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• removing duplicate strings from a massive array in java efficiently?

  - by Preator Darmatheon

  I'm considering the best possible way to remove duplicates from an (Unsorted) array of strings - the array contains millions or tens of millions of stringz..The array is already prepopulated so the optimization goal is only on removing dups and not preventing dups from initially populating!! I was thinking along the lines of doing a sort and then binary search to get a log(n) search instead of n (linear) search. This would give me nlogn + n searches which althout is better than an unsorted (n^2) search = but this still seems slow. (Was also considering along the lines of hashing but not sure about the throughput) Please help! Looking for an efficient solution that addresses both speed and memory since there are millions of strings involved without using Collections API!

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• Application crash when using an NSTimer and pushViewController

  - by Cesar

  I'm using an NSTimer to implement a 3 seconds splash screen. If a don't use a timer the view it's correctly pushed but if I use the timer for adding a little delay the application crash with a EXC_BAD_ACCESS. I'm pretty sure the answer contains "memory management" but I can't get the point... @interface RootViewController : UIViewController { NSTimer *timer; } -(void)changeView:(NSTimer*)theTimer; @property(nonatomic,retain) NSTimer *timer; ... @implementation RootViewController @synthesize timer; - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; [[self navigationController] setNavigationBarHidden:YES]; timer = [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(changeView:) userInfo:nil repeats:NO]; } -(void)changeView:(NSTimer*)theTimer { NSLog(@"timer fired"); //Crash here, but only if called using a timer [[self navigationController] pushViewController:list animated:YES]; }

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• How to serialize a collection of base type and see the concrete types in easy to read XML

  - by Jason Coyne

  I have a List which is populated with objects of various concrete types which subclass BaseType I am using the WCF DataContractSerializer <Children> <BaseType xmlns:d3p1="http://schemas.datacontract.org/2004/07/Tasks" i:type="d3p1:ConcreteTypeA"></BaseType> <BaseType xmlns:d3p1="http://schemas.datacontract.org/2004/07/Tasks" i:type="d3p1:ConcreteTypeB"></BaseType> </Children> Is there any way to get this to generate <Children> <ConcreteTypeA/> <ConcreteTypeB/> </Children> ? The real goal is to let users generate some XML to load into memory, and the users are of a skill level that asking them for the original XML is not going to be successful.

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• Why can final object be modified?

  - by Matt McCormick

  I came across the following code in a code base I am working on: public final class ConfigurationService { private static final ConfigurationService INSTANCE = new ConfigurationService(); private List providers; private ConfigurationService() { providers = new ArrayList(); } public static void addProvider(ConfigurationProvider provider) { INSTANCE.providers.add(provider); } ... INSTANCE is declared as final. Why can objects be added to INSTANCE? Shouldn't that invalidate the use of final. (It doesn't). I'm assuming the answer has to do something with pointers and memory but would like to know for sure.

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• Make compiler copy characters using movsd

  - by Suma

  I would like to copy a relatively short sequence of memory (less than 1 KB, typically 2-200 bytes) in a time critical function. The best code for this on CPU side seems to be rep movsd. However I somehow cannot make my compiler to generate this code. I hoped (and I vaguely remember seeing so) using memcpy would do this using compiler built-in instrinsic, but based on disassembly and debugging it seems compiler is using call to memcpy/memmove library implementation instead. I also hoped the compiler might be smart enough to recognize following loop and use rep movsd on its own, but it seems it does not. char *dst; const char *src; // ... for (int r=size; --r>=0; ) *dst++ = *src++; Is there some way to make the Visual Studio compiler to generate rep movsd sequence other than using inline assembly?

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• BigDecimal precision not persisted with javax.persistence annotations

  - by dkaczynski

  I am using the javax.persistence API and Hibernate to create annotations and persist entities and their attributes in an Oracle 11g Express database. I have the following attribute in an entity: @Column(precision = 12, scale = 9) private BigDecimal weightedScore; The goal is to persist a decimal value with a maximum of 12 digits and a maximum of 9 of those digits to the right of the decimal place. After calculating the weightedScore, the result is 0.1234, but once I commit the entity with the Oracle database, the value displays as 0.12. I can see this by either by using an EntityManager object to query the entry or by viewing it directly in the Oracle Application Express (Apex) interface in a web browser. How should I annotate my BigDecimal attribute so that the precision is persisted correctly? Note: We use an in-memory HSQL database to run our unit tests, and it does not experience the issue with the lack of precision, with or without the @Column annotation.

