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  • std::vector elements initializing

    - by Chameleon
    std::vector<int> v1(1000); std::vector<std::vector<int>> v2(1000); std::vector<std::vector<int>::const_iterator> v3(1000); How elements of these 3 vectors initialized? About int, I test it and I saw that all elements become 0. Is this standard? I believed that primitives remain undefined. I create a vector with 300000000 elements, give non-zero values, delete it and recreate it, to avoid OS memory clear for data safety. Elements of recreated vector were 0 too. What about iterator? Is there a initial value (0) for default constructor or initial value remains undefined? When I check this, iterators point to 0, but this can be OS When I create a special object to track constructors, I saw that for first object, vector run the default constructor and for all others it run the copy constructor. Is this standard? Is there a way to completely avoid initialization of elements? Or I must create my own vector? (Oh my God, I always say NOT ANOTHER VECTOR IMPLEMENTATION) I ask because I use ultra huge sparse matrices with parallel processing, so I cannot use push_back() and of course I don't want useless initialization, when later I will change the value.

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  • crash when using stl vector at instead of operator[]

    - by Jamie Cook
    I have a method as follows (from a class than implements TBB task interface - not currently multithreading though) My problem is that two ways of accessing a vector are causing quite different behaviour - one works and the other causes the entire program to bomb out quite spectacularly (this is a plugin and normally a crash will be caught by the host - but this one takes out the host program as well! As I said quite spectacular) void PtBranchAndBoundIterationOriginRunner::runOrigin(int origin, int time) const // NOTE: const method { BOOST_FOREACH(int accessMode, m_props->GetAccessModes()) { // get a const reference to appropriate vector from member variable // map<int, vector<double>> m_rowTotalsByAccessMode; const vector<double>& rowTotalsForAccessMode = m_rowTotalsByAccessMode.find(accessMode)->second; if (origin != 129) continue; // Additional debug constrain: I know that the vector only has one non-zero element at index 129 m_job->Write("size: " + ToString(rowTotalsForAccessMode.size())); try { // check for early return... i.e. nothing to do for this origin if (!rowTotalsForAccessMode[origin]) continue; // <- this works if (!rowTotalsForAccessMode.at(origin)) continue; // <- this crashes } catch (...) { m_job->Write("Caught an exception"); // but its not an exception } // do some other stuff } } I hate not putting in well defined questions but at the moment my best phrasing is : "WTF?" I'm compiling this with Intel C++ 11.0.074 [IA-32] using Microsoft (R) Visual Studio Version 9.0.21022.8 and my implementation of vector has const_reference operator[](size_type _Pos) const { // subscript nonmutable sequence #if _HAS_ITERATOR_DEBUGGING if (size() <= _Pos) { _DEBUG_ERROR("vector subscript out of range"); _SCL_SECURE_OUT_OF_RANGE; } #endif /* _HAS_ITERATOR_DEBUGGING */ _SCL_SECURE_VALIDATE_RANGE(_Pos < size()); return (*(_Myfirst + _Pos)); } (Iterator debugging is off - I'm pretty sure) and const_reference at(size_type _Pos) const { // subscript nonmutable sequence with checking if (size() <= _Pos) _Xran(); return (*(begin() + _Pos)); } So the only difference I can see is that at calls begin instead of simply using _Myfirst - but how could that possibly be causing such a huge difference in behaviour?

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  • C++ STL: How to iterate vector while requiring access to element and its index?

    - by Ashwin
    I frequently find myself requiring to iterate over STL vectors. While I am doing this I require access to both the vector element and its index. I used to do this as: typedef std::vector<Foo> FooVec; typedef FooVec::iterator FooVecIter; FooVec fooVec; int index = 0; for (FooVecIter i = fooVec.begin(); i != fooVec.end(); ++i, ++index) { Foo& foo = *i; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } After discovering BOOST_FOREACH, I shortened this to: typedef std::vector<Foo> FooVec; FooVec fooVec; int index = -1; BOOST_FOREACH( Foo& foo, fooVec ) { ++index; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } Is there a better or more elegant way to iterate over STL vectors when both reference to the vector element and its index is required? I am aware of the alternative: for (int i = 0; i < fooVec.size(); ++i) But I keep reading about how it is not a good practice to iterate over STL containers like this.

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  • Syntax for finding structs in multisets - C++

    - by Sarah
    I can't seem to figure out the syntax for finding structs in containers. I have a multiset of Event structs. I'm trying to find one of these structs by searching on its key. I get the compiler error commented below. struct Event { public: bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } bool operator > ( const Event & rhs ) const { return ( time > rhs.time ); } bool operator == ( const Event & rhs ) const { return ( time == rhs.time ); } double time; int eventID; int hostID; int s; }; typedef std::multiset< Event, std::less< Event > > EventPQ; EventPQ currentEvents; double oldRecTime = 20.0; EventPQ::iterator ceItr = currentEvents.find( EventPQ::key_type( oldRecTime ) ); // no matching function call I've tried a few permutations to no avail. I thought defining the conditional equality operator was going to be enough.

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  • Does operator precedence in C++ differ for pointers and iterators?

    - by oraz
    The code below demonstrates this difference: #include <iostream> #include <string> int main() { char s[] = "ABCD"; std::string str(s); char *p = s; while(*p) { *p++ = tolower(*p); // <-- incr after assignment } std::cout << s << std::endl; std::string::iterator it = str.begin(), end = str.end(); while(it != end) { *it++ = tolower(*it); // <-- incr before assignment ? } std::cout << str << std::endl; return 0; } the code above outputs: abcd bcd if we separate assignment operation and increment operator: while(it != end) { *it = tolower(*it); // <-- incr before assignment ? it++; } the output will be as expected. What's wrong with the original code? $ g++ --version g++ (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125) Copyright (C) 2004 Free Software Foundation, Inc.

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  • C++ bughunt - High-score insertion in a vector crashes the program

    - by Francisco P.
    Hello, everyone! I have a game I'm working on. My players are stored in a vector, and, at the end of the game, the game crashes when trying to insert the high-scores in the correct positions. Here's what I have (please ignore the portuguese comments, the code is pretty straightforward :P): //TOTAL_HIGHSCORES is the max. number of hiscores that i'm willing to store. This is set as 10. bool Game::updateHiScores() { bool stopIterating; bool scoresChanged = false; //Se ainda nao existirem TOTAL_HISCORES melhores pontuacoes ou se a pontuacao for melhor que uma das existentes for (size_t i = 0; i < players.size(); ++i) { //&& !(players[i].isAI()) if (players[i].getScoreValue() > 0 && (hiScores.size() < TOTAL_HISCORES || hiScores.back() < players[i].getScore())) { scoresChanged = true; if(hiScores.empty() || hiScores.back() >= players[i].getScore()) hiScores.push_back(players[i].getScore()); else { //Ciclo que encontra e insere a pontuacao no lugar desejado stopIterating = false; for(vector<Score>::iterator it = hiScores.begin(); it < hiScores.end() && !(stopIterating); ++it) { if(*it <= players[i].getScore()) { //E inserida na posicao 'it' o Score correspondente hiScores.insert(it, players[i].getScore()); //Verifica se o comprimento do vector esta dentro do desejado, se nao estiver, este e rectificado if (hiScores.size() > TOTAL_HISCORES) hiScores.pop_back(); stopIterating = true; } } } } } if (scoresChanged) sort(hiScores.begin(), hiScores.end(), higher); return scoresChanged; } What am I doing wrong here? Thanks for your time, fellas.

