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• Where is the bottleneck in this code?

  - by Mikhail

  I have the following tight loop that makes up the serial bottle neck of my code. Ideally I would parallelize the function that calls this but that is not possible. //n is about 60 for (int k = 0;k < n;k++) { double fone = z[k*n+i+1]; double fzer = z[k*n+i]; z[k*n+i+1]= s*fzer+c*fone; z[k*n+i] = c*fzer-s*fone; } Are there any optimizations that can be made such as vectorization or some evil inline that can help this code? I am looking into finding eigen solutions of tridiagonal matrices. http://www.cimat.mx/~posada/OptDoglegGraph/DocLogisticDogleg/projects/adjustedrecipes/tqli.cpp.html

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• find a duplicate entry in an array in constant space and O(n) time [closed]

  - by Anubhav Agarwal

  Possible Duplicate: Algorithm to find a duplicate entry in constant space and O(n) time Given an array of N integer such that only one integer is repeated. Find the repeated integer in O(n) time and constant space. There is no range for the value of integers or the value of N For example given an array of 6 integers as 23 45 67 87 23 47. The answer is 23 (I hope this covers ambiguous and vague part) I searched on the net but was unable to find any such question in which range of integers was not fixed. Also here is an example that answers a similar question to mine but here he created a hash table with the highest integer value in C++.But the cpp does not allow such to create an array with 2^64 element(on a 64-bit computer).

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• friend declaration block an external function access to the private section of a class

  - by MiP

  I'm trying to force function caller from a specific class. For example this code bellow demonstrate my problem. I want to make 'use' function would be called only from class A. I'm using a global namespace all over the project. a.h #include "b.h" namespace GLOBAL{ class A{ public: void doSomething(B); } } a.cpp #include "a.h" using namespace GLOBAL; void A::doSomething(B b){ b.use(); } b.h namespace GLOBAL{ class B{ public: friend void GLOBAL::A::doSomething(B); private: void use(); } Compiler says: ‘GLOBAL::A’ has not been declared ‘void GLOBAL::B::use()’ is private Can anyone help here ? Thanks a lot, Mike.

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• 'Generating code' and stop in building release mode (Visual Studio 2005 )

  - by cchcc

  Hi! I have a problem about release build I'm using Visual Studio 2005. The project is worked on MFC When I build the project what I working in debug mode, It builds done successfully. but in release mode, Output window shows next 1Compiling resources... 1Linking... 1Generating code and then.. it doesn't pass. It seems like be stoped. After 20 min ,I just canceld build. It has been built well before. I just added some files(.h .cpp) and resorces(.bmp), not special code and it happened. Do you have any idea about that? please help me

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• C++: Create abstract class with abstract method and override the method in a subclass

  - by Martijn Courteaux

  Hi, How to create in C++ an abstract class with some abstract methods that I want to override in a subclass? How should the .h file look? Is there a .cpp, if so how should it look? In Java it would look like this: abstract class GameObject { public abstract void update(); public abstract void paint(Graphics g); } class Player extends GameObject { @Override public void update() { // ... } @Override public void paint(Graphics g) { // ... } } // In my game loop: for (int i = 0; i < objects.size(); i++) { objects.get(i).update(); } for (int i = 0; i < objects.size(); i++) { objects.get(i).paint(g); } Translating this code to C++ is enough for me.

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• How can I reuse a base class function in a derived class

  - by Armen Ablak

  Let's say we have these four classes: BinaryTree, SplayTree (which is a sub-class of BinaryTree), BinaryNode and SplayNode (which is a sub-class of BinaryNode). In class BinaryTree I have 2 Find functions, like this bool Find(const T &) const; virtual Node<T> * Find(const T &, Node<T> *) const; and in SplayTree I would like to reuse the second one, because it works in the same way (for example) as in SplayTree, the only thing different is the return type, which is SplayNode. I thought it might be enough if I use this line in SplayTree.cpp using BinaryTree::Find; but it isn't. So, how can I do this?

