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  • Is it possible to read infinity or NaN values using input streams?

    - by Drise
    I have some input to be read by a input filestream (for example): -365.269511 -0.356123 -Inf 0.000000 When I use std::ifstream mystream; to read from the file to some double d1 = -1, d2 = -1, d3 = -1, d4 = -1; (assume mystream has already been opened and the file is valid), mystream >> d1 >> d2 >> d3 >> d4; mystream is in the fail state. I would expect std::cout << d1 << " " << d2 << " " << d3 << " " << d4 << std::endl; to output -365.269511 -0.356123 -1 -1. I would want it to output -365.269511 -0.356123 -Inf 0 instead. This set of data was output using C++ streams. Why can't I do the reverse process (read in my output)? How can I get the functionality I seek? From MooingDuck: #include <iostream> #include <limits> using namespace std; int main() { double myd = std::numeric_limits<double>::infinity(); cout << myd << '\n'; cin >> myd; cout << cin.good() << ":" << myd << endl; return 0; } Input: inf Output: inf 0:inf See also: http://ideone.com/jVvei Also related to this problem is NaN parsing, even though I do not give examples for it.

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  • How to obtain a pointer out of a C++ vtable?

    - by Josh Haberman
    Say you have a C++ class like: class Foo { public: virtual ~Foo() {} virtual DoSomething() = 0; }; The C++ compiler translates a call into a vtable lookup: Foo* foo; // Translated by C++ to: // foo->vtable->DoSomething(foo); foo->DoSomething(); Suppose I was writing a JIT compiler and I wanted to obtain the address of the DoSomething() function for a particular instance of class Foo, so I can generate code that jumps to it directly instead of doing a table lookup and an indirect branch. My questions are: Is there any standard C++ way to do this (I'm almost sure the answer is no, but wanted to ask for the sake of completeness). Is there any remotely compiler-independent way of doing this, like a library someone has implemented that provides an API for accessing a vtable? I'm open to completely hacks, if they will work. For example, if I created my own derived class and could determine the address of its DoSomething method, I could assume that the vtable is the first (hidden) member of Foo and search through its vtable until I find my pointer value. However, I don't know a way of getting this address: if I write &DerivedFoo::DoSomething I get a pointer-to-member, which is something totally different. Maybe I could turn the pointer-to-member into the vtable offset. When I compile the following: class Foo { public: virtual ~Foo() {} virtual void DoSomething() = 0; }; void foo(Foo *f, void (Foo::*member)()) { (f->*member)(); } On GCC/x86-64, I get this assembly output: Disassembly of section .text: 0000000000000000 <_Z3fooP3FooMS_FvvE>: 0: 40 f6 c6 01 test sil,0x1 4: 48 89 74 24 e8 mov QWORD PTR [rsp-0x18],rsi 9: 48 89 54 24 f0 mov QWORD PTR [rsp-0x10],rdx e: 74 10 je 20 <_Z3fooP3FooMS_FvvE+0x20> 10: 48 01 d7 add rdi,rdx 13: 48 8b 07 mov rax,QWORD PTR [rdi] 16: 48 8b 74 30 ff mov rsi,QWORD PTR [rax+rsi*1-0x1] 1b: ff e6 jmp rsi 1d: 0f 1f 00 nop DWORD PTR [rax] 20: 48 01 d7 add rdi,rdx 23: ff e6 jmp rsi I don't fully understand what's going on here, but if I could reverse-engineer this or use an ABI spec I could generate a fragment like the above for each separate platform, as a way of obtaining a pointer out of a vtable.

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  • How do I do high quality scaling of a image?

    - by pbhogan
    I'm writing some code to scale a 32 bit RGBA image in C/C++. I have written a few attempts that have been somewhat successful, but they're slow and most importantly the quality of the sized image is not acceptable. I compared the same image scaled by OpenGL (i.e. my video card) and my routine and it's miles apart in quality. I've Google Code Searched, scoured source trees of anything I thought would shed some light (SDL, Allegro, wxWidgets, CxImage, GD, ImageMagick, etc.) but usually their code is either convoluted and scattered all over the place or riddled with assembler and little or no comments. I've also read multiple articles on Wikipedia and elsewhere, and I'm just not finding a clear explanation of what I need. I understand the basic concepts of interpolation and sampling, but I'm struggling to get the algorithm right. I do NOT want to rely on an external library for one routine and have to convert to their image format and back. Besides, I'd like to know how to do it myself anyway. :) I have seen a similar question asked on stack overflow before, but it wasn't really answered in this way, but I'm hoping there's someone out there who can help nudge me in the right direction. Maybe point me to some articles or pseudo code... anything to help me learn and do. Here's what I'm looking for: 1. No assembler (I'm writing very portable code for multiple processor types). 2. No dependencies on external libraries. 3. I am primarily concerned with scaling DOWN, but will also need to write a scale up routine later. 4. Quality of the result and clarity of the algorithm is most important (I can optimize it later). My routine essentially takes the following form: DrawScaled( uint32 *src, uint32 *dst, src_x, src_y, src_w, src_h, dst_x, dst_y, dst_w, dst_h ); Thanks! UPDATE: To clarify, I need something more advanced than a box resample for downscaling which blurs the image too much. I suspect what I want is some kind of bicubic (or other) filter that is somewhat the reverse to a bicubic upscaling algorithm (i.e. each destination pixel is computed from all contributing source pixels combined with a weighting algorithm that keeps things sharp. EXAMPLE: Here's an example of what I'm getting from the wxWidgets BoxResample algorithm vs. what I want on a 256x256 bitmap scaled to 55x55. And finally: the original 256x256 image

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  • How can I create a Base64-Encoded string from an GDI+ Image in C++?

    - by Schnapple
    I asked a question recently, How can I create an Image in GDI+ from a Base64-Encoded string in C++?, which got a response that led me to the answer. Now I need to do the opposite - I have an Image in GDI+ whose image data I need to turn into a Base64-Encoded string. Due to its nature, it's not straightforward. The crux of the issue is that an Image in GDI+ can save out its data to either a file or an IStream*. I don't want to save to a file, so I need to use the resulting stream. Problem is, this is where my knowledge breaks down. This first part is what I figured out in the other question // Initialize GDI+. GdiplusStartupInput gdiplusStartupInput; ULONG_PTR gdiplusToken; GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL); // I have this decode function from elsewhere std::string decodedImage = base64_decode(Base64EncodedImage); // Allocate the space for the stream DWORD imageSize = decodedImage.length(); HGLOBAL hMem = ::GlobalAlloc(GMEM_MOVEABLE, imageSize); LPVOID pImage = ::GlobalLock(hMem); memcpy(pImage, decodedImage.c_str(), imageSize); // Create the stream IStream* pStream = NULL; ::CreateStreamOnHGlobal(hMem, FALSE, &pStream); // Create the image from the stream Image image(pStream); // Cleanup pStream->Release(); GlobalUnlock(hMem); GlobalFree(hMem); (Base64 code) And now I'm going to perform an operation on the resulting image, in this case rotating it, and now I want the Base64-equivalent string when I'm done. // Perform operation (rotate) image.RotateFlip(Gdiplus::Rotate180FlipNone); IStream* oStream = NULL; CLSID tiffClsid; GetEncoderClsid(L"image/tiff", &tiffClsid); // Function defined elsewhere image.Save(oStream, &tiffClsid); // And here's where I'm stumped. (GetEncoderClsid) So what I wind up with at the end is an IStream* object. But here's where both my knowledge and Google break down for me. IStream shouldn't be an object itself, it's an interface for other types of streams. I'd go down the road from getting string-Image in reverse, but I don't know how to determine the size of the stream, which appears to be key to that route. How can I go from an IStream* to a string (which I will then Base64-Encode)? Or is there a much better way to go from a GDI+ Image to a string?