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  • Apache POI rows number

    - by sys_debug
    I am using Apache POI java and want to get the total number of rows which are not empty. I successfully processed a whole row with all its columns. Now I am assuming that I get an excel sheet with multiple rows and not a single row...so how to go about that? I was thinking of getting total number of rows (int n) and then loop until i<=n but not sure. Suggestions are most welcome :) Note: Apache POI version is 3.8. I am not dealing with Xlsx format...only xls. Yes I tried this code but got 20 in return....which is not possible given I have only 5 rows FileInputStream fileInputStream = new FileInputStream("COD.xls"); HSSFWorkbook workbook = new HSSFWorkbook(fileInputStream); HSSFSheet worksheet = workbook.getSheet("COD"); HSSFRow row1 = worksheet.getRow(3); Iterator rows = worksheet.rowIterator(); int noOfRows = 0; while( rows.hasNext() ) { HSSFRow row = (HSSFRow) rows.next(); noOfRows++; } System.out.println("Number of Rows: " + noOfRows);

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  • need help with C++ using maps to keep track of words in a INPUT file

    - by eNetik
    Let say i have a text file with today is today but tomorrow is today tomorrow then using maps how can i keep track of the words that are repeated? and on which line it repeats? so far i have each string in the file read in as a temp and it is stored in the following way: map<string,int> storage; int count = 1 // for the first line of the file if(infile.is_open()){ while( !infile.eof() ){ getline(in, line); istringstream my_string(line); while(my_string.good()){ string temp; my_string >> temp; storage[temp] = count } count++;// so that every string read in the next line will be recorded as that line. } } map<string,int>::iterator m; for(int m = storage.begin(); m!= storage.end(); m++){ out<<m->first<<": "<<"line "<<m->second<<endl; } right now the output is just but: line 1 is: line 2 today: line 2 tomorrow: line 2 But instead.. it should print out(no repeating strings): today : line 1 occurred 2 times, line 2 occurred 1 time. is: line 1 occurred 1 time, line 2 occurred 1 time. but: line 1 occurred 1 time. tomorrow: line 2 occurred 2 times. Note: the order of the string does not matter. Any help would be appreciated. Thanks.

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  • How to call shared_ptr<boost::signal> from a vector in a loop?

    - by BTR
    I've got a working callback system that uses boost::signal. I'm extending it into a more flexible and efficient callback manager which uses a vector of shared_ptr's to my signals. I've been able to successfully create and add callbacks to the list, but I'm unclear as to how to actually execute the signals. ... // Signal aliases typedef boost::signal<void (float *, int32_t)> Callback; typedef std::shared_ptr<Callback> CallbackRef; // The callback list std::vector<CallbackRef> mCallbacks; // Adds a callback to the list template<typename T> void addCallback(void (T::* callbackFunction)(float * data, int32_t size), T * callbackObject) { CallbackRef mCallback = CallbackRef(new Callback()); mCallback->connect(boost::function<void (float *, int32_t)>(boost::bind(callbackFunction, callbackObject, _1, _2))); mCallbacks.push_back(mCallback); } // Pass the float array and its size to the callbacks void execute(float * data, int32_t size) { // Iterate through the callback list for (vector<CallbackRef>::iterator i = mCallbacks.begin(); i != mCallbacks.end(); ++i) { // What do I do here? // (* i)(data, size); // <-- Dereferencing doesn't work } } ... All of this code works. I'm just not sure how to run the call from within a shared_ptr from with a vector. Any help would be neat-o. Thanks, in advance.

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  • C++ map performance - Linux (30 sec) vs Windows (30 mins) !!!

    - by sonofdelphi
    I need to process a list of files. The processing action should not be repeated for the same file. The code I am using for this is - using namespace std; vector<File*> gInputFileList; //Can contain duplicates, File has member sFilename map<string, File*> gProcessedFileList; //Using map to avoid linear search costs void processFile(File* pFile) { File* pProcessedFile = gProcessedFileList[pFile->sFilename]; if(pProcessedFile != NULL) return; //Already processed foo(pFile); //foo() is the action to do for each file gProcessedFileList[pFile->sFilename] = pFile; } void main() { size_t n= gInputFileList.size(); //Using array syntax (iterator syntax also gives identical performance) for(size_t i=0; i<n; i++){ processFile(gInputFileList[i]); } } The code works correctly, but... My problem is that when the input size is 1000, it takes 30 minutes - HALF AN HOUR - on Windows/Visual Studio 2008 Express (both Debug and Release builds). For the same input, it takes only 40 seconds to run on Linux/gcc! What could be the problem? The action foo() takes only a very short time to execute, when used separately. Should I be using something like vector::reserve for the map?

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  • servlet and jsp sending query result following MVC framework

    - by kawtousse
    Hi every one, in order to separate java code and html code and be more faithful to MVC framework i am coding like that; in the servlet i put the following: net.sf.hibernate.Session s = null; net.sf.hibernate.Transaction tx; try { s= HibernateUtil.currentSession(); tx=s.beginTransaction(); Query query = s.createQuery("select opcemployees.Nom,opcemployees.Prenom,dailytimesheet.TrackingDate,dailytimesheet.Activity," + "dailytimesheet.ProjectCode,dailytimesheet.WAName,dailytimesheet.TaskCode," + "dailytimesheet.TimeSpent,dailytimesheet.PercentTaskComplete from Opcemployees opcemployees,Dailytimesheet dailytimesheet " + "where opcemployees.Matricule=dailytimesheet.Matricule and dailytimesheet.Etat=3 " + "group by opcemployees.Nom,opcemployees.Prenom" ); for(Iterator it=query.iterate();it.hasNext();) { if(it.hasNext()){ Object[] row = (Object[]) it.next(); request.setAttribute("items", row); }} } catch (HibernateException e){ e.printStackTrace(); } request.getRequestDispatcher("EspaceValidation.jsp").forward(request, response); and in jsp i start like that: <table> <c:forEach items="${items}" var="item"> <tr> <td>? </td> <td>?</td> </tr> </c:forEach> in this case what should i put exactly to obtain my result.a table fulled with the right value from the request

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  • STLifying C++ classes

    - by shambulator
    I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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  • an error "has no member named"

    - by helloWorld
    I have this snippet of the code account.cpp #include "account.h" #include <iostream> #include <string> using namespace std; Account::Account(string firstName, string lastName, int id) : strFirstName(firstName), strLastName(lastName), nID(id) {} void Account::printAccount(){ cout << strFirstName; } account.h #include <string> using std::string; class Account{ private: string strLastName; //Client's last name string strFirstName; //Client's first name int nID; //Client's ID number int nLines; //Number of lines related to account double lastBill; public: Account(string firstName, string lastName, int id); void printAccount(); }; company.h #ifndef CELLULAR_COMPANY_H #define CELLULAR_COMPANY_H #include <string> #include <list> #include <iostream> #include "account.h" using namespace std; class Company { private: list<Account> listOfAccounts; public: void addAccount(string firstName, string lastName, int id) { Account newAccount(firstName, lastName, id); listOfAccounts.push_back(newAccount); } void printAccounts(){ for(list<Account>::iterator i = listOfAccounts.begin(); i != listOfAccounts.end(); ++i){ i.printAccount; //here bug } } }; #endif // CELLULAR_COMPANY_H main.cpp #include "cellularcompany.h" int main(){ Company newCompany; newCompany.addAccount("Pavel", "Nedved", 11111); newCompany.printAccounts(); return 0; } can somebody please explain what does my error mean? thanks in advance (I have it in company.h see comment there) I have bug 'struct std::_List_iterator<Account>' has no member named 'printAccount'

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  • Returning a lua table on SWIG call

