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  • Optimizing processing and management of large Java data arrays

    - by mikera
    I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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  • Why is creating a ring buffer shared by different processes so hard (in C++), what I am doing wrong?

    - by recipriversexclusion
    I am being especially dense about this but it seems I'm missing an important, basic point or something, since what I want to do should be common: I need to create a fixed-size ring buffer object from a manager process (Process M). This object has write() and read() methods to write/read from the buffer. The read/write methods will be called by independent processes (Process R and W) I have implemented the buffer, SharedBuffer<T&>, it allocates buffer slots in SHM using boost::interprocess and works perfectly within a single process. I have read the answers to this question and that one on SO, as well as asked my own, but I'm still in the dark about how to have different processes access methods from a common object. The Boost doc has an example of creating a vector in SHM, which is very similar to what I want, but I want to instantiate my own class. My current options are: Use placement new, as suggested by Charles B. to my question; however, he cautions that it's not a good idea to put non-POD objects in SHM. But my class needs the read/write methods, how can I handle those? Add an allocator to my class definition, e.g. have SharedBuffer<T&, Alloc> and proceed similarly to the vector example given in boost. This sounds really complicated. Change SharedBuffer to a POD class, i.e. get rid of all the methods. But then how to synchronize reading and writing between processes? What am I missing? Fixed-length ring buffers are very common, so either this problem has a solution or else I'm doing something wrong.

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  • Access Violation

    - by Justin
    I've been learning how to NOP functions in C++ or even C but there are very few tutorials online about it. I've been googling for the past few hours now and I'm just stuck. Here is my code. #include <iostream> #include <windows.h> #include <tlhelp32.h> using namespace std; //#define NOP 0x90 byte NOP[] = {0x90}; void enableDebugPrivileges() { HANDLE hcurrent=GetCurrentProcess(); HANDLE hToken; BOOL bret=OpenProcessToken(hcurrent,40,&hToken); LUID luid; bret=LookupPrivilegeValue(NULL,"SeDebugPrivilege",&luid); TOKEN_PRIVILEGES NewState,PreviousState; DWORD ReturnLength; NewState.PrivilegeCount =1; NewState.Privileges[0].Luid =luid; NewState.Privileges[0].Attributes=2; AdjustTokenPrivileges(hToken,FALSE,&NewState,28,&PreviousState,&ReturnLength); } DWORD GetProcId(char* ProcName) { PROCESSENTRY32 pe32; HANDLE hSnapshot = NULL; pe32.dwSize = sizeof( PROCESSENTRY32 ); hSnapshot = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 ); if( Process32First( hSnapshot, &pe32 ) ) { do{ if( strcmp( pe32.szExeFile, ProcName ) == 0 ) break; }while( Process32Next( hSnapshot, &pe32 ) ); } if( hSnapshot != INVALID_HANDLE_VALUE ) CloseHandle( hSnapshot ); return pe32.th32ProcessID; } void WriteMem(DWORD Address, void* Value, size_t Size) { DWORD Protect = NULL; VirtualProtect((LPVOID)Address, 3, PAGE_READWRITE, &Protect); memcpy((void*)Address, Value, 3); VirtualProtect((LPVOID)Address, 3, Protect, &Protect); } void nop_(PVOID address, int bytes){ DWORD d, ds; VirtualProtect(address, bytes, PAGE_EXECUTE_READWRITE, &d); memset(address, 144, bytes); VirtualProtect(address,bytes,d,&ds); } void MemCopy(HANDLE pHandle, void* Dest, const void* Src, int Len) { DWORD OldProtect; DWORD OldProtect2; VirtualProtect(Dest, Len, PAGE_EXECUTE_READWRITE, &OldProtect); memcpy(Dest, Src, Len); VirtualProtect(Dest, Len, OldProtect, &OldProtect2); FlushInstructionCache(pHandle, Dest, Len); } int main() { enableDebugPrivileges(); DWORD pid; HANDLE phandle; // Obtain the process ID pid = GetProcId("gr.exe"); if(GetLastError()) { cout << "Error_PID_: " << GetLastError() << endl; system("pause"); return -1; } // Obtain the process handle phandle = OpenProcess(PROCESS_ALL_ACCESS,0,pid); if(GetLastError()) { cout << "Error_HANDLE_: " << GetLastError() << endl; system("pause"); return -1; } // Debug info, 0 = bad cout <<"pid : " << pid << endl; cout <<"HANDLE: " << phandle << endl << endl; system("pause"); // Change value to short iValue = -1; int choice = 0; BYTE * bGodMode = (BYTE *) (0x409A7E); // Lives Address bool hack = true; while(hack) { system("cls"); cout << "What hack?\n0. Exit\n1. Lives\n\n!> "; cin >> choice; switch(choice) { case 0: { hack=false; break; } case 1: // Modify Time cout << "God Mode On\n!> "; // cin >> iValue; // nop_((PVOID)(0x409A7E), 3); // MemCopy(phandle, (PVOID)0x409A7E, &NOP, 1); WriteMem((DWORD)(0x00409A7E), (void*)NOP, sizeof NOP); if(GetLastError()) { cout << "Error: " << GetLastError() << endl; system("pause"); } break; default: cout << "ERROR!\n"; break; } Sleep(100); } system("pause"); return 0; } This is suppose to NOP the DEC function that is 3 bytes long preventing me from losing lives. However each time I try it, it crashes the hack and says I had a access violation. I tried to look up the reasons and most of them dealt with with the size of the location I'm writing to and what I'm copying from. Otherwise, I have absolutely no idea. Any help would be nice. The game is GunRoar and the base address "0x409A7E" is where the DEC function is.