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  • vim plugin to show current Perl subroutine

    - by Andrew
    I'm trying to make a vim plugin that will split the window on load and simulate a info bar at the top of my terminal. I've got it sorta working but I think I've either reached limits of my knowledge of vim syntax or there's a logic problem in my code. The desired effect would be to do a reverse search for any declaration of a Perl subroutine form my current location in the active buffer and display the line in the top buffer. I'm also trying to make it skip that buffer when I switch buffers with <C-R>. My attempt at that so far can be seen in the mess of nested if statements. Anyway, here's the code. I would greatly appreciate feedback from anyone. (pastebin pastebin.com/8cuMPn1Q) let s:current_function_bufname = 'Current\ Function\/Subroutine' function! s:get_current_function_name(no_echo) let lnum = line(".") let col = col(".") if a:no_echo let s:current_function_name = getline(search("^[^s]sub .$", 'bW')) else echohl ModeMsg echo getline(search("^[^s]sub .$", 'bW')) "echo getline(search("^[^ \t#/]\{2}.[^:]\s$", 'bW')) echohl None endif endfunction let s:previous_winbufnr = 1 let s:current_function_name = '' let s:current_function_buffer_created = 0 let s:current_function_bufnr = 2 function! s:show_current_function() let total_buffers = winnr('$') let current_winbufnr = winnr() if s:previous_winbufnr != current_winbufnr if bufname(current_winbufnr) == s:current_function_bufname if s:previous_winbufnr < current_winbufnr let i = current_winbufnr + 1 if i total_buffers let i = 1 endif if i == s:current_function_bufnr let i = i + 1 endif if i total buffers let i = 1 endif exec i.'wincmd w' else let i = current_winbufnr - 1 if i < 1 let i = total_buffers endif if i == s:current_function_bufnr let i = i - 1 endif if i < 1 let i = total_buffers endif try exec i.'wincmd w' finally exec total_buffers.'wincmd w' endtry endif endif let s:previous_winbufnr = current_winbufnr return 1 endif if s:current_function_buffer_created == 0 exec 'top 1 split '.s:current_function_bufname call s:set_as_scratch_buffer() let s:current_function_buffer_created = 1 let s:current_function_bufnr = winnr() endif call s:activate_buffer_by_name(s:current_function_bufname) setlocal modifiable call s:get_current_function_name(1) call setline(1, s:current_function_name) setlocal nomodifiable call s:activate_buffer_by_name(bufname(current_winbufnr)) endfunction function! s:set_as_scratch_buffer() setlocal noswapfile setlocal nomodifiable setlocal bufhidden=delete setlocal buftype=nofile setlocal nobuflisted setlocal nonumber setlocal nowrap setlocal cursorline endfunction function! s:activate_buffer_by_name(name) for i in range(1, winnr('$')) let name = bufname(winbufnr(i)) let full_name = fnamemodify(bufname(winbufnr(i)), ':p') if name == a:name || full_name == a:name exec i.'wincmd w' return 1 endif endfor return 0 endfunction set laststatus=2 autocmd! CursorMoved,CursorMovedI,BufWinEnter * call s:show_current_function() (pastebin pastebin.com/8cuMPn1Q) similar to VIM: display custom reference bar on top of window and http://vim.wikia.com/wiki/Show_current_function_name_in_C_programs

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  • Representing xml through a single class

    - by Charles
    I am trying to abstract away the difficulties of configuring an application that we use. This application takes a xml configuration file and it can be a bit bothersome to manually edit this file, especially when we are trying to setup some automatic testing scenarios. I am finding that reading xml is nice, pretty easy, you get a network of element nodes that you can just go through and build your structures quite nicely. However I am slowly finding that the reverse is not quite so nice. I want to be able to build a xml configuration file through a single easy to use interface and because xml is composed of a system of nodes I am having a lot of struggle trying to maintain the 'easy' part. Does anyone know of any examples or samples that easily and intuitively build xml files without declaring a bunch of element type classes and expect the user to build the network themselves? For example if my desired xml output is like so <cook version="1.1"> <recipe name="chocolate chip cookie"> <ingredients> <ingredient name="flour" amount="2" units="cups"/> <ingredient name="eggs" amount="2" units="" /> <ingredient name="cooking chocolate" amount="5" units="cups" /> </ingredients> <directions> <direction name="step 1">Preheat oven</direction> <direction name="step 2">Mix flour, egg, and chocolate</direction> <direction name="step 2">bake</direction> </directions> </recipe> <recipe name="hot dog"> ... How would I go about designing a class to build that network of elements and make one easy to use interface for creating recipes? Right now I have a recipe object, an ingredient object, and a direction object. The user must make each one, set the attributes in the class and attach them to the root object which assembles the xml elements and outputs the formatted xml. Its not very pretty and I just know there has to be a better way. I am using python so bonus points for pythonic solutions

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  • Any thoughts on how to create a true 'punch-out' area in a Sprite?

    - by rhtx
    I've been working on this for awhile, now. You might also call it a 'reverse mask', or an 'inverse mask'. Basically, I'm creating a view window within a display object. I need to allow objects on the stage that are under the window to be able to interact with the mouse. This is similar to a WPF question: http://stackoverflow.com/questions/740994/use-wpf-object-to-punch-hole-in-another, which has a much shorter write-up. I've got a Class called PunchOutShield, which creates a Sprite that covers the stage (or over some desired area). The Sprite's Graphics object is filled using the color and transparency of Flex's modal screen. The result is a screen that looks like the screen which appears behind a modal PopUp. PunchOutShield has a method called punch, which takes two arguments - the first is a Shape object, which defines the shape of the punch-through area; the second is a Point object, which indicates where to position the punch-through area. It took some experimenting, but I found that I can successfully create a punch-out area (i.e. - the modal screen does not display within the bounds of the given Shape). To do this, I set cacheAsBitmap to true on the Sprite that is used to create the modal screen, and also on the Shape object, which is added to the modal screen Sprite's displayList. If I set the blend mode of the Shape to ERASE, a completely transparent area is created in the modal screen. So far, great. The problem is that Shape does not subclass InteractiveObject, so there is no way to set mouseEnabled = false on it. And so, it prevents interaction between the mouse and any objects that are visible through the punch-out area. On top of that, InteractiveObject isn't available to look at, so I can't see if there is a way to borrow what it's doing to provide the mouseEnabled functionality and apply it to a subclass of Shape. I've tried using another Sprite object, rather than a Shape object, but the blending doesn't work out correctly. I'm not sure why there is a difference, but the Shape object seems to somehow combine with the parenting Sprite, allowing the ERASE blendMode to effect the desired punch-out visual appearance. It wouldn't be the end of the world if I had to draw up the screen with a series of rectangles so that the punch-out area was just simply not drawn, but that approach won't work if the punch-out area is complex. Or round. Any thoughts on this approach, or on an alternative approach?

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  • Endianness conversion and g++ warnings

    - by SuperBloup
    I've got the following C++ code : template <int isBigEndian, typename val> struct EndiannessConv { inline static val fromLittleEndianToHost( val v ) { union { val outVal __attribute__ ((used)); uint8_t bytes[ sizeof( val ) ] __attribute__ ((used)); } ; outVal = v; std::reverse( &bytes[0], &bytes[ sizeof(val) ] ); return outVal; } inline static void convertArray( val v[], uint32_t size ) { // TODO : find a way to map the array for (uint32_t i = 0; i < size; i++) for (uint32_t i = 0; i < size; i++) v[i] = fromLittleEndianToHost( v[i] ); } }; Which work and has been tested (without the used attributes). When compiling I obtain the following errors from g++ (version 4.4.1) || g++ -Wall -Wextra -O3 -o t t.cc || t.cc: In static member function 'static val EndiannessConv<isBigEndian, val>::fromLittleEndianToHost(val)': t.cc|98| warning: 'used' attribute ignored t.cc|99| warning: 'used' attribute ignored || t.cc: In static member function 'static val EndiannessConv<isBigEndian, val>::fromLittleEndianToHost(val) [with int isBigEndian = 1, val = double]': t.cc|148| instantiated from here t.cc|100| warning: unused variable 'outVal' t.cc|100| warning: unused variable 'bytes' I've tried to use the following code : template <int size, typename valType> struct EndianInverser { /* should not compile */ }; template <typename valType> struct EndianInverser<4, valType> { static inline valType reverseEndianness( const valType &val ) { uint32_t castedVal = *reinterpret_cast<const uint32_t*>( &val ); castedVal = (castedVal & 0x000000FF << (3 * 8)) | (castedVal & 0x0000FF00 << (1 * 8)) | (castedVal & 0x00FF0000 >> (1 * 8)) | (castedVal & 0xFF000000 >> (3 * 8)); return *reinterpret_cast<valType*>( &castedVal ); } }; but it break when enabling optimizations due to the type punning. So, why does my used attribute got ignored? Is there a workaround to convert endianness (I rely on the enum to avoid type punning) in templates?