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• Optimizing a large iteration of PHP objects (EAV-based)

  - by Aron Rotteveel

  I am currently working on a project that utilizes the EAV model. This turns out to work quite well, but like many others I am now stumbling upon some performance issues. The data set in this particular case consists of aproximately 2500 entities, each with aprox. 150 attributes. Each entity and each attribute is represented by a PHP-object. Since most parts of the application only iterate through a filtered set of entities, we have not had very large issues yet. Now, however, I am working on an algorithm that requires iteration over the entire dataset, which causes a major impact on performance. This information is perhaps not very much to work with, but since this is an architectural problem, I am hoping for a architectural pattern to help me on the way as well. Each entity, including it's attributes takes up aprox. 500KB of memory.

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• OSX: Why is GetProcessInformation() causing a segfault?

  - by anthony

  Here's my C method to get the pid of the Finder process. GetProcessInformation() is causing a segfault. Why? Here's the function: static OSStatus GetFinderPID(pid_t *pid) { ProcessSerialNumber psn = {kNoProcess, kNoProcess}; ProcessInfoRec info; OSStatus status = noErr; info.processInfoLength = sizeof(ProcessInfoRec); info.processName = nil; while (!status) { status = GetNextProcess(&psn); if (!status) { status = GetProcessInformation(&psn, &info); } if (!status && info.processType == 'FNDR' && info.processSignature == 'MACS') { return GetProcessPID(&psn, pid); } } return status; } Here's the backtrace: Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x0000000032aaaba7 0x00007fffffe00623 in __bzero () (gdb) bt #0 0x00007fffffe00623 in __bzero () #1 0x00007fff833adaed in CreateFSRef () #2 0x00007fff833ab53b in FSPathMakeRefInternal () #3 0x00007fff852fc32d in _CFGetFSRefFromURL () #4 0x00007fff852fbfe0 in CFURLGetFSRef () #5 0x00007fff85dd273f in GetProcessInformation () #6 0x0000000100000bef in GetFinderPID [inlined] () at /path/to/main.c:21

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• Infix to Postfix and unary/binary operators

  - by Jaapjan

  I have a piece of code that converts an infix expression to an expression tree in memory. This works just fine. There's just one small trouble. I just connect work out how to involve the unary operators correctly (the right associative ones). With the following infix expression : +1 + +2 - -3 - -4 I would expect an RPN of: 1+2++3-4-- Yet, none of the online infix-post converters I can find handle this example in the way I would expect. Does anyone have a clear explanation of handling right associative operators, specifically the binary ones that can be mistaken for the unary ones?

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• Caching generated QR Code

  - by Michal K

  I use zxing to encode a qr code and store it as a bitmap and then show it in ImageView. Since the image generation time is significant I'm planning to move it to a separate thread (AsyncTaskLoader will be fine I think). The problem is - it's an image and I know that to avoid memory leaks one should never store a strong reference to it in an Activity. So how would you do it? How to cache an image to survive config changes (phone rotation) and generally avoid generating it onCreate()? Just point me in the right direction, please.

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• Compiling my own PHP extension on Windows with Visual Studio 2008

  - by Mickey Shine

  I wrote a PHP extension and it could be compiled and run under linux successfully. But on windows, I met some problems. I did the compiling on windows according to http://blog.slickedit.com/?p=128 with PHP source version 5.2.10, and after the compiling it generated the dll file. But when I tried to use the dll file, it reported me the memory problems when starting Apache(Wamp server). And then I started the debugging process, it seemed that REGISTER_INI_ENTRIES() had problems. Here is the PHP extension source code, http://www.bluefly.cn/xsplit.tar.gz , and it works fine on Linux. But I also want to make it work on Windows. Sorry I am not a pro so that I hope someone can help me. Any help is appreciated and thanks in advance~

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• The speed of .NET in numerical computing

  - by Yin Zhu

  In my experience, .net is 2 to 3 times slower than native code. (I implemented L-BFGS for multivariate optimization). I have traced the ads on stackoverflow to http://www.centerspace.net/products/ the speed is really amazing, the speed is close to native code. How can they do that? They said that: Q. Is NMath "pure" .NET? A. The answer depends somewhat on your definition of "pure .NET". NMath is written in C#, plus a small Managed C++ layer. For better performance of basic linear algebra operations, however, NMath does rely on the native Intel Math Kernel Library (included with NMath). But there are no COM components, no DLLs--just .NET assemblies. Also, all memory allocated in the Managed C++ layer and used by native code is allocated from the managed heap. Can someone explain more to me? Thanks!

