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• What exactly is saved in SQL Server Statistics? When they get updated? Is SQL Server itself is taking care of them?

  - by Pritesh

  I have been working with SQL Server as a Developer a while. One thing I learnt is SQL Server manages Statistics which help Engine to create optimized execution plan. I could not figure out what exactly is stores in Statistics? (I read it saves Vector, but what Vector?) When/In which scenario SQL Server updates Statistics? How/why some time they go out of sync (old Statistics) In case of old Statistics is a manual DBA/Developer intervention is required or SQL Server Will get them updated. As a DBA/Developer how to find out if Statistics OLD? What should we do?

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• is there a way to use cin.getline() without having to define a char array size before hand?

  - by zebraman

  Basically my task is having to sort a bunch of strings of variable length ignoring case. I understand there is a function strcasecmp() that compares cstrings, but doesn't work on strings. Right now I'm using getline() for strings so I can just read in the strings one line at a time. I add these to a vector of strings, then convert to cstrings for each call of strcasecmp(). Instead of having to convert each string to a cstring before comparing with strcasecmp(), I was wondering if there was a way I could use cin.getline() for cstrings without having a predefined char array size. Or, would the best solution be to just read in string, convert to cstring, store in vector, then sort?

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• How to change size of STL container in C++

  - by Jaime Pardos

  I have a piece of performance critical code written with pointers and dynamic memory. I would like to rewrite it with STL containers, but I'm a bit concerned with performance. Is there a way to increase the size of a container without initializing the data? For example, instead of doing ptr = new BYTE[x]; I want to do something like vec.insert(vec.begin(), x, 0); However this initializes every byte to 0. Isn't there a way to just make the vector grow? I know about reserve() but it just allocates memory, it doesn't change the size of the vector, and doesn't allows me to access it until I have inserted valid data. Thank you everyone.

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• Contents changed(cleared?) when access the pointer returned by std::string::c_str()

  - by justamask

  string conf()     {         vector v;         //..         v = func(); //this function returns a vector         return v[1];     }     void test()     {         const char* p = conf().c_str();         // the string object will be alive as a auto var         // so the pointer should be valid till the end of this function,right?           // ... lots of steps, but none of them would access the pointer p         // when access p here, SOMETIMES the contents would change ... Why?         // the platform is solaris 64 bit         // compiler is sun workshop 12         // my code is compiled as  ELF 32-bit MSB relocatable SPARC32PLUS Version 1, V8+ Required         // but need to link with some shared lib which are ELF 32-bit MSB dynamic lib SPARC Version 1, dynamically linked, stripped     }

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• Multiple key map in c++

  - by Morgan

  Hi, I'm wondering if any of you know of a c++ associative map container type which I can perform multiple key lookups on. The map needs to have constant time lookups but I don't care if it's ordered or unordered. It just needs to be fast. For example, I want to store a bunch of std::vector objects in a map with an integer and a void* as the lookup keys. Both the int and the void* must match for my vector to be retrieved. Does anything like this exist already? Or am I going to have to roll my own. If so, any suggestions? I've been trying to store a boost::unordered_map inside another boost::unordered_map, but I have not had any success with this method yet. Maybe I will continue Pershing this method if there is no simpler way. Thanks!

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• How to make this jpeg compression faster

  - by Richard Knop

  I am using OpenCV to compress binary images from a camera: vector<int> p; p.push_back(CV_IMWRITE_JPEG_QUALITY); p.push_back(75); // JPG quality vector<unsigned char> jpegBuf; cv::imencode(".jpg", fIplImageHeader, jpegBuf, p); The code above compresses a binary RGB image stored in fIplImageHeader to a JPEG image. For a 640*480 image it takes about 0.25 seconds to execute the five lines above. Is there any way I could make it faster? I really need to repeat the compression more than 4 times a second.

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• Split a long string into an array of shorter strings

  - by Dave

  How can I split a string of around 400 words into a vector of lots of 30 word strings?

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• Doesn't Matlab optimize the following?

  - by kloop

  I have a very long vector 1xr v, and a very long vector w 1xs, and a matrix A rxs, which is sparse (but very big in dimensions). I was expecting the following to be optimized by Matlab so I won't run into trouble with memory: A./(v'*w) but it seems like Matlab is actually trying to generate the full v'*w matrix, because I am running into Out of memory issue. Is there a way to overcome this? Note that there is no need to calculate all v'*w because many values of A are 0. EDIT: If that were possible, one way to do it would be to do A(find(A)) ./ (v'*w)(find(A)); but you can't select a subset of a matrix (v'*w in this case) without first calculating it and putting it in a variable.

