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  • Fast find near users using PostGIS

    - by opedge
    I have 5 tables: - users - information about user with current location_id (fk to geo_location_data) - geo_location_data - information about location, with PostGIS geography(POINT, 4326) column - user_friends - relationships between users. I want to find near friends for current user, but it takes a lot of time of executing select query to know if user is a friend and after that execute select using ST_DWithin.. May be something wrong in domain model or in queries?

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  • ASP.NET - fast Segmented downoad of file through webservice

    - by H4mm3rHead
    Hi, Im doing this project where i need to download files through a webservice (images, videos). The download MUST go through an existing webservice. The existing webservice was made when there were no need to upload and download files but the project has changed and now we need to do It through a webservice. Right now I have implemented the download as a method that returns a byte[], I open a streamreader and resds the entire file into a byte[] and returns it to my method. This is working file on small files <~1Mb, above it takes too long time. I want to show some progress (e.g. when the user downlaods a 20Mb video) which i cannot do right now. And i want to make it download much faster (is a strategy to use multithreading and several threads that downloads a part of the file?). It is within a WPF application i need to do this. Any ideas on how to approach this?

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  • Fast CGI, Lighttpd, Ubuntu

    - by Gosh
    Is this log file familiar to someone of UBUNTU users? Lighttpd log file: > 2009-08-30 21:37:45: (log.c.75) server started > 2009-08-30 21:37:45: (mod_fastcgi.c.1029) the fastcgi-backend php5-cgi *failed* to start: > 2009-08-30 21:37:45: (mod_fastcgi.c.1033) *child exited with status 9 php5-cgi* > 2009-08-30 21:37:45: (mod_fastcgi.c.1036) If you're trying to run PHP as a FastCGI backend, make sure you're using the FastCGI-enabled version. > You can find out if it is the right one by executing 'php -v' and it should display '(cgi-fcgi)' in the output, NOT '(cgi)' NOR '(cli)'. > For more information, check http://trac.lighttpd.net/trac/wiki/Docs%3AModFastCGI#preparing-php-as-a-fastcgi-programIf this is PHP on Gentoo, add 'fastcgi' to the USE flags. > 2009-08-30 21:37:45: (mod_fastcgi.c.1340) [ERROR]: *spawning fcgi failed*. > 2009-08-30 21:37:45: (server.c.908) Configuration of plugins failed. Going down. Please open a secret how did you solved fcgi problem and made lighttpd to start, if you did. Thx, Gosh.

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  • Looking for fast, minimal, preferrably free disc cloning software [closed]

    - by Dave
    We have to test our application installation and functionality on many Windows operating system versions and languages (XP, Vista, Win7; English, Spanish, Portuguese, etc; 32-bit & b4-bit.) While we can do much of this in virtual machines, we have noticed that VM's sometimes hide problems, or raise false bugs. So, we need to do "bare metal" OS installation for much of our testing. I have been using Acronis True Image for the past year, and am not impressed. It often gives random errors which require a reboot, and is really slow. For example, when trying to restore an image, it goes through a "Locking partition" cycle about three times (once after you click OK on each step of the wizard), each of which can take 5 minutes to complete. This all happens BEFORE it actually starts the image copy, which is sometimes quick (3-5 minutes), sometimes long (hours). The size of all of our images are roughly the same, so that is not related. So, anyway, I'm looking to switch to something else: I only need very basic functionality--just creating images of entire discs, and then restoring those images onto the exact same hard drive at a later date. That's it. I'm not opposed to paying for a good piece of software, but if there is something free out there that does the job well, that would be a preference. My OS on which the imaging software would run is Windows Vista, but a bootable media (into a Linux flavor) would be fine also, as long as its quick to use and reliable. Recommendations? (Also, moderators, if this should be a CW, I'll be happy to mark it as such; unclear about the rules there.)

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  • vector collision on polygon in 3d space detection/testing?

