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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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• 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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• DDMS Not Showing Threads From Device

  - by polyclef

  I'd like to check for memory leaks in my Android app using the DDMS feature in Eclipse. When I launch an emulated device, the threads display properly for the emulated device, starting with 8600 and up. However, when I connect my Droid to the PC, the device shows up just fine in DDMS. The logcat is generated correctly, and I can view the file structure. However, threads do not display. I get "no client selected" in the Threads pane, and there is no drop-down icon next to the device listing. Do I need to change some particular setting in Eclipse? Is this maybe a driver issue?

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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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• How is thread synchronization implemented, at the assembly language level?

  - by Martin

  While I'm familiar with concurrent programming concepts such as mutexes and semaphores, I have never understood how they are implemented at the assembly language level. I imagine there being a set of memory "flags" saying: lock A is held by thread 1 lock B is held by thread 3 lock C is not held by any thread etc But how is access to these flags synchronized between threads? Something like this naive example would only create a race condition: mov edx, [myThreadId] wait: cmp [lock], 0 jne wait mov [lock], edx ; I wanted an exclusive lock but the above ; three instructions are not an atomic operation :(

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• On Windows XP, programmatically set Pagefile to "No Paging File" on single c: drive

  - by NBPC77

  I'm trying to write a C#/.NET application that optimizes the hard drives for our XP workstations Set pagefile to "No paging file" Reboot Run a defrag utility to optimize the data and apps Create a contiguous page file Reboot, run pagedefrag from Sysinternals I'm really struggling with #1. I delete the following key: SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PagingFiles Upon reboot, the System Control Panel shows "No page file", but c:\pagefile.sys still exists and its in use by the SYSTEM process so I can't delete it and I can't optimize HD. I tried using PendingFileRenamingOperations and that bombs out too. I tried using WMI: Win32_PageFileSetting, but that only lets you set sizes (not zero--defaults to 2MB). Of course, if I do the manual steps outlined above, it works. I think I need an API call to make this happen.

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• Are these tables too big for SQL Server or Oracle

  - by Jeffrey Cameron

  Hey all, I'm not much of a database guru so I would like some advice. Background We have 4 tables that are currently stored in Sybase IQ. We don't currently have any choice over this, we're basically stuck with what someone else decided for us. Sybase IQ is a column-oriented database that is perfect for a data warehouse. Unfortunately, my project needs to do a lot of transactional updating (we're more of an operational database) so I'm looking for more mainstream alternatives. Question Given these tables' dimensions, would anyone consider SQL Server or Oracle to be a viable alternative? Table 1 : 172 columns * 32 million rows Table 2 : 453 columns * 7 million rows Table 3 : 112 columns * 13 million rows Table 4 : 147 columns * 2.5 million rows Given the size of data what are the things I should be concerned about in terms of database choice, server configuration, memory, platform, etc.?

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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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• C++ Win32 Unhandled Exception Handler

  - by uray

  currently I used SetUnhandledExceptionFilter() to provide callback to get information when an unhandled exception was occurred, that callback will provides me with EXCEPTION_RECORD which provides ExceptionAddress. [1]what is actually ExceptionAddress is? does it the address of function / code that gives exception, or the memory address that some function tried to access? [2]is there any better mechanism that could give me better information when unhandled exception occured? (I can't use debug mode or add any code that affect runtime performance, since crash is rare and only on release build when code run as fast as possible) [3]is there any way for me to get several callstack address when unhandled exception occured. [4]suppose ExceptionAddress has address A, and I have DLL X loaded and executed at base address A-x, and some other DLL Y at A+y, is it good to assume that crash was PROBABLY caused by code on DLL X?

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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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• Problem with between join for sqlalchemy orm relation.

  - by Gary van der Merwe

  I'm trying to create a relation that has a between join. Here is a shortish example of what I'm trying to do: #!/usr/bin/env python import sqlalchemy as sa from sqlalchemy import orm from sqlalchemy.engine.base import Engine from sqlalchemy.ext.declarative import declarative_base metadata = sa.MetaData() Base = declarative_base(metadata=metadata) engine = sa.create_engine('sqlite:///:memory:') class Network(Base): __tablename__ = "network" id = sa.Column(sa.Integer, primary_key=True) ip_net_addr_db = sa.Column('ip_net_addr', sa.Integer, index=True) ip_broadcast_addr_db = sa.Column('ip_broadcast_addr', sa.Integer, index=True) # This can be determined from the net address and the net mask, but we store # it in the db so that we can join with the address table. ip_net_mask_len = sa.Column(sa.SmallInteger) class Address(Base): __tablename__ = "address" ip_addr_db = sa.Column('ip_addr', sa.Integer, primary_key=True, index=True, unique=True) Network.addresses = orm.relation(Address, primaryjoin=Address.ip_addr_db.between( Network.ip_net_addr_db, Network.ip_broadcast_addr_db), foreign_keys=[Address.ip_addr_db]) metadata.create_all(engine) Session = orm.sessionmaker(bind=engine) Network() I you run this, you get this error: ArgumentError: Could not determine relation direction for primaryjoin condition 'address.ip_addr BETWEEN network.ip_net_addr AND network.ip_broadcast_addr', on relation Network.addresses. Do the columns in 'foreign_keys' represent only the 'foreign' columns in this join condition ? The answer to that question is Yes, but I cant figure out how to tell it that

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• Help with parsing lxml

  - by Casey

  Hi To implement a college project, I need to handle XML files. For this I choose lxml after doing some research. However I can't seem to find some nice tutorial to help me get started. I can't choose most specifically which type of parsing I need to use. My XML files don't have that much data but speed is main concern, not memory. Can anyone point me to some tutorial that would help me or some book that I can lookup? I have already tried the tutorial on lxml site but that didn't help me much. Is there some small application I can look up to get a hang of parsing XML with lxml

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• Dereferencing pointers without pointing them at a variable

  - by Miguel

  I'm having trouble understanding how some pointers work. I always thought that when you created a pointer variable (p), you couldn't deference and assign (*p = value) unless you either malloc'd space for it (p = malloc(x)), or set it to the address of another variable (p = &a) However in this code, the first assignment works consistently, while the last one causes a segfault: typedef struct { int value; } test_struct; int main(void) { //This works int* colin; *colin = 5; //This never works test_struct* carter; carter->value = 5; } Why does the first one work when colin isn't pointing at any spare memory? And why does the 2nd never work? I'm writing this in C, but people with C++ knowledge should be able to answer this as well.

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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• Temp file that exists only in RAM?

  - by Auraomega

  I'm trying to write an encrpytion using the OTP method. In keeping with the security theories I need the plain text documents to be stored only in memory and never ever written to a physical drive. The tmpnam command appears to be what I need, but from what I can see it saves the file on the disk and not the RAM. Using C++ is there any (platform independent) method that allows a file to exist only in RAM? I would like to avoid using a RAM disk method if possible. Thanks Edit: Thanks, its more just a learning thing for me, I'm new to encryption and just working through different methods, I don't actually plan on using many of them (esspecially OTP due to doubling the original file size because of the "pad"). If I'm totally honest, I'm a Linux user so ditching Windows wouldn't be too bad, I'm looking into using RAM disks for now as FUSE seems a bit overkill for a "learning" thing.

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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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• 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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• 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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