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• How to load modules in Java

  - by gerardorn

  I'm building a server that loads modules. Each module is a .jar file. Inside the jar there's all the classes that the module needs. The server needs to read the jar, find the main class (it doesnt have the main method on it is just the class that makes the module work but not as a different program), build an object of that class and store it in a vector of modules so that it can acces to a specific module depending on the job to be done. How can I do that? As far as the server, it is listening and receiving request, but there's no modules to delegate the job to, since my vector of modules is empty.

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• Do While loop breaks after incorrect input?

  - by Daminkz

  I am trying to have a loop continue to prompt the user for an option. When I get a string of characters instead of an int, the program loops indefinitely. I have tried setting the variable result to NULL, clearing the input stream, and have enclosed in try{}catch blocks (not in this example). Can anyone explain to me why this is? #include <iostream> #include <vector> #include <string> using namespace std; int menu(string question, vector<string> options) { int result; cout << question << endl; for(int i = 0; i < options.size(); i++) { cout << '[' << i << ']' << options[i] << endl; } bool ans = false; do { cin >> result; cin.ignore(1000, 10); if (result < options.size() ) { ans = true; } else { cout << "You must enter a valid option." << endl; result = NULL; ans = false; } } while(!ans); return result; } int main() { string menuQuestion = "Welcome to my game. What would you like to do?"; vector<string> mainMenu; mainMenu.push_back("Play Game"); mainMenu.push_back("Load Game"); mainMenu.push_back("About"); mainMenu.push_back("Exit"); int result = menu(menuQuestion, mainMenu); cout << "You entered: " << result << endl; return 0; }

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• Plotting a grouped 2 dimensional vevtor in MATLAB

  - by Hossein

  Hi, I am trying to make a plot of a 2-Dimensional vector(2D Plot).But I don't want all the datapoints to have the same color on the plot.Each datapoint corresponds to a group.I want to have different colors for each group of datapoints. class=[1 3 2 5 2 5 1 3 3 4 2 2 2] says each datapoint belongs to which group X=[x1,y1;x2,y2;x3,y3;.....] the number of thes datapoints are the same as the number of elements in th class vector. Now I want to plot these based on colors. Can someone help me? Thanks

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• Java how to load modules

  - by gerardorn

  heres my problem: im building a server that loads modules. each module is a .jar file. inside the jar theres all the classes that the module need. the server needs to read the jar, find the main class (it doesnt have the main method on it is just the class that makes the module work but not as a different program), build an object of that class and store it in a vector of modules so that it can acces to a specific module depending on the job to be done. how can i do that? as far as the server, it is listening and reciving request, but thes no modules to delegate the job to, since my vector of modules is empty

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• Recursion: using values passed in parameters

  - by Tom Lilletveit

  I got this line of code that pops a int of the array saves it to int element then removes it from array. then in the return statement return CountCriticalVotes(rest, blockIndex + element); it ads it to the blockIndex variable and if it reaches 10 before the array is empty it returns 1. But my problem is this, I do not want it to add up all the values in the array in the parameter, but only add one then revert the parameter value back to it´s original state, then add a new, revert etc... How would i do this? int NumCriticalVotes :: CountCriticalVotes(Vector<int> & blocks, int blockIndex) { if (blockIndex >= 10) { return 1; } if (blocks.isEmpty()) { return 0; } else { int element = blocks.get(0); Vector<int> rest = blocks; rest.remove(0); return CountCriticalVotes(rest, blockIndex + element);

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• C++ Euler-Problem 14 Program Freezing