    - by LRFLEW
    In the 3d fps in java I'm working on, I need a bullet to be fired and to tell if it hit someone. All visual objects in the game are defined through OpenGL, so the object it can be colliding with can be any drawable polygon (although they will most likely be triangles and rectangles anyways). The bullet is not an object, but will be treated as a vector that instantaneously moves all the way across the map (like the snipper riffle in Halo). What's the best way to detect/test collisions with the polygon and the vector. I have access to OpenCL, however I have absolutely no experience with it. I am very early in the developmental stage, so if you think there's a better way of going about this, feel free to tell me (I barley have a player model to collide with anyways, so I'm flexible with it). Thanks

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  • Fast read of certain bytes of multiple files in C/C++

    - by Alejandro Cámara
    I've been searching in the web about this question and although there are many similar questions about read/write in C/C++, I haven't found about this specific task. I want to be able to read from multiple files (256x256 files) only sizeof(double) bytes located in a certain position of each file. Right now my solution is, for each file: Open the file (read, binary mode): fstream fTest("current_file", ios_base::out | ios_base::binary); Seek the position I want to read: fTest.seekg(position*sizeof(test_value), ios_base::beg); Read the bytes: fTest.read((char *) &(output[i][j]), sizeof(test_value)); And close the file: fTest.close(); This takes about 350 ms to run inside a for{ for {} } structure with 256x256 iterations (one for each file). Q: Do you think there is a better way to implement this operation? How would you do it?

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  • Android AES and init vector

    - by Donald_W
    I have an issue with AES encryptio and decryption: I can change my IV entirely and still I'm able to decode my data. public static final byte[] IV = { 65, 1, 2, 23, 4, 5, 6, 7, 32, 21, 10, 11, 12, 13, 84, 45 }; public static final byte[] IV2 = { 65, 1, 2, 23, 45, 54, 61, 81, 32, 21, 10, 121, 12, 13, 84, 45 }; public static final byte[] KEY = { 0, 42, 2, 54, 4, 45, 6, 7, 65, 9, 54, 11, 12, 13, 60, 15 }; public static final byte[] KEY2 = { 0, 42, 2, 54, 43, 45, 16, 17, 65, 9, 54, 11, 12, 13, 60, 15 }; //public static final int BITS = 256; public static void test() { try { // encryption Cipher c = Cipher.getInstance("AES"); SecretKeySpec keySpec = new SecretKeySpec(KEY, "AES"); c.init(Cipher.ENCRYPT_MODE, keySpec, new IvParameterSpec(IV)); String s = "Secret message"; byte[] data = s.getBytes(); byte[] encrypted = c.doFinal(data); String encryptedStr = ""; for (int i = 0; i < encrypted.length; i++) encryptedStr += (char) encrypted[i]; //decryoption Cipher d_c = Cipher.getInstance("AES"); SecretKeySpec d_keySpec = new SecretKeySpec(KEY, "AES"); d_c.init(Cipher.DECRYPT_MODE, d_keySpec, new IvParameterSpec(IV2)); byte[] decrypted = d_c.doFinal(encrypted); String decryptedStr = ""; for (int i = 0; i < decrypted.length; i++) decryptedStr += (char) decrypted[i]; Log.d("", decryptedStr); } catch (Exception ex) { Log.d("", ex.getMessage()); } } Any ideas what I'm doing wrong? How can I get 256 bit AES encryption (only change key to 32-byte long array?) Encryption is a new topic for me so please for newbie friendly answers.

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  • Matlab - applying low-pass filter to a vector?

    - by waitinforatrain
    If I have a simple low-pass filter, e.g. filt = fir1(20, 0.2); and a matrix with a list of numbers (a signal), e.g. [0.1, -0.2, 0.3, -0.4] etc, how do I actually apply the filter I've created to this signal? Seems like a simple question but I've been stuck for hours. Do I need to manually calculate it from the filter coefficients?

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  • signed angle between two 3d vectors with same origin within the same plane? recipe?

    - by Advanced Customer
    Was looking through the web for an answer but it seems like there is no clear recipe for it. What I need is a signed angle of rotation between two vectors Va and Vb lying within the same 3D plane and having the same origin knowing that: the plane contatining both vectors is an arbitrary and is not parallel to XY or any other of cardinal planes Vn - is a plane normal both vectors along with the normal have the same origin O = { 0, 0, 0 } Va - is a reference for measuring the left handed rotation at Vn The angle should be measured in such a way so if the plane would be XY plane the Va would stand for X axis unit vector of it. I guess I should perform a kind of coordinate space transformation by using the Va as the X-axis and the cross product of Vb and Vn as the Y-axis and then just using some 2d method like with atan2() or something. Any ideas? Formulas?

