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• Strange profiling results: definitely non-bottleneck method pops up

  - by jkff

  I'm profiling a program using sampling profiling in YourKit and JProfiler, and also "manually" (I launch it and press Ctrl-Break several times to get thread dumps). All three methods give me extremely strange results: some tens of percents of time spent in a 3-line method that does not even do any allocation or synchronization and doesn't have loops etc. Moreover, after I made this method into a NOP and even removed its invocation completely, the observable program performance didn't change at all (although it got a negligible memory leak, since it was a method for freeing a cheap resource). I'm thinking that this might be because of the constraints that JVM puts on the moments at which a thread's stacktrace may be taken, and it somehow turns out that in my program it is exactly the moments where this method is invoked, although there is absolutely nothing special about it or the context in which it is invoked. What can be the explanation for this phenomenon? What are the aforementioned constraints? What further measurements can I take to clarify the situation?

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• Linux Kernel - Slab Allocator Question

  - by Drex

  I am playing around with the kernel and am looking at the kmem_cache files_cachep belonging to fork.c. It detects the sizeof(files_struct). My question is this: I have altered files_struct and added a rb_root (red/black tree root) using the built-in functionality in linux/rbtree.h. I can properly insert values into this tree. However, at some point, a segfault occurs and GDB backtraces the following information: (gdb) backtrace 0 0x08066ad7 in page_ok (page=) at arch/um/os-Linux/sys-i386/task_size.c:31 1 0x08066bdf in os_get_top_address () at arch/um/os-Linux/sys-i386/task_size.c:100 2 0x0804a216 in linux_main (argc=1, argv=0xbfb05f14) at arch/um/kernel/um_arch.c:277 3 0x0804acdc in main (argc=1, argv=0xbfb05f14, envp=0xbfb05f1c) at arch/um/os-Linux/main.c:150 I have spent many hours trying to figure out why there is a segfault given that the red/black tree inserts properly. I'm thinking it's a memory allocation issue with new processes made by fork() of a parent process. Could this be the case and could it have something to do with kmem_cache files_cachep?

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• Java appliction design question

  - by ring bearer

  Hi I have a hobby project, which is basically to maintain 'todo' tasks in the way I like. One task can be described as: public class TodoItem { private String subject; private Date dueBy; private Date startBy; private Priority priority; private String category; private Status status; private String notes; } as you can imagine I would have 1000 todo items at a given time. What is the best strategy to store a todo item? (currently on an XML file) such that all the items are loaded quickly up on app start up(the application shows kind of a dashboard of all the items at start up) What is the best way to design its back-end so that it can be ported to android/or a J2ME based phone Currently this is done using java swing. What should be the concerns so that it works efficiently on a device where memory is limited? Thanks!

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• What is the largest file size we can transfer through air application?

  - by Naveen kumar

  Hi all, I'm trying to transfer large file(1Gb+) using UDP(in packets) through air application. I'm transfering byteArray by taking chunks of packets from FileStream. But its giving 'Error #1000: The system is out of memory' at sender side after certain number of packets sent and by this time the downloaded file size at server side is 256 MB. I tried with other files but after downloading 256MB, sender is giving the same error. Is it because of the file stream size? How can I solve this problem so that I can transfer files of GB size.

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• How to diganose an unlogged Error 500 on Apache?

  - by samuel morhaim

  We are running a very simple Symfony script, that randomly returns an Error 500. The system administrator says he can't find any trace of an Error 500 on the error logs, however using Curl or Firebug, it is obvious that an Error 500 is being returned. The script simply parses a POST request submitted to an URL on our server. We already checked for performance, memory etc but nothing seems to be the problem. How is this possible? We already enabled all debugging, logging, on Apache, PHP, etc and nothing.

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• How to use a dialog in an Excel shared addin

  - by user169867

  I'm writing a shared addin for Excel. It adds a CommandBarButton that when clicked opens a WPF window to collect some information from the user. I wanted to keep the same WPF dialog in memory and reuse it so that if the user clicks the CommandBarButton again their previous values would still be there. So I made a reference to my WPD as a private member of my addin object that implements Extensibility.IDTExtensibility2. I created the window during OnStartupComplete(), but for some reason when I run Excel the window immediately opens even though I never called ShowDialog() and when I do call ShowDialog() when the CommandBarButton is clicked to reOpen the window it fails to load. Does anyone know why this happens and what the correct way to handle this is? Thanks very much for any help.