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• SQL CE not loading from network share

  - by David Veeneman

  I installed VS 2010 RC yesterday, and suddenly, SQL Server CE isn't loading files from a network share. In projects compiled with VS 2008, if I try to open a SQL CE file located on a network share, I get an error that reads like this: Internal error: Cannot open the shared memory region. If I try to create a data connection in VS 2010 to a SQL CE file on a network share, I get this error: SQL Server Compact does not support opening database files on a network share. Can anyone shed any light on what's going on? Thanks.

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• Is there a faster alternative to using textures in XNA?

  - by Matthew Bowen

  I am writing a map editing program for a 2D game using XNA. To create a Texture2D for all of the tiles that a map requires takes too long. Are there any alternatives to using textures for drawing with XNA? I attempted to create just one texture per tile set instead of a texture for every tile in a tile set, but there is a limit to the size of textures and I could not fit all the tiles of a tile set into one texture. Currently the program contains all the would-be textures in memory as Bitmap objects. Is there a way to simply draw a Bitmap object to the screen in XNA? I have searched but I cannot find any information on this. This approach would avoid having to create textures altogether, however any tinting or effects I would have to do to the bitmap directly. Any help would be very much appreciated. Thanks

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• VC7.1 C1204 internal compiler error

  - by Nathan Ernst

  I'm working on modifying Firaxis' Civilization 4 core game DLL. The host application is built using VC7, hence the constraint (source not provided for the host EXE). I've been working on rewriting a large chunk of the code (focusing on low-hanging performance issues & memory leaks). I recently ran into an internal compiler error when trying to mod the code to use an array class instead of dynamically allocated 2-d arrays, I was going to use matrices from the boost lib (Civ4 is already using boost, so why not?). Basically, the issue comes down to: if I include "boost/numeric/ublas/matrix.hpp", I run into an internal compiler error C1204. MSDN has this to say: MSDN C1204 KB has this to say: KB 883655 So, I'm curious, is it possible to solve this error without a KB/SP being applied and dramatically reducing the complexity of the code? Additionally, as VC7 is no longer "supported", does anyone have a valid (supported) link for a VC7 service pack?

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• Processing potentially large STDIN data, more than once

  - by d11wtq

  I'd like to provide an accessor on a class that provides an NSInputStream for STDIN, which may be several hundred megabytes (or gigabytes, though unlikely, perhaps) of data. When I caller gets this NSInputStream it should be able to read from it without worrying about exhausting the data it contains. In other words, another block of code may request the NSInputStream and will expect to be able to read from it. Without first copying all of the data into an NSData object which (I assume) would cause memory exhaustion, what are my options for handling this? The returned NSInputStream does not have to be the same instance, it simply needs to provide the same data. The best I can come up with right now is to copy STDIN to a temporary file and then return NSInputStream instances using that file. Is this pretty much the only way to handle it? Is there anything I should be cautious of if I go the temporary file route?

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• Advantage of using a static member function instead of an equivalent non-static member function?

  - by jonathanasdf

  I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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• C++ Static array vs. Dynamic array?

  - by user69514

  What is the difference between a static array and a dynamic array in C++? I have to do an assignment for my class and it says not to use static arrays, only dynamic arrays. I've looked in the book and online, but I don't seem to understand. I thought static was created at compile time and dynamic at runtime, but I might be mistaken this with memory allocation. Can you explain to me the difference between static array and dynamic array in C++? Thnaks.

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• How do laziness and I/O work together in Haskell?

  - by Bill

  I'm trying to get a deeper understanding of laziness in Haskell. I was imagining the following snippet today: data Image = Image { name :: String, pixels :: String } image :: String -> IO Image image path = Image path <$> readFile path The appeal here is that I could simply create an Image instance and pass it around; if I need the image data it would be read lazily - if not, the time and memory cost of reading the file would be avoided: main = do image <- image "file" putStrLn $ length $ pixels image But is that how it actually works? How is laziness compatible with IO? Will readFile be called regardless of whether I access pixels image or will the runtime leave that thunk unevaluated if I never refer to it? If the image is indeed read lazily, then isn't it possible I/O actions could occur out of order? For example, what if immediately after calling image I delete the file? Now the putStrLn call will find nothing when it tries to read.