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• Reuse C++ Header files

  - by Amrish

  Guys, I have a Visual C++ solution with 2 projects AlgorithmA & AlgorithmB and both share a common header file RunAlgo.h with the class declaration. Each project in the solution has its own unique implementation for the header file. I am trying to compile a DLL out of the common header file RunAlgo.h and add reference to this DLL in the projects AlgorithmA & AlgorithmB. I have then included separate RunAlgo.cpp definition file in both my projects. The problem is that I am getting linker errors while compiling the new DLL project which has only the header file. So, the question is Can a header file with only class declaration be compiled into a DLL (Similar to class library containing an Interface in C#)? For the above scenario, is there a better approach to reuse the common Header file among projects? Should the above method work (re-check my code?)

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• Visual Studio - How to use an existing vsproj's project settings as a template for new project?

  - by Jakobud

  There is some software I want to write a plugin for. The software includes some sample plugins. I want to create a new fresh project but I want to use one of the sample plugin vsproj's project settings as a template. It doesn't seem very clear on how to do this. If I do "New Project From Existing Code" that only imports the cpp, h, etc files into the new project. Right now the only way I can see to copy a sample projects settings is to open two instances of VS2005 next to each other and simply mimic the settings... Surely there is a built in method of doing this?

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• How does one write extconf.rb files when one extension includes header files from another?

  - by mohawkjohn

  This is a follow-up question for: Multiple Ruby modules under one directory What happens if these extensions include each other? For example, you have the following structure: ext/foo ext/bar In ext/bar/bar.h, you have a #include "foo.h" foo.h and foo.cpp compile to form foo.o, to make life a little more complicated. Finally, it is necessary that foo and bar be separate extensions. How is this managed? I can't figure out how to add ../foo to the search path for bar.h, primarily. Symbolic links seem hack-ish.

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• C++ Header Guard issues

  - by JP

  I am making a small C++ framework, which contains many .h and .cpp. I have created a general include which include all my .h file such as: framework.h #include "A.h" #include "B.h" #include "C.h" each .h header are protected with include guard such as #ifndef A_HEADER #define A_HEADER ... #endif The issues is, I would like to be able to include "framework.h" inside all the sub .h such as, but it cause lots of compiler error: #ifndef A_HEADER #define A_HEADER #include "framework.h" ... #endif If instead I use the real header file for each sub header, and the framework.h for what ever use my framework it works fine.. I would just like to include the main header inside all my sub .h so I dont need to include all the dependency everytime. Thanks :)

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• CSV parser in C++

  - by User1

  All I need is a good CSV file parser for C++. At this point it can really just be a comma-delimited parser (ie don't worry about escaping new lines and commas). The main need is a line-by-line parser that will return a vector for the next line each time the method is called. I found this article which looks quite promising: http://www.boost.org/doc/libs/1_35_0/libs/spirit/example/fundamental/list_parser.cpp I've never used Boost's Spirit, but am willing to try it. Is it overkill/bloated or is it fast and efficient? Does anyone have faster algorithms using STL or anything else? Thanks!

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• How to include header files in Visual Studio 2008?

  - by Sergio

  I am currently trying to compile a simple program that includes two header files. I see them in the Solution Explorer, where I included them through "include existing files". However, when I run my program it get the following error. fatal error C1083: Cannot open include file: 'FileWrite.h': No such file or directory. THe problem is that I see the file included in the Header's folder and in the code I have written: #include "FileWrite.h" and then the rest of the program code. Is there something else needed to do so that the compiler can see the header file and link it to the .cpp file I'm trying to compile?

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• LLVM Clang 5.0 explicit in copy-initialization error

  - by kevzettler

  I'm trying to compile an open source project on OSX that has only been tested on Linux. $: g++ -v Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn) Target: x86_64-apple-da I'm trying to compile with the following command line options g++ -MMD -Wall -std=c++0x -stdlib=libc++ -Wno-sign-compare -Wno-unused-variable -ftemplate-depth=1024 -I /usr/local/Cellar/boost/1.55.0/include/boost/ -g -O3 -c level.cpp -o obj-opt/level.o I am seeing several errors that look like this: ./square.h:39:70: error: chosen constructor is explicit in copy-initialization int strength = 0, double flamability = 0, map<SquareType, int> constructions = {}, bool ticking = false); The project states the following are requirements for the Linux setup. How can I confirm I'm making that? gcc-4.8.2 git libboost 1.5+ with libboost-serialize libsfml-dev 2+ (Ubuntu ppa that contains libsfml 2: ) freeglut-dev libglew-dev

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• How do I bypass GUI in MFC app if command line options exist?