    - by Tom J Nowell
    I have a class with a methodcalled GetEnemiesLua. I have bound this class to lua using SWIG, and I can call this method using my lua code. I am trying to get the method to return a lua table of objects. Here is my current code: void CSpringGame::GetEnemiesLua(){ std::vector<springai::Unit*> enemies = callback->GetEnemyUnits(); if( enemies.empty()){ lua_pushnil(ai->L); return; } else{ lua_newtable(ai->L); int top = lua_gettop(ai->L); int index = 1; for (std::vector<springai::Unit*>::iterator it = enemies.begin(); it != enemies.end(); ++it) { //key lua_pushinteger(ai->L,index);//lua_pushstring(L, key); //value CSpringUnit* unit = new CSpringUnit(callback,*it,this); ai->PushIUnit(unit); lua_settable(ai->L, -3); ++index; } ::lua_pushvalue(ai->L,-1); } } PushIUnit is as follows: void CTestAI::PushIUnit(IUnit* unit){ SWIG_NewPointerObj(L,unit,SWIGTYPE_p_IUnit,1); } To test this I have the following code: t = game:GetEnemiesLua() if t == nil then game:SendToConsole("t is nil! ") end The result is always 't is nil', despite this being incorrect. I have put breakpoints in the code and it is indeed going over the loop, rather than doing lua_pushnil. So how do I make my method return a table when called via lua?

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  • Bizarre C++ compiler problem

    - by Yassin
    Hi, I have the following C++ code: typedef istream_iterator<string> isi; // (1) vector<string> lineas(isi(cin), isi()); // (2) //vector<string> lineas; //copy(isi(cin), isi(), back_inserter(lineas)); typedef vector<string>::iterator vci; for (vci it = lineas.begin(); it != lineas.end(); ++it) cout &lt;&lt; *it &lt;&lt; endl; However, I get the error while compiling: test.cpp: In function 'int main(int, char**)': test.cpp:16: error: request for member 'begin' in 'lineas', which is of non-class type 'std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >(main(int, char**)::isi, main(int, char**)::isi (*)())' test.cpp:16: error: request for member 'end' in 'lineas', which is of non-class type 'std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >(main(int, char**)::isi, main(int, char**)::isi (*)())' However, if I replace (1) by (2), it compiles. I'm using g++ 4.4.0 What's wrong?

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  • Difference between these two functions that find Palindromes....

    - by Moin
    I wrote a function to check whether a word is palindrome or not but "unexpectedly", that function failed quite badly, here it is: bool isPalindrome (const string& s){ string reverse = ""; string original = s; for (string_sz i = 0; i != original.size(); ++i){ reverse += original.back(); original.pop_back(); } if (reverse == original) return true; else return false; } It gives me "string iterator offset out of range error" when you pass in a string with only one character and returns true even if we pass in an empty string (although I know its because of the intialisation of the reverse variable) and also when you pass in an unassigned string for example: string input; isPalindrome(input); Later, I found a better function which works as you would expect: bool found(const string& s) { bool found = true; for (string::const_iterator i = s.begin(), j = s.end() - 1; i < j; ++i, --j) { if (*i != *j) found = false; } return found; } Unlike the first function, this function correctly fails when you give it an unassigned string variable or an empty string and works for single characters and such... So, good people of stackoverflow please point out to me why the first function is so bad... Thank You.

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  • C++ Segmentation Fault when Iterating through a Vector

    - by user1790374
    I have a program that maintains an integer vector. I have three functions that add an integer, remove an integer and check whether an integer is already in the vector. The problem is with the last one. vector<int> children; void CtpTestingApplication::addChild(int child) { for (int i=0; i<children.size(); i++) { //already a child if (children[i]==child) return; } //child not yet recorded children.push_back(child); received.push_back(false); cout<<"added child "<<child; } void CtpTestingApplication::removeChild(int child) { Enter_Method("removeChild"); for (int i=0; i<children.size(); i++) { //already a child, remove it if (children[i]==child) { children.erase(children.begin()+i); received.erase(received.begin()+i); cout<<"removed child "<<child; } } //not recorded, no need to remove } bool CtpTestingApplication::isChild(int child) { Enter_Method("isChild"); vector<int>::iterator ic; bool result = false; for (ic= children.begin(); ic < children.end(); ic++) { cout<<*ic<<" vs "<<child; // if (child==*ic) result = true; } return result; } I always get segmentation fault when I uncomment "if (child==*ic)", even though printouts show that the vector is not empty and contains the expected integers. For example, with the if statements commented, I can see 1 vs 4, 2 vs 4, 4 vs 4, 12 vs 4 I also attempted looping using children[i] and so on, but to no avail. Any help would be appreciated. Thank you.

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  • How can I avoid garbage collection delays in Java games? (Best Practices)

    - by Brian
    I'm performance tuning interactive games in Java for the Android platform. Once in a while there is a hiccup in drawing and interaction for garbage collection. Usually it's less than one tenth of a second, but sometimes it can be as large as 200ms on very slow devices. I am using the ddms profiler (part of the Android SDK) to search out where my memory allocations come from and excise them from my inner drawing and logic loops. The worst offender had been short loops done like, for(GameObject gob : interactiveObjects) gob.onDraw(canvas); where every single time the loop was executed there was an iterator allocated. I'm using arrays (ArrayList) for my objects now. If I ever want trees or hashes in an inner loop I know that I need to be careful or even reimplement them instead of using the Java Collections framework since I can't afford the extra garbage collection. That may come up when I'm looking at priority queues. I also have trouble where I want to display scores and progress using Canvas.drawText. This is bad, canvas.drawText("Your score is: " + Score.points, x, y, paint); because Strings, char arrays and StringBuffers will be allocated all over to make it work. If you have a few text display items and run the frame 60 times a second that begins to add up and will increase your garbage collection hiccups. I think the best choice here is to keep char[] arrays and decode your int or double manually into it and concatenate strings onto the beginning and end. I'd like to hear if there's something cleaner. I know there must be others out there dealing with this. How do you handle it and what are the pitfalls and best practices you've discovered to run interactively on Java or Android? These gc issues are enough to make me miss manual memory management, but not very much.

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  • for loop vs std::for_each with lambda

    - by Andrey
    Let's consider a template function written in C++11 which iterates over a container. Please exclude from consideration the range loop syntax because it is not yet supported by the compiler I'm working with. template <typename Container> void DoSomething(const Container& i_container) { // Option #1 for (auto it = std::begin(i_container); it != std::end(i_container); ++it) { // do something with *it } // Option #2 std::for_each(std::begin(i_container), std::end(i_container), [] (typename Container::const_reference element) { // do something with element }); } What are pros/cons of for loop vs std::for_each in terms of: a) performance? (I don't expect any difference) b) readability and maintainability? Here I see many disadvantages of for_each. It wouldn't accept a c-style array while the loop would. The declaration of the lambda formal parameter is so verbose, not possible to use auto there. It is not possible to break out of for_each. In pre- C++11 days arguments against for were a need of specifying the type for the iterator (doesn't hold any more) and an easy possibility of mistyping the loop condition (I've never done such mistake in 10 years). As a conclusion, my thoughts about for_each contradict the common opinion. What am I missing here?

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  • Including typedef of child in parent class

    - by Baz
    I have a class which looks something like this. I'd prefer to have the typedef of ParentMember in the Parent class and rename it Member. How might this be possible? The only way I can see is to have std::vector as a public member instead of using inheritance. typedef std::pair<std::string, boost::any> ParentMember; class Parent: public std::vector<ParentMember> { public: template <typename T> std::vector<T>& getMember(std::string& s) { MemberFinder finder(s); std::vector<ParentMember>::iterator member = std::find_if(begin(), end(), finder); boost::any& container = member->second; return boost::any_cast<std::vector<T>&>(container); } private: class Finder { ... }; };

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  • Why can't my vector access the variables in my nested structs?