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  • Fast serarch of 2 dimensional array

    - by Tim
    I need a method of quickly searching a large 2 dimensional array. I extract the array from Excel, so 1 dimension represents the rows and the second the columns. I wish to obtain a list of the rows where the columns match certain criteria. I need to know the row number (or index of the array). For example, if I extract a range from excel. I may need to find all rows where column A =”dog” and column B = 7 and column J “a”. I only know which columns and which value to find at run time, so I can’t hard code the column index. I could use a simple loop, but is this efficient ? I need to run it several thousand times, searching for different criteria each time. For r As Integer = 0 To UBound(myArray, 0) - 1 match = True For c = 0 To UBound(myArray, 1) - 1 If not doesValueMeetCriteria(myarray(r,c) then match = False Exit For End If Next If match Then addRowToMatchedRows(r) Next The doesValueMeetCriteria function is a simple function that checks the value of the array element against the query requirement. e.g. Column A = dog etc. Is it more effiecent to create a datatable from the array and use the .select method ? Can I use Linq in some way ? Perhaps some form of dictionary or hashtable ? Or is the simple loop the most effiecent ? Your suggestions are most welcome.

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  • Hashtable is that fast

    - by Costa
    Hi s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]. Is the hash function of the java string, I assume the rest of languages is similar or close to this implementation. If we have hash-Table and a list of 50 elements. each element is 7 chars ABCDEF1, ABCDEF2, ABCDEF3..... ABCDEFn If each bucket of hashtable contains 5 strings (I think this function will make it one string per bucket, but let us assume it is 5). If we call col.Contains("ABCDEFn"); // will do 6 comparisons and discover the difference on the 7th. The hash-table will take around 70 operations (multiplication and additions) to get the hashcode and to compare with 5 strings in bucket. and BANG it found. For list it will take around 300 comparisons to find it. for the case that there is only 10 elements, the list will take around 70 operations but the Hashtable will take around 50 operations. and note that hashtable operations are more time consuming (it is multiplications). I conclude that HybirdDictionary in .Net probably is the best choice for that most cases that require Hashtable with unknown size, because it will let me use a list till the list becomes more than 10 elements. still need something like HashSet rather than a Dictionary of keys and values, I wonder why there is no HybirdSet!! So what do u think? Thanks

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  • How do you return a pointer to a base class with a virtual function?

    - by Nick Sweet
    I have a base class called Element, a derived class called Vector, and I'm trying to redefine two virtual functions from Element in Vector. //element.h template <class T> class Element { public: Element(); virtual Element& plus(const Element&); virtual Element& minus(const Element&); }; and in another file //Vector.h #include "Element.h" template <class T> class Vector: public Element<T> { T x, y, z; public: //constructors Vector(); Vector(const T& x, const T& y = 0, const T& z =0); Vector(const Vector& u); ... //operations Element<T>& plus(const Element<T>& v) const; Element<T>& minus(const Element<T>& v) const; ... }; //sum template <class T> Element<T>& Vector<T>::plus(const Element<T>& v) const { Element<T>* ret = new Vector((x + v.x), (y + v.y), (z + v.z)); return *ret; } //difference template <class T> Element<T>& Vector<T>::minus(const Element<T>& v) const { Vector<T>* ret = new Vector((x - v.x), (y - v.y), (z - v.z)); return *ret; } but I always get error: 'const class Element' has no member named 'getx' So, can I define my virtual functions to take Vector& as an argument instead, or is there a way for me to access the data members of Vector through a pointer to Element? I'm still fairly new to inheritance polymorphism, fyi.

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  • Fast parsing of PHP in C#

    - by Jessica Shea
    Hello there, I've got a requirement for parsing PHP files in C#. We essentially require some of the devs in another country to upload PHP files and once uploaded we need to check the php files and get a list of all the methods and classes/functions etc. I thought of using a regex but I can't workout if a function belongs to a class etc, so I was wondering if theres already something 'out there' that will parse out PHP files and spit out its functions (I'm trying to avoid writing a full blow AST implementation). Does anyone have any idea? I looked at Coco/R but I couldn't find a PHP grammar file. I'm using .NET 2.0 and C#.