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  • Are Objective-C initializers allowed to share the same name?

    - by NattKatt
    I'm running into an odd issue in Objective-C when I have two classes using initializers of the same name, but differently-typed arguments. For example, let's say I create classes A and B: A.h: #import <Cocoa/Cocoa.h> @interface A : NSObject { } - (id)initWithNum:(float)theNum; @end A.m: #import "A.h" @implementation A - (id)initWithNum:(float)theNum { self = [super init]; if (self != nil) { NSLog(@"A: %f", theNum); } return self; } @end B.h: #import <Cocoa/Cocoa.h> @interface B : NSObject { } - (id)initWithNum:(int)theNum; @end B.m: #import "B.h" @implementation B - (id)initWithNum:(int)theNum { self = [super init]; if (self != nil) { NSLog(@"B: %d", theNum); } return self; } @end main.m: #import <Foundation/Foundation.h> #import "A.h" #import "B.h" int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; A *a = [[A alloc] initWithNum:20.0f]; B *b = [[B alloc] initWithNum:10]; [a release]; [b release]; [pool drain]; return 0; } When I run this, I get the following output: 2010-04-26 20:44:06.820 FnTest[14617:a0f] A: 20.000000 2010-04-26 20:44:06.823 FnTest[14617:a0f] B: 1 If I reverse the order of the imports so it imports B.h first, I get: 2010-04-26 20:45:03.034 FnTest[14635:a0f] A: 0.000000 2010-04-26 20:45:03.038 FnTest[14635:a0f] B: 10 For some reason, it seems like it's using the data type defined in whichever @interface gets included first for both classes. I did some stepping through the debugger and found that the isa pointer for both a and b objects ends up the same. I also found out that if I no longer make the alloc and init calls inline, both initializations seem to work properly, e.g.: A *a = [A alloc]; [a initWithNum:20.0f]; If I use this convention when I create both a and b, I get the right output and the isa pointers seem to be different for each object. Am I doing something wrong? I would have thought multiple classes could have the same initializer names, but perhaps that is not the case.

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  • C++ string sort like a human being?

    - by Walter Nissen
    I would like to sort alphanumeric strings the way a human being would sort them. I.e., "A2" comes before "A10", and "a" certainly comes before "Z"! Is there any way to do with without writing a mini-parser? Ideally it would also put "A1B1" before "A1B10". I see the question "Natural (human alpha-numeric) sort in Microsoft SQL 2005" with a possible answer, but it uses various library functions, as does "Sorting Strings for Humans with IComparer". Below is a test case that currently fails: #include <set> #include <iterator> #include <iostream> #include <vector> #include <cassert> template <typename T> struct LexicographicSort { inline bool operator() (const T& lhs, const T& rhs) const{ std::ostringstream s1,s2; s1 << toLower(lhs); s2 << toLower(rhs); bool less = s1.str() < s2.str(); std::cout<<s1.str()<<" "<<s2.str()<<" "<<less<<"\n"; return less; } inline std::string toLower(const std::string& str) const { std::string newString(""); for (std::string::const_iterator charIt = str.begin(); charIt!=str.end();++charIt) { newString.push_back(std::tolower(*charIt)); } return newString; } }; int main(void) { const std::string reference[5] = {"ab","B","c1","c2","c10"}; std::vector<std::string> referenceStrings(&(reference[0]), &(reference[5])); //Insert in reverse order so we know they get sorted std::set<std::string,LexicographicSort<std::string> > strings(referenceStrings.rbegin(), referenceStrings.rend()); std::cout<<"Items:\n"; std::copy(strings.begin(), strings.end(), std::ostream_iterator<std::string>(std::cout, "\n")); std::vector<std::string> sortedStrings(strings.begin(), strings.end()); assert(sortedStrings == referenceStrings); }

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  • C++ Exam Question

    - by Carlucho
    I just took an exam where i was asked the following: Write the function body of each of the methods GenStrLen, InsertChar and StrReverse for the given code bellow. You must take into consideration the following; How strings are constructed in C++ The string must not overflow Insertion of character increases its length by 1 An empty string is indicated by StrLen = 0 class Strings { private: char str[80]; int StrLen; public: // Constructor Strings() { StrLen=0; }; // A function for returning the length of the string 'str' int GetStrLen(void) { }; // A function to inser a character 'ch' at the end of the string 'str' void InsertChar(char ch) { }; // A function to reverse the content of the string 'str' void StrReverse(void) { }; }; The answer I gave was something like this (see bellow). My one of problem is that used many extra variables and that makes me believe am not doing it the best possible way, and the other thing is that is not working.... class Strings { private: char str[80]; int StrLen; int index; // *** Had to add this *** public: Strings(){ StrLen=0; } int GetStrLen(void){ for (int i=0 ; str[i]!='\0' ; i++) index++; return index; // *** Here am getting a weird value, something like 1829584505306 *** } void InsertChar(char ch){ str[index] = ch; // *** Not sure if this is correct cuz I was not given int index *** } void StrRevrse(void){ GetStrLen(); char revStr[index+1]; for (int i=0 ; str[i]!='\0' ; i++){ for (int r=index ; r>0 ; r--) revStr[r] = str[i]; } } }; I would appreciate if anyone could explain me toughly what is the best way to have answered the question and why. Also how come my professor closes each class function like " }; " i thought that was only used for ending classes and constructors only. Thanks a lot for your help.

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  • Building a DataTable in C# with one column at a time

    - by Awaken
    I am trying to build a Retirement Calculator as a chance to make something useful and learn C# better. Currently, I am trying to build a DataTable with a dynamic amount of rows/columns. For context, I ask the user for some inputs regarding salary, % of salary being invested, and expected ROI. I have some other stuff too, but it isn't really part of the issue I am having. Because the number of columns I need for the DataTable is unknown until the formula is run (while+for loop completes), I am having trouble doing things as DataColumns. Hopefully the code below will help. I am really trying to build the table one column at a time. I realize I could reverse it to build it one row at a time because the Years before retirement (yearsRetire) is known, but I would prefer not to and I want to learn more. Sorry for the indentation and commenting. I tried to leave some of my commented coding attempts in there. Thanks for any help. public double calcROI() { double testROI = 0.00; double tempRetireAmount = 0; double adjustRetire = goalAmount * (1 + (Math.Pow(inflation,yearsRetire))); // Loop through ROI values until the calculated retire amount with the test ROI // is greater than the target amount adjusted for inflation while (tempRetireAmount < adjustRetire) { //Increment ROI by 1% per while iteration testROI += .01; //Make a new Column to hold the values for ROI for this while iteration //dtMain.Columns.Add(Convert.ToString(testROI)); //DataColumn tempdc = new DataColumn(Convert.ToString(testROI)); //Loop through the number of years entered by user and see the amount //at Retirement with current ROI for (int i = 0; i < yearsRetire; i++) { //Main formula to calculate amount after i years tempRetireAmount = (tempRetireAmount + salary*savingsPct) * (1 + testROI); // Add value for this year/ROI to table/column //DataRow dr = .NewRow(); //dr tempRetireAmount; //tempdc[i] = tempRetireAmount; } //Need to add column of data to my Main DataTable //dtMain.Rows.Add(dr); //dtMain.Columns.Add(tempdc); } return testROI; }