    - by chucknorris
    #include<iostream> #include<vector> #include<string> #include<list> using namespace std; struct record{ int id; string fName; }; struct cells{ list<record> rec; }; vector<cells> hp; int main() { **hp.front().rec.front().fName = "jon"; return 0; } I have 2 structs. The first struct, struct record, is composed of 2 regular variables. In struct 2, I have a linked list of type "record", which includes all the variable listed in struct 1. Why is it that when ever I attempt to access a variable in the structs, using my vector, I get the error "linked list iterator not dereferencable?"

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  • Entity Framework v1 &hellip; Brief Synopsis and Tips &ndash; Part 2

    - by Rohit Gupta
    Using Entity Framework with ASMX Web sErvices and WCF Web Service: If you use ASMX WebService to expose Entity objects from Entity Framework... then the ASMX Webservice does not  include object graphs, one work around is to use Facade pattern or to use WCF Service. The other important aspect of using ASMX Web Services along with Entity Framework is that the ASMX Client is not aware of the existence of EF v1 since the client solely deals with C# objects (not EntityObjects or ObjectContext). Since the client is not aware of the ObjectContext hence the client cannot participate in change tracking since the client only receives the Current Values and not the Orginal values when the service sends the the Entity objects to the client. Thus there are 2 drawbacks to using EntityFramework with ASMX Web Service: 1. Object state is not maintained... so to overcome this limitation we need insert/update single entity at a time and retrieve the original values for the entity being updated on the server/service end before calling Save Changes. 2. ASMX does not maintain object graphs... i.e. Customer.Reservations or Customer.Reservations.Trip relationships are not maintained. Thus you need to send these relationships separately from service to client. WCF Web Service overcomes the object graph limitation of ASMX Web Service, but we need to insure that we are populating all the non-null scalar properties of all the objects in the object graph before calling Update. WCF Web service still cannot overcome the second limitation of tracking changes to entities at the client end. Also note that the "Customer" class in the Client is very different from the "Customer" class in the Entity Framework Model Entities. They are incompatible with each other hence we cannot cast one to the other. However the .NET Framework translates the client "Customer" Entity to the EFv1 Model "customer" Entity once the entity is serialzed back on the ASMX server end. If you need change tracking enabled on the client then we need to use WCF Data Services which is available with VS 2010. ====================================================================================================== In WCF when adding an object that has relationships, the framework assumes that every object in the object graph needs to be added to store. for e.g. in a Customer.Reservations.Trip object graph, when a Customer Entity is added to the store, the EFv1 assumes that it needs to a add a Reservations collection and also Trips for each Reservation. Thus if we need to use existing Trips for reservations then we need to insure that we null out the Trip object reference from Reservations and set the TripReference to the EntityKey of the desired Trip instead. ====================================================================================================== Understanding Relationships and Associations in EFv1 The Golden Rule of EF is that it does not load entities/relationships unless you ask it to explicitly do so. However there is 1 exception to this rule. This exception happens when you attach/detach entities from the ObjectContext. If you detach an Entity in a ObjectGraph from the ObjectContext, then the ObjectContext removes the ObjectStateEntry for this Entity and all the relationship Objects associated with this Entity. For e.g. in a Customer.Order.OrderDetails if the Customer Entity is detached from the ObjectContext then you cannot traverse to the Order and OrderDetails Entities (that still exist in the ObjectContext) from the Customer Entity(which does not exist in the Object Context) Conversely, if you JOIN a entity that is not in the ObjectContext with a Entity that is in the ObjContext then the First Entity will automatically be added to the ObjContext since relationships for the 2 Entities need to exist in the ObjContext. ========================================================= You cannot attach an EntityCollection to an entity through its navigation property for e.g. you cannot code myContact.Addresses = myAddressEntityCollection ========================================================== Cascade Deletes in EDM: The Designer does not support specifying cascase deletes for a Entity. To enable cascasde deletes on a Entity in EDM use the Association definition in CSDL for the Entity. for e.g. SalesOrderDetail (SOD) has a Foreign Key relationship with SalesOrderHeader (SalesOrderHeader 1 : SalesOrderDetail *) if you specify a cascade Delete on SalesOrderHeader Entity then calling deleteObject on SalesOrderHeader (SOH) Entity will send delete commands for SOH record and all the SOD records that reference the SOH record. ========================================================== As a good design practise, if you use Cascade Deletes insure that Cascade delete facet is used both in the EDM as well as in the database. Even though it is not absolutely mandatory to have Cascade deletes on both Database and EDM (since you can see that just the Cascade delete spec on the SOH Entity in EDM will insure that SOH record and all related SOD records will be deleted from the database ... even though you dont have cascade delete configured in the database in the SOD table) ============================================================== Maintaining relationships in Code When Setting a Navigation property of a Entity (for e.g. setting the Contact Navigation property of Address Entity) the following rules apply : If both objects are detached, no relationship object will be created. You are simply setting a property the CLR way. If both objects are attached, a relationship object will be created. If only one of the objects is attached, the other will become attached and a relationship object will be created. If that detached object is new, when it is attached to the context its EntityState will be Added. One important rule to remember regarding synchronizing the EntityReference.Value and EntityReference.EntityKey properties is that when attaching an Entity which has a EntityReference (e.g. Address Entity with ContactReference) the Value property will take precedence and if the Value and EntityKey are out of sync, the EntityKey will be updated to match the Value. ====================================================== If you call .Load() method on a detached Entity then the .Load() operation will throw an exception. There is one exception to this rule. If you load entities using MergeOption.NoTracking, you will be able to call .Load() on such entities since these Entities are accessible by the ObjectContext. So the bottomline is that we need Objectontext to be able to call .Load() method to do deffered loading on EntityReference or EntityCollection. Another rule to remember is that you cannot call .Load() on entities that have a EntityState.Added State since the ObjectContext uses the EntityKey of the Primary (Parent) Entity when loading the related (Child) Entity (and not the EntityKey of the child (even if the EntityKey of the child is present before calling .Load()) ====================================================== You can use ObjContext.Add() to add a entity to the ObjContext and set the EntityState of the new Entity to EntityState.Added. here no relationships are added/updated. You can also use EntityCollection.Add() method to add an entity to another entity's related EntityCollection for e.g. contact has a Addresses EntityCollection so to add a new address use contact.Addresses.Add(newAddress) to add a new address to the Addresses EntityCollection. Note that if the entity does not already exist in the ObjectContext then calling contact.Addresses.Add(myAddress) will cause a new Address Entity to be added to the ObjContext with EntityState.Added and it will also add a RelationshipEntry (a relationship object) with EntityState.Added which connects the Contact (contact) with the new address newAddress. Note that if the entity already exists in the Objectcontext (being part theOtherContact.Addresses Collection), then calling contact.Addresses.Add(existingAddress) will add 2 RelationshipEntry objects to the ObjectStateEntry Collection, one with EntityState.Deleted and the other with EntityState.Added. This implies that the existingAddress Entity is removed from the theOtherContact.Addresses Collection and Added to the contact.Addresses Collection..effectively reassigning the address entity from the theOtherContact to "contact". This is called moving an existing entity to a new object graph. ====================================================== You usually use ObjectContext.Attach() and EntityCollection.Attach() methods usually when you need to reconstruct the ObjectGraph after deserializing the objects as received from a ASMX Web Service Client. Attach is usually used to connect existing Entities in the ObjectContext. When EntityCollection.Attach() is called the EntityState of the RelationshipEntry (the relationship object) remains as EntityState.unchanged whereas when EntityCollection.Add() method is called the EntityState of the relationship object changes to EntityState.Added or EntityState.Deleted as the situation demands. ========================================================= LINQ To Entities Tips: Select Many does Inner Join by default.   for e.g. from c in Contact from a in c.Address select c ... this will do a Inner Join between the Contacts and Addresses Table and return only those Contacts that have a Address. ======================================================== Group Joins Do LEFT Join by default. e.g. from a in Address join c in Contact ON a.Contact.ContactID == c.ContactID Into g WHERE a.CountryRegion == "US" select g; This query will do a left join on the Contact table and return contacts that have a address in "US" region The following query : from c in Contact join a in Address.Where(a1 => a1.CountryRegion == "US") on c.ContactID  equals a.Contact.ContactID into addresses select new {c, addresses} will do a left join on the Address table and return All Contacts. In these Contacts only those will have its Address EntityCollection Populated which have a Address in the "US" region, the other contacts will have 0 Addresses in the Address collection (even if addresses for those contacts exist in the database but are in a different region) ======================================================== Linq to Entities does not support DefaultIfEmpty().... instead use .Include("Address") Query Builder method to do a Left JOIN or use Group Joins if you need more control like Filtering on the Address EntityCollection of Contact Entity =================================================================== Use CreateSourceQuery() on the EntityReference or EntityCollection if you need to add filters during deferred loading of Entities (Deferred loading in EFv1 happens when you call Load() method on the EntityReference or EntityCollection. for e.g. var cust=context.Contacts.OfType<Customer>().First(); var sq = cust.Reservations.CreateSourceQuery().Where(r => r.ReservationDate > new DateTime(2008,1,1)); cust.Reservations.Attach(sq); This populates only those reservations that are older than Jan 1 2008. This is the only way (in EFv1) to Attach a Range of Entities to a EntityCollection using the Attach() method ================================================================== If you need to get the Foreign Key value for a entity e.g. to get the ContactID value from a Address Entity use this :                                address.ContactReference.EntityKey.EntityKeyValues.Where(k=> k.Key == "ContactID")