  - by Tim

  I'm working on Euler Problem 14: http://projecteuler.net/index.php?section=problems&id=14 I figured the best way would be to create a vector of numbers that kept track of how big the series was for that number... for example from 5 there are 6 steps to 1, so if ever reach the number 5 in a series, I know I have 6 steps to go and I have no need to calculate those steps. With this idea I coded up the following: #include <iostream> #include <vector> #include <iomanip> using namespace std; int main() { vector<int> sizes(1); sizes.push_back(1); sizes.push_back(2); int series, largest = 0, j; for (int i = 3; i <= 1000000; i++) { series = 0; j = i; while (j > (sizes.size()-1)) { if (j%2) { j=(3*j+1)/2; series+=2; } else { j=j/2; series++; } } series+=sizes[j]; sizes.push_back(series); if (series>largest) largest=series; cout << setw(7) << right << i << "::" << setw(5) << right << series << endl; } cout << largest << endl; return 0; } It seems to work relatively well for smaller numbers but this specific program stalls at the number 113382. Can anyone explain to me how I would go about figuring out why it freezes at this number? Is there some way I could modify my algorithim to be better? I realize that I am creating duplicates with the current way I'm doing it: for example, the series of 3 is 3,10,5,16,8,4,2,1. So I already figured out the sizes for 10,5,16,8,4,2,1 but I will duplicate those solutions later. Thanks for your help!

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• C++ struct sorting error

  - by Betamoo

  I am trying to sort a vector of custom struct in C++ struct Book{ public:int H,W,V,i; }; with a simple functor class CompareHeight { public: int operator() (Book lhs,Book rhs) { return lhs.H-rhs.H; } }; when trying : vector<Book> books(X); ..... sort(books.begin(),books.end(), CompareHeight()); it gives me exception "invalid operator <" What is the meaning of this error? Thanks

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• C++ STL make_heap and pop_heap not working.

  - by Henrique

  I need to use a Heap, so i've searched about the STL one, but it doesn't seem to work, i wrote some code to explain what i mean: #include <stdio.h> #include <stdlib.h> #include <vector> #include <algorithm> struct data { int indice; int tamanho; }; bool comparator2(const data* a, const data* b) { return (a->tamanho < b->tamanho); } int main() { std::vector<data*> mesas; data x1, x2, x3, x4, x5; x1.indice = 1; x1.tamanho = 3; x2.indice = 2; x2.tamanho = 5; x3.indice = 3; x3.tamanho = 2; x4.indice = 4; x4.tamanho = 6; x5.indice = 5; x5.tamanho = 4; mesas.push_back(&x1); mesas.push_back(&x2); mesas.push_back(&x3); mesas.push_back(&x4); mesas.push_back(&x5); make_heap(mesas.begin(), mesas.end(), comparator2); for(int i = 0 ; i < 5 ; i++) { data* mesa = mesas.front(); pop_heap(mesas.begin(),mesas.end()); mesas.pop_back(); printf("%d, %d\n", mesa->indice, mesa->tamanho); } return 0; }; and this is what i get: 4, 6 2, 5 1, 3 3, 2 5, 4 So it's not working as a heap, as the maximum element on the vector is not being returned right. Or am i doing something wrong?

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• C++ split string

  - by Mike

  I am trying to split a string using spaces as a delimiter. I would like to store each token in an array or vector. I have tried. string tempInput; cin >> tempInput; string input[5]; stringstream ss(tempInput); // Insert the string into a stream int i=0; while (ss >> tempInput){ input[i] = tempInput; i++; } The problem is that if i input "this is a test", the array only seems to store input[0] = "this". It does not contain values for input[2] through input[4]. I have also tried using a vector but with the same result.

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• Call function from object instantiated in one class in another

  - by Dk43

  I have two classes, both of which need to be able to call the same instance of entitymanager class Engine { EntityManager::Entitymanager EManager; } And I need to add an object to a vector contained by this particular instance of Engine. What I want to do is be able to add a bullet spawned by the player to the vector that contains all my entities. class Player : Entity { void SpawnBullet() {Engine::EManager.Add(BULLET);} } The above returns this error: error: object missing in reference to ‘Engine::EManager’ How do I resolve this? Any help or pointers in the right direction would be much appreciated!

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• Declare variables that depend on unknown type in template functions.

  - by rem

  Suppose I'm writing a template function foo that has type parameter T. It gets an object of type T that must have method bar(). And inside foo I want to create a vector of objects of type returned by bar. In GNU C++ I can write something like that: template<typename T> void foo(T x) { std::vector<__typeof(x.bar())> v; v.push_back(x.bar()); v.push_back(x.bar()); v.push_back(x.bar()); std::cout << v.size() << std::endl; } How to do the same thing in Microsoft Visual C++? Is there some way to write this code that works in both GNU C++ and Visual C++?

