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  • Lifetime of javacript variables.

    - by The Machine
    What is the lifetime of a variable in javascript, declared with "var". I am sure, it is definitely not according to expectation. <script> function(){ var a; var fun=function(){ // a is accessed and modified } }(); </script> Here how and when does javascript garbage collect the variable a? Since 'a' is a part of the closure of the inner function, it ideally should never get garbage collected, since the inner function 'fun', may be passed as a reference to an external context.So 'fun' should still be able to access 'a', from the external context. If my understanding is correct, how does garbage collection happen then, and how does it ensure to have enough memory space, since keeping all variables in memory until the execution of the program might not be tenable ?

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  • Algorithm for non-contiguous netmask match

    - by Gianluca
    Hi, I have to write a really really fast algorithm to match an IP address to a list of groups, where each group is defined using a notation like 192.168.0.0/252.255.0.255. As you can see, the bitmask can contain zeros even in the middle, so the traditional "longest prefix match" algorithms won't work. If an IP matches two groups, it will be assigned to the group containing most 1's in the netmask. I'm not working with many entries (let's say < 1000) and I don't want to use a data structure requiring a large memory footprint (let's say 1-2 MB), but it really has to be fast (of course I can't afford a linear search). Do you have any suggestion? Thanks guys. UPDATE: I found something quite interesting at http://www.cse.usf.edu/~ligatti/papers/grouper-conf.pdf, but it's still too memory-hungry for my utopic use case

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  • Tuning JVM (GC) for high responsive server application

    - by elgcom
    I am running an application server on Linux 64bit with 8 core CPUs and 6 GB memory. The server must be highly responsive. After some inspection I found that the application running on the server creates rather a huge amount of short-lived objects, and has only about 200~400 MB long-lived objects(as long as there is no memory leak) After reading http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html I use these JVM options -Xms2g -Xmx2g -XX:MaxPermSize=256m -XX:NewRatio=1 -XX:+UseConcMarkSweepGC Result: the minor GC takes 0.01 ~ 0.02 sec, the major GC takes 1 ~ 3 sec the minor GC happens constantly. How can I further improve or tune the JVM? larger heap size? but will it take more time for GC? larger NewSize and MaxNewSize (for young generation)? other collector? parallel GC? is it a good idea to let major GC take place more often? and how?

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  • Leak caused by fread

    - by Jack
    I'm profiling code of a game I wrote and I'm wondering how it is possible that the following snippet causes an heap increase of 4kb (I'm profiling with Heapshot Analysis of Xcode) every time it is executed: u8 WorldManager::versionOfMap(FILE *file) { char magic[4]; u8 version; fread(magic, 4, 1, file); <-- this is the line fread(&version,1,1,file); fseek(file, 0, SEEK_SET); return version; } According to the profiler the highlighted line allocates 4.00Kb of memory with a malloc every time the function is called, memory which is never released. This thing seems to happen with other calls to fread around the code, but this was the most eclatant one. Is there anything trivial I'm missing? Is it something internal I shouldn't care about? Just as a note: I'm profiling it on an iPhone and it's compiled as release (-O2).

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  • What wording in the C++ standard allows static_cast<non-void-type*>(malloc(N)); to work?

    - by ben
    As far as I understand the wording in 5.2.9 Static cast, the only time the result of a void*-to-object-pointer conversion is allowed is when the void* was a result of the inverse conversion in the first place. Throughout the standard there is a bunch of references to the representation of a pointer, and the representation of a void pointer being the same as that of a char pointer, and so on, but it never seems to explicitly say that casting an arbitrary void pointer yields a pointer to the same location in memory, with a different type, much like type-punning is undefined where not punning back to an object's actual type. So while malloc clearly returns the address of suitable memory and so on, there does not seem to be any way to actually make use of it, portably, as far as I have seen.