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  • top Tweets SOA Partner Community – August 2012

    - by JuergenKress
    Send your tweets @soacommunity #soacommunity and follow us at http://twitter.com/soacommunity Lucas Jellema ?Published an article about organizing Fusion Middleware Administration: http://technology.amis.nl/2012/07/31/organizing-fusion-middleware-administration-in-a-smart-and-frugal-way … - many organizations are struggling with this. ServiceTechSymposium Countdown to the Early Bird Registration Discount deadline. Only 4 days left! http://ow.ly/cBCiv demed ?Good chatting w Bob Rhubart, Thomas Erl & Tim Hall on SOA & Cloud Symposium https://blogs.oracle.com/archbeat/entry/podcast_show_notes_thomas_erl … @soaschool @OTNArchBeat -- CU in London! SOA Community top Tweets SOA Partner Community July 2012 - are you one of them? If yes please rt! https://soacommunity.wordpress.com/2012/07/30/top-tweets-soa-partner-community-july-2012/ … #soacommunity SOA Community ?Are You a facebook member - do You follow http://www.facebook.com/soacommunity ? #soacommunity #soa SOA Community ?SOA 24/7 - Home Page: http://soa247.com/#.UBJsN8n3kyk.twitter … #soacommunity OracleBlogs ?Handling Large Payloads in SOA Suite 11g http://ow.ly/1lFAih OracleBlogs ?SOA Community Newsletter July 2012 http://ow.ly/1lFx6s OTNArchBeat Podcast Show Notes: Thomas Erl on SOA, Cloud, and Service Technology http://bit.ly/OOHTUJ SOA Community SOA Community Newsletter July 2012 http://wp.me/p10C8u-s7 OTNArchBeat ?OTN ArchBeat Podcast: Thomas Erl on SOA, Cloud, and Service Technology - Part 1 http://pub.vitrue.com/fMti OProcessAccel ?Just released! White Paper: Oracle Process Accelerators Best Practices http://www.oracle.com/technetwork/middleware/bpm/learnmore/processaccelbestpracticeswhitepaper-1708910.pdf … OTNArchBeat ?SOA, Cloud, and Service Technologies - Part 1 of 4 - A conversation with SOA, Cloud, and Service Technology Symposiu... http://ow.ly/1lDyAK OracleBlogs ?SOA Suite 11g PS5 Bundled Patch 3 (11.1.1.6.3) http://ow.ly/1lCW1S Simon Haslam My write-up of the virtues of the #ukoug App Server & Middleware SIG http://bit.ly/LMWdfY What's important to you for our next meeting? SOA Community SOA Partner Community Survey 2012 http://wp.me/p10C8u-qY Simone Geib ?RT @jswaroop: #Oracle positioned in the Leader's quadrant - Gartner Magic Quadrants for Application Infrastructure (SOA & SOA Gov)... ServiceTechSymposium New Supporting Organization, IBTI has joined the Symposium! http://www.servicetechsymposium.com/ orclateamsoa ?A-Team Blog #ateam: BPM 11g Task Form Version Considerations http://ow.ly/1lA7XS OTNArchBeat Oracle content at SOA, Cloud and Service Technology Symposium (and discount code!) http://pub.vitrue.com/FPcW OracleBlogs ?BPM 11g Task Form Version Considerations http://ow.ly/1lzOrX OTNArchBeat BPM 11g #ADF Task Form Versioning | Christopher Karl Chan #fusionmiddleware http://pub.vitrue.com/0qP2 OTNArchBeat Lightweight ADF Task Flow for BPM Human Tasks Overview | @AndrejusB #fusionmiddleware http://pub.vitrue.com/z7x9 SOA Community Oracle Fusion Middleware Summer Camps in Lisbon report by Link Consulting http://middlewarebylink.wordpress.com/2012/07/20/oracle-fusion-middleware-summer-camps-in-lisbon/ … #ofmsummercamps #soa #bpm SOA Community ?Clemens Utschig-Utschig & Manas Deb The Successful Execution of the SOA and BPM Vision Using a Business Capability Framework: Concepts… Simone Geib ?RT @oprocessaccel: Just released! White Paper: Oracle Process Accelerators Best Practices http://www.oracle.com/technetwork/middleware/bpm/learnmore/processaccelbestpracticeswhitepaper-1708910.pdf … jornica ?Report from Oracle Fusion Middleware Summer Camps in Munich: SOA Suite 11g advanced training experiences @soacommunity http://bit.ly/Mw3btE Simone Geib ?Bruce Tierney: Update - SOA & BPM Customer Insights Webcast Series: | https://blogs.oracle.com/SOA/entry/update_soa_bpm_customer_insights … OTNArchBeat Business SOA: Thinking is Dead | @mosesjones http://pub.vitrue.com/k8mw esentri ?had 3 great days in Munich at #Oracle #soacommunity Summercamp! Special thanks to Geoffroy de Lamalle from eProseed! Danilo Schmiedel ?Used my time in train to setup the ps5 soa/bpm vbox-image.Works like a dream. Setup-Readme is perfect! Saves a lot of time!!! @soacommunity 18 Jul SOA Community ?THANKS for the excellent OFM summer camps - save trip home - share your pictures at http://www.facebook.com/soacommunity #ofmsummercamps #soacommunity doors BBQ-party with Oracle @soacommunity. 5Star! #lovemunich #ofmsummercamps pic.twitter.com/ztfcGn2S leonsmiers ?New #Capgemini blog post "Continuous Improvement of Business Agility" http://bit.ly/Lr0EwG #bpm #yam Eric Elzinga ?MDS Explorer utility, http://see.sc/4qdb43 #soasuite ServiceTechSymposium ?