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  • Can this way of storing typed objects be improved?

    - by Pindatjuh
    This is an "can it be improved"-question. Topic: Storing typed objects in memory. Background information: I'm building a compiler for the x86-32 Windows platform for my language. My goal includes typed objects. Idea: Every primitive is a semi-class (it can be used as if it was a normal class, but it's stored more compact). Every class is represented by primitives and some meta-data (containing class-properties, inheritance stuff, etc.). The meta-data is complex: it doesn't use fields but instead context-switches. For primitives, the meta-data is very small, compared to a "real" class, which is alot bigger. This enables another idea that "primitives are objects", in my language, which I found nessecairy. Example: If I have an array of 32 booleans, then the pure content of this array is exactly 4 byte (32 bits of booleans). The meta-data will contain flags that the type is an array of booleans, which contains 32 entries. The meta-data is very compacted, on bit-level: using a sort of "packing" mechanism, which is read by a FSM at runtime, when doing inspection of the type (like when passing the object to methods for checking, etc.) For instance (read from left to right, top to bottom, remember vertical position when going to the right, and check nearest column header for meaning of switch): Primitive? Array? Type-Meta 1 Byte? || Size (1 byte) 1 1 [...] 1 [...] done 0 2 Bytes? || Size (2 bytes) 1 [...] done || Size (4 bytes) 0 [...] done Integer? 1 Byte? 2 Bytes? 0 1 0 1 done 1 done 0 done Boolean? Byte? 0 1 0 done 1 done More-Primitives 0 .... Class-Stuff (Huge) 0 ... (After reaching done the data is inserted. || = byte alignment. [...] is variable sized. ... is not described here, for simplicity. And let's call them cost-based-data-structures.) For an array of 32 booleans containing all true values, the memory for this type would be (read top-down): 1 Primitive 1 Array 1 ArrayType: Primitive 0 Not-Array 0 Not-Integer 1 Boolean 0 Not-Byte (thus bit) 1 Integer Size: 1 Byte 00100000 Array size 01010101 01010101 01010101 01010101 Data (user defined) Thus, 8 bytes represent 32 booleans in an array: 11100101 00100000 01010101 01010101 01010101 01010101 How can I improve this? (Both performance- and memory-consumption wise)

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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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  • How to do "See Also" to a book using doxygen

    - by Paul J. Lucas
    The Javadoc @see allows a simple string as an argument to refer to something like a book, e.g.: @see "The Java Programming Language." As far as I can tell, the Doxygen \see offers no equivalent. Is there any way to have a book reference generated in the documentation, e.g.: See Also The C++ Programming Language, Bjarne Stroustrup, Addison-Wesley, 2000, section 19.4.1: The Standard Allocator ? Clarification This question is about how to do a "See Also" as part of a comment, e.g.: /** * Allocates memory in an amazing way. * \param size The number of bytes to allocate. * \return Returns a pointer to the start of the allocated memory. * \see MyOtherClass::alloc() * \see "The C++ Programming Language," Bjarne Stroustrup, Addison-Wesley, 2000, * section 19.4.1: The Standard Allocator. */ void* my_alloc( size_t size ); Of course the above does not work in Doxygen. Note that if there are multiple \see tags, they should be merged into a single "See Also" section (like the way \see normally works.

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  • Marshal managed string[] to unmanaged char**

    - by Vince
    This is my c++ struct (Use Multi-Byte Character Set) typedef struct hookCONFIG { int threadId; HWND destination; const char** gameApps; const char** profilePaths; } HOOKCONFIG; And .Net struct [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)] public struct HOOKCONFIG { public int threadId; public IntPtr destination; // MarshalAs? public string[] gameApps; // MarshalAs? public string[] profilePaths; } I got some problem that how do I marshal the string array? When I access the struct variable "profilePaths" in C++ I got an error like this: An unhandled exception of type 'System.AccessViolationException' occurred in App.exe Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. MessageBox(0, cfg.profilePaths[0], "Title", MB_OK); // error ... Orz

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  • How to debug macruby?

    - by Dan
    Hi, I've encountered an inconsistent bug with MacRuby and have no idea how to go about debugging this. If anyone could help would be great. I don't know if this is due to my own code or is it a bug in the MacRuby framework. I have a feeling it's my own code, something about over-retaining a piece of memory and hence the garbage collection failed. This is the error from Xcode. Thanks. CSV Wizard(30245,0x7fff704f7ca0) malloc: resurrection error for object 0x20199da20 while assigning {conservative-block}[196608](0x302360060)[117616] = Array[64](0x20199da20) garbage pointer stored into reachable memory, break on auto_zone_resurrection_error to debug CSV Wizard(30245,0x103781000) malloc: garbage block 0x20199da20(Array[64]) was over-retained during finalization, refcount = 1 This could be an unbalanced CFRetain(), or CFRetain() balanced with -release. Break on auto_zone_resurrection_error() to debug. CSV Wizard(30245,0x103781000) malloc: fatal resurrection error for garbage block 0x20199da20(Array[64]): over-retained during finalization, refcount = 1

