when using C++ vector, time spent is 718 milliseconds, while when I use Array, time is almost 0 milliseconds. Why so much performance difference? int _tmain(int argc, _TCHAR* argv[]) { const int size = 10000; clock_t start, end; start = clock(); vector<int> v(size*size); for(int i = 0; i < size; i++) { for(int j = 0; j < size; j+...
I have a system that stores vectors and allows a user to find the n most similar vectors to the user's query vector. That is, a user submits a vector (I call it a query vector) and my system spits out "here are the n most similar vectors." I generate the similar vectors using a KD-Tree and everything works well, but I want to do more. I ...
For example, bitmask({1, 2, 3, 4}, {2, 4}) returns {False, True, False, True} The naive way to do this is to map a membership function over the list: map(lambda(x, member(x, subset)), list) but that's O(n*m) and it can be done in O(n+m). What's the best way to implement bitmask() in your favorite language? PS: It doesn't actua...
I want to know the simplest way to plot vectors in MATLAB. For example: a = [2 3 5]; b = [1 1 0]; c = a + b; I want to visualize this vector addition as head-to-tail/parallelogram method. How do I plot these vectors with an arrow-head? ...
In my code, I want to use a byte-vector to store some data in memory. The problem is, that my current approach uses many lines of code: std::vector<byte> v; v.push_back(0x13); v.push_back(0x37); v.push_back(0xf0); v.push_back(0x0d); How can I shorten this procedure so that I have for example something like: std::vector<byte> v(4) = "...
Hi All, How to convert a vector to a list? ...
vector is included in only one source file. The only stl include in the header files is string. Yet I cannot get rid of multiple definition errors (example below). Any ideas? ./plugin_dfb.o:mipsel-linux-uclibc/include/c++/4.2.0/bits/stl_bvector.h:182: multiple definition of `std::operator-(std::_Bit_iterator_base const&, std::_Bit_itera...
Hi I have a file with some text in it. Is there some easy way to get the number of lines in the file without traversing through the file? I also need to put the lines of the file into a vector. I am new to C++ but I think vector is like ArrayList in java so I wanted to use a vector and insert things into it. So how would I do it? Thank...
I tried to add objects to the "content" vector, and use show() on all of them. But the objects that are children (A, B) of "Base" behave like they were of "Base" type, what is not my intention. As it seems, I tried to use virtual functions but it doesn't work. I hope that the code will speak for itself. class Base { public: ...
Hi, I have two p*n arrays, y and ymiss. y contains real numbers and NA's. ymiss contains 1's and 0's, so that if y(i,j)==NA, ymiss(i,j)==0, and 1 otherwise. I also have 1*n array ydim which tells how many real numbers there is at y(1:p,n), so ydim has values 0 to p In R programming language, I can do following: if(ydim!=p && ydim!=0...
I defined a class named nth_best_parse this way: class nth_best_parse { public: int traversal; int nth_best_active; int nth_best_passive; double viterbi_prob; nth_best_parse(); nth_best_parse(int t, int nbl, int nbr, double v) {traversal = t; nth_best_active = nbl; nth_best_passive ...
Hi! is it safe to memcopy myvect.size()*sizeof(foo) bytes from the memoryadress of the first element of a std::vector<std::pair<T1, T2> > myvect into an array of struct foo{ T1 first; T2 second; } if the array is allocated with the same number of elements as the vector's size? thanks ...
Is there a way to use getters and setters for Vectors? Say, in my Main class, I would like to write myVector.push(item); and in another class, I have written: public function get myVector():Vector.<int> { return _opponentCardList; } public function set myVector(myVector:Vector.<int>):void { _myVector = myVector; } This ...
Hi, How to translate properly the following Java code to C++? Vector v; v = getLargeVector(); ... Vector getLargeVector() { Vector v2 = new Vector(); // fill v2 return v2; } So here v is a reference. The function creates a new Vector object and returns a reference to it. Nice and clean. However, let's see the following C...
Hi, I have file (*.shp used in GIS) that contains collection of polygons and maybe other vector objects (but polygons are most important for me). I need to remove non printable objects it. I don't know what criteria chose. I think removing objects with small border length would be better then removing objects with small area (so long ...
is there any reason why foo = (bar->at(x))->at(y); works but foo = bar[x][y]; does not work, where bar is a vector of vectors (using the c++ stl) the declaration is: std::vector< std::vector < Object * > * > ...
I'm trying to achieve something like the following in C++: class MyVector; // 3 component vector class MyVector const kA = /* ... */; MyVector const kB = /* ... */; MyVector const kC = /* ... */; MyVector const kD = /* ... */; // I'd like to shorten the remaining lines, ideally making it readable but less code/operations. MyVector ...
Hi all, I have a vector class in C# (a fragment below). My issue is that when I call GetMagnitude(), it always returns 0.0f - even with the debugger running and I check that Sq has a valid value, as soon as it gets passed back into other function (eg: Normalize() ), it has return 0.0f. Can someone explain this and help me fix it? My gue...
Hopefully easy answer, but I cannot get it. I have a 3D render engine I have written. I have the camera position, the lookat position and the up vector. I want to be able to "tilt" the camera left, right, up and down. Like a camera on a fixed tripod that you can grab the handle and tilt it it up, down, left right etc. The maths stum...
I'm having difficulties reading in a .shp (esri shape file) into R. I have tried several options in R, and tried to convert the shape file in ArcMap to something that correctly reads in the shape file but nothing worked yet. (In ArcMap I corrected the geometry, converted from single to multipolygon, etc which was probably not necessary o...