@techsymp New speaker Demed L’Her from Oracle has been added to the symposium calendar. http://ow.ly/cjnyw SOA Community ?Last day of the Fusion Middleware summer camps - we continue at 9.00 am. send us your barbecue pictures! #ofmsummercamps #soacommunity SOA Community ?Delivering SOA Governance with EAMS and Oracle Enterprise Repository by Link Consulting http://middlewarebylink.wordpress.com/2012/06/26/delivering-soa-governance-with-eams-and-oracle-enterprise-repository/ … #soacommunity #soa #oer OracleBlogs ?Process Accelerator Kit http://ow.ly/1loaCw 15 Jul SOA Community ?Sun is back in Munich! Send your pictures Middleware summer camps! #ofmsummercamps We start tomorrow 11.00 at Oracle pic.twitter.com/6FStxomk Walter Montantes ?Gracias, Obrigado, Thank you, Danke a Lisboa y a @soacommunity @wlscommunity. From the Mexican guys!! cc @mikeintoch #ofmsummercamps Andrejus Baranovskis Tips & Tricks How to Run Oracle BPM 11g PS5 Workspace from Custom ADF 11g Application http://fb.me/1zOf3h2K8 JDeveloper & ADF ?Fusion Apps Enterprise Repository - Explained http://dlvr.it/1rpjWd Steve Walker ?Oracle #Exalogic is the logical choice for running business applications. Exalogic Software 2.0 launches 7/25. Reg at http://bit.ly/NedQ9L A. Chatziantoniou ?Landed in rainy Amsterdam after a great week in Lisbon for the #ofmsummercamps - multo obrigado for Jürgen for another fantastic event SOA Community ?Teams present #BPM11g POC results at #ofmsummercamps - great job! #soacommunity pic.twitter.com/0d4txkWF Sabine Leitner ?#DOAG SIG Middleware 29.08.2012 Köln über MW, Administration, Monitoring http://bit.ly/P47w82 @soacommunity @OracleMW @OracleFMW 12 Jul philmulhall ?Thanks @soacommunity for a great week at the #ofmsummercamps. Hard work done so time for a few cold ones in Lisboa. pic.twitter.com/LVUUuwTh peter230769 ?RT: andrea_rocco_31: RT @soacommunity: Enjoy the networking event at #ofmsummercamps want to attend next time ... pic.twitter.com/D1HRndi4 Niels Gorter ?#ofmsummercamps dinner in Lisbon. Great weather, scenery, training, people, on and on. Big THANKS @soacommunity JDeveloper & ADF ?Running Oracle BPM 11g PS5 Worklist Task Flow and Human Task Form on Non-SOA Domain http://dlvr.it/1r0c2j Andrea Rocco ?RT @soacommunity: Jamy pastry at cafe Belem - who is the ghost there?!? http://via.me/-2x33uk6 Simon Haslam ?Sounds great - sorry I couldn't make it. RT @soacommunity: 6pm BPM advanced training hard work to build the POC #ofmsummercamps philmulhall ?A well earned rest after a hard days work @soacommunity #summercamps pic.twitter.com/LKK7VOVS philmulhall ?Some more hard working delegates @soacommunity #summercamps pic.twitter.com/gWpk1HZh SOA Community ?Error message at the BPM POC - will The #ace director understand the message and solve it? #ofmsummercamps pic.twitter.com/LFTEzNck Daniel Kleine-Albers ?posted on the #thecattlecrew blog: Assigning more memory to JDeveloper http://thecattlecrew.wordpress.com/2012/07/10/jdeveloper-quicktip-assigning-more-memory/ … OTNArchBeat ?BAM design pointers | Kavitha Srinivasan http://pub.vitrue.com/TOhP SOA Community ?Did you receive the July SOA community newsletter? read it! Want to become a member http://www.oracle.com/goto/emea/soa #soacommunity #soa #opn OracleBlogs ?Markus Zirn, Big Data with CEP and SOA @ SOA, Cloud &amp; Service Technology Symposium 2012 http://ow.ly/1lcSkb Andrejus Baranovskis Running Oracle BPM 11g PS5 Worklist Task Flow and Human Task Form on Non-SOA Eric Elzinga ?Service Facade design pattern in OSB, http://bit.ly/NnOExN Eric Elzinga ?New BPEL Thread Pool in SOA 11g for Non-Blocking Invoke Activities from 11.1.1.6 (PS5), http://bit.ly/NnOc2G Gilberto Holms New Post: Siebel Connection Pool in Oracle Service Bus 11g http://wp.me/pRE8V-2z Oracle UPK & Tutor ?UPK Pre-Built Content Update: UPK pre-built content development efforts are always underway and growing. Ove... http://bit.ly/R2HeTj JDeveloper & ADF ?Troubleshooting BPMN process editor problems in 11.1.1.6 http://dlvr.it/1p0FfS orclateamsoa ?A-Team Blog #ateam: BAM design pointers - In working recently with a large Oracle customer on SOA and BAM, I discove... http://ow.ly/1kYqES SOA Community BPMN process editor problems in 11.1.1.6 by Mark Nelson http://redstack.wordpress.com/2012/06/27/bpmn-process-editor-problems-in-11-1-1-6 … #soacommunity #bpm OTNArchBeat ?SOA Learning Library: free short, topic-focused training on Oracle SOA & BPM products | @SOACommunity http://pub.vitrue.com/NE1G Andrejus Baranovskis ?ADF 11g PS5 Application with Customized BPM Worklist Task Flow (MDS Seeded Customization) http://fb.me/1coX4r1X1 OTNArchBeat ?A Universal JMX Client for Weblogic –Part 1: Monitoring BPEL Thread Pools in SOA 11g | Stefan Koser http://pub.vitrue.com/mQVZ OTNArchBeat ?BPM – Disable DBMS job to refresh B2B Materialized View | Mark Nelson http://pub.vitrue.com/3PR0 SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: SOA Community twitter,SOA Community,Oracle SOA,Oracle BPM,BPM Community,OPN,Jürgen Kress

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  • Craftsmanship is ALL that Matters