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  • OutOfMemoryException, stack size is huge, large number of threads

    - by Captain Comic
    Hello, I was profiling my .net windows service. I was trying to discover OutOfMemoryException and discovered that my stack size is huge and is growing because the the number of threads keeps growing. Each thread gets 1024 KB on Windows x64 machine. Thus when my app has 754 threads the stack size would be 772 MB. The problem for me is that i don't know where these thread come from. Initially my app has a very limited number of threads and they keep growing with time. I have two suspicions - either these threads are created by WCF or by database connection. My application uses both WCF and datasets. Also I tried to profile my app in Ants do Trace i can see large number of System.ServiceModel.Channels.ClientReliableDuplexSessionChannel and this number is increasing with time. I can see thousands of these objects created. So what I want to know is who is creating threads (tools to discover, profilers) and if it is WCF who is creating these threads.

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  • Deallocating NSMutableArray of custom objects

    - by Dave
    I need help with deallocation of my NSMutableArray of custom objects. I need to retain the array and so I have added a property in .h and I release it in dealloc in .m file. When I add objects to the array, I do the following: myarray = [[NSMutableArray alloc] init]; [myarray addObject:[[mycustomObject alloc]initWithObject:obj1]]; [myarray addObject:[[mycustomObject alloc]initWithObject:obj2]]; Now, I don't know how to release mycustomobject. If I do the following: [myarray addObject:[[[mycustomObject alloc]initWithObject:obj1] autorelease]; I run in to problems when I access the array later. Please advice.

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  • Heap corruption detected error when attempting to free pointer

    - by AndyGeek
    Hi, I'm pretty new to C++ and have run into a problem which I have not been able to solve. I'm trying to convert a System::String to a wchar_t pointer that I can keep for longer than the scope of the function. Once I'm finished with it, I want to clean it up properly. Here is my code: static wchar_t* g_msg; int TestConvert() { pin_ptr<const wchar_t> wchptr = PtrToStringChars("Test"); g_msg = (wchar_t*)realloc(g_msg, wcslen(wchptr) + 1); wcscpy(g_msg, wchptr); free (g_msg); // Will be called from a different method } When the free is called, I'm getting "HEAP CORRUPTION DETECTED: after Normal block (#137) at 0x02198F90." Why would I be getting this error? Andrew L

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  • How does the NSAutoreleasePool autorelease pool work?