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  • Python fCGI + sqlAlchemy = malformed header from script. Bad header=FROM tags : index.py

    - by crgwbr
    I'm writing an Fast-CGI application that makes use of sqlAlchemy & MySQL for persistent data storage. I have no problem connecting to the DB and setting up ORM (so that tables get mapped to classes); I can even add data to tables (in memory). But, as soon as I query the DB (and push any changes from memory to storage) I get a 500 Internal Server Error and my error.log records malformed header from script. Bad header=FROM tags : index.py, when tags is the table name. Any idea what could be causing this? Also, I don't think it matters, but its a Linux development server talking to an off-site (across the country) MySQL server.

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  • GlassFish JDO and global object

    - by bach
    Hi, I'm thinking about the GlassFish platform for my new app. My app env. doesn't have a big volume of data to handle, but a lot of users writing/reading the same data A very volotile portion of the data updates every 200milsec by diff users. Therefore I'd like that type of data to be in memory only and accessible to the whole app My questions: How do I use a global object in memory with GF? a. use a static variable object - for that I guess I need to make sure GF is running on only 1 JVM -- how to I configure GF to run on 1 jvm? b. use HttpContext - same as a. How do I persist to the DB? a. can I use JDO interface? How do I Schedule tasks to be performed in the future (something like the task queue in GAE) thanks, J.S. Bach

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  • hidden forms and thr handles

    - by shraddha
    i am hiding the form using SetVisibleCore to false, but now i cant get the handle of this form in other application which i am retrieving using EnumWindow its giving me exception "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." an ACCESS VIOLATION EXCEPTION. so i am searching on 2 ways 1. find out the other way to get handle here we cant use FindWindow cause its not returning any handle 2. find a another way to hide the form but this should be done before loading of the form so,,,plz help me if anybody can

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  • internet explorer, google chrome injection

    - by Volim Te
    I wrote code that injects a function in Internet Explorer/Chrome but it doesn't work with these processes. Basically, it fills one big structure with all the APIs my function needs, strings, and other data, then it opens a process to get a handle, virtualallocex to allocate enough memory to store a function and structure there, and it writes the function and the structure in allocated memory. It then runs createremotethread there with the function as a starting address and structure as parameter. It works all great with calc/notepad/winamp processes but I have problems with browser injection. I'm wondering what could it be, I'm using these APIs. x.xCreateFile x.xWriteFile x.xCloseHandle x.xSleep x.xVirtualAlloc x.xVirtualFree x.xMessageBox x.xLoadLibrary x.xShellExecute Is it because browsers are protected now and they're running with lowest privileges?

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  • Deciphering a queer compiler warning about unsigned decimal constant

    - by Artagnon
    This large application has a memory pool library which uses a treap internally to store nodes of memory. The treap is implemented using cpp macros, and the complete file trp.h can be found here. I get the following compiler warning when I attempt to compile the application: warning: this decimal constant is unsigned only in ISO C90 By deleting portions of the macro code and using trial-and-error, I finally found the culprit: #define trp_prio_get(a_type, a_field, a_node) \ (2654435761*(uint32_t)(uintptr_t)(a_node)) I'm not sure what that strange number is doing there, but I assume it's there for a good reason, so I just want to leave it alone. I do want to fix the warning though- any idea why the compiler's saying that it's unsigned only in ISO C90? EDIT: I'm using gcc-4.1

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  • C++: Best text accumulator

    - by MInner
    Text gets accumulates piecemeal before being sent to client. Now we use own class that allocates memory for each piece as char massive. (Anyway, works like char[][] + std::list<char*>). Then we build the whole string, convert it into std::sting and then create boost::asio::streambuf using it. That's slow enough, I assume. Correct me if I'm wrong. I know, in many cases simple FILE type from stdio.h is used. How does it works? Allocates memory at every write into it. So, is it faster and is there any way to read into boost::asio::streambuf from FILE?

