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Search found 4126 results on 166 pages for 'bitwise operations'.

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• write cache and write sequence order

  - by excanoe

  ok, here i have some weird question: let say we have some binary file (.log), and sequence of write operations, for example log1, log2, log3 and each has some block size n (raw data). question: can I be sure that log1,log2 and log3 sequences can be written in the correct order in ONE file, even if i have few cache levels (disk hardware and os level)? update very interested in what will be with records order (not with records) if we have software or hardware failure (reboot or another reason). update there can be some percent of write failures, but main question is: will write order stay correct?

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• Counting bits set in a .Net BitArray Class

  - by Sam

  I am implementing a library where I am extensively using the .Net BitArray class and need an equivalent to the Java BitSet.Cardinality() method, i.e. a method which returns the number of bits set. I was thinking of implementing it as an extension method for the BitArray class. The trivial implementation is to iterate and count the bits set (like below), but I wanted a faster implementation as I would be performing thousands of set operations and counting the answer. Is there a faster way than the example below? count = 0; for (int i = 0; i < mybitarray.Length; i++) { if (mybitarray [i]) count++; }

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• How to create a voldemort store?

  - by Pankaj

  I am trying to understand the Voldemort java API. I am new to non relational databases, so as I understand, Voldemort's store can be compared to a table in relational model. I saw the following code in the documentation. String bootstrapUrl = "tcp://localhost:6666"; StoreClientFactory factory = new SocketStoreClientFactory(new ClientConfig().setBootstrapUrls(bootstrapUrl)); // create a client that executes operations on a single store StoreClient client = factory.getStoreClient("test"); Here, we got a Store client based on the an existing store (test). How can I actually create a store for Voldemort through java?

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• Is there a Windows utility that will let me do multiple programmatic find/replaces on text that I cu

  - by billmaya

  I've inherited some C# code that contains about a thousand lines of source that I need to modify, transforming it from this: newDataRow["to_dir"] = comboBox108.Text; To this: assetAttributes.Add("to_dir", comboBox108.Text); The lines occur in various places throughout the application in groups of 40 or 50. Modifying each line by hand in Visual Studio 2008 can be done but it's labor intensive and prone to errors. Is there a Windows utility out there that will let me cut and paste groups of code into it and then run some sort of reg-ex expression to transform the individual lines one-by-one? I'd also be willing to use some sort of VS 2008 add-in that performed the same set of reg-ex operations against a selection of code. Thanks in advance.

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• Apache and Rewrite Module

  - by Yvon Blais

  I created a file .htaccess in the /var/www directory., The rights are root root --wxrwxrwxr The content of the file is : Options +FollowSymlinks RewriteEngine on RewriteLogLevel 3 RewriteLog "/var/log/apache2/rewrite.log" RewriteRule ^(.*?)$ testphp.php When I call the page phpinfo.php, I've got: Loaded Modules ... mod_rewrite ... Therefore, the modules is loaded Afer each modification,I restared the server manually with sudo /etc/init.d/apache2 restart The error.log gives Apache/2.2.14 (Ubuntu) PHP/5.3.2-1ubuntu4.2 with Suhosin-Patch configured -- resuming normal operations When I call a page anyone.htm or anyone.php, the rewrite.log does contain nothing and the real page is called. If I understand, the page anyone.php should be replaced by testphp.php Did I make siomething wrong ? Thanks

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• boost.asio's socket's recieve/send functions are bad?

  - by the_drow

  Data may be read from or written to a connected TCP socket using the receive(), async_receive(), send() or async_send() member functions. However, as these could result in short writes or reads, an application will typically use the following operations instead: read(), async_read(), write() and async_write(). I don't really understand that remark as read(), async_read(), write() and async_write() can also end up in short writes or reads, right? Why are those functions not the same? Should I use them at all? Can someone clarify that remark for me?