    - by Wayne Molina
    Today, I'm going to talk about a touchy subject: the notion of working in a company that doesn't use the prescribed "best practices" in its software development endeavours.  Over the years I have, using a variety of pseudonyms, asked this question on popular programming forums.  Although I always add in some minor variation of the story to avoid suspicion that it's the same person posting, the crux of the tale remains the same: A Programmer’s Tale A junior software developer has just started a new job at an average company, creating average line-of-business applications for internal use (the most typical scenario programmers find themselves in).  This hypothetical newbie has spent a lot of time reading up on the "theory" of software development, devouring books, blogs and screencasts from well-known and respected software developers in the community in order to broaden his knowledge and "do what the pros do".  He begins his new job, eager to apply what he's learned on a real-world project only to discover that his new teammates doesn't use any of those concepts and techniques.  They hack their way through development, or in a best-case scenario use some homebrew, thrown-together semblance of a framework for their applications that follows not one of the best practices suggested by the “elite” in the software community - things like TDD (TDD as a "best practice" is the only subjective part of this post, but it's included here due to a very large following of respected developers who consider it one), the SOLID principles, well-known and venerable tools, even version control in a worst case and truly nightmarish scenario.  Our protagonist is frustrated that he isn't doing things the "proper" way - a way he's spent personal time digesting and learning about and, more importantly, a way that some of the top developers in the industry advocate - and turns to a forum to ask the advice of his peers. Invariably the answer I, in the guise of the concerned newbie, will receive is that A) I don't know anything and should just shut my mouth and sling code the bad way like everybody else on the team, and B) These "best practices" are fade or a joke, and the only thing that matters is shipping software to your customers. I am here today to say that anyone who says this, or anything like it, is not only full of crap but indicative of exactly the type of “developer” that has helped to give our industry a bad name.  Here is why: One Who Knows Nothing, Understands Nothing On one hand, you have the cognoscenti of the .NET development world.  Guys like James Avery, Jeremy Miller, Ayende Rahien and Rob Conery; all well-respected and noted programmers that are pretty much our version of celebrities.  These guys write blogs, books, and post videos outlining the "correct" way of writing software to make sure it not only works but is maintainable and extensible and a joy to work with.  They tout the virtues of the SOLID principles, or of using TDD/BDD, or using a mature ORM like NHibernate, Subsonic or even Entity Framework. On the other hand, you have Joe Everyman, Lead Software Developer at Initrode Corporation - in our hypothetical story Joe is the junior developer's new boss.  Joe's been with Initrode for 10 years, starting as the company’s very first programmer and over the years building up a little fiefdom of his own until at the present he’s in charge of all Initrode’s software development.  Joe writes code the same way he always has, without bothering to learn much, if anything.  He looked at NHibernate once and found it was "too hard", so he uses a primitive implementation of the TableDataGateway pattern as a wrapper around SqlClient.SqlConnection and SqlClient.SqlCommand instead of an actual ORM (or, in a better case scenario, has created his own ORM); the thought of using LINQ or Entity Framework or really anything other than his own hastily homebrew solution has never occurred to him.  He doesn't understand TDD and considers “testing” to be using the .NET debugger to step through code, or simply loading up an app and entering some values to see if it works.  He doesn't really understand SOLID, and he doesn't care to.  He's worked as a programmer for years, and that's all that counts.  Right?  WRONG. Who would you rather trust?  Someone with years of experience and who writes books, creates well-known software and is akin to a celebrity, or someone with no credibility outside their own minute environment who throws around their clout and company seniority as the "proof" of their ability?  Joe Everyman may have years of experience at Initrode as a programmer, and says to do things "his way" but someone like Jeremy Miller or Ayende Rahien have years of experience at companies just like Initrode, THEY know ten times more than Joe Everyman knows or could ever hope to know, and THEY say to do things "this way". Here's another way of thinking about it: If you wanted to get into politics and needed advice on the best way to do it, would you rather listen to the mayor of Hicktown, USA or Barack Obama?  One is a small-time nobody while the other is very well-known and, as such, would probably have much more accurate and beneficial advice. NOTE: The selection of Barack Obama as an example in no way, shape, or form suggests a political affiliation or political bent to this post or blog, and no political innuendo should be mistakenly read from it; the intent was merely to compare a small-time persona with a well-known persona in a non-software field.  Feel free to replace the name "Barack Obama" with any well-known Congressman, Senator or US President of your choice. DIY Considered Harmful I will say right now that the homebrew development environment is the WORST one for an aspiring programmer, because it relies on nothing outside it's own little box - no useful skill outside of the small pond.  If you are forced to use some half-baked, homebrew ORM created by your Director of Software, you are not learning anything valuable you can take with you in the future; now, if you plan to stay at Initrode for 10 years like Joe Everyman, this is fine and dandy.  However if, like most of us, you want to advance your career outside a very narrow space you will do more harm than good by sticking it out in an environment where you, to be frank, know better than everybody else because you are aware of alternative and, in almost most cases, better tools for the job.  A junior developer who understands why the SOLID principles are good to follow, or why TDD is beneficial, or who knows that it's better to use NHibernate/Subsonic/EF/LINQ/well-known ORM versus some in-house one knows better than a senior developer with 20 years experience who doesn't understand any of that, plain and simple.  Anyone who disagrees is either a liar, or someone who, just like Joe Everyman, Lead Developer, relies on seniority and tenure rather than adapting their knowledge as things evolve. In many cases, the Joe Everymans of the world act this way out of fear - they cannot possibly fathom that a “junior” could know more than them; after all, they’ve spent 10 or more years in the same company, doing the same job, cranking out the same shoddy software.  And here comes a newbie who hasn’t spent 10+ years doing the same things, with a fresh and often radical take on the craft, and Joe Everyman is afraid he might have to put some real effort into his career again instead of just pointing to his 10 years of service at Initrode as “proof” that he’s good, or that he might have to learn something new to improve; in most cases the problem is Joe Everyman, and by extension Initrode itself, has a mentality of just being “good enough”, and mediocrity is the rule of the day. A Thorn Bush is No Place for a Phoenix My advice is that if you work on a team where they don't use the best practices that some of the most famous developers in our field say is the "right" way to do things (and have legions of people who agree), and YOU are aware of these practices and can see why they work, then LEAVE the company.  Find a company where they DO care about quality, and craftsmanship, otherwise you will never be happy.  There is no point in "dumbing" yourself down to the level of your co-workers and slinging code without care to craftsmanship.  In 95% of these situations there will be no point in bringing it to the attention of Joe Everyman because he won't listen; he might even get upset that someone is trying to "upstage" him and fire the newbie, and replace someone with loads of untapped potential with a drone that will just nod affirmatively and grind out the tasks assigned without question. Find a company that has people smart enough to listen to the "best and brightest", and be happy.  Do not, I repeat, DO NOT waste away in a job working for ignorant people.  At the end of the day software development IS a craft, and a level of craftsmanship is REQUIRED for any serious professional.  When you have knowledgeable people with the credibility to back it up saying one thing, and small-time people who are, to put it bluntly, nobodies in the field saying and doing something totally different because they can't comprehend it, leave the nobodies to their own devices to fade into obscurity.  Work for a company that uses REAL software engineering techniques and really cares about craftsmanship.  The biggest issue affecting our career, and the reason software development has never been the respected, white-collar career it was meant to be, is because hacks and charlatans can pass themselves off as professional programmers without following a lick of good advice from programmers much better at the craft than they are.  These modern day snake-oil salesmen entrench themselves in companies by hoodwinking non-technical businesspeople and customers with their shoddy wares, end up in senior/lead/executive positions, and push their lack of knowledge on everybody unfortunate enough to work with/for/under them, crushing any dissent or voices of reason and change under their tyrannical heel and leaving behind a trail of dismayed and, often, unemployed junior developers who were made examples of to keep up the facade and avoid the shadow of doubt being cast upon them. To sum this up another way: If you surround yourself with learned people, you will learn.  Surround yourself with ignorant people who can't, as the saying goes, see the forest through the trees, and you'll learn nothing of any real value.  There is more to software development than just writing code, and the end goal should not be just "shipping software", it should be shipping software that is extensible, maintainable, and above all else software whose creation has broadened your knowledge in some capacity, even if a minor one.  An eager newbie who knows theory and thirsts for knowledge can easily be moulded and taught the advanced topics, but the same can't be said of someone who only cares about the finish line.  This industry needs more people espousing the benefits of software craftsmanship and proper software engineering techniques, and less Joe Everymans who are unwilling to adapt or foster new ways of thinking. Conclusion - I Cast “Protection from Fire” I am fairly certain this post will spark some controversy and might even invite the flames.  Please keep in mind these are opinions and nothing more.  A little healthy rant and subsequent flamewar can be good for the soul once in a while.  To paraphrase The Godfather: It helps to get rid of the bad blood.

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  • Investigation: Can different combinations of components effect Dataflow performance?