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  • Bad_alloc exception when using new for a struct c++

    - by bsg
    Hi, I am writing a query processor which allocates large amounts of memory and tries to find matching documents. Whenever I find a match, I create a structure to hold two variables describing the document and add it to a priority queue. Since there is no way of knowing how many times I will do this, I tried creating my structs dynamically using new. When I pop a struct off the priority queue, the queue (STL priority queue implementation) is supposed to call the object's destructor. My struct code has no destructor, so I assume a default destructor is called in that case. However, the very first time that I try to create a DOC struct, I get the following error: Unhandled exception at 0x7c812afb in QueryProcessor.exe: Microsoft C++ exception: std::bad_alloc at memory location 0x0012f5dc.. I don't understand what's happening - have I used up so much memory that the heap is full? It doesn't seem likely. And it's not as if I've even used that pointer before. So: first of all, what am I doing that's causing the error, and secondly, will the following code work more than once? Do I need to have a separate pointer for each struct created, or can I re-use the same temporary pointer and assume that the queue will keep a pointer to each struct? Here is my code: struct DOC{ int docid; double rank; public: DOC() { docid = 0; rank = 0.0; } DOC(int num, double ranking) { docid = num; rank = ranking; } bool operator>( const DOC & d ) const { return rank > d.rank; } bool operator<( const DOC & d ) const { return rank < d.rank; } }; //a lot of processing goes on here; when a matching document is found, I do this: rank = calculateRanking(table, num); //if the heap is not full, create a DOC struct with the docid and rank and add it to the heap if(q.size() < 20) { doc = new DOC(num, rank); q.push(*doc); doc = NULL; } //if the heap is full, but the new rank is greater than the //smallest element in the min heap, remove the current smallest element //and add the new one to the heap else if(rank > q.top().rank) { q.pop(); cout << "pushing doc on to queue" << endl; doc = new DOC(num, rank); q.push(*doc); } Thank you very much, bsg.

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  • How can I create the XML::Simple data structure using a Perl XML SAX parser?

    - by DVK
    Summary: I am looking a fast XML parser (most likely a wrapper around some standard SAX parser) which will produce per-record data structure 100% identical to those produced by XML::Simple. Details: We have a large code infrastructure which depends on processing records one-by-one and expects the record to be a data structure in a format produced by XML::Simple since it always used XML::Simple since early Jurassic era. An example simple XML is: <root> <rec><f1>v1</f1><f2>v2</f2></rec> <rec><f1>v1b</f1><f2>v2b</f2></rec> <rec><f1>v1c</f1><f2>v2c</f2></rec> </root> And example rough code is: sub process_record { my ($obj, $record_hash) = @_; # do_stuff } my $records = XML::Simple->XMLin(@args)->{root}; foreach my $record (@$records) { $obj->process_record($record) }; As everyone knows XML::Simple is, well, simple. And more importantly, it is very slow and a memory hog—due to being a DOM parser and needing to build/store 100% of data in memory. So, it's not the best tool for parsing an XML file consisting of large amount of small records record-by-record. However, re-writing the entire code (which consist of large amount of "process_record"-like methods) to work with standard SAX parser seems like an big task not worth the resources, even at the cost of living with XML::Simple. I'm looking for an existing module which will probably be based on a SAX parser (or anything fast with small memory footprint) which can be used to produce $record hashrefs one by one based on the XML pictured above that can be passed to $obj->process_record($record) and be 100% identical to what XML::Simple's hashrefs would have been. I don't care much what the interface of the new module is; e.g whether I need to call next_record() or give it a callback coderef accepting a record.

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  • GCC/XCode equivalent of _CrtCheckMemory?

    - by Chris Becke
    When dealing with random memory overwrites, in MSVC it is possible to validate the state of the heap at various points with a call to _CrtCheckMemory, and know with at least a small level of confidence that the code up until the check was not responsible for any errors that might cause new or malloc to fail later. In XCode, whats the equivalent way to try and box in a memory overwrite? All I have at the moment is a random failure of a call to new, somewhere deep in the bowels of some code with no real idea of how long the code has been running with a corrupt heap up until that point.

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  • Inserting rows while fetching(from another table) in SQLite

    - by Samuel
    I'm getting this error no matter what with python and sqlite. File "addbooks.py", line 77, in saveBook conn.commit() sqlite3.OperationalError: cannot commit transaction - SQL statements in progress The code looks like this: conn = sqlite3.connect(fname) cread = conn.cursor() cread.execute('''select book_text from table''') while True: row = cread.fetchone() if row is None: break .... for entry in getEntries(doc): saveBook(entry, conn) Can't do a fetchall() because table and column size are big, and the memory is scarce. What can be done without resorting to dirty tricks(as getting the rowids in memory, which would probably fit, and then selecting the rows one by one)?.

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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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  • [Python] How do I read binary pickle data first, then unpickle it?