    - by jsumners
    As I understand it, anything created with an alloc, new, or copy needs to be manually released. For example: int main(void) { NSString *string; string = [[NSString alloc] init]; /* use the string */ [string release]; } My question, though, is wouldn't this be just as valid?: int main(void) { NSAutoreleasePool *pool; pool = [[NSAutoreleasePool alloc] init]; NSString *string; string = [[[NSString alloc] init] autorelease]; /* use the string */ [pool drain]; }

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  • Optimizing a shared buffer in a producer/consumer multithreaded environment

    - by Etan
    I have some project where I have a single producer thread which writes events into a buffer, and an additional single consumer thread which takes events from the buffer. My goal is to optimize this thing for a single machine to achieve maximum throughput. Currently, I am using some simple lock-free ring buffer (lock-free is possible since I have only one consumer and one producer thread and therefore the pointers are only updated by a single thread). #define BUF_SIZE 32768 struct buf_t { volatile int writepos; volatile void * buffer[BUF_SIZE]; volatile int readpos;) }; void produce (buf_t *b, void * e) { int next = (b->writepos+1) % BUF_SIZE; while (b->readpos == next); // queue is full. wait b->buffer[b->writepos] = e; b->writepos = next; } void * consume (buf_t *b) { while (b->readpos == b->writepos); // nothing to consume. wait int next = (b->readpos+1) % BUF_SIZE; void * res = b->buffer[b->readpos]; b->readpos = next; return res; } buf_t *alloc () { buf_t *b = (buf_t *)malloc(sizeof(buf_t)); b->writepos = 0; b->readpos = 0; return b; } However, this implementation is not yet fast enough and should be optimized further. I've tried with different BUF_SIZE values and got some speed-up. Additionaly, I've moved writepos before the buffer and readpos after the buffer to ensure that both variables are on different cache lines which resulted also in some speed. What I need is a speedup of about 400 %. Do you have any ideas how I could achieve this using things like padding etc?

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  • tidy/efficient function writing in R

    - by romunov
    Excuse my ignorance, as I'm not a computer engineer but with roots in biology. I have become a great fan of pre-allocating objects (kudos to SO and R inferno by Patrick Burns) and would like to improve my coding habits. In lieu of this fact, I've been thinking about writing more efficient functions and have the following question. Is there any benefits in removing variables that will be overwritten at the start of the next loop, or is this just a waste of time? For the sake of argument, let's assume that the size of old and new variables is very similar or identical.

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  • iPhone NSCFString leaks in fetchRequest

    - by camilo
    In the following code: - (NSMutableArray *) fetchNotesForGroup: (NSString *)groupName { // Variables declaration NSMutableArray *result; NSFetchRequest *fetchRequest; NSEntityDescription *entity; NSSortDescriptor *sortDescriptor; NSPredicate *searchPredicate; NSError *error = nil; // Creates the fetchRequest and executes it fetchRequest = [[[NSFetchRequest alloc] init] autorelease]; entity = [NSEntityDescription entityForName:@"Note" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"noteName" ascending:YES] autorelease]; [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]]; [fetchRequest setReturnsDistinctResults:YES]; searchPredicate = [NSPredicate predicateWithFormat:@"categoryName like %@", groupName]; [fetchRequest setPredicate:searchPredicate]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:@"noteName"]]; result = [[managedObjectContext executeFetchRequest:fetchRequest error:&error] mutableCopy]; // Variables release return result; } ... I Fetch notes for a given categoryName. When I'm running Instruments, it says that a NSCFString is leaking. I know leaks are mean for iPhone developers... but I don't have any idea on how to plug this one. Any clues? All help is welcome. Thanks a lot!

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  • Python ValueError: not allowed to raise maximum limit

    - by Ricky Bobby
    I'm using python 2.7.2 on mac os 10.7.3 I'm doing a recursive algorithm in python with more than 50 000 recursion levels. I tried to increase the maximum recursion level to 1 000 000 but my python shell still exit after 18 000 recursion levels. I tried to increase the resources available : import resource resource.setrlimit(resource.RLIMIT_STACK, (2**29,-1)) sys.setrecursionlimit(10**6) and I get this error : Traceback (most recent call last): File "<pyshell#58>", line 1, in <module> resource.setrlimit(resource.RLIMIT_STACK,(2**29,-1)) ValueError: not allowed to raise maximum limit I don't know why I cannot raise the maximum limit ? thanks for your suggestions .

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  • iPhone: Leak with UIWebView loading Office documents. Any ideas how to avoid it?