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  • .Net Custom Components "disappear" after file save

    - by EatATaco
    I might have a hard time explaining this because I am at a total loss for what is happening so I am just looking for some guidance. I might be a bit wordy because I don't know exactly what is the relevant information. I am developing a GUI for a project that I am working on in using .Net (C#) Part of the interface mimics, exactly, what we do in another product. For consistency reasons, my boss wants me to make it look the same way. So I got the other software and basically copied and pasted the components into my new GUI. This required me to introduce a component library (the now defunct Graphics Server GSNet, so I can't go to them for help) so I could implement some simple graphs and temperature/pressure "widgets." The components show up fine, and when I compile, everything seems to work fine. However, at some point during my programming it just breaks. Sometimes the tab that these components are on starts throwing exceptions when I view the designer page (A missing method exception) so it won't display. Sometimes JUST those components from the GSNet library don't show up. Sometimes, if I try to run it, I get a not-instantiated exception on one of their lines of code in the designer code file. Sometimes I can't view the designer at all. No matter what I do I can't reverse it. Even if I undo what I just did it won't fix it. If it happens, I have to revert to a backup and start over again. So I started to backup pretty much every step. I compile it and it works. I comment out a line of code, save it, and then uncomment that same line of code (so I am working with the same exact code) and the components all disappear. It doesn't matter what line of code I actually comment out, as long as it is in the same project that these components are being used. I pretty much have to use the components. . . so does anyone have any suggestion or where I can look to debug this?

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  • C++ exam question on string class implementation

    - by Carlucho
    I just took an exam where i was asked the following: Write the function body of each of the methods GenStrLen, InsertChar and StrReverse for the given code bellow. You must take into consideration the following; How strings are constructed in C++ The string must not overflow Insertion of character increases its length by 1 An empty string is indicated by StrLen = 0 class Strings { private: char str[80]; int StrLen; public: // Constructor Strings() { StrLen=0; }; // A function for returning the length of the string 'str' int GetStrLen(void) { }; // A function to inser a character 'ch' at the end of the string 'str' void InsertChar(char ch) { }; // A function to reverse the content of the string 'str' void StrReverse(void) { }; }; The answer I gave was something like this (see bellow). My one of problem is that used many extra variables and that makes me believe am not doing it the best possible way, and the other thing is that is not working.... class Strings { private: char str[80]; int StrLen; int index; // *** Had to add this *** public: Strings(){ StrLen=0; } int GetStrLen(void){ for (int i=0 ; str[i]!='\0' ; i++) index++; return index; // *** Here am getting a weird value, something like 1829584505306 *** } void InsertChar(char ch){ str[index] = ch; // *** Not sure if this is correct cuz I was not given int index *** } void StrRevrse(void){ GetStrLen(); char revStr[index+1]; for (int i=0 ; str[i]!='\0' ; i++){ for (int r=index ; r>0 ; r--) revStr[r] = str[i]; } } }; I would appreciate if anyone could explain me toughly what is the best way to have answered the question and why. Also how come my professor closes each class function like " }; " i thought that was only used for ending classes and constructors only. Thanks a lot for your help.

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  • True / false evaluation doesn't work as expected in Scheme

    - by ron
    I'm trying to compare two booleans : (if (equal? #f (string->number "123b")) "not a number" "indeed a number") When I run this in the command line of DrRacket I get "not a number" , however , when I put that piece of code in my larger code , the function doesn't return that string ("not a number") , here's the code : (define (testing x y z) (define badInput "ERROR") (if (equal? #f (string->number "123b")) "not a number" "indeed a number") (display x)) And from command line : (testing "123" 1 2) displays : 123 Why ? Furthermore , how can I return a value , whenever I choose ? Here is my "real" problem : I want to do some input check to the input of the user , but the thing is , that I want to return the error message if I need , before the code is executed , because if won't - then I would run the algorithm of my code for some incorrect input : (define (convert originalNumber s_oldBase s_newBase) (define badInput "ERROR") ; Input check - if one of the inputs is not a number then return ERROR (if (equal? #f (string->number originalNumber)) badInput) (if (equal? #f (string->number s_oldBase)) badInput) (if (equal? #f (string->number s_newBase)) badInput) (define oldBase (string->number s_oldBase)) (define newBase (string->number s_newBase)) (define outDecimal (convertIntoDecimal originalNumber oldBase)) (define result "") ; holds the new number (define remainder 0) ; remainder for each iteration (define whole 0) ; the whole number after dividing (define temp 0) (do() ((= outDecimal 0)) ; stop when the decimal value reaches 0 (set! whole (quotient outDecimal newBase)) ; calc the whole number (set! temp (* whole newBase)) (set! remainder (- outDecimal temp)) ; calc the remainder (set! result (appending result remainder)) ; append the result (set! outDecimal (+ whole 0)) ; set outDecimal = whole ) ; end of do (if (> 1 0) (string->number (list->string(reverse (string->list result))))) ) ;end of method This code won't work since it uses another method that I didn't attach to the post (but it's irrelevant to the problem . Please take a look at those three IF-s ... I want to return "ERROR" if the user put some incorrect value , for example (convert "23asb4" "b5" "9") Thanks

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  • How can I maintain a sorted hash in Perl?

    - by srk
    @aoh =( { 3 => 15, 4 => 8, 5 => 9, }, { 3 => 11, 4 => 25, 5 => 6, }, { 3 => 5, 4 => 18, 5 => 5, }, { 0 => 16, 1 => 11, 2 => 7, }, { 0 => 21, 1 => 13, 2 => 31, }, { 0 => 11, 1 => 14, 2 => 31, }, ); I want the hashes in each array index sorted in reverse order based on values.. @sorted = sort { ........... please fill this..........} @aoh; expected output @aoh =( { 4 => 8, 5 => 9, 3 => 15, }, { 5 => 6, 3 => 11, 4 => 25, }, { 5 => 5, 3 => 5, 4 => 18, }, { 2 => 7, 1 => 11, 0 => 16, }, { 1 => 13, 0 => 21, 2 => 31, }, { 0 => 11, 1 => 14, 2 => 31, }, ); Please help.. Thanks in advance.. Stating my request again: I only want the hashes in each array index to be sorted by values.. i dont want the array to be sorted..

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  • Cisco ASA (Client VPN) to LAN - through second VPN to second LAN