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  • java servlet: generate zip file from BLOBs

    - by Zack
    I'm trying to zip a large number of pdf files (stored as BLOBs in the DB) and then return the zip as an attachment to the user. What's the best way to do this without running into memory issues? Another note: I actually need to merge some PDFs prior to adding them to the ZipOutputStream. Therefore, a couple PDFs will need to be stored in memory at a time. I assume it would be best to then store them as temporary files on the server before zipping them all?

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  • Sqlite. How to create an index in attached DB?

    - by kappa
    I have a problem with adding index to memory database attached to main database. 1) I open the database (F) from file 2) Attach the :memory: (M) database 3) Create tables in database M 4) Copy data from F to M I would also like to create an index in database M, but don't know how to do that. This code creates index but in F database: sQuery = "CREATE INDEX IF NOT EXISTS [INDID] ON [PANEL]([ID] ASC);"; I tried to add the name qualifier before table name like this: sQuery = "CREATE INDEX IF NOT EXISTS [INDID] ON [M.PANEL]([ID] ASC);"; but SQLite returns with message that column main.M.PANEL does not exist. What can I do?

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  • CUDA small kernel 2d convolution - how to do it

    - by paulAl
    I've been experimenting with CUDA kernels for days to perform a fast 2D convolution between a 500x500 image (but I could also vary the dimensions) and a very small 2D kernel (a laplacian 2d kernel, so it's a 3x3 kernel.. too small to take a huge advantage with all the cuda threads). I created a CPU classic implementation (two for loops, as easy as you would think) and then I started creating CUDA kernels. After a few disappointing attempts to perform a faster convolution I ended up with this code: http://www.evl.uic.edu/sjames/cs525/final.html (see the Shared Memory section), it basically lets a 16x16 threads block load all the convolution data he needs in the shared memory and then performs the convolution. Nothing, the CPU is still a lot faster. I didn't try the FFT approach because the CUDA SDK states that it is efficient with large kernel sizes. Whether or not you read everything I wrote, my question is: how can I perform a fast 2D convolution between a relatively large image and a very small kernel (3x3) with CUDA?

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  • Core Data data type for just the date - not including time

    - by Jason
    I am new at Core Data, and it seems like it is a great way to manage the data store. However I am also very memory-conscious due to the fact that the iPhone doesn't have that much of it. I was a little surprised to see that the data types are so limited - eg. there is a Date type which includes also the time, but no Date type for just the date! All the time information takes up precious bytes of memory, if I just wanted an attribute with the date (e.g. 2/15/2010 rather than 2/15/2010 02:34:48), how could I do this? Is it possible?

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  • Resolving Assemblies, the fuzzy way

    - by David Rutten
    Here's the setup: A pure DotNET class library is loaded by an unmanaged desktop application. The Class Library acts as a plugin. This plugin loads little baby plugins of its own (all DotNET Class Libraries), and it does so by reading the dll into memory as a byte-stream, then Assembly asm = Assembly.Load(COFF_Image); The problem arises when those little baby plugins have references to other dlls. Since they are loaded via the memory rather than directly from the disk, the framework often cannot find these referenced assemblies and is thus incapable of loading them. I can add an AssemblyResolver handler to my project and I can see these referenced assemblies drop past. I have a reasonably good idea about where to find these referenced assemblies on the disk, but how can I make sure that the Assmebly I load is the correct one? In short, how do I reliably go from the System.ResolveEventArgs.Name field to a dll file path, presuming I have a list of all the folders where this dll could be hiding)?

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  • Singelton on iPhone Simulator vs Singelton on real Device

    - by Helge Becker
    I am using a Singelton for some shared stuff. In the simulator, the app crashes ocasionally. Tracking the crash down shows that the the properties of my Singelton became dealocated. Those crashes never happend on a real device. Does the iPHone simulator handle memory managemend different? GC maybe? Changed the singelton to match this pattern. The iPhone Simulator dont crash now, but I am not sure about the memory handling on the real device. I assume that this solution will cause problems. What do you think?