    - by Thomas Tempelmann
    While there are already quite a few posts about leaks around UIWebView, mine is a bit more special, I believe, and thus deserves its own post here. I see a reproducible large leak every time I load a Office document such as a Word or Excel file. For instance, every time I display a 180KB .doc file, I get a 100KB leak. And that happens with both the simulator and an actual device, running OS 3.1.3. The leak is not visible with the Leaks instrument but only by looking at the malloc instances via the ObjectAlloc instrument. Here's a picture from the instruments trace: I've also made a demo project, UIWebView-Leak.zip, so you can verify this yourself. To see the leak, use the ObjectAlloc instrument, switch to the view where you see individual allocation objects, and sort by size so that you see the large ones in a group, just like in my picture above. Then view a Office document a few times and find the Malloc objects that keep staying "Live" even after the actual UIWebView has been freed. Is this a known bug? Or is there any way I can avoid these leaks? I.e, have you successfully shown Office documents on an iPhone withing getting such leaks? Note: I've reported this as a bug to Apple now, too (ID 7950594) I am still waiting for someone (including Apple) to confirm this as a true leak or show why it isn't (i.e. that I do something wrong or make wrong assumptions)

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  • What is the difference between these two different lines of Objective-C, and why does one work and n

    - by jrtc27
    If I try and release tempSeedsArray after seedsArray = tempSeedsArray , I get an EXEC_BAD_ACCESS, and Instruments shows that tempSeedsArray has been released twice. Here is my viewWillAppear method: - (void)viewWillAppear:(BOOL)animated { NSString *arrayFilePath = [[NSBundle mainBundle] pathForResource:@"SeedsArray" ofType:@"plist"]; NSLog(@"HIT!"); NSMutableArray *tempSeedsArray = [[NSMutableArray alloc] initWithContentsOfFile:arrayFilePath]; seedsArray = tempSeedsArray; NSLog(@"%u", [seedsArray retainCount]); [seedsArray sortUsingSelector:@selector(localizedCaseInsensitiveCompare:)]; [super viewWillAppear:animated]; } seedsArray is an NSMutableArray set as a nonatomic and a retain property, and is synthesised. However, if I change seedsArray = tempSeedsArray to self.seedsArray = tempSeedsArray (or [self seedsArray] = tempSeedsArray etc.), I can release tempSeedsArray. Could someone please explain simply to me why this is, as I am very confused! Thanks

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  • NSString potencial leak

    - by VansFannel
    Hello. When I build and analyze my project on XCode, I obtain a 'warning' on the following line: NSString *contactEmail = (NSString *)ABMultiValueCopyValueAtIndex(emailInfo, 0); The message is: Potencial leak on object allocated on line ... and stored into contactEmail. Is there any error on that line?

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  • resizing an array with C

    - by Gary
    So I need to have an array of structs in a game I'm making - but I don't want to limit the array to a fixed size. I'm told there is a way to use realloc to make the array bigger when it needs to, but can't find any working examples of this. Could someone please show me how to do this? Thanks!

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  • How can I tell the size of my app during development?

    - by Newbyman
    My programming decissions are directly related to how much room I have left, or worse perhaps how much I need to shave off in order to get up the 10mb limit. I have read that Apple has quietly increased the 3G & Edge download limit from 10mb up to 20mb in preparation for the iPad in April. Either way, my real question is how can I gauge a rough estimate of how large my app will end while I'm still in the development phase? Is the file size of my development folder roughly 1 to 1 ratio? Is the compressed file size of my development a better approximation? My .xcodeproj file is only a couple hundred kB, but the size of my folder is 11.8 MB. I have a .sqlite database, less than 20 small png images and a Settings.Bundle. The rest are unknown Xcode files related to build, build for iphoneOS, simulator etc.... My source code is rather large with around 1000 lines in most of the major controllers, all in all around 48 .h&.m files. But my classes folder inside my development folder is less than 800kb. Digging around inside my Build file, there is lots of iphone simulator files and debugging files which I don't think will contribute to the final product. The Application file states that it is around 2.3 MB. However, this is such a large difference from the 11.8 MB, I have to wonder if this is just another piece of the equation. I have the app on the my device, I'm in the testing phase. Therefore, I though that I would try to see how large the working version was on the device by checking in iTunes, however my development app is visible on the right-hand the application's iphone screen, but no information about the app most importantly its size. I also checked in Organizer, I used the lower portion of the screen-(Applications), found my application and selected the drop down arrow which gave my "Application Data" and a download arrow button to the right to save a file on my desktop, named with the unique AppleID. Inside the folder it had three folders-(documents, library, tmp) the documents had a copy of my .sqlite database, the library a few more files but not anything obvious or of size, and the tmp was empty. All in all the entire folder was only 164kb-which tells me that this is not the right place to find the size either. I understand that the size is considered to be the size of my binary plus all the additional files and images that I have add. Does anyone have a effective way of guaging how large the binary is or the relating the development folder size to what the final App Store application size will end up. I know that questions have been posted with similar aspects, but I could not find any answered post that really described...what files, or how to determine size specifically. I know that this question looks like a book, but I just wanted to be specific in conveying exactly what I'm looking for and the attempts thus far. *Note all files are unzipped and still in regular working Xcode order of a single app with no brought-in builds or referenced projects. I'm sure that this is straight forward, I just don't know where to look?