    - by user50855
    We have 2 site that is linked by an IPSEC VPN to remote Cisco ASAs: Site 1 1.5Mb T1 Connection Cisco(1) 2841 Site 2 1.5Mb T1 Connection Cisco 2841 In addition: Site 1 has a 2nd WAN 3Mb bonded T1 Connection Cisco 5510 that connects to same LAN as Cisco(1) 2841. Basically, Remote Access (VPN) users connecting through Cisco ASA 5510 needs access to a service at the end of Site 2. This is due to the way the service is sold - Cisco 2841 routers are not under our management and it is setup to allow connection from local LAN VLAN 1 IP address 10.20.0.0/24. My idea is to have all traffic from Remote Users through Cisco ASA destined for Site 2 to go via the VPN between Site 1 and Site 2. The end result being all traffic that hits Site 2 has come via Site 1. I'm struggling to find a great deal of information on how this is setup. So, firstly, can anyone confirm that what I'm trying to achieve is possible? Secondly, can anyone help me to correct the configuration bellow or point me in the direction of an example of such a configuration? Many Thanks. interface Ethernet0/0 nameif outside security-level 0 ip address 7.7.7.19 255.255.255.240 interface Ethernet0/1 nameif inside security-level 100 ip address 10.20.0.249 255.255.255.0 object-group network group-inside-vpnclient description All inside networks accessible to vpn clients network-object 10.20.0.0 255.255.255.0 network-object 10.20.1.0 255.255.255.0 object-group network group-adp-network description ADP IP Address or network accessible to vpn clients network-object 207.207.207.173 255.255.255.255 access-list outside_access_in extended permit icmp any any echo-reply access-list outside_access_in extended permit icmp any any source-quench access-list outside_access_in extended permit icmp any any unreachable access-list outside_access_in extended permit icmp any any time-exceeded access-list outside_access_in extended permit tcp any host 7.7.7.20 eq smtp access-list outside_access_in extended permit tcp any host 7.7.7.20 eq https access-list outside_access_in extended permit tcp any host 7.7.7.20 eq pop3 access-list outside_access_in extended permit tcp any host 7.7.7.20 eq www access-list outside_access_in extended permit tcp any host 7.7.7.21 eq www access-list outside_access_in extended permit tcp any host 7.7.7.21 eq https access-list outside_access_in extended permit tcp any host 7.7.7.21 eq 5721 access-list acl-vpnclient extended permit ip object-group group-inside-vpnclient any access-list acl-vpnclient extended permit ip object-group group-inside-vpnclient object-group group-adp-network access-list acl-vpnclient extended permit ip object-group group-adp-network object-group group-inside-vpnclient access-list PinesFLVPNTunnel_splitTunnelAcl standard permit 10.20.0.0 255.255.255.0 access-list inside_nat0_outbound_1 extended permit ip 10.20.0.0 255.255.255.0 10.20.1.0 255.255.255.0 access-list inside_nat0_outbound_1 extended permit ip 10.20.0.0 255.255.255.0 host 207.207.207.173 access-list inside_nat0_outbound_1 extended permit ip 10.20.1.0 255.255.255.0 host 207.207.207.173 ip local pool VPNPool 10.20.1.100-10.20.1.200 mask 255.255.255.0 route outside 0.0.0.0 0.0.0.0 7.7.7.17 1 route inside 207.207.207.173 255.255.255.255 10.20.0.3 1 crypto ipsec transform-set ESP-3DES-SHA esp-3des esp-sha-hmac crypto ipsec security-association lifetime seconds 28800 crypto ipsec security-association lifetime kilobytes 4608000 crypto dynamic-map outside_dyn_map 20 set transform-set ESP-3DES-SHA crypto dynamic-map outside_dyn_map 20 set security-association lifetime seconds 288000 crypto dynamic-map outside_dyn_map 20 set security-association lifetime kilobytes 4608000 crypto dynamic-map outside_dyn_map 20 set reverse-route crypto map outside_map 20 ipsec-isakmp dynamic outside_dyn_map crypto map outside_map interface outside crypto map outside_dyn_map 20 match address acl-vpnclient crypto map outside_dyn_map 20 set security-association lifetime seconds 28800 crypto map outside_dyn_map 20 set security-association lifetime kilobytes 4608000 crypto isakmp identity address crypto isakmp enable outside crypto isakmp policy 20 authentication pre-share encryption 3des hash sha group 2 lifetime 86400 group-policy YeahRightflVPNTunnel internal group-policy YeahRightflVPNTunnel attributes wins-server value 10.20.0.9 dns-server value 10.20.0.9 vpn-tunnel-protocol IPSec password-storage disable pfs disable split-tunnel-policy tunnelspecified split-tunnel-network-list value acl-vpnclient default-domain value YeahRight.com group-policy YeahRightFLVPNTunnel internal group-policy YeahRightFLVPNTunnel attributes wins-server value 10.20.0.9 dns-server value 10.20.0.9 10.20.0.7 vpn-tunnel-protocol IPSec split-tunnel-policy tunnelspecified split-tunnel-network-list value YeahRightFLVPNTunnel_splitTunnelAcl default-domain value yeahright.com tunnel-group YeahRightFLVPN type remote-access tunnel-group YeahRightFLVPN general-attributes address-pool VPNPool tunnel-group YeahRightFLVPNTunnel type remote-access tunnel-group YeahRightFLVPNTunnel general-attributes address-pool VPNPool authentication-server-group WinRadius default-group-policy YeahRightFLVPNTunnel tunnel-group YeahRightFLVPNTunnel ipsec-attributes pre-shared-key *

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  • Building nginx 1.0.4 on Amazon EC2 micro - perl and python problems

    - by digitaltoast
    I'd like to run nginx as a reverse proxy with apache2 on my EC2 micro instance. yum install nginx gives me nginx-0.8.53-1.2.amzn1.x86_64.rpm The current nginx is 1.0.4 I found and followed this guide: http://kdn2.info/2011/05/install-nginx-on-amazon-ec2/ It works fine up to and including "make". When I get to checkinstall --fstrans=no I get ERROR: ld.so: object '/usr/lib/installwatch.so' from LD_PRELOAD cannot be preloaded: ignored. test -d '/var/log/nginx' || mkdir -p '/var/log/nginx' ERROR: ld.so: object '/usr/lib/installwatch.so' from LD_PRELOAD cannot be preloaded: ignored. make[1]: Leaving directory `/root/src/nginx-1.0.4' ======================== Installation successful ========================== Copying documentation directory... ./ ./CHANGES ./LICENSE ./README cp: cannot stat `//var/tmp/gRWoVgIcdbmjfTjoVGBM/newfiles.tmp': No such file or directory Copying files to the temporary directory...OK Striping ELF binaries and libraries...OK Compressing man pages...OK Building file list...OK Building RPM package... FAILED! *** Failed to build the package ...and the logfile is full of: Building target platforms: x86_64 Building for target x86_64 Processing files: nginx-1.0.4-1.x86_64 error: File not found: /usr/src/rpm/BUILDROOT/nginx-1.0.4-1.x86_64/usr error: File not found: /usr/src/rpm/BUILDROOT/nginx-1.0.4-1.x86_64/usr/doc There IS /usr/src/rpm/BUILDROOT/nginx-1.0.4-1.x86_64/ but no /usr Following further down the page, it says: "If we want to use, for example, PHP 5.2 we can download PHP and Nginx compatible with Amazon Kernel(Xen Kernel) from the CentosALT Repository." So I install the two repositories, but when I yum install http://centos.alt.ru/pub/nginx/1.0/RPMS/x86_64/nginx-stable-1.0.4-1.el5.x86_64.rpm I get Error: Package: nginx-stable-1.0.4-1.el5.x86_64 (/nginx-stable-1.0.4-1.el5.x86_64) Requires: perl(:MODULE_COMPAT_5.8.8) You could try using --skip-broken to work around the problem but that doesn't fix it. When I do yum update, I get --> Finished Dependency Resolution Error: Package: python-distribute-0.6.19-10.1.x86_64 (devel_languages_python) Requires: python < 2.5 Installed: 1:python-2.6-1.19.amzn1.noarch (@amzn-main) python = 1:2.6-1.19.amzn1 Error: Package: python-distribute-0.6.19-10.1.i586 (devel_languages_python) Requires: python < 2.5 Installed: 1:python-2.6-1.19.amzn1.noarch (@amzn-main) python = 1:2.6-1.19.amzn1 I've tried everything - yum clean all and various other suggestions found on other sites. If anyone has any suggestions or a known package of the current 1.04 nginx working on EC2 Micro (Linux ip-10-56-63-85 2.6.35.11-83.9.amzn1.x86_64 #1 SMP Sat Feb 19 23:42:04 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux - which I think is RHEL 5?) then I'd be grateful. Incidentally, does this repolist look right? repo id repo name status CentALT CentALT Packages for Enterprise Linux 5 - x86_64 enabled: 112+157 amzn-main amzn-main-Base enabled: 2,706 amzn-main-debuginfo amzn-main-debuginfo disabled amzn-main-nosrc amzn-main-nosrc disabled amzn-updates amzn-updates-Base enabled: 328 amzn-updates-debuginfo amzn-updates-debuginfo disabled amzn-updates-nosrc amzn-updates-nosrc disabled devel_languages_python Python and Python Modules (SLE_10) enabled: 1,452+768 epel Extra Packages for Enterprise Linux 5 - x86_64 enabled: 5,892+604 epel-debuginfo Extra Packages for Enterprise Linux 5 - x86_64 - Debug disabled epel-source Extra Packages for Enterprise Linux 5 - x86_64 - Source disabled epel-testing Extra Packages for Enterprise Linux 5 - Testing - x86_64 disabled epel-testing-debuginfo Extra Packages for Enterprise Linux 5 - Testing - x86_64 - Debug disabled epel-testing-source Extra Packages for Enterprise Linux 5 - Testing - x86_64 - Source disabled s3tools Tools for managing Amazon S3 - Simple Storage Service (RHEL_6) enabled: 2+1 repolist: 10,492

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  • Ubuntu server random hangups.