  - by Brandon

  I've got an existing simple MFC app that the user specifies the input file, output file, and then a "Process" button. I'd like to just add the capability so that the input/output files are command line parameters. But, if they exist, I don't want the GUI to show up. I just want the "Process" to execute. I see where I can get the command line parameters (m_lpCmdLine) but how can I bypass the displaying of the GUI? If I step into the app, it goes directly to winmain.cpp and displays the GUI without stepping into any of my code.

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• GUI by using Qt

  - by kishorebjv

  hi all... i dont know any thing about Qt other than my friend told that it generates the GUI for c++ code.... please let me know 1.How to execute some command when a button in window is clicked..? "g++ encryption.cpp -lgmp" command should be executed when i pressed "enc" button.. 2.How to accept the text from text area(in the window) to a textfile and the text(need not be text,it can be any data..) in a text file should be displayed in Textarea of window ? please help me out... im running out of time... thanks in advance....

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• C++, create an instance from a static method

  - by Manux

  Hello, let's say I want my users to use only one class, say SpecialData. Now, this data class would have many methods, and depending on the type of data, the methods do different things, internally, but return externally similar results. Therefore my wanting to have one "public" class and other "private", child classes that would change the behavior of methods, etc... It would be amazingly more simple for some types of data that need to be built to do something like this: SpecialData& sm = SpecialData::new_supermatrix(); and new_supermatrix() would return a SuperMatrix instance, which inherits from most behaviors of SpecialData. my header: static SpecialData& new_supermatrix(); my cpp: SpecialData& SpecialData::new_supermatrix()(){ return SuperMatrix(MATRIX_DEFAULT_MAGNITUDE,1000,1239,FLOAT32,etc...); } The problem is, I get this error, which is probably logical due to the circumstances: invalid initialization of non-const reference of type ‘SpecialData&’ from a temporary of type ‘SpecialData’ So, any ideas?

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• Generating code at compile-time using scripts

  - by Manux

  Hello, I would ideally like to be able to add (very repetitive) C/C++ code to my actual code, but at compile time, code which would come from say, the stdout of a python script, the same way one does with macros. For example, let's say I want to have functions that depend on the public attributes of a given class, being able to just write the following in my C++ code would be a blessing: generate_boring_functions(FooBarClass,"FooBarClass.cpp") Is that feasible using conventional means? Or must I hack with Makefiles and temporary source files? Thanks.

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• Track Pedestrians

  - by 2vision2

  I am using OpenCV sample code “peopledetect.cpp” to detect and track pedestrians. The code uses HoG for feature extraction and SVM for classification. Please find the reference paper used here. The camera is mounted on the wall at a height of 10 feet and 45 degree down. There is no restriction on the pedestrian movement within the frame. I want to track the detected pedestrians’ movement within the frame. The issue I am facing is pedestrians are detected only in the middle region of the frame as most of the features are not visible as soon as the pedestrian enters the frame region. I want to track each person’s movement in the entire frame region. How to do it? Is tracking required? Can anyone give any reference to blogs/codes?

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• Unresolved external symbol

  - by kriau

  I have two WIN32 DLL projects in the solution, main.dll should call a function in mgn.dll. mgn.dll has mgn.h header file: #ifdef MGN_EXPORTS #define MGN_API __declspec(dllexport) #else #define MGN_API __declspec(dllimport) #endif extern "C" bool MGN_API AttachMGN(void); and mgn.cpp source file: #include "stdafx.h" #include "mgn.h" MGN_API bool AttachMGN(void) { ... } main.dll calls AttachMGN function from one of the source file: #include "stdafx.h" #include "..\mgn\mgn.h" bool CreateClient() { return ::AttachMGN(); } mgn.dll compiles successfully. main.dll doesn't show any errors in VS text editor, I can navigate using "Go To Definition" function. However during build I get the error: error LNK2019: unresolved external symbol _imp_AttachMGN referenced in function "bool __cdecl CreateClient(void)" (?CreateClient@@AW4XZ) Both DLLs compile into the same folder. DependencyWalker shows the function AttachMGN as exported. Main project has a dependency set to Mgn project, if that matters. I believe that I simply have overlooked something.... Thanks in advance.

