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  • Why is the destructor called when the CPython garbage collector is disabled?

    - by Frederik
    I'm trying to understand the internals of the CPython garbage collector, specifically when the destructor is called. So far, the behavior is intuitive, but the following case trips me up: Disable the GC. Create an object, then remove a reference to it. The object is destroyed and the __del__ method is called. I thought this would only happen if the garbage collector was enabled. Can someone explain why this happens? Is there a way to defer calling the destructor? import gc import unittest _destroyed = False class MyClass(object): def __del__(self): global _destroyed _destroyed = True class GarbageCollectionTest(unittest.TestCase): def testExplicitGarbageCollection(self): gc.disable() ref = MyClass() ref = None # The next test fails. # The object is automatically destroyed even with the collector turned off. self.assertFalse(_destroyed) gc.collect() self.assertTrue(_destroyed) if __name__=='__main__': unittest.main() Disclaimer: this code is not meant for production -- I've already noted that this is very implementation-specific and does not work on Jython.

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  • Why isn't Hadoop implemented using MPI?

    - by artif
    Correct me if I'm wrong, but my understanding is that Hadoop does not use MPI for communication between different nodes. What are the technical reasons for this? I could hazard a few guesses, but I do not know enough of how MPI is implemented "under the hood" to know whether or not I'm right. Come to think of it, I'm not entirely familiar with Hadoop's internals either. I understand the framework at a conceptual level (map/combine/shuffle/reduce and how that works at a high level) but I don't know the nitty gritty implementation details. I've always assumed Hadoop was transmitting serialized data structures (perhaps GPBs) over a TCP connection, eg during the shuffle phase. Let me know if that's not true.

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  • What is the best way to get support from microsoft developers [closed]

    - by Malcolm Frexner
    I have a problem at my production web, that I am not able to solve. I am not able to reproduce the problem in stage or development. It only appears when the website is under heavy load. I think it is solvable if somebody who has a very good understanding of the internals of FormsAuthentication would have a look at it by logging into our system. It should be at least Scottgu! Somebody told me that Microsoft Premier Support is a good choice for this kind of problems. We have no MSDN subscription or other connection to microsoft that enables us to use MPS. Is there a way to get support on a incident base? Are there other ways to get this kind of support? EDIT Here is the problem itself: http://stackoverflow.com/questions/2448720/different-users-get-the-same-cookie-value-in-aspxanonymous

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  • How to interpret mono profiler results?

    - by Ovidiu Pacurar
    I created a console application in C# and running it on windows/.NET is 5x faster than on linux/mono or windows/mono. The app encodes some binary files into text format(JSON). I profiled the app on linux/mono using: mono --profile=default:stat myconsoleapp.exe Here is the first part of the result: prof counts: total/unmanaged: 32274/25062 23542 72.95 % mono 459 1.42 % System.Decimal:Divide (System.Decimal,System.Decimal) 457 1.42 % System.Decimal:Round (System.Decimal,int,System.MidpointRounding) 411 1.27 % /lib/libz.so.1 262 0.81 % /lib/tls/i686/cmov/libc.so.6(memmove 253 0.78 % System.Decimal:IsZero () 247 0.77 % System.NumberFormatter:Init (string,double,int) 213 0.66 % System.NumberFormatter:AppendDigits (int,int) 72.95 % mono? Are mono internals using 3 quarters of the total execution time?

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  • Nesting maximum amount of shapes on a surface

    - by Fuu
    In industry, there is often a problem where you need to calculate the most efficient use of material, be it fabric, wood, metal etc. So the starting point is X amount of shapes of given dimensions, made out of polygons and/or curved lines, and target is another polygon of given dimensions. I assume many of the current CAM suites implement this, but having no experience using them or of their internals, what kind of computational algorithm is used to find the most efficient use of space? Can someone point me to a book or other reference that discusses this topic?

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  • How to use QMetaMethod with QObject::connect

    - by VestniK
    I have two instances of QObject subclasses and two QMetaMethod instances of signal in one of objects and slot in another object. I want to connect this signal and slot with each other. I've looked through the qobject.h file and find that SIGNAL() and SLOT() macro are just add "1" or "2" character to the beginning of method signature so it looks like it should be possible to add the same character to the beginning of string returned by QMetaMethod::signature() but this approach depends on some undocumented internals of toolkit and may be broken at any time by a new version of Qt. Does anybody know reliable way to connect signals and slots through their QMetaMethod reflection representation?

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  • How secure are GUIDs in terms of predictability?