    - by conradlee
    I'm unpickling a NetworkX object that's about 1GB in size on disk. Although I saved it in the binary format (using protocol 2), it is taking a very long time to unpickle this file---at least half an hour. The system I'm running on has plenty of system memory (128 GB), so that's not the bottleneck. I've read here that pickling can be sped up by first reading the entire file into memory, and then unpickling it (that particular thread refers to python 3.0, which I'm not using, but the point should still be true in python 2.6). How do I first read the binary file, and then unpickle it? I have tried: import cPickle as pickle f = open("big_networkx_graph.pickle","rb") bin_data = f.read() graph_data = pickle.load(bin_data) But this returns: TypeError: argument must have 'read' and 'readline' attributes Any ideas?

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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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  • 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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  • Monitor and Terminate Python script based on system resource use

    - by Vincent
    What is the "right" or "best" way to monitor the system resources a python script is using and terminate it if the resource use exceeds some predetermined values. In my case memory usage is of concern. I am not asking how to measure the system resource use although I am open to suggestions. As a simple example, let's assume I have a function that finds prime numbers less than some large number and adds them to a list based on some condition. I don't know ahead of time how many prime numbers will satisfy the condition so I what to be sure to terminate the function if I use up to much system memory (8gb lets say). I know that there are ways to monitor the size of python objects. What I don't know is the proper way to monitor the size of the list and exit is to just include a size test in the prime function loop and exit if it exceeds 8gb or if there is an "external" way to monitor and exit.

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  • Strange error with CreateCompatibleDC

    - by sevaxx
    Maybe this is a foolish question, I can't see why I can not get a DC created in the following code : HBITMAP COcrDlg::LoadClippedBitmap(LPCTSTR pathName,UINT maxWidth,UINT maxHeight) { HBITMAP hBmp = (HBITMAP)::LoadImage(NULL, pathName, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | LR_CREATEDIBSECTION); if (!hBmp) return NULL; HDC hdc = (HDC)GetDC(); HDC hdcMem = CreateCompatibleDC(hdc); if (!hdcMem) { DWORD err = GetLastError(); } ... ... ... The bitmap hBmp is loaded fine and hdc has a valid value. But the call to CreateCompatibleDC() returns a NULL pointer. Then, GetLastError() returns 0 ! Anybody can guess what's going on here , please ? PS : There are no memory allocations or GDI routines called before this one...so I think memory leaks should be ruled out.

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  • A PHP object server for business logic

    - by Matthieu
    I wonder if such a thing is possible or even exist : In the MVC pattern, I would like to have the Model part to be persistant in memory, instead of reloading my instances at each execution. So I want only the Controller and View part to be executed. Is there any solution of server that would provide PHP objects (just like a Mysql server provides data records), and that keeps these objects in memory ? A problem would be also : how to have a constructed query to get objects ? Maybe PHP Linq ?

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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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  • Stack recommendations for small/medium-sized web application in Python

    - by reto
    I'm looking for some recommendations for a python web application. We have some memory restrictions and we try to keep it small and lean. We thought about using WSGI (and a python webserver) and build the rest ourself. We already have a template engine we'd like to use, but we are open for some suggestions regarding the whole request handling (the controller). The application has to run in a single process and the requests have to be processed with multiple threads. We've looked at django, but we are a not sure if it fits into our memory budget. Your feedback is very welcome! Cheers, Reto

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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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  • Windows Service suddenly doing nothing

    - by TB
    Hi, My windows service is using a Thread (not a timer) which is always looping and sleeps for 1 second every loop using : evet.WaitOne(interval); When I start the service it works fine and I can see in the task manager that it is running, consuming and releasing memory, consuming processor ... etc that is all normal, but after a while (random amount of time) the service simply stops!! it is still there in the task manager but it is not consuming any processor work now and its consumption to the memory is not changing. it simply (died but still there in the task manager like a Zombie). I know that many exceptions might have happened during running the service (it is really doing many things) but all those exceptions are handled in Try catch blocks, so why is my "always looping" thread stops ??? This thread also logs every time he loops, when he is freezig in this way he is not logging anything (of course)

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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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  • 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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  • Why doesn't this work?

    - by user146780
    I'v tried to solve a memory leak in the GLU callback by creating a global variable but now it dos not draw anything: GLdouble *gluptr = NULL; void CALLBACK combineCallback(GLdouble coords[3], GLdouble *vertex_data[4], GLfloat weight[4], GLdouble **dataOut) { GLdouble *vertex; if(gluptr == NULL) { gluptr = (GLdouble *) malloc(6 * sizeof(GLdouble)); } vertex = (GLdouble*)gluptr; vertex[0] = coords[0]; vertex[1] = coords[1]; vertex[2] = coords[2]; for (int i = 3; i < 6; i++) { vertex[i] = weight[0] * vertex_data[0][i] + weight[1] * vertex_data[0][i] + weight[2] * vertex_data[0][i] + weight[3] * vertex_data[0][i]; } *dataOut = vertex; } basically instead of doing malloc each time in the loop (thus the memory leak) im using a global pointer, but this doesn't work (drawing to the screen). Why would using malloc to a pointer created in the function work any different than a global variable? Thanks

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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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