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• C++/CLI value class constraint won't compile. Why?

  - by Simon

  Hello, a few weeks ago a co-worker of mine spent about two hours finding out why this piece of C++/CLI code won't compile with Visual Studio 2008 (I just tested it with Visual Studio 2010... same story). public ref class Test { generic<class T> where T : value class void MyMethod(Nullable<T> nullable) { } }; The compiler says: Error 1 error C3214: 'T' : invalid type argument for generic parameter 'T' of generic 'System::Nullable', does not meet constraint 'System::ValueType ^' C:\Users\Simon\Desktop\Projektdokumentation\GridLayoutPanel\Generics\Generics.cpp 11 1 Generics Adding ValueType will make the code compile. public ref class Test { generic<class T> where T : value class, ValueType void MyMethod(Nullable<T> nullable) { } }; My question is now. Why? What is the difference between value class and ValueType?

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• C++ - Print Out Objects From Set

  - by John Smith

  If I have a C++ set, declaration set personList; with iterator, set::const_iterator location; how can I print out the contents of the set? They are all person objects, and I have overridden the operator<< for Person. The line that errors is: cout << location and it's in a basic for loop. Netbeans gives the following error: proj.cpp:78: error: no match for ‘operator<<’ in ‘std::cout << location’ so it looks like it wants an override for the iterator's <<. Basically, I am taking objects that used to be stored in an array format, but are now in a set. What is the equivalent to cout << array[i] for sets?

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• Vista Basic theme ribbon issue

  - by Alain Rist

  Under Vista, when in Basic theme, after calling IUIFramework::Destroy() the Vista theme is lost, and enlarging the window does not display outside of the initial area. You can repro it easily with the SimpleRibbon SDK sample. In simpleribbon.cpp, insert in the WndProc switch block: case WM_KEYUP: DestroyFramework(); InvalidateRect(hWnd, NULL, TRUE); break; Compile, run, hit a key and try to enlarge in Vista Basic Theme (no problem in Win7 or Vista aero or Windows classic). How to work around? cheers, AR

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• c++ inheritance

  - by Meloun

  Hi, i am trouble with this.. Is there some solution or i have to keep exactly class types? //header file Class Car { public: Car(); virtual ~Car(); }; class Bmw:Car { public: Bmw(); virtual ~Bmw(); }; void Start(Car& mycar) {}; //cpp file Car::Car(){} Car::~Car() {} Bmw::Bmw() :Car::Car(){} Bmw::~Bmw() {} int main() { Car myCar; Bmw myBmw; Start(myCar); //works Start(myBmw); //!! doesnt work return 0; }

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• Vector.erase(Iterator) causes bad memory access

  - by xon1c

  Hi, I am trying to do a Z-Index reordering of videoObjects stored in a vector. The plan is to identify the videoObject which is going to be put on the first position of the vector, erase it and then insert it at the first position. Unfortunately the erase() function always causes bad memory access. Here is my code: testApp.h: vector<videoObject> videoObjects; vector<videoObject>::iterator itVid; testApp.cpp: // Get the videoObject which relates to the user event for(itVid = videoObjects.begin(); itVid != videoObjects.end(); ++itVid){ if(videoObjects.at(itVid - videoObjects.begin()).isInside(ofPoint(tcur.getX(), tcur.getY()))){ videoObjects.erase(itVid); } } This should be so simple but I just don't see where I'm taking the wrong turn. Thx, xonic

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• haar transformation on an image

  - by kabatusuka

  hello, i need some help with haar transformation, i have to apply it on an image. My math is bad, my english not all that awesome and i find it hard to understand from articles on the internet. I found this page http://www.cs.ucf.edu/~mali/haar/haar.cpp where the haar transformation is applied on 2d matrix. I suppose if i give image pixels matrix in there, it should work? im confused about this stuff, could someone enlighten me a bit please? Thank you!

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