    - by ssg
    We're using .NET's Guid.NewGuid() to generate activation codes and API keys currently. I wonder if that poses a security problem since their algorithm is open. .NET Guid uses Win32 CoCreateGuid and I don't know it's internals (possibly MAC address + timestamp?). Can someone derive a second GUID out of the first one, or can he hit it with some smart guesses or is the randomness good enough so search space becomes too big? Generating random keys have the problem of collision, they need a double check before adding to a database. That's why we stuck with GUIDs but I'm unsure about their security for these purposes. Here are the 4 consecutive UUIDGEN outputs: c44dc549-5d92-4330-b451-b29a87848993 d56d4c8d-bfba-4b95-8332-e86d7f204c1c 63cdf958-9d5a-4b63-ae65-74e4237888ea 6fd09369-0fbd-456d-9c06-27fef4c8eca5 Here are 4 of them by Guid.NewGuid(): 0652b193-64c6-4c5e-ad06-9990e1ee3791 374b6313-34a0-4c28-b336-bb2ecd879d0f 3c5a345f-3865-4420-a62c-1cdfd2defed9 5b09d7dc-8546-4ccf-9c85-de0bf4f43bf0

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  • creating a custom upload progress bar

    - by michael
    hi, i have seen all the upload progress bar plugins , widgets, etc. they all suck. their either too bulky with too much useless code or they dont work. what i want to know is where can i read up on how to display an easy upload progress indicator. most browsers have a status progress bar on them below but it isnt very professional to use just that when dealing with clients. how does the browser do it? i want to know the internals of how the browser work with indication a status of something uploading and maybe i can make something using php & jquery. thanks

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  • Implications of Fulltext Search over many columns

    - by Alex
    Hello, I have a really wide table which includes separate columns for billing address, shipping address, primary address, names, aliases etc. (I can't normalize this table further, and that's not the question here anyways). I'm implementing SQL Server fulltext search, and I'm wondering whether I should limit the search ability to just the primary fields (primary address and names for example), or if I can extend the search ability across all columns without occurring too much of a performance or memory penalty. I've done some basic testing with 10,000 sample rows and it's quite fast but I don't have much experience with fulltext indexing, especially its dictionary internals, so I don't know if the index is going to grow over time, or if there is anything else to consider. Thoughts?

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  • Can I turn off implicit Python unicode conversions to find my mixed-strings bugs?

    - by Tal Weiss
    When profiling our code I was surprised to find millions of calls to C:\Python26\lib\encodings\utf_8.py:15(decode) I started debugging and found that across our code base there are many small bugs, usually comparing a string to a unicode or adding a sting and a unicode. Python graciously decodes the strings and performs the following operations in unicode. How kind. But expensive! I am fluent in unicode, having read Joel Spolsky and Dive Into Python... I try to keep our code internals in unicode only. My question - can I turn off this pythonic nice-guy behavior? At least until I find all these bugs and fix them (usually by adding a u'u')? Some of them are extremely hard to find (a variable that is sometimes a string...). Python 2.6.5 (and I can't switch to 3.x).

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  • Book resources for x86/x64 assembly programming on Win platform

    - by Scott Davies
    Hello, I ran a search for assembly language resources on stackoverflow.com and found some interesting results, but they seemed to boil down to two groups: 1) Assembly references to old ia32 architecture, such as the 80386 to Pentium 2) Windows agnostic books. Most of the commenters make the point that assembler is CPU dependent and that the OS is irrelevant, but it seems pointless to me to pick a book that has assembly examples that refer to MS-DOS interrupts and memory layouts. Likewise, learning assembler on Linux would seem to produce Linux executables Are there any: 1) Modern 2) x86/x64 3) on Windows platform - book resources available ? The reason I am targeting the Win platform is I would like to do low-level, OS internals programming, to supplement my Win C/C++ work. Thanks

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  • Fitting maximum amount of shapes on a surface

    - by Fuu
    In industry, there is often a problem where you need to calculate the most efficient use of material, be it fabric, wood, metal etc. So the starting point is X amount of shapes of given dimensions, made out of polygons and/or curved lines, and target is another polygon of given dimensions. I assume many of the current CAM suites implement this, but having no experience using them or of their internals, what kind of computational algorithm is used to find the most efficient use of space? Can someone point me to a book or other reference that discusses this subject?

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  • Where could I get the information about the in-memory layout info of .NET Object Model?