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• PHP: how to stop ignore_user_abort, is it a good solution for long run program

  - by user192344

  let say i have send email program which need to run arround 7 hours. but i cant open the browser for 7 hours beside cronjob, ignore_user_abort() will it be a solution? will the script stop when all email has sent and the program has finish the loop? or it will keep eating the server memory? some people said u may need to add some output at the end of the program to avoid the program run forever? and some people also said echo a litte bit string will not stop the script, but has to use ob_flush, any example for this?

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• How does multiple implementing multiple COM interfaces work in C++?

  - by Martin

  I am trying to understand this example code regarding Browser Helper Objects. Inside, the author implements a single class which exposes multiple interfaces (IObjectWithSite, IDispatch). His QueryInterface function performs the following: if(riid == IID_IUnknown) *ppv = static_cast<BHO*>(this); else if(riid == IID_IObjectWithSite) *ppv = static_cast<IObjectWithSite*>(this); else if (riid == IID_IDispatch) *ppv = static_cast<IDispatch*>(this); I have learned that from a C perspective, interface pointers are just pointers to VTables. So I take it to mean that C++ is capable of returning the VTable of any implemented interface using static_cast. Does this mean that a class constructed in this way has a bunch of VTables in memory (IObjectWithSite, IDispatch, etc)? What does C++ do with the name collisions on the different interfaces (they each have a QueryInterface, AddRef and Release function), can I implement different methods for each of these?

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• Linux, how to capture screen, and simulate mouse movements.

  - by 2di

  Hi All I need to capture screen (as print screen) in the way so I can access pixel color data, to do some image recognition, after that I will need to generate mouse events on the screen such as left click, drag and drop (moving mouse while button is pressed, and then release it). Once its done, image will be deleted. Note: I need to capture whole screen everything that user can see, and I need to simulate clicks outside window of my program (if it makes any difference) Spec: Linux ubuntu Language: C++ Performance is not very important,"print screen" function will be executed once every ~10 sec. Duration of the process can be up to 24 hours so method needs to be stable and memory leaks free (as usuall :) I was able to do in windows with win GDI and some windows events, but I'ev no idea how to do it in Linux. Thanks a lot

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• Exception on malloc for a structure in C

  - by Derek

  Hi all, I have a structure defined like so: typedef struct { int n; int *n_p; void **list_pp; size_t rec_size; int n_buffs; size_t buff_size } fl_hdr_type; and in my code I Have a function for initlialization that has the following fl_hdr_type *fl_hdr; fl_hdr = malloc(sizeof(fl_hdr_type) + (buff_size_n * rec_size_n)); where those buffer size are passed in to the function to allow space for the buffers as well. The size is pretty small typically..100*50 or something like that..plenty of memory on this system to allocate it. Any ideas why this fails?

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• Where should I catch WM_HIBERNATE and WM_CLOSE in Windows Mobile/WinCE?

  - by afriza

  I have read about Windows Mobile's X button's behaviour, WM_HIBERNATE, and WM_CLOSE on Low Memory Situation. MSDN on WM_HIBERNATE: This message is sent to an application when system resources are running low. An application should attempt to release as many resources as possible when sent this message by unloading dialog boxes, destroying windows, or freeing up as much local storage as possible without changing the internal state. MSDN on WM_CLOSE: This message is sent as a signal that a window or an application should terminate. Where should I catch the message? in the main message pump? in every window? or only some windows? If I am using MFC, where should I catch it?