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• PHP: Simulate multiple MySQL connections to same database

  - by Varun

  An insert query is constantly getting logged in my MySQL slow query log. I want to see how much time the INSERT query is taking with 100 simultaneous insert operations(to the same table). So I need to simulate the follwoing. 500 different simultaneous connections from PHP to the same database on a mysql server, all of which are inserting a row(simultaneously) to the same table. DO I need to use any load testing tool? Or Can I simply write a PHP script to do this? Any thoughts?

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• g++: Use ZIP files as input

  - by Notinlist

  We have the Boost library in our side. It consists of huge amount of files which are not changing ever and only a tiny portion of it is used. We swap the whole boost directory if we are changing versions. Currently we have the Boost sources in our SVN, file by file which makes the checkout operations very slow, especially on Windows. It would be nice if there were a notation / plugin to address C++ files inside ZIP files, something like: // @ZIPFS ASSIGN 'boost' 'boost.zip/boost' #include <boost/smart_ptr/shared_ptr.hpp> Are there any support for compiler hooks in g++? Are there any effort regarding ZIP support? Other ideas?

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• how to protect an imported win32 dll into a .net application from memory issues

  - by Eric

  I have a c# application that needs to use a legacy win32 dll. The dll is almost its own app, it has dialogs, operations with hardware, etc. When this dll is imported and used, there are a couple of problems that occur: Dragging a dialog (not a windows system dialog, but one created by the dll) across the managed code app causes the UI to not repaint. Further it generates a system out of memory exception from various ui controls. The performance is incredibly slow. There seems to be no way to unload the dll so the memory never gets cleaned up. When we close our managed app, we get another memory exception. At the moment we import each method call as such: [DllImport("dllname.dll", EntryPoint = "MethodName", SetLastError = true, CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]

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• C++ Translation Phase Confusion

  - by blakecl

  Can someone explain why the following doesn't work? int main() // Tried on several recent C++ '03 compilers. { #define FOO L const wchar_t* const foo = FOO"bar"; // Will error out with something like: "identifier 'L' is undefined." #undef FOO } I thought that preprocessing was done in an earlier translation phase than string literal operations and general token translation. Wouldn't the compiler be more or less seeing this: int main() { const wchar_t* const foo = L"bar"; } It would be great if someone could cite an explanation from the standard.

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• What is a simple C library for a set of integer sets?

  - by conradlee

  I've got to modify a C program and I need to include a set of unsigned integer sets. That is, I have millions of sets of integers (each of these integer sets contains between 3 and 100 integers), and I need to store these in some structure, lets call it the directory, that can in logarithmic time tell me whether a given integer set already exists in the directory. The only operations that need to be defined on the directory is lookup and insert. This would be easy in languages with built-in support for useful data structures, but I'm a foreigner to C and looking around on Google did (surprisingly) not answer my question satisfactorily. This project looks about right: http://uthash.sourceforge.net/ but I would need to come up with my own hash key generator. This is a standard, simple problem, so I hope there is a standard and simple solution.

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• Windows Phone: Updating backend datastore (via web service) while keeping UI very responsive

  - by will

  I am developing a Windows Phone app where users can update a list. Each update, delete, add etc need to be stored in a database that sits behind a web service. As well as ensuring all the operations made on the phone end up in the cloud, I need to make sure the app is really responsive and the user doesn’t feel any lag time whatsoever. What’s the best design to use here? Each check box change, each text box edit fires a new thread to contact the web service? Locally store a list of things that need to be updated then send to the server in batch every so often (what about the back button)? Am I missing another even easier implementation? Thanks in advance,

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• Representing a very large array of bits in little memory

  - by user614624

  Hello, I would like to represent a structure containing 250 M states(1 bit each) somehow into as less memory as possible (100 k maximum). The operations on it are set/get. I cold not say that it's dense or sparse, it may vary. The language I want to use is C. I looked at other threads here to find something suitable also. A probabilistic structure like Bloom filter for example would not fit because of the possible false answers. Any suggestions please?