    - by Ebbe
    Hello all. this is my first post to this forum which I found through the superb podcast "It Conversations" from StackOverFlow. I am quite in my role as server administrator for an exhibition center in London. Basically we have a central file and sql server to which roughly 40 stations connects to to upload/download data used/captured by a set of applications. Over the last weeks we have experienced a few random hangups to our applications, and as it always happen to multiple applications simultaneously I do not believe that the applications are the source of the problem. We also monitor the network using Dartware Intermapper which indicates that all switches and stations on the network has been reachable during the downtime. Thus, its all pointing to the server. I have been looking through all log files I can think of and the only thing so far that I have found suspicious is the following lines in the syslog which are from the time of one of the hangups: Feb 6 17:14:27 es named[5582]: client 127.0.0.1#33721: RFC 1918 response from Internet for 150.0.168.192.in-addr.arpa Feb 6 17:14:40 es named[5582]: client 127.0.0.1#32899: RFC 1918 response from Internet for 152.0.168.192.in-addr.arpa Feb 6 17:15:01 es /USR/SBIN/CRON[1956]: (es) CMD (/home/es/apps/es/bin/es_checksum.sh) Feb 6 17:16:06 es /USR/SBIN/CRON[2031]: (es) CMD (/home/es/apps/es/bin/es_checksum.sh) Feb 6 17:21:00 es named[5582]: *** POKED TIMER *** Feb 6 17:21:00 es last message repeated 2 times Feb 6 17:21:07 es named[5582]: client 127.0.0.1#44194: RFC 1918 response from Internet for 143.0.168.192.in-addr.arpa Feb 6 17:21:12 es named[5582]: client 127.0.0.1#59004: RFC 1918 response from Internet for 164.0.168.192.in-addr.arpa I find a few lines of interesting lines here: 1) "RFC 1918 response from Internet for 150.1.168.192.in-addr.arpa". I see this a lot in the syslog. And basically everytime I do a nslookup for any of the computers in the cluster I get a new similar line in the syslog. I understand from google that this has to do with reverse lookup problems. But I do not know how that could effect the systems. Lets say that one of these lines appear every time one of the userstations connects to the server, which may happen several times a second. Could this possible cause a hangup of the entire server? 2) POKED TIMER, I have googled this quite a lot, but not found an explaination that I can relate to. What does this mean? 3) The timestamps, it seems like the entire server has stopped responding for several minutes. Normally there are many printouts to the syslog per minute on this server. Furthermore the CRON job is set to run once every minute. Which according to the log, hasent happened here. OS: Ubuntu 8.04 Kernel: Linux 2.6.24-24-server x86_64 GNU/Linux. Hardware: Dell R710, RAID1, CPU: 2x XEON E5530. 16GB Memory. Average load is very low, and memory should not be a problem. Please let me know if you need any additional information. Best wishes, Ebbe

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  • apache+mod_wsgi configuration for django project(s) on a quad core

    - by Stefano
    I've been experiment quite some time with a "typical" django setting upon nginx+apache2+mod_wsgi+memcached(+postgresql) (reading the doc and some questions on SO and SF, see comments) Since I'm still unsatisfied with the behavior (definitely because of some bad misconfiguration on my part) I would like to know what a good configuration would look like with these hypotesis: Quad-Core Xeon 2.8GHz 8 gigs memory several django projects (anything special related to this?) These are excerpts form my current confs: apache2 SetEnv VHOST null #WSGIPythonOptimize 2 <VirtualHost *:8082> ServerName subdomain.domain.com ServerAlias www.domain.com SetEnv VHOST subdomain.domain AddDefaultCharset UTF-8 ServerSignature Off LogFormat "%{X-Real-IP}i %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"" custom ErrorLog /home/project1/var/logs/apache_error.log CustomLog /home/project1/var/logs/apache_access.log custom AllowEncodedSlashes On WSGIDaemonProcess subdomain.domain user=www-data group=www-data threads=25 WSGIScriptAlias / /home/project1/project/wsgi.py WSGIProcessGroup %{ENV:VHOST} </VirtualHost> wsgi.py import os import sys # setting all the right paths.... _realpath = os.path.realpath(os.path.dirname(__file__)) _public_html = os.path.normpath(os.path.join(_realpath, '../')) sys.path.append(_realpath) sys.path.append(os.path.normpath(os.path.join(_realpath, 'apps'))) sys.path.append(os.path.normpath(_public_html)) sys.path.append(os.path.normpath(os.path.join(_public_html, 'libs'))) sys.path.append(os.path.normpath(os.path.join(_public_html, 'django'))) os.environ['DJANGO_SETTINGS_MODULE'] = 'settings' import django.core.handlers.wsgi _application = django.core.handlers.wsgi.WSGIHandler() def application(environ, start_response): """ Launches django passing over some environment (domain name) settings """ application_group = environ['mod_wsgi.application_group'] """ wsgi application group is required. It's also used to generate the HOST.DOMAIN.TLD:PORT parameters to pass over """ assert application_group fields = application_group.replace('|', '').split(':') server_name = fields[0] os.environ['WSGI_APPLICATION_GROUP'] = application_group os.environ['WSGI_SERVER_NAME'] = server_name if len(fields) > 1 : os.environ['WSGI_PORT'] = fields[1] splitted = server_name.rsplit('.', 2) assert splitted >= 2 splited.reverse() if len(splitted) > 0 : os.environ['WSGI_TLD'] = splitted[0] if len(splitted) > 1 : os.environ['WSGI_DOMAIN'] = splitted[1] if len(splitted) > 2 : os.environ['WSGI_HOST'] = splitted[2] return _application(environ, start_response)` folder structure in case it matters (slightly shortened actually) /home/www-data/projectN/var/logs /project (contains manage.py, wsgi.py, settings.py) /project/apps (all the project ups are here) /django /libs Please forgive me in advance if I overlooked something obvious. My main question is about the apache2 wsgi settings. Are those fine? Is 25 threads an /ok/ number with a quad core for one only django project? Is it still ok with several django projects on different virtual hosts? Should I specify 'process'? Any other directive which I should add? Is there anything really bad in the wsgi.py file? I've been reading about potential issues with the standard wsgi.py file, should I switch to that? Or.. should this conf just be running fine, and I should look for issues somewhere else? So, what do I mean by "unsatisfied": well, I often get quite high CPU WAIT; but what is worse, is that relatively often apache2 gets stuck. It just does not answer anymore, and has to be restarted. I have setup a monit to take care of that, but it ain't a real solution. I have been wondering if it's an issue with the database access (postgresql) under heavy load, but even if it was, why would the apache2 processes get stuck? Beside these two issues, performance is overall great. I even tried New Relic and got very good average results.

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  • Why do GPUs overheat?