    - by smwikipedia
    I want to know the in-memory representation of .NET constructs such as "interface", "class", "struct", etc. There's an excellent book for C++ object model - <Inside the C++ Object Model by Stanley. Lippman, I want a similar book for .NET and C#. Could someone provide some hints about books and articles? I have read about the "Drill Into .NET Framework Internals to See How the CLR Creates Runtime Objects" Anything more? If this info is not publicly avaialble. Shared source one like Mono or Shared Source CLI could be an option. Many thanks.

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  • YUI and/or jQuery for a new project?

    - by Hortitude
    If I am starting a new project how should I pick between using YUI 2, YUI 3 and jQuery? I know there are a bunch of questions/answers already about can you use them together, but I am trying to figure out what criteria I should be thinking about to make my decision. Are they overlapping? Is one better at GUI and the other better at internals? Do they play well together? My understanding from other questions is that they can live in different namespaces, so they can live together, but that doesn't necessarily mean that it is good to use both. Thanks!

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  • Using WCF to expose underlying process

    - by Steven
    I have a server application that spins up and monitors about 8 separate processes that gather data from different systems. The server app then runs some calculations over the aggregated data and stores it in a db. Simple stuff. I now have a requirement to modify the process so that it no longer saves data to the db but rather exposes it directly to clients via WCF. That's cool, I've used WCF a fair bit but I'm struggling a little with it for some reason. Basically my plan is to HOST the WCF service in my application and have calls redirect into the internals of my existing application but I can figure out how to do that without getting the WCF class to encapsulate the existing app. I want the service to inside my current app, not become it. Any suggestions?

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  • Is there a library / tool to query MySQL data files (MyISAM / InnoDB) without the server? (the SQLit

    - by MGW
    Oftentimes I want to query my MySQL data directly without a server running or without having access to the server (but having read / write rights to the files). Is there a tool or maybe even a library around to query MySQL data files like it is possible with SQLite? I'm specifically looking for InnoDB and MyISAM support. Performance is not a factor. I don't have any knowledge about MySQL internals, but I presume it should be possible to do and not too hard to get the specific code out? Thank you for any suggestions!

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  • Is there any real world reason to use throw ex?

    - by Michael Stum
    In C#, throw ex is almost always wrong, as it resets the stack trace. I just wonder, is there any real world use for this? The only reason I can think of is to hide internals of your closed library, but that's a really weak reason. Apart from that, I've never encountered in the real world. Edit: I do mean throw ex, as in throwing the exact same exception that was caught but with an empty stacktrace, as in doing it exactly wrong. I know that throw ex has to exist as a language construct to allow throwing a different exception (throw new DifferentException("ex as innerException", ex)) and was just wondering if there is ever a situration where a throw ex is not wrong.

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  • How can I clear the appcache on the Google Chrome iPad app?

    - by Jannis
    I've written a little HTML5 based web app that I am trying to debug on the iPad using the Chrome for iPad app. I have added a cache.manifest file to my app which has some heavy caching in it of most static resources however since I am now wanting to debug the app I need a way to clear this cache. I know that on Chrome for Mac you can use: chrome://appcache-internals/ however this page does not exist in the iPad app of Chrome. The regular "Clear Browsing Data" does not empty the appcache —at least not in my case. Does anyone know how I can clear the appcache for the Chrome iPad app?

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  • How do I get my custom requiredif attribute to prevent other attributes from firing

    - by user1757804
    I'm working on an MVC application. I've decorated a property with EqualTo found here: http://dataannotationsextensions.org/EqualTo/Create As well as a custom RequiredIf attribute as suggested here: http://blogs.msdn.com/b/simonince/archive/2011/02/04/conditional-validation-in-asp-net-mvc-3.aspx My issue is that even when the field is supposed to be required and isn't the EqualTo logic is firing. So I get error messages saying the field is required but also that the field doesn't match. If I replace the Requiredif with a regular Required only the Required message will show. What I'm trying to figure out is how the EqualTo logic is prevented when combined with the Required attribute but not prevented when combined with my custom RequiredIf. Any suggestions would be most appreciated, I've been racking my brain most of the day trying to figure out the mvc internals around Required.

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  • Using the windows api and C++, how could I load an exe from the hard drive and run it in its own thread?