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  • -(void)dealloc - How ? Objective - C

    - by sagar
    Please Note that - this is not similar than this question. OK. To understand my question, First of all please see both of these destructors. - (void)dealloc { [Marketdetails release]; Marketdetails=nil; [parsedarray release]; parsedarray=nil; [Marketid release]; Marketid=nil; [marketname release]; marketname=nil; [super dealloc]; } - (void)dealloc { [super dealloc]; [Marketdetails release]; Marketdetails=nil; [parsedarray release]; parsedarray=nil; [Marketid release]; Marketid=nil; [marketname release]; marketname=nil; } See, Both destructors have different code. In First Destructor first current class objects are released & then [super dealloc] is called. In second Desctructor first [super dealloc] is called. My question is as follows. Where should we write [super dealloc] ? first or last ? or it doesn't matter ?

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  • dealloc on Background Thread

    - by Mark Brackett
    Is it an error to call dealloc on a UIViewController from a background thread? It seems that UITextView (can?) eventually call _WebTryThreadLock which results in: bool _WebTryThreadLock(bool): Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Background: I have a subclassed NSOperation that takes a selector and a target object to notify. -(id)initWithTarget:(id)target { if (self = [super init]) { _target = [target retain]; } return self; } -(void)dealloc { [_target release]; [super dealloc]; } If the UIViewController has already been dismissed when the NSOperation gets around to running, then the call to release triggers it's dealloc on a background thread.

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  • Leak in NSScanner category method

    - by jluckyiv
    I created an NSScanner category method that shows a leak in instruments. - (BOOL)scanBetweenPrefix:(NSString *)prefix andSuffix:(NSString *)suffix intoString:(NSString **)value { NSCharacterSet *charactersToBeSkipped = [self charactersToBeSkipped]; [self setCharactersToBeSkipped:nil]; BOOL result = NO; // find the prefix; the scanString method below fails if you don't do this if (![self scanUpToString:prefix intoString:nil]) { MY_LOG(@"Prefix %@ is missing.", prefix); return result; } //scan the prefix and discard [self scanString:prefix intoString:nil]; // scan the important part and save it if ([self scanUpToString:suffix intoString:value]) // this line leaks { result = YES; } [self setCharactersToBeSkipped:charactersToBeSkipped]; return result; } I figure it's the way I'm passing the value to/from the method, but I'm not sure. It's a small leak (32 bytes), but I'd like to do this right if I can. Thanks in advance.

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  • UIWebView in multithread ViewController

    - by Tao
    I have a UIWebView in a viewcontroller, which has two methods as below. The question is if I pop out(tap back on navigation bar) this controller before the second thread is done, the app will crash after [super dealloc], because "Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread.". Any help would be really appreciated. -(void)viewDidAppear:(BOOL)animated { [super viewWillAppear:animated]; NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(load) object:nil]; [operationQueue addOperation:operation]; [operation release]; } -(void)load { [NSThread sleepForTimeInterval:5]; [self performSelectorOnMainThread:@selector(done) withObject:nil waitUntilDone:NO]; }

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