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• System::IDisposable woes

  - by shadeMe

  public ref class ScriptEditor : public Form { public: typedef map<UInt32, ScriptEditor^> AlMap; static AlMap AllocationMap; Form^ EditorForm; RichTextBox^ EditorBox; StatusBar^ EditorStatusBar; StatusBarPanel^ StatusBarLineNo; void Destroy() { EditorForm->Close(); } ScriptEditor(unsigned int PosX, unsigned int PosY); }; The above code throws an Error C2039: '{dtor}' : is not a member of 'System::IDisposable'. I'm quite lost after having looked into articles that explain how the CLR manages memory. Any advice on getting rid of it would be appreciated. My first dabble in C+++/CLI isn't going too well.

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• Major performance difference between two Oracle database instances

  - by jrdioko

  I am working with two instances of an Oracle database, call them one and two. two is running on better hardware (hard disk, memory, CPU) than one, and two is one minor version behind one in terms of Oracle version (both are 11g). Both have the exact same table table_name with exactly the same indexes defined. I load 500,000 identical rows into table_name on both instances. I then run, on both instances: delete from table_name; This command takes 30 seconds to complete on one and 40 minutes to complete on two. Doing INSERTs and UPDATEs on the two tables has similar performance differences. Does anyone have any suggestions on what could have such a drastic impact on performance between the two databases?

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• Beagleboard: How do I send/receive data to/from the DSP?

  - by snakile

  I have a beagleboard with TMS320C64x+ DSP. I'm working on an image processing beagleboard application. Here's how it's going to work: The ARM reads an image from a file and put the image in a 2D array. The arm sends the matrix to the DSP. The DSP receives the matrix. The DSP performs the image processing algorithm on the received matrix (the algorithm code uses about 5MB of dynamically allocated memory). The DSP sends the processed image (matrix) to the ARM. The arm received the matrix. The arm saved the processed image to a file. I'v already written the code for steps 1,3,5. What is the easiest way to do steps 3+4 (sending the data)? Code examples are welcome.

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• Java multi-threading - what is the best way to monitor the activity of a number of threads?

  - by MalcomTucker

  I have a number of threads that are performing a long runing task. These threads themselves have child threads that do further subdivisions of work. What is the best way for me to track the following: How many total threads my process has created What the state of each thread currently is What part of my process each thread has currently got to I want to do it in as efficient a way as possible and once threads finish, I don't want any references to them hanging around becasuse I need to be freeing up memory as early as possible. Any advice?

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• Are bit operations quick?

  - by flashnik

  I'm dealing with a problem which needs to work with a lot of data. Currently its' values are represented as unsigned int. I know that real values do not exceed some limit, say 1000. That means that I can use unsigned short to store it. One profit is that it'll use less space. Do I have to pay for it by loosing in performance? Another assumption. I decided to store data as short but all calling functions use int, so I need to convert between these datatypes when storing/extracting values. Wiil the performance lost be dramatic? Third assumption. Due to great wish to econom memory I decided to use not short but just 10 bits packed into array of unsigned int. What will happen in this case comparing with previous ones?

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• What libraries are available for manipulating super large images in .Net

  - by tpower

  I have some really large files for example 320 MB tif file with 14000 X 9000 pixels. The operations I need to perform are basically scaling the images to get smaller versions of it and breaking the image into tiles. My code works fine with small files and I use the .Net Bitmap objects but I will occasionally get Out of Memory exceptions for larger files. I've tried using the FreeImage libraries FreeImageBitmap but have the same problems. I'm using something like the following to scale the image: using (Graphics g = Graphics.FromImage((Image)result)) { g.DrawImage( source, xOffset, yOffset, source.Width * scale, source.Height * scale ); } Ideally I'd like a third party library to do all the hardwork, but if you have any tips or resources with more information I would appreciate it.

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• C++ smart pointer for non-object type?

  - by Brian

  Hi, I'm trying to use smart pointers such as auto_ptr, shared_ptr. However, I don't know how to use it in this situation. CvMemStorage *storage = cvCreateMemStorage(); ... use the pointer ... cvReleaseMemStorage(&storage); I'm not sure, but I think that the storage variable is just malloc'ed memory, not object. Is there a way to use the smart pointers for the storage variable? Thank you.