    - by JAD
    About a year ago, I added a 9800GT (1 GB version) and a Corsair CX500 PSU to an HP M8000N computer. A few weeks ago, the HDD overheated and I decided to transfer the GPU & PSU to a new build, which consists of: i3 @ 3.3Ghz Gigabyte H61 Micro ATX Mobo 4GB RAM 500GB WD HDD DVD RW Drive Cooler Master Elite 430 Tower Once I had Win7 up and running, I installed all the essential drivers that came with the Gigabyte Mobo CD. However, whenever I tried installing the Graphics Media Accelerator driver, the computer would crash and enter an endless boot sequence on the next startup. I skipped installing this driver and installed the CD driver for the 9800GT, which by now is a year old. Everything was working fine, WEI rated my GPU at 6.6 graphics & aero performance. However, after updating my Nvidia drivers to the latest, the WEI dropped my rating to 3.3 for Aero, and 4.7 for graphics performance. Just to make sure that everything was ok, I ran Bad Company 2 on medium settings. The first few minutes ran just fine at a smooth framerate, so I dismissed this as Windows being Windows. About 6 hours later, I ran BC2 again. This time I averaged anywhere from 2-5 FPS. I checked the GPU temperature through GPU-Z, and it came back as 120C. The problem with this, is that the computer was on for six hours up to that point. Wouldn't the card have experienced a reactor core meltdown a lot sooner than that? Granted, the computer was "sleeping" some of the time, but still... The next day I took out a temperature gun and ran some tests. I would point the laser at a very specific area on the reverse side of the card (not the fan or "front"), and compare the temp reading with GPU-Z. After leaving the system on idle on idle for a few minutes, I ran BC2 twice. Here are the results: GPU-Z Reading / Temp Gun Reading / Time Null / 22.3°C / Comp is Off 53°C / 33.5°C / 1:49 78°C / 46°C / 1:53 - (First BC2 run; good framerate) 102°C / 64.6°C / 2:01 - (System is again on idle) 113°C / 64.8°C / 2:10 119°C / 71.8°C / 2:17 - (Second BC2 run; poor framerate) I should also mention that I also took a temp recording of another part of the GPU from 2:01-2:17. The temp in this area jumped from 75°C to 82.9°C in that time frame. This pretty much confirms that GPU-Z is reporting the temperature accurately, and the card is overheating. But I'd like to know why; the cars is doing nothing and still the temperature climbs at a steady rate. I thoroughly cleaned the GPU and PSU when I salvaged them from the old HP M8000N computer with a can of compressed air, dust cant be the issue. Similarly, the rest of the computer is brand new. I installed various Nvidia drivers, but no luck. It seems strange to me that a year-old card is suddenly failing on me; aren't they supposed to last at least two years? Could this be a driver issue? Is the motherboard faulty? Could the PSU be overfeeding the card on voltage? Neither case seems likely, as the CPU, RAM and otherwise the rest of the comp has worked flawlessly and has stayed well within respectable temp ranges (the i3 lingers around 50C, the HDD stays at 30C, so does the PSU). How can I pinpoint the issue?

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  • Diagnosing packet loss / high latency in Ubuntu

    - by Sam Gammon
    We have a Linux box (Ubuntu 12.04) running Nginx (1.5.2), which acts as a reverse proxy/load balancer to some Tornado and Apache hosts. The upstream servers are physically and logically close (same DC, sometimes same-rack) and show sub-millisecond latency between them: PING appserver (10.xx.xx.112) 56(84) bytes of data. 64 bytes from appserver (10.xx.xx.112): icmp_req=1 ttl=64 time=0.180 ms 64 bytes from appserver (10.xx.xx.112): icmp_req=2 ttl=64 time=0.165 ms 64 bytes from appserver (10.xx.xx.112): icmp_req=3 ttl=64 time=0.153 ms We receive a sustained load of about 500 requests per second, and are currently seeing regular packet loss / latency spikes from the Internet, even from basic pings: sam@AM-KEEN ~> ping -c 1000 loadbalancer PING 50.xx.xx.16 (50.xx.xx.16): 56 data bytes 64 bytes from loadbalancer: icmp_seq=0 ttl=56 time=11.624 ms 64 bytes from loadbalancer: icmp_seq=1 ttl=56 time=10.494 ms ... many packets later ... Request timeout for icmp_seq 2 64 bytes from loadbalancer: icmp_seq=2 ttl=56 time=1536.516 ms 64 bytes from loadbalancer: icmp_seq=3 ttl=56 time=536.907 ms 64 bytes from loadbalancer: icmp_seq=4 ttl=56 time=9.389 ms ... many packets later ... Request timeout for icmp_seq 919 64 bytes from loadbalancer: icmp_seq=918 ttl=56 time=2932.571 ms 64 bytes from loadbalancer: icmp_seq=919 ttl=56 time=1932.174 ms 64 bytes from loadbalancer: icmp_seq=920 ttl=56 time=932.018 ms 64 bytes from loadbalancer: icmp_seq=921 ttl=56 time=6.157 ms --- 50.xx.xx.16 ping statistics --- 1000 packets transmitted, 997 packets received, 0.3% packet loss round-trip min/avg/max/stddev = 5.119/52.712/2932.571/224.629 ms The pattern is always the same: things operate fine for a while (<20ms), then a ping drops completely, then three or four high-latency pings (1000ms), then it settles down again. Traffic comes in through a bonded public interface (we will call it bond0) configured as such: bond0 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:5d inet addr:50.xx.xx.16 Bcast:50.xx.xx.31 Mask:255.255.255.224 inet6 addr: <ipv6 address> Scope:Global inet6 addr: <ipv6 address> Scope:Link UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 RX packets:527181270 errors:1 dropped:4 overruns:0 frame:1 TX packets:413335045 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:240016223540 (240.0 GB) TX bytes:104301759647 (104.3 GB) Requests are then submitted via HTTP to upstream servers on the private network (we can call it bond1), which is configured like so: bond1 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:5c inet addr:10.xx.xx.70 Bcast:10.xx.xx.127 Mask:255.255.255.192 inet6 addr: <ipv6 address> Scope:Link UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 RX packets:430293342 errors:1 dropped:2 overruns:0 frame:1 TX packets:466983986 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:77714410892 (77.7 GB) TX bytes:227349392334 (227.3 GB) Output of uname -a: Linux <hostname> 3.5.0-42-generic #65~precise1-Ubuntu SMP Wed Oct 2 20:57:18 UTC 2013 x86_64 GNU/Linux We have customized sysctl.conf in an attempt to fix the problem, with no success. Output of /etc/sysctl.conf (with irrelevant configs omitted): # net: core net.core.netdev_max_backlog = 10000 # net: ipv4 stack net.ipv4.tcp_ecn = 2 net.ipv4.tcp_sack = 1 net.ipv4.tcp_fack = 1 net.ipv4.tcp_tw_reuse = 1 net.ipv4.tcp_tw_recycle = 0 net.ipv4.tcp_timestamps = 1 net.ipv4.tcp_window_scaling = 1 net.ipv4.tcp_no_metrics_save = 1 net.ipv4.tcp_max_syn_backlog = 10000 net.ipv4.tcp_congestion_control = cubic net.ipv4.ip_local_port_range = 8000 65535 net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_thin_dupack = 1 net.ipv4.tcp_thin_linear_timeouts = 1 net.netfilter.nf_conntrack_max = 99999999 net.netfilter.nf_conntrack_tcp_timeout_established = 300 Output of dmesg -d, with non-ICMP UFW messages suppressed: [508315.349295 < 19.852453>] [UFW BLOCK] IN=bond1 OUT= MAC=<mac addresses> SRC=118.xx.xx.143 DST=50.xx.xx.16 LEN=68 TOS=0x00 PREC=0x00 TTL=51 ID=43221 PROTO=ICMP TYPE=3 CODE=1 [SRC=50.xx.xx.16 DST=118.xx.xx.143 LEN=40 TOS=0x00 PREC=0x00 TTL=249 ID=10220 DF PROTO=TCP SPT=80 DPT=53817 WINDOW=8190 RES=0x00 ACK FIN URGP=0 ] [517787.732242 < 0.443127>] Peer 190.xx.xx.131:59705/80 unexpectedly shrunk window 1155488866:1155489425 (repaired) How can I go about diagnosing the cause of this problem, on a Debian-family Linux box?