    - by jamiet
    Introduction The Dataflow task is one of the core components (if not the core component) of SQL Server Integration Services (SSIS) and often the most misunderstood. This is not surprising, its an incredibly complicated beast and we’re abstracted away from that complexity via some boxes that go yellow red or green and that have some lines drawn between them. Example dataflow In this blog post I intend to look under that facade and get into some of the nuts and bolts of the Dataflow Task by investigating how the decisions we make when building our packages can affect performance. I will do this by comparing the performance of three dataflows that all have the same input, all produce the same output, but which all operate slightly differently by way of having different transformation components. I also want to use this blog post to challenge a common held opinion that I see perpetuated over and over again on the SSIS forum. That is, that people assume adding components to a dataflow will be detrimental to overall performance. Its not surprising that people think this –it is intuitive to think that more components means more work- however this is not a view that I share. I have always been of the opinion that there are many factors affecting dataflow duration and the number of components is actually one of the less important ones; having said that I have never proven that assertion and that is one reason for this investigation. I have actually seen evidence that some people think dataflow duration is simply a function of number of rows and number of components. I’ll happily call that one out as a myth even without any investigation!  The Setup I have a 2GB datafile which is a list of 4731904 (~4.7million) customer records with various attributes against them and it contains 2 columns that I am going to use for categorisation: [YearlyIncome] [BirthDate] The data file is a SSIS raw format file which I chose to use because it is the quickest way of getting data into a dataflow and given that I am testing the transformations, not the source or destination adapters, I want to minimise external influences as much as possible. In the test I will split the customers according to month of birth (12 of those) and whether or not their yearly income is above or below 50000 (2 of those); in other words I will be splitting them into 24 discrete categories and in order to do it I shall be using different combinations of SSIS’ Conditional Split and Derived Column transformation components. The 24 datapaths that occur will each input to a rowcount component, again because this is the least resource intensive means of terminating a datapath. The test is being carried out on a Dell XPS Studio laptop with a quad core (8 logical Procs) Intel Core i7 at 1.73GHz and Samsung SSD hard drive. Its running SQL Server 2008 R2 on Windows 7. The Variables Here are the three combinations of components that I am going to test:     One Conditional Split - A single Conditional Split component CSPL Split by Month of Birth and income category that will use expressions on [YearlyIncome] & [BirthDate] to send each row to one of 24 outputs. This next screenshot displays the expression logic in use: Derived Column & Conditional Split - A Derived Column component DER Income Category that adds a new column [IncomeCategory] which will contain one of two possible text values {“LessThan50000”,”GreaterThan50000”} and uses [YearlyIncome] to determine which value each row should get. A Conditional Split component CSPL Split by Month of Birth and Income Category then uses that new column in conjunction with [BirthDate] to determine which of the same 24 outputs to send each row to. Put more simply, I am separating the Conditional Split of #1 into a Derived Column and a Conditional Split. The next screenshots display the expression logic in use: DER Income Category         CSPL Split by Month of Birth and Income Category       Three Conditional Splits - A Conditional Split component that produces two outputs based on [YearlyIncome], one for each Income Category. Each of those outputs will go to a further Conditional Split that splits the input into 12 outputs, one for each month of birth (identical logic in each). In this case then I am separating the single Conditional Split of #1 into three Conditional Split components. The next screenshots display the expression logic in use: CSPL Split by Income Category         CSPL Split by Month of Birth 1& 2       Each of these combinations will provide an input to one of the 24 rowcount components, just the same as before. For illustration here is a screenshot of the dataflow containing three Conditional Split components: As you can these dataflows have a fair bit of work to do and remember that they’re doing that work for 4.7million rows. I will execute each dataflow 10 times and use the average for comparison. I foresee three possible outcomes: The dataflow containing just one Conditional Split (i.e. #1) will be quicker There is no significant difference between any of them One of the two dataflows containing multiple transformation components will be quicker Regardless of which of those outcomes come to pass we will have learnt something and that makes this an interesting test to carry out. Note that I will be executing the dataflows using dtexec.exe rather than hitting F5 within BIDS. The Results and Analysis The table below shows all of the executions, 10 for each dataflow. It also shows the average for each along with a standard deviation. All durations are in seconds. I’m pasting a screenshot because I frankly can’t be bothered with the faffing about needed to make a presentable HTML table. It is plain to see from the average that the dataflow containing three conditional splits is significantly faster, the other two taking 43% and 52% longer respectively. This seems strange though, right? Why does the dataflow containing the most components outperform the other two by such a big margin? The answer is actually quite logical when you put some thought into it and I’ll explain that below. Before progressing, a side note. The standard deviation for the “Three Conditional Splits” dataflow is orders of magnitude smaller – indicating that performance for this dataflow can be predicted with much greater confidence too. The Explanation I refer you to the screenshot above that shows how CSPL Split by Month of Birth and salary category in the first dataflow is setup. Observe that there is a case for each combination of Month Of Date and Income Category – 24 in total. These expressions get evaluated in the order that they appear and hence if we assume that Month of Date and Income Category are uniformly distributed in the dataset we can deduce that the expected number of expression evaluations for each row is 12.5 i.e. 1 (the minimum) + 24 (the maximum) divided by 2 = 12.5. Now take a look at the screenshots for the second dataflow. We are doing one expression evaluation in DER Income Category and we have the same 24 cases in CSPL Split by Month of Birth and Income Category as we had before, only the expression differs slightly. In this case then we have 1 + 12.5 = 13.5 expected evaluations for each row – that would account for the slightly longer average execution time for this dataflow. Now onto the third dataflow, the quick one. CSPL Split by Income Category does a maximum of 2 expression evaluations thus the expected number of evaluations per row is 1.5. CSPL Split by Month of Birth 1 & CSPL Split by Month of Birth 2 both have less work to do than the previous Conditional Split components because they only have 12 cases to test for thus the expected number of expression evaluations is 6.5 There are two of them so total expected number of expression evaluations for this dataflow is 6.5 + 6.5 + 1.5 = 14.5. 14.5 is still more than 12.5 & 13.5 though so why is the third dataflow so much quicker? Simple, the conditional expressions in the first two dataflows have two boolean predicates to evaluate – one for Income Category and one for Month of Birth; the expressions in the Conditional Split in the third dataflow however only have one predicate thus they are doing a lot less work. To sum up, the difference in execution times can be attributed to the difference between: MONTH(BirthDate) == 1 && YearlyIncome <= 50000 and MONTH(BirthDate) == 1 In the first two dataflows YearlyIncome <= 50000 gets evaluated an average of 12.5 times for every row whereas in the third dataflow it is evaluated once and once only. Multiply those 11.5 extra operations by 4.7million rows and you get a significant amount of extra CPU cycles – that’s where our duration difference comes from. The Wrap-up The obvious point here is that adding new components to a dataflow isn’t necessarily going to make it go any slower, moreover you may be able to achieve significant improvements by splitting logic over multiple components rather than one. Performance tuning is all about reducing the amount of work that needs to be done and that doesn’t necessarily mean use less components, indeed sometimes you may be able to reduce workload in ways that aren’t immediately obvious as I think I have proven here. Of course there are many variables in play here and your mileage will most definitely vary. I encourage you to download the package and see if you get similar results – let me know in the comments. The package contains all three dataflows plus a fourth dataflow that will create the 2GB raw file for you (you will also need the [AdventureWorksDW2008] sample database from which to source the data); simply disable all dataflows except the one you want to test before executing the package and remember, execute using dtexec, not within BIDS. If you want to explore dataflow performance tuning in more detail then here are some links you might want to check out: Inequality joins, Asynchronous transformations and Lookups Destination Adapter Comparison Don’t turn the dataflow into a cursor SSIS Dataflow – Designing for performance (webinar) Any comments? Let me know! @Jamiet

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