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• Optimality of Binary Search

  - by templatetypedef

  Hello all- This may be a silly question, but does anyone know of a proof that binary search is asymptotically optimal? That is, if we are given a sorted list of elements where the only permitted operation on those objects is a comparison, how do you prove that the search can't be done in o(lg n)? (That's little-o of lg n, by the way.) Note that I'm restricting this to elements where the only operation permitted operation is a comparison, since there are well-known algorithms that can beat O(lg n) on expectation if you're allowed to do more complex operations on the data (see, for example, interpolation search). Thanks so much! This has really been bugging me since it seems like it should be simple but has managed to resist all my best efforts. :-)

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• Reading files with Java

  - by sikas

  I would like to know how can I read a file byte by byte then perform some operation every n bytes. for example: Say I have a file of size = 50 bytes, I want to divide it into blocks each of n bytes. Then each block is sent to a function for some operations to be done on those bytes. The blocks are to be created during the read process and sent to the function when the block reaches n bytes so that I don`t use much memory for storing all blocks. I want the output of the function to be written/appended on a new file. This is what I've reached to read, yet I don't know it it is right: fc = new JFileChooser(); File f = fc.getSelectedFile(); FileInputStream in = new FileInputStream(f); byte[] b = new byte[16]; in.read(b); I haven't done anything yet for the write process.

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• Hibernate Hql find result size for paginator

  - by KCore

  Hi, I need to add paginator for my Hibernate application. I applied it to some of my database operations which I perform using Criteria by setting Projection.count().This is working fine. But when I use hql to query, I can't seem to get and efficient method to get the result count. If I do query.list().size() it takes lot of time and I think hibernate does load all the objects in memory. Can anyone please suggest an efficient method to retrieve the result count when using hql?

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• Iterate attributes and IBOutlets of a UIViewController

  - by Espuz

  I've a generic UIViewController on my app. All the UIViewController on the app inherits from this generic one. I'm trying to automate the deallocation and releasing of attributes and IBOutlets as properties. I'm doing the first (attributes) on dealloc method and the second (IBOutlets as properties) on viewDidUnload. - (void) dealloc { [_att1 release]; _att1 = nil; [_att2 release]; _att2 = nil; // ... } - (void) viewDidUnload { self.att1 = nil; // att1 is an IBOutlet self.att2 = nil; // att2 is an IBOutlet // ... } Is there any way to iterate all my attributes and IBOutlets to simplify this operations? I want to avoid do it for each outlet and attribute and delegate it to the generic UIViewController. Thanks.

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• Even lighter than SQLite

  - by Richard Fabian

  I've been looking for a C++ SQL library implementation that is simple to hook in like SQLite, but faster and smaller. My projects are in games development and there's definitely a cutoff point between needing to pass the ACID test and wanting some extreme performance. I'm willing to move away from SQL string style queries, allowing it to be code driven, but I haven't found anything out there that provides SQL like flexibility while also preferring performance over the ACID test. I don't want to go reinventing the wheel, and the idea of implementing an SQL library on my own is quite daunting, even if it's only going to be simple subset of all the calls you could make. I need the basic commands (SELECT, MODIFY, DELETE, INSERT, with JOIN, and WHERE), not data operations (like sorting, min, max, count) and don't need the database to be atomic, or even enforce consistency (I can use a real SQL service while I'm testing and debugging).

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• Access static constant variable from multiple threads in C

  - by user325519

  I have some experience with multithread programming under Linux (C/C++ & POSIX threads), however most obvious cases are sometimes very complicated. I have several static constant variables (global and function local) in my code, can I access them simultaneously from multiple threads without using mutexes? Because I don't modify them it should be ok, but it's always better to ask. I have to do heavy speed optimization, so even as fast operations as mutex lock/unlock are quite expensive for me, especially because my application is going to access these variables form long loops.