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• C++: Allocation of variables in a loop

  - by Rosarch

  Let's say I have a loop like this: vector<shared_ptr<someStruct>> vec; int i = 0; while (condition) { i++ shared_ptr<someStruct> sps(new someStruct()); WCHAR wchr[20]; memset(wchr, i, 20); sps->pwsz = wchr; vec.push_back(sps); } At the end of this loop, I see that for each sps element of the vector, sps->pwsz is the same. Is this because I'm passing a pointer to memory allocated in a loop, which is destructed after each iteration, and then refilling that same memory on the next iteration?

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• Reading function pointer syntax

  - by bobobobo

  Everytime I look at a C function pointer, my eyes glaze over. I can't read them. From here, here are 2 examples of function pointer TYPEDEFS: typedef int (*AddFunc)(int,int); typedef void (*FunctionFunc)(); Now I'm used to something like: typedef vector<int> VectorOfInts ; Which I read as typedef vector<int> /* as */ VectorOfInts ; But I can't read the above 2 typedefs. The bracketing and the asterisk placement, it's just not logical. Why is the * beside the word AddFunc..?

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• JTable.removeColumn() method throws exception

  - by sanjeev

  To hide a column from only the view of JTable, i am using the removeColumn() method. But it throws the exception Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 7 >= 7 at java.util.Vector.elementAt(Vector.java:470) at javax.swing.table.DefaultTableColumnModel.getColumn(DefaultTableColumnModel.java:294) at javax.swing.plaf.basic.BasicTableHeaderUI.paint(BasicTableHeaderUI.java:648) i think, after removing column from the view, if i modified the model, then this exception pops out. is it because of there is no column in view, while the model is updating the table ? What is the best way to hide the column in view in JTable ? insteading of setting the sizes to 0.

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• can't compile min_element in c++

  - by Vincenzo

  This is my code: #include <algorithm> #include <vector> #include <string> using namespace std; class A { struct CompareMe { bool operator() (const string*& s1, const string*& s2) const { return true; } }; void f() { CompareMe comp; vector<string*> v; min_element(v.begin(), v.end(), comp); } }; And this is the error: error: no match for call to ‘(A::CompareMe) (std::string*&, std::string*&)’ test.cpp:7: note: candidates are: bool A::CompareMe::operator()(const std::string*&, const std::string*&) const I feel that there is some syntax defect, but can't find out which one. Please, help!

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• efficientcy effort: grep with a vectored pattern or match with a list of values

  - by Elad663

  I guess this is trivial, I apologize, I couldn't find how to do it. I am trying to abstain from a loop, so I am trying to vectorize the process: I need to do something like grep, but where the pattern is a vector. Another option is a match, where the value is not only the first location. For example data (which is not how the real data is, otherswise I would exploit it structure): COUNTRIES=c("Austria","Belgium","Denmark","France","Germany", "Ireland","Italy","Luxembourg","Netherlands", "Portugal","Sweden","Spain","Finland","United Kingdom") COUNTRIES_Target=rep(COUNTRIES,times=4066) COUNTRIES_Origin=rep(COUNTRIES,each=4066) Now, currently I got a loop that: var_pointer=list() for (i in 1:length(COUNTRIES_Origin)) { var_pointer[[i]]=which(COUNTRIES_Origin[i]==COUNTRS_Target) } The problem with match is that match(x=COUNTRIES_Origin,table=COUNTRIES_Target) returns a vector of the same length as COUNTRIES_Origin and the value is the first match, while I need all of them. The issue with grep is that grep(pattern=COUNTRIES_Origin,x=COUNTRIES_Target) is the given warning: Warning message: In grep(pattern = COUNTRIES_Origin, x = COUNTRIES_Target) : argument 'pattern' has length > 1 and only the first element will be used Any suggestions?

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• How to check the type name of an object in derived classes?

  - by Vincenzo

  This is my code: class Base { /* something */ }; class Derived : public Base { /* something */ }; vector<Base*> v; // somebody else initializes it, somewhere int counter = 0; for (vector<Base*>::iterator i=v.begin(); i!=v.end(); ++i) { if (typeof(*i) == "Derived") { // this line is NOT correct counter++; } } cout << "Found " << counter << " derived classes"; One line in the code is NOT correct. How should I write it properly? Many thanks in advance!

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