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  • What is the most efficient Java Collections library?

    - by dehmann
    What is the most efficient Java Collections library? A few years ago, I did a lot of Java and had the impression back then that trove is the best (most efficient) Java Collections implementation. But when I read the answers to the question "Most useful free Java libraries?" I noticed that trove is hardly mentioned. So which Java Collections library is best now? UPDATE: To clarify, I mostly want to know what library to use when I have to store millions of entries in a hash table etc. (need a small runtime and memory footprint).

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  • Avoiding Mixup of Language Details

    - by DarenW
    Today someone asked me what was wrong with their source code. It was obvious. "Use double equals in place of that single equal in that if statement. Um, i think..." As i remember some languages actually take a single equals for comparison. Since i sometimes forget or mix up the syntax details among the several languages i use, i stepped over to my laptop to try a quickie experiment... It costs a bit of time and is a break in the flow to try "quick" experiments (though maybe the practice is good for memory.) What tips do you have for keeping straight in your mind the syntax (and other) details of multiple languages? (And nowadays, this applies just as well to the many wiki-like markups!)

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  • Expression Tree

    - by nettguy
    My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally in LINQ to SQL query the compiler translates it into parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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  • Tomcat - virtualhosting - name / ip / port - based

    - by lisak
    Hey, what are the usage scenarios for these kinds of virtual hosting ? Name Based - typical tomcat virtual hosting, one HOME instance with many contexts, each as an individual host IP based / port based - multiple instances of tomcat ( how is it with performance and memory consuption?) running on IP aliases (virtual IPs) for one network adapter, usually behind http apache server that can run name based virtual hostings. Otherwise I can't figure out how would I forward requests in iptables/firewall based on IP address, which is just one. How is IP based virtual hosting done as to Tomcat and multiple instances ? I'd like to hear some usage scenarios from your experience. How are you running your applications. Cause there are applications having it's own modified classloader and they are developed in a way to run alone withing a tomcat instance. Then there are trivial applications which can run within one instance without problems. Many thanks

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  • How to walk through two files simultaneously in Perl?

    - by Alex Reynolds
    I have two text files that contain columnar data of the variety position-value. Here is an example of the first file (file A): 100 1 101 1 102 0 103 2 104 1 ... Here is an example of the second file (B): 20 0 21 0 ... 100 2 101 1 192 3 193 1 ... Instead of reading one of the two files into a hash table, which is prohibitive due to memory constraints, what I would like to do is walk through two files simultaneously, in a stepwise fashion. What this means is that I would like to stream through lines of either A or B and compare position values. If the two positions are equal, then I perform a calculation on the values associated with that position. Otherwise, if the positions are not equal, I move through lines of file A or file B until the positions are equal (when I again perform my calculation) or I reach EOF of both files. Is there a way to do this in Perl?

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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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  • Piping SoX in Python - subprocess alternative?

    - by Cochise Ruhulessin
    I use SoX in an application. The application uses it to apply various operations on audiofiles, such as trimming. This works fine: from subprocess import Popen, PIPE kwargs = {'stdin': PIPE, 'stdout': PIPE, 'stderr': PIPE} pipe = Popen(['sox','-t','mp3','-', 'test.mp3','trim','0','15'], **kwargs) output, errors = pipe.communicate(input=open('test.mp3','rb').read()) if errors: raise RuntimeError(errors) This will cause problems on large files hower, since read() loads the complete file to memory; which is slow and may cause the pipes' buffer to overflow. A workaround exists: from subprocess import Popen, PIPE import tempfile import uuid import shutil import os kwargs = {'stdin': PIPE, 'stdout': PIPE, 'stderr': PIPE} tmp = os.path.join(tempfile.gettempdir(), uuid.uuid1().hex + '.mp3') pipe = Popen(['sox','test.mp3', tmp,'trim','0','15'], **kwargs) output, errors = pipe.communicate() if errors: raise RuntimeError(errors) shutil.copy2(tmp, 'test.mp3') os.remove(tmp) So the question stands as follows: Are there any alternatives to this approach, aside from writing a Python extension to the Sox C API?

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  • Interface Builder and Xcode integration not working

    - by Martin Cote
    After having installed the iPhone SDK 3.1.2, Interface Builder is not in sync with Xcode anymore. The light indicator at the bottom of the XIB window is grey. IB doesn't see any files from the Xcode project. Xcode is always open when I start IB. I tried rebooting. No luck. I tried removing the preferences files for Xcode/IB. No luck. I tried reinstalling Xcode/IB. Still no luck. This page explains how IB monitors the changes in Xcode. While it was an interesting read, it didn't provide any help about how to investigate my problem. Any help would be appreciated. EDIT Here's additional information. I enabled the debug logs for launchd, and I noticed the following line that appears every time Interface Builder is started: [0x0-0x1b01b].com.apple.InterfaceBuilder3[315]: Couldn't open shared capabilities memory GSCapabilities (No such file or directory) This really seems to be related to my issue.