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• Copying a database into a new database including structure and data

  - by Jason

  In phpMyAdmin under operations I can "Copy database to:" and select Structure and data CREATE DATABASE before copying Add AUTO_INCREMENT value I need to be able to do that without using phpMyAdmin. I know how to create the database and user. I have a source database that's a shell that I can work from so all I really need is the how to copy all the table structure and data part. (I know, the harder part) system() & exec() are not options for me which rules out mysqldump. (I think) How can I loop through each table and recreate it's structure and data? Is it just looping through the results of SHOW TABLES then for each table looping through DESCRIBE tablename Then, is there an easy way for getting the data copied?

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• How to avoid Mercurial repo corruption when sharing a repository between Windows/Mac?

  - by Stabledog

  I have several projects which are shared between Windows and Mac. The dev machine is a Mac running Parallels: the files are stored on the Mac side, and the source is shared to the Windows side. This is very convenient, as I can switch back and forth between Windows and Mac tools rapidly without having to sync files. Recently I switched from Subversion to Mercurial, and now I'm having problems with the Mercurial repository becoming corrupt if I use the Windows tools to add/update, etc. I have to be very careful about which operations on the Windows side are safe (mainly the read-only stuff) and of course I forget rather regularly. Does anybody know why the corruption occurs? I thought Mercurial repositories were platform-agnostic. Any ideas how to prevent it without removing the Windows tools entirely?

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• Construction an logical expression which will count bits in a byte.

  - by danatel

  When interviewing new candidates, we usually ask them to write a piece of C code to count the number of bits with value 1 in a given byte variable (e.g. the byte 3 has two 1-bits). I know all the common answers, such as right shifting eight times, or indexing constant table of 256 precomputed results. But, is there a smarter way without using the precomputed table? What is the shortest combination of byte operations (AND, OR, XOR, +, -, binary negation, left and right shift) which computes the number of bites?

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• How to detect if breaking an edge will make a graph disjoint?

  - by the_graph_guy

  I have a graph that starts off with a single, root node. Nodes are added one by one to the graph. At node creation time, they have to be linked either to the root node, or to another node, by a single edge. Edges can also be created and deleted (one by one, between any two nodes). Nodes can be deleted one at a time. Node and edge creation, deletion operations can happen in any arbitrary order. OK, so here's my question: When an edge is deleted, is it possible do determine, in constant time (i.e. with an O(1) algorithm), if doing this will divide the graph into two disjoint subgraphs? If it will, then which side of the edge will the root node belong? I'm willing to maintain, within reasonable limits, any additional data structure that can facilitate the derivation of this information. Maybe it is not possible to do it in O(1), if so any pointers to literature will be appreciated.

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• C++ / Java: Toggle boolean statement?

  - by Martijn Courteaux

  Hi, Is there a short way to toggle a boolean? With integers we can do operations like this: int i = 4; i *= 4; // equals 16 /* Which is equivalent to */ i = i * 4; So is there also something for booleans (like the *= operator for ints)? In C++: bool booleanWithAVeryLongName = true; booleanWithAVeryLongName = !booleanWithAVeryLongName; // Can it shorter? booleanWithAVeryLongName !=; // Or something? In Java: boolean booleanWithAVeryLongName = true; booleanWithAVeryLongName = !booleanWithAVeryLongName; // Can it shorter? booleanWithAVeryLongName !=; // Or something?

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• How to integrate Python scripting in my Android App (like SL4A)

  - by Seraphim's host

  I need to add scripting layer to my android App. So I can remotely prepare a script that my app download form a web service and execute on the user device. I found a interesting project called Scripting Layer for Android (SL4A) here: http://code.google.com/p/android-scripting/ I'm not sure I can execute Python script without installing the PythonForAndroid_r4.apk first. I can't force my customer to install that application! So my question is, can the SL4A layer be integrated in my app without the need to install other apk? I need to execute actions like update data in the DB, create/read/delete a file on the sd card... Not so complex but I see SL4A can do a lot of things like these. Other scripting libraries? EDIT: Found also MVEL: http://mvel.codehaus.org/ but I think it needs to be integrated to execute complex operations like accessing a DB...

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