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  • Troubleshooting unwanted NTP Traffic

    - by Jaxaeon
    A domain controller running Windows Server 2012 is sending NTP and NETBIOS traffic to an address that has never been configured as a time provider. The server logs give no indication that any NTP traffic is failing. The only place I see any evidence of this traffic is in pfSense system logs: (Blocked) Jun 9 08:48:50 DOMAIN 10.0.1.100:123 192.128.127.254:123 UDP (Blocked) Jun 9 08:48:53 DOMAIN 10.0.1.100:137 192.128.127.254:137 UDP As far as I can tell the NTP service is working normally otherwise: DC2.domain.com[10.0.1.101:123]: ICMP: 0ms delay NTP: -0.0131705s offset from DC1.domain.com RefID: DC1.domain.com [10.0.1.100] Stratum: 3 DC1.domain.com *** PDC ***[10.0.1.100:123]: ICMP: 0ms delay NTP: +0.0000000s offset from DC1.domain.com RefID: clock1.albyny.inoc.net [64.246.132.14] Stratum: 2 The time provider NtpClient is currently receiving valid time data from 1.pool.ntp.org,0×1 (ntp.m|0x0|0.0.0.0:123->204.2.134.163:123). The time provider NtpClient is currently receiving valid time data from 0.pool.ntp.org,0×1 (ntp.m|0x0|0.0.0.0:123->64.246.132.14:123). The time service is now synchronizing the system time with the time source 0.pool.ntp.org,0×1 (ntp.m|0x0|0.0.0.0:123->64.246.132.14:123). I've been inside and out of the NTP configuration and cannot find any reason for this traffic. Reverse DNS points the destination address to nothing.attdns.com. pinging nothing.attdns.com from the domain controller in question leads to a response from loopback (127.0.0.2) which makes my head hurt. Any ideas? EDIT1: It should probably be noted that after a dns flush, nslookup 192.128.127.254 returns nothing.attdns.com. 192.128.127.254 is not present in domain.com DNS records. The attdns.com domain is not present in cached lookups. 127.in-addr.arpa is clean of any funkyness. EDIT2: The loopback ping response from nothing.attdns.com is possibly unrelated. Machines on other networks are also displaying this behavior. EDIT3: As mentioned in the comments, I tracked the problem network adapter back to my pfSense VM hosted in esxi 5.5 (I know shame on me for virtualizing a firewall). pfSense was configured to use DC1.domain.com as its primary time provider, but upon changing it back to pool.ntp.org the problem persists. pfSense logs give no indication of NTP misconfiguration. Everywhere I can think to look this VM is identified as 10.0.1.253, so I still have no idea why it’s sending NTP requests as 192.128… Since this firewall was a temporary solution to a problem that no longer exists so I am going to decommission it. EDIT4: The queries were coming from another machine sharing the same virtual adapter as the firewall. The machine has two local adapters: one for LAN, and the other for attached hardware that uses an Ethernet connection. That hardware sits in the the mystery subnet, and the machine is broadcasting NTP requests over both adapters.

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  • Strange enduser experience with Liferay, Glassfish and Apache on RedHat

    - by Pete Helgren
    Tried multiple forums to get to the bottom of this. I hope I can get some direction here: Here is the stack I am working with: Red Hat Enterprise Linux Server release 5.6 (Tikanga) Liferay 6.0.6 on Glassfish 3.0.1 MySQL 5.0.77 Apache 2.2.3 The Liferay portal provides a variety of portlets to end users. Static content (web pages), static resources (primarily pdf and mp3 files 1mb - 80mb in size), File upload and download capabilities (primarily 40-60mb mp3 files) and online streaming of those MP3 files. Here is the strange end user experiences: Under normal load: (20-30) users uploading, downloading or streaming files and 20-30 accessing static content (some of it downloads), we see the following: 1) Clicking a link triggers the download of a portion of an MP3 (the portion is a few seconds long). 2) Clicking on a link tiggers the download of the page content rather than rendering. 3) Clicking a link causes the page to dump binary data to the end user rather than the expected content. 4) Clicking a link returns the text of a javascript file rather than rendering the page. Each occurrence is totally random (or appears so). Sometimes it works, sometimes it doesn't. It seems to have no relation to browser or client OS. The strange events seem to occur much more frequently when using an SSL connection rather than regular http. Apache serves as a proxy server only (reverse). It basically passes all the requests through to Glassfish. There isn't any static content proxy served by Apache. We rebuilt the entire stack from scratch and redeployed the portlet wars and still have the same issues. Liferay is running as a single server (not clustered). We disabled mod_cache in Apache. The problems are more frequent as the server load grows. This morning the load is pretty light and we are seeing few problems but the use of the site will grow, particularly tonight around 9pm CST through Wednesday morning. You could try the site (http://preview.bsfinternational.org) during those times and I would expect that you might experience one of the weirdnesses as you randomly click links on the site (https is invoked only when signed in). Again, https seems to exacerbate the issue. This seems very much like a caching issue but I don't know where in the stack to start peeling the onion. Apache? Liferay? Glassfish? MySQL? Maybe even Redhat? We are stumped and most forums we have posted to (LifeRay and Glassfish) have returned very few suggestions. I just need an idea of where to start looking. I understand that we could have a portlet EDIT: Opening the files in a Hex editor that appear to be pages that download rather than render, we see that the first 4000 characters are "junk" and then the "HTTP/1.1 ...." 'normal' header is seen. So something is dumping a jumble of characters up to offset 4000 (when viewing it in a Hex editor). Perhaps a clue? Ideas?

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  • Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

    - by vmiazzo
    Hi, Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not good for high availability. When 1 IP goes down clients will continue to use it for minutes. A load balancer is often suggested as a better choice. Both claims are not completely true: When the traffic is HTTP then, most of the HTML browsers are able to automatically try the next A record if the previous is down, without a new DNS look-up. Read here chapter 3.1 and here. When multiple data centers are involved then, DNS RR is the only option to distribute traffic across them. So, is it true that, with multiple data centers and HTTP traffic, the use of DNS RR is the ONLY way to assure instant fail-over when one data center goes down? Thanks, Valentino Edit: Off course each data center has a local Load Balancer with hot spare. It's OK to sacrifice session affinity for an instant fail-over. AFAIK the only way for a DNS to suggest a data center instead of another is to reply with just the IP (or IPs) associated to that data center. If the data center becomes unreachable then all those IP are also unreachables. This means that, even if smart HTML browsers are able to instantly try another A record , all the attempts will fail until the local cache entry expires and a new DNS lookup is done, fetching the new working IPs (I assume DNS automatically suggests to a new data center when one fail). So, "smart DNS" cannot assure instant fail-over. Conversely a DNS round-robin permits it. When one data center fail, the smart HTML browsers (most of them) instantly try the other cached A records jumping to another (working) data center. So, DNS round-robin doesn't assure session affinity or the lowest RTT but seems to be the only way to assure instant fail-over when the clients are "smart" HTML browsers. Edit 2: Some people suggest TCP Anycast as a definitive solution. In this paper (chapter 6) is explained that Anycast fail-over is related to BGP convergence. For this reason Anycast can employ from 15 minutes to 20 seconds to complete. 20 seconds are possible on networks where the topology was optimized for this. Probably just CDN operators can grant such fast fail-overs. Edit 3:* I did some DNS look-ups and traceroutes (maybe some expert can double check) and: The only CDN using TCP Anycast seems to be CacheFly, other operators like CDN networks and BitGravity use CacheFly. Seems that their edges cannot be used as reverse proxies. Therefore, they cannot be used to grant instant failover. Akamai and LimeLight seems to use geo-aware DNS. But! They return multiple A records. From traceroutes seems that the returned IPs are on the same data center. So, I'm puzzled on how they can offer a 100% SLA when one data center goes down.

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