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  • Optimizing Mysql to avoid redundancy but still have fast access to calculable data

    - by diglettpotato
    An example for the sake of the question: I have a database which contains users, questions, and answers. Each user has a score which can be calculated using the data from the questions and answers tables. Therefore if I had a score field in the users table, it would be redundant. However, if I don't use a score field, then calculating the score every time would significantly slow down the website. My current solution is to put it in a score field, and then have a cron running every few hours which recalculates everybody's score, and updates the field. Is there a better way to handle this?

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  • How fast should an interpreted language be today?

    - by Tarbal
    Is speed of the (main/only viable) implementation of an interpreted programming language a criteria today? What would be the optimal balance between speed and abstraction? Should scripting languages completely ignore all thoughts about performance and just follow the concepts of rapid development, readability, etc.? I'm asking this because I'm currently designing some experimental languages and interpreters

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  • Delphi fast large bitmap creation (without clearing)

    - by Ritsaert Hornstra
    When using the TBitmap wrapper for a GDI bitmap from the unit Graphics I noticed it will always clear out the bitmap (using a PatBlt call) when setting up a bitmap with SetSize( w, h ). When I copy in the bits later on (see routine below) it seems ScanLine is the fastest possibility and not SetDIBits. function ToBitmap: TBitmap; var i, N, x: Integer; S, D: PAnsiChar; begin Result := TBitmap.Create(); Result.PixelFormat := pf32bit; Result.SetSize( width, height ); S := Src; D := Result.ScanLine[ 0 ]; x := Integer( Result.ScanLine[ 1 ] ) - Integer( D ); N := width * sizeof( longword ); for i := 0 to height - 1 do begin Move( S^, D^, N ); Inc( S, N ); Inc( D, x ); end; end; The bitmaps I need to work with are quite large (150MB of RGB memory). With these iomages it takes 150ms to simply create an empty bitmap and a further 140ms to overwrite it's contents. Is there a way of initializing a TBitmap with the correct size WITHOUT initializing the pixels itself and leaving the memory of the pixels uninitialized (eg dirty)? Or is there another way to do such a thing. I know we could work on the pixels in place but this still leaves the 150ms of unnessesary initializtion of the pixels.

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  • Convolve a column vector

    - by Geoff
    This is an OpenCV2 question. I have a matrix: cv::Mat_<Point3f> points; representing some space curve. I want to smooth it (using, for example a Gaussian kernel). I have tried using: cv::Mat_<Point3f> result; cv::GaussianBlur(points, result, cv::Size(4 * sigma, 1), sigma, sigma, cv::BORDER_WRAP); But I get the error: Assertion failed (columnBorderType != BORDER_WRAP)

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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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  • Best way to insert items from a Derived class's constructor into a Base class's private std::vector?

    - by Will
    I have these classes: class Base { ... private: std::vector<X> v; }; class Derived { Derived(X*, int n); } where the constructor of Derived is passed an array of item Xs, which I need to insert into my vector v in the Base class. (X is a smart pointer) Currently I see two ways to do this: 1) Create a function in Base: InsertItem(X*) that will insert an item into the vector. 2) Create a vector in Derived that contains the full list, then get it into Base by moving the entire vector. I dont see any advantages to #2, but was wondering if #1 was a good solution, or if there are better ways to do this. Thanks!

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  • How to track the touch vector?

    - by mystify
    I need to calculate the direction of dragging a touch, to determine if the user is dragging up the screen, or down the screen. Actually pretty simple, right? But: 1) Finger goes down, you get -touchesBegan:withEvent: called 2) Must wait until finger moves, and -touchesMoved:withEvent: gets called 3) Problem: At this point it's dangerous to tell if the user did drag up or down. My thoughts: Check the time and accumulate calculates vectors until it's secure to tell the direction of touch. Easy? No. Think about it: What if the user holds the finger down for 5 minutes on the same spot, but THEN decides to move up or down? BANG! Your code would fail, because it tried to determine the direction of touch when the finger didn't move really. Problem 2: When the finger goes down and stays at the same spot for a few seconds because the user is a bit in the wind and thinks about what to do now, you'll get a lot of -touchesMoved:withEvent: calls very likely, but with very minor changes in touch location. So my next thought: Do the accumulation in -touchesMoved:withEvent:, but only if a certain threshold of movement has been exceeded. I bet you have some better concepts in place?

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