    - by returneax
    For the sake of learning I'm trying to do what the OS does when launching a program ie. parsing a PE file and giving it a thread of execution. If I have two exe's one called foo.exe and the other bar.exe, how could I have foo.exe load the contents of bar.exe into memory then have it execute from there in its own thread? I know how to get it into memory using MapViewOfFile or by simple loading the contents on the hard drive into a buffer. I'm assuming simply copying the contents of bar.exe on disk into its own suspended thread and running it wouldn't work. I am semi-familiar with PE file internals. All help is very much appreciated, of course :)

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  • recommend a server side technology for gwt (beginner)

    - by user486503
    hi all ! I am developing a gwt project and am looking for an appropriate server side technology. it should support be open source and support user login (and not using openID...) with password recovery etc it seems that the de-facto standard would be spring + hibernate. however, I am unfamiliar with neither of them and understand that the learning curve (especially for spring) is very high. gwt was quite easy to learn using GOOG's excellent online tutorials but the spring equivalent seem to impose lots of configuration files and deeper understanding of its internals. so I am looking for a simpler server side technology to deploy my gwt app. I am definitely prepared to learn a new framework if necessary but not something that would take me 2 months just to understand the fundamentals... any ideas...?

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  • Fastest way to check for value existance.

    - by Itay Moav
    I have a list of values I have to check my input against it for existence. What is the faster way? This is really out of curiosity on how the internals work, not any stuff about premature optimization etc... 1. $x=array('v'=>'','c'=>'','w'=>); .. .. array_key_exists($input,$x); 2. $x=array('v','c','w'); .. .. in_array($input,$x);

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  • Silently binding a variable instance to a class in C++?

    - by gct
    So I've got a plugin-based system I'm writing. Users can create a child class of a Plugin class and then it will be loaded at runtime and integrated with the rest of the system. When a Plugin is run from the system, it's run in the context of a group of plugins, which I call a Session. My problem is that inside the user plugins, two streaming classes called pf_ostream and pf_istream can be used to read/write data to the system. I'd like to bind the plugin instance's session variable to pf_ostream and pf_istream somehow so that when the user instantiates those classes, it's already bound to the session for them (basically I don't want them to see the session internals) I could just do this with a macro, wrapping a call to the constructor like: #define MAKE_OSTREAM = pf_ostream_int(this->session) But I thought there might be a better way. I looked at using a nested class inside Plugin wrapping pf_ostream but it appears nested classes don't get access to the enclosing classes variables in a closure sort of way. Does anyone know of a neat way to do this?

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  • How do I package an SDK (static lib + xibs) for the iPhone?

    - by twhipple
    I am creating an SDK for a client that includes predefined view controllers. What is the recommended way to package everything (static lib, .xib(s), and .png(s)) for easy use? SDKs that I've used (e.g. Pinch Media) do a good job of just providing a .h and .a file that expose only user accessible functionality and hiding everything else. As I read Apple's documentation, a framework would be ideal but is not permitted on iPhoneOS. Some key requirements: Don't expose source or object internals. Be easy to use & set up. Work on both the device and simulator. Thanks!

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  • The best, in the West

    - by Fatherjack
    As many of you know, I run the SQL South West user group and we are currently in full flow preparing to stage the UK’s second SQL Saturday. The SQL Saturday spotlight is going to fall on Exeter in March 2013. We have full-day session on Friday 8th with some truly amazing speakers giving their insights and experience into some vital areas of working with SQL Server: Dave Ballantyne and Dave Morrison – TSQL and internals Christian Bolton and Gavin Payne – Mission critical data platforms on Windows Server 2012 Denny Cherry – SQL Server Security André Kamman – Powershell 3.0 for SQL Server Administrators and Developers Mladen Prajdic – From SQL Traces to Extended Events – The next big switch. A number of people have claimed that the choice is too good and they’d have trouble selecting just one session to attend. I can see how this is a problem but hope that they make their minds up quickly. The venue is a bespoke conference suite in the centre of Exeter but has limited capacity so we are working on a first-come first-served basis. All the session details and booking and travel information can be found on our user group website. The Saturday will be a day of free, 50 minute sessions on all aspects SQL Server from almost 30 different speakers. If you would like to submit a session then get a move on as submissions close on 8th January 2013 (That’s less than a month away). We are really interested in getting new speakers started so we have a lightning talk session where you can come along and give a small talk (anywhere from 5 to 15 minutes long) about anything connected with SQL Server as a way to introduce you to what it’s like to be a speaker at an event. Details on registering to attend and to submit a session (Lightning talks need to be submitted too please) can be found on our SQL Saturday pages. This is going to be the biggest and best bespoke SQL Server conference to ever take place this far South West in the UK and we aim to give everyone who comes to either day a real experience of the South West so we have a few surprises for you on the day.

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