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  • Init modules in apache2

    - by user306963
    Hello, I used to write apache modules in apache 1.3, but these days I am willing to pass to apache2. The module that I am writing at the moment has is own binary data, not a database, for performance purposes. I need to load this data in shared memory, so every child can access it without making his own copy, and it would be practical to load/create the binary data at startup, as I was used to do with apache 1.3. Problem is that I don't find an init event in apache2, in 1.3 in the module struct, immediatly after STANDARD_MODULE_STUFF you find a place for a /** module initializer */, in which you can put a function that will be executed early. Body of the function I used to write is something like: if ( getppid == 1 ) { // Load global data here // this is the parent process void* data = loadGlobalData( someFilePath ); setGlobalData( config, data ); } else { // this is the init of a child process // do nothing } I am looking for a place in apache2 in where I can put a similar function. Can you help? Thanks Benvenuto

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  • Passing Activity to non-activity object properly

    - by rayman
    In my app ive got a non-activity object which it's role is being a manager class. many times i need to pass "source activity" to methods as parameter to that manager class in order to make some operations on that activity. for exaple let's assume we have MyActivity which gotta do some toast. so i have this manager class called MyManager, and i have this method in it raiseToast(Activity sourceActivity) { Toast.makeText(sourceActivity, demo, Toast.LENGTH_LONG).show(); } and from Myactivity class we calling that method this way: MyManager manager=new MyManager(); manager.raitetoast(MyActivity.this); it works fine. what I'm asking here, is this a proper way to pass an Activity as parameter to a non-activity object? I'm having a memory leaks on real device(not the emulator), I wonder if this could also causing any reason for that? Thanks Idan.

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  • Django admin causes high load for one model...

    - by Joe
    In my Django admin, when I try to view/edit objects from one particular model class the memory usage and CPU rockets up and I have to restart the server. I can view the list of objects fine, but the problem comes when I click on one of the objects. Other models are fine. Working with the object in code (i.e. creating and displaying) is ok, the problem only arises when I try to view an object with the admin interface. The class isn't even particularly exotic: class Comment(models.Model): user = models.ForeignKey(User) thing = models.ForeignKey(Thing) date = models.DateTimeField(auto_now_add=True) content = models.TextField(blank=True, null=True) approved = models.BooleanField(default=True) class Meta: ordering = ['-date'] Any ideas? I'm stumped. The only reason I could think of might be that the thing is quite a large object (a few kb), but as I understand it, it wouldn't get loaded until it was needed (correct?).

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  • Saving a huge dataset into SQL table in a XML column - MS SQL, C#.Net

    - by NLV
    Hello all I'm having a requirement where i've to save a dataset which has multiple tables in it in a sql table XML column by converting into an XML. The problem is that in some cases the dataset grows extremely huge and i get OutOfMemoryException. What i basically do is that i convert the dataset into an xml file and save it in the local disk and then load the XML again and send it as a stored procedure parameter. But when i write the dataset xml into the disk the file sizes over 700 Mb and when i load it in the XMLDocument object in memory i get OutOfMemoryException. How can get the dataset xml without saving it in a file and re-reading it again? Thank You NLV

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  • Changing system colors for a single application (Windows, .NET)

    - by Michal Czardybon
    I know I should generally avoid messing up with such system settings, but my application do already use nonstandard colors and I have no influence on that. I would like to be able to add standard .NET controls in some places, but their colors do not match. I would like to have a hack that would replace system colors for this one application. One more important thing to note is that it is a .NET application. My (incomplete) ideas so far were: To create a proxy User32.dll library with replaced GetSysColor, but it would be very tedious (731 functions to be redirected, 1 to be replaced) and I do not know how to force my application to use that particular copy. To intercept somehow invocations to GetSysColors (unfortunatelly it is somewhere in the CLR I think). To modify somehow .NET class SystemColors (in memory? is it possible?). Do you have any idea, what is the best (and complete) way to achieve this?

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  • (iPhone) Instruments can't "Attach to Process"

    - by AlexLive
    Actually, I'm using a second generation Ipod Touch. What I'm trying to do is to debug my app on XCode and look for any memory leaks on Instruments at the same time. Is it even possible? Because the "Attach to Process" submenu lists when my app is running (or debugging in this case) but all the items inside this menu are disabled. All I can do is start the app from Instruments but later I come across some bug and I want to see the variables and properties affected. I'm also new to Instruments. Please, could someone give me any advice? Help would be greatly appreciated!