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• how to match a regulas expresion like (%i1) in python pexpect

  - by mike

  I want to use maxima from python using pexpect, whenever maxima starts it will print a bunch of stuff of this form: $ maxima Maxima 5.27.0 http://maxima.sourceforge.net using Lisp SBCL 1.0.57-1.fc17 Distributed under the GNU Public License. See the file COPYING. Dedicated to the memory of William Schelter. The function bug_report() provides bug reporting information. (%i1) i would like to start up pexpect like so: import pexpect cmd = 'maxima' child = pexpect.spawn(cmd) child.expect (' match all that stuff up to and including (%i1)') child.sendline ('integrate(sin(x),x)') chil.expect( match (%o1 ) ) print child.before how do i match the starting banner up to the prompt (%i1)? and so on, also maxima increments the (%i1)'s by one as the session goes along, so the next expect would be: child.expect ('match (%i2)') child.sendline ('integrate(sin(x),x)') chil.expect( match (%o2 ) ) print child.before how do i match the (incrementing) integers?

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• Disabling Xdebug's dumping of caught exceptions

  - by nuqqsa

  By default Xdebug will dump any exception regardless of whether it is caught or not: try { throw new Exception(); } catch (Exception $e) { } echo 'life goes on'; With XDebug enabled and the default settings this piece of code will actually output something like the following (nicely formatted): ( ! ) Exception: in /test.php on line 3 Call Stack # Time Memory Function Location 1 0.0003 52596 {main}( ) ../test.php:0 life goes on Is it possible to disable this behaviour and have it dumping only the uncaught exceptions? Thanks in advance. UPDATE: I'm about to conclude that this is a bug, since xdebug.show_exception_trace is disabled by default yet it doesn't behave as expected (using Xdebug v2.0.5 with PHP 5.2.10 on Ubuntu 9.10).

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• Asp.net TreeView control - maximum number of nodes

  - by mas_oz2k1

  I have a treeView control in ASP.NET page that will be loaded with up to 12,000 nodes in different levels. For example: Node 1 Node 1.1 … Node 1.400 Node 1.400.1 … Node 1.400.6400 Node 2 Node 3 Node 4 According to this link: http://msdn.microsoft.com/en-us/library/ms529261.aspx the node limit is 1000. Is this correct or is it dependent on available memory(please specify value)? Assuming it is correct. is there any way to split the 4600 child nodes in say in chunks of 300 hundred? I am thinking that if dummy nodes are used (previous /next navigation) to navigate the chunks will easy the load of the html page. Sample code in C# will be greatly appreciated. (Or VB.NET if you can not translate it to C#)

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• What is the best way to manage one's session variables?

  - by donde

  In my .NET web app, I keep basic user info in a user session object. I also usually keep a director class in the session; which is basically just has info about whatever thing it being worked on on that screen (like a customer id). I am trying to keep from adding a ton of sessions. I also want to make sure at any given time ONLY the sessions that are necessary are in memory. This means I need an effective way of managing my session variables. Any suggestions?

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• Inserting Large volume of data in SQL Server 2005

  - by Manjoor

  We have a application (written in c#) to store live stock market price in the database (SQL Server 2005). It insert about 1 Million record in a single day. Now we are adding some more segment of market into it and the no of records would be double (2 Millions/day). Currently the average record insertion per second is about 50, maximum is 450 and minimum is 0. To check certain conditions i have used service broker (asynchronous trigger) on my price table. It is running fine at this time(about 35% CPU utilization). Now i am planning to create a in memory dataset of current stock price. we would like to do some simple calculations. I want to know different views of members on this. Please provide your way of dealing with such situation.

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• Copy Structure To Another Program

  - by Steven

  Long story, long: I am adding a web interface (ASPX.NET: VB) to a data acquisition system developed with LabVIEW which outputs raw data files. These raw data files are the binary representation of a LabVIEW cluster (essentially a structure). LabVIEW provides functions to instantiate a class or structure or call a method defined in a .NET DLL file. I plan to create a DLL file containing a structure definition and a class with methods to transfer the structure. When the webpage requests data, it would call a LabVIEW executable with a filename parameter. The LabVIEW code would instantiate the structure, populate the structure from the data file, then call the method to transfer the data back to the website. Long story, short: How do you recommend I transfer (copy) an instance of a structure from one .NET program to a VB.NET program? Ideas considered: sockets, temp file, xml file, config file, web services, CSV, some type of serialization, shared memory

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