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• Object sent -autorelease too many times

  - by mongeta

  I have this code that simple returns Today's date as a string formatted: +(NSString*) getTodayString_YYYY_MM_DD { NSDate * today = [NSDate date]; NSDateFormatter *formatter = [[NSDateFormatter alloc] init]; [formatter setDateFormat:@"yyyy-MM-dd"]; return [[formatter stringFromDate:today] autorelease]; } With instruments I'm not getting a memory leak, but when I Analyze, XCode says: Object sent -autorelease too many times If I understand correctly, I have to release manually the formatter as I'm creating it using 'alloc', but I can't release here because I have to return the value, so I add the autorelease. How I can do it better to improve it ? thanks, r.

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• Create Out-Of-Process COM in C#/.Net ?

  - by Huck

  Hi, I need to create an out-of-process COM server (.exe) in C# that will be accessed by multiple other processes on the same box. The component has to be a single process because it will cache the information it provides to its consumers in memory. Note: the processes that will access my COM Server are mostly Matlab processes, thus the necessity for a COM interface. I have seen threads regarding creating in-process COM components in .Net on stack overflow (Create COM ...) and on the web, but am having a hard time to find a way to create out-of-process components with .Net. How is this achievable? Any suggested references? Thanks.

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• Are there Python ORMs out there that support multiple independent databases concurrently in use?

  - by sdt

  I'm writing an application in Python where I wish to use sqlite as the backing store for documents edited by the app, with documents generally living in memory, but being saved to disk-based databases when the application saves. Ideally I'd like to use something like an ORM to make access to the data from my Python application code simple. Unfortunately it seems like the majority of Python ORMs, including SQLAlchemy, SQLObject, Django, and Storm, associate the database connection (or engine or whatever) with the classes representing table data, rather than instances of those classes. This restricts these ORMs to working with a single database connection across all instances. Since I'd like to support having multiple documents open simultaneously, this isn't going to work for me. Are there any ORMs out there that support this usage model in Python? Bazaar seems to support this, but it's quite out of date, and at first glance appears to have some other shortcomings. Thanks for any suggestions!

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• Error after updating to the latest version Azure SDK

  - by Mikael Johansson

  After I updated to the newest version the Azure SDK I have started to get this error several times each day when I press build in Visual Studio. The only way for me to fix it at the moment is to restart my visual studio. The error I get is: Windows Azure Tools: Invalid access to memory location Is there someone else that have got this error? And also what did you do to fix it? Thanks in advance! Update 2012-08-28: The same error still exist in VS2012 and Azure 1.7 SDK. However the frequency have gone down with VS2012.

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• Display Computer Info on C# Web Application

  - by Gene

  I want to build a page for end users to visit (in our MPLS Network) and it show the following information in regards to them: Computer Name OS Disk Space Memory IP Address Active Directory User Name Password Expiration Time (As defined by Global Policy) Maybe a few other things such as Trend Micro Office current version vs. their version, # of MS Updates needed (we utilize WSUS), and a few other things in the future. My question is how would I pull this information from the user when they visit the page? What is the proper function for this? Anyone have examples they wish to share for me to learn by if possible? Thanks so much in advance, Gene

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• ASCII in Windows XP and Ubuntu Linux

  - by Mikey D

  I've made a program in MVSC++ which outputs memory contents (in ASCII). The ASCII I see in windows console seem to match what I see in various ASCII tables (smiley, diamond, club, right arrow etc). This program needs to compile under Linux (which is does), but the ASCII output looks completely different. A few symbols are the same but the rest are so different. Is there any way to change how terminal displays ASCII code? EDIT: The program executes correctly, it's just the ASCII that is being displayed differently.

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• About local Final varibles in java

  - by Sathish

  In java Program, parameters which is defined as String in method declaration.But in method definition it is accessed as final String variable. Whether it'll lead to some issues (like security, memory problem)? For Example: Method Declaration join(String a,String b); Method definition public void join(final String a,final String b) { Authenticator au = new Authenticator(){ public PasswordAuthentication getPasswordAuthentication(){ return new PasswordAuthentication(a,b)} }; } Please help for me and clarify my doubts. Thanks in advance P.S. I;m accessing a and b as final variable because i've to use it in the inner class.

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