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  • PHP website Optimization

    - by ana
    I have a high traffic website and I need make sure my site is fast enough to display my pages to everyone rapidly. I searched on Google many articles about speed and optimization and here's what I found: Cache the page Save it to the disk Caching the page in memory: This is very fast but if I need to change the content of my page I have to remove it from cache and then re-save the file on the disk. Save it to disk This is very easy to maintain but every time the page is accessed I have to read on the disk. Which method should I go with? Thanks

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  • Android MediaPlayer crashing app

    - by user1555863
    I have an android app with a button that plays a sound. the code for playing the sound: if (mp != null) { mp.release(); } mp = MediaPlayer.create(this, R.raw.match); mp.start(); mp is a field in the activity: public class Game extends Activity implements OnClickListener { /** Called when the activity is first created. */ //variables: MediaPlayer mp; //... The app runs ok, but after clicking the button about 200 times on the emulator, app crashed and gave me this error https://dl.dropbox.com/u/5488790/error.txt (couldn't figure how to post it here so it will appear decently) i am assuming this is because the MediaPlayer object is consuming up too much memory, but isn't mp.release() supposed to take care of this? What am i doing wrong here?

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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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  • How to determine if an application is using the GPU

    - by Andrew
    I'm looking for a way to determine how to know whether an application is using the GPU with Objective-C. I want to be able to determine if any applications currently running on the system have work going on on the GPU (ie: a reason why the latest MacBook Pros would switch to the discrete graphics over the Intel HD graphics). I've tried getting the information by crossing the list of active windows with the list of windows that have their backing location stored in video memory using Quartz Window Services, but all that does is return the Dock application and I have other applications open that I know are using the GPU (Photoshop CS5, Interface Builder), that and the Dock doesn't require the 330m.

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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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  • 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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  • Classes, constructor and pointer class members

    - by pocoa
    I'm a bit confused about the object references. Please check the examples below: class ListHandler { public: ListHandler(vector<int> &list); private: vector<int> list; } ListHandler::ListHandler(vector<int> &list) { this->list = list; } Here I would be wasting memory right? So the right one would be: class ListHandler { public: ListHandler(vector<int>* list); private: vector<int>* list; } ListHandler::ListHandler(vector<int>* list) { this->list = list; } ListHandler::~ListHandler() { delete list; }

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  • Is release without prior retain dangerous?

    - by BankStrong
    I have some code which I think has extra release statements. Is the code incorrect? What is the end result? I don't understand memory management well yet - even after reading lots of articles and stackoverflow answers. Thanks for straightening me out. NSMutableArray *points = [NSMutableArray new]; for (Segment *s in currentWorkout.segments) { [points addObjectsFromArray:[s.track locationPoints]]; } [routeMap update:points]; [points release];

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  • Light weight C++ SAX XML parser

    - by John Bartholomew
    I know of at least three light weight C++ XML parsers: RapidXML, TinyXML and PugiXML. However, all three use a DOM based interface (ie, they build their own in-memory representation of the XML document and then provide an interface to traverse and manipulate it). For most situations that I have to deal with, I much prefer the SAX interface (where the parser just spits out a stream of events like start-of-tag, and the application code is responsible for doing whatever it wants based on those events). Can anyone recommend a light weight C++ XML library with a SAX interface? Edit: I should also note the Microsoft XmlLite library, which does use a SAX interface. Unfortunately, it's ruled out for me at the moment since as far as I know it's closed source and Windows only (please correct me if I'm wrong on this).

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  • Django as S3 proxy

    - by schneck
    Hi there, I extended a ModelAdmin with a custom field "Download file", which is a link to a URL in my Django project, like: http://www.myproject.com/downloads/1 There, I want to serve a file which is stored in a S3-bucket. The files in the bucket are not public readable, and the user may not have direct access to it. Now I want to avoid that the file has to be loaded in the server memory (these are multi-gb-files) avoid to have temp files on the server The ideal solution would be to let django act as a proxy that streams S3-chunks directly to the user. I use boto, but did not find a possibility to stream the chunks. Any ideas? Thanks.

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  • Why Read In UTF-16LE File Won't Convert "\r\n" Into "\n" In Windows

    - by Dbger
    I am using Perl to read UTF-16LE files in Windows 7. If I read in an ascii file with following code: open CUR_FILE, "<", $asciiFile; Then each "\r\n" in file will be converted into a "\n" in memory; if I read in an UTF-16LE(windows 1200) file with following code: open CUR_FILE, "<:encoding(UTF-16LE)", $utf16leFile; Then "\r\n" will keep unchanged. This inconsistency cause problems when I trying to regexp lines with line breaks. My questions is: Is this how unicode works in Perl & Windows? Or Am I using the wrong code? Thanks so much!

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