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  • Performance of Managed C++ Vs UnManaged/native C++

    - by bsobaid
    I am writing a very high performance application that handles and processes hundreds of events every millisecond. Is Unmanaged C++ faster than managed c++? and why? Managed C++ deals with CLR instead of OS and CLR takes care of memory management, which simplifies the code and is probably also more efficient than code written by "a programmer" in unmanaged C++? or there is some other reason? When using managed, how can one then avoid dynamic memory allocation, which causes a performance hit, if it is all transparent to the programmer and handled by CLR? So coming back to my question, Is managed C++ more efficient in terms of speed than unmanaged C++ and why?

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  • C# compile finalize method's on runtime?

    - by Royi Namir
    As im reading through 3 books about GC , ive notice some strange fact : C# via CLR CriticalFinalizerObject : the CLR treats this class and classes derived from it in a very special manner what ??? "not find enough memory to COMPILE a method? " IMHO - the code should be already compiled... no ? when Im writing c# code - the whole code is compiled to IL before its running... no? but according to the text - at RUNTIME - he MAY find insufficient memory for compile... Help ?

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  • Can you create a HIPAA compliant Amazon S3 Web Application?

    - by xkingpin
    I am facing some questions when trying to design an S3 application using ASP.NET MVC and trying to stay HIPAA compliant. My initial plan was to require an SSL connection to my web server, encrypt the images on my server, then send them to s3 using my private keys. Here's my obvious concerns: You cannot store unencrypted images in any temporary file cache when client views images within the browser. Even if I setup an ashx to generically handle the image in memory, couldn't this get stored in cache? Saying the images will be encrpyted because you will be connecting to my server via https still does not guarantee all browsers will not cache data. It's not possible to even consider the "Query String" with expiration option since data will be encrypted before being stored on disk at s3, and will again be decrypted at my server in memory. I think my only option would be to write/purchase some sort of ActiveX component that will not expose the image as a simple html image source or write my app as a client side WinForm application.

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  • Capturing stdout within the same process in Python

    - by danben
    I've got a python script that calls a bunch of functions, each of which writes output to stdout. Sometimes when I run it, I'd like to send the output in an e-mail (along with a generated file). I'd like to know how I can capture the output in memory so I can use the email module to build the e-mail. My ideas so far were: use a memory-mapped file (but it seems like I have to reserve space on disk for this, and I don't know how long the output will be) bypass all this and pipe the output to sendmail (but this may be difficult if I also want to attach the file)

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  • Pointers, links, object and reference count

    - by EugeneP
    String a = "a"; // allocate memory and write address of a memory block to a variable String b = "b"; // in a and b hold addresses b = a; // copy a address into b. // Now what? b value is completely lost and will be garbage collected //* next step a = null; // now a does not hold a valid address to any data, // still data of a object exist somewhere, yet we cannot get access to it. Correct me if there's a mistake somewhere in my reflexions. My question is: suppose anInstance object of type Instance has a property ' surname ' anInstance.getSurname() returns "MySurname". now String s = anInstance.getSurname(); anInstance = null; question is - is it true that getSurname value, namely MySurname will not be garbage collected because and only because it has active reference counter 0, and if other properties of anInstance have a zero reference counter, they'll be garbage collected?

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  • Can my app arrange a gdb breakpoint or watch?

    - by Larry Gritz
    Is there a way for my code to be instrumented to insert a break point or watch on a memory location that will be honored by gdb? (And presumably have no effect when gdb is not attached.) I know how to do such things as gdb commands within the gdb session, but for certain types of debugging it would be really handy to do it "programmatically", if you know what I mean -- for example, the bug only happens with a particular circumstance, not any of the first 11,024 times the crashing routine is called, or the first 43,028,503 times that memory location is modified, so setting a simple break point on the routine or watch point on the variable is not helpful -- it's all false positives. I'm concerned mostly about Linux, but curious about if similar solutions exist for OS X (or Windows, though obviously not with gdb).

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