepzoom xap object to add some visual stimulation, perhaps by featuring a high res photo of the bandshardware/equipment which zooms when mouseover occurs. Does anyone have any cool ideas for a central feature for this site, and which way to approact it in terms of technique (js,css,silverlight etc) If anyone has any immediate ideas which they think would be cool then I am eager to hear them! Also if anyone can link me to any cool band sites they have come across recently I would be greatful,nothing too complicated though please I will be doing all the work myself. Im want the site to be simple but have a certain wow factor!

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  • scaleX scaleY increasing left, top margin, and line spacing

    - by Mark
    If you have Text with a font that is 72 point for example (and scaleX scaleY = 1) you can achieve the same size with a font size of 12 and scaleX,scaleY = 6. For reasons that would take too long to explain I am applying a large scale factor as in the latter example. The problem is, even though the text is the same size, the line spacing and left and top margins have all been increased but I want them to be the same size as well. As far as the line spacing, I discovered that TextFormat.leading was being automatically increased when scaleX, scaleY was greater than 1, so I just had to reset TextFormat.leading back to 0. That leaves the left and top margins, and I have no idea how those are being increased. I tried TextFormat.blockIndent=0 and TextFormat.leftMargin=0 (and also ignorePadding=true) and it had no effect. And have no clue how to reset the top margin either to its orginal size, in case anyone has an idea for all these.

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  • Python 3: Recursivley find if number is even

    - by pythonhack
    I am writing a program that must find if a number is even or not. It needs to follow this template. I can get it to find if a number is even or not recursively (call function and subtract 2, base case zero), but I am having a hard time following this template, based on how the isEven function is called in the main function. Any help would be greatly appreciated. Write a recursive function called isEven that finds whether a number is even or not: def isEven() #recursivley determine whether number is even or not def main(): number=int(input(“Enter a number : “)) if (isEven(number)): print(“Number is even”) else: print(“Number is not even”) main() Thank you! Appreciate it.

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  • Mix and match class in C++/MFC

    - by Coder
    I'm trying to re-factor a code base, and there is some common functionality among unrelated classes that I'd love to unite. I would like to add that functionality in common base class, but I'm not sure if it's clean and good approach. Say I have CMyWnd class and CMyDialogEx class, both different, so they cannot inherit from one base class. I want to add a button to both classes and add the message handlers to both classes as well. So I'd like to do something like this: CMyWnd : public CWnd, public COnOkBtnFunctionality, public COnCancelBtnFunctionality CMyDialogEx: public CWnd, public COnOkBtnFunctionality Where COnOkBtnFunctionality would define CButton m_buttonOk, and all the afx_msg functions it should have. And so on. Is this approach doable/good? Or are there better patterns I should resort to?

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  • Sound sample recognition library/code

    - by Daniel Mošmondor
    I don't want sound-to-text software. What I need is the following: I'll record multiple (say 50+) audio streams (recordings of radio stations) from that recordings, I'll mark interesting audio clips - their length ranges from 2 to 60 seconds - there will be few thousands of such audio clips library should be able to find other instances of same audio clips from recorded sound streams confidence factor should be reported to used and additional input provided so the recognition could perform better next time Do you know of such software library? LGPL would be most valuable to me, but I can go for commercial license as well.

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  • Best choice for off-site backup: dd vs tar

    - by plok
    I have two 1TB single-partition hard disks configured as RAID1, of which I would like to make an off-site backup on a third disk, which I am still to buy. The idea is to store the backup at a relative's house, considerably far away from my place, in the hope that all the information will be safe in the case of a global thermonuclear apocalypse. Of course, this backup would be well encrypted. What I still have to decide is whether I am going to simply tar the entire partition or, instead, use dd to create an image of the disks. Is there any non-trivial difference between these two approaches that I could be overlooking? This off-site backup would be updated no more than two or three times a year, in the best of the cases, so performance should not be a factor to be pondered at all. What, and why, would you use if you were me? dd, tar, or a third option?

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  • File.Exists() returns false, but not in debug

    - by Tor Haugen
    I'm being completely confused here folks, My code throws an exception because File.Exists() returns false public override sealed TCargo ReadFile(string fileName) { if (!File.Exists(fileName)) { throw new ArgumentException("Provided file name does not exist", "fileName"); } Visual studio breaks at the throw statement, and I immediately check the value of File.Exists(fileName) in the immediate window. It returns true. When I drag the breakpoint back up to the if statement and execute it again, it throws again. fileName is an absolute path to a file. I'm not creating the file, nor writing to it (it's there all along). If I paste the path into the open dialog in Notepad, it reads the file without problems. The code is executing in a background worker. It's the only complicating factor I can think of. I am positive the file has not been opened already, either in the worker thread or elsewhere. What's going on here?

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  • Tree + Recursion..

    - by RBA
    Hi.. I came across an article on Binary Trees Search . It uses intensive Recursive Algorithms.. I am just so confused with these stuff.. Please guide my path so as I understand these problems at ease, or any good website to read about recursion first and then solving these problems.. Please share your experience on it.. Its very urgent, and I want to learn these concepts as soon as possible.. Thankss... Regards.

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  • wget: retrieving files recursively

    - by Shadow
    When using wget with the recursive option turned on I am getting an error message when it is trying to download a file. It thinks the link is a downloadable file when in reality it should just be following it to get to the page that actually contains the files that I want. wget -r -l 16 --accept=jpg website.com The error message is: .... since it should be rejected. This usually occurs when the website link it is trying to fetch ends with a sql statement. The problem however doesn't occur when using the very same wget command on that link. I want to know how exactly it is trying to fetch the pages. I guess I could always take a poke around the source although I don't know how messy the project is.

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