boost-multi-array

问题 Which is the fastest? A boost::multi_array or a std::vector ? I will have (not constant) 17.179.869 elements stored in 3 dimensions which will need to be accessed inside a for loop very rapidly and very often. What would be the most performing? An std::vector or a boost::multi_array ? (I don't expect it to be done within a second, but I would like to have it as efficient as possible because a nanosecond difference can save a lot of time.) 回答1: Best advice is to benchmark it by yourself. In

问题 What is faster - accessing elements of a multiarray using element selection operator, or traversing over the multiarray using iterators? In my case, I need to do a full pass over all elements of multiarray each time. 回答1: The fastest way to access every element of a boost::multi_array is via data() and num_elements() . With data() you gain access to the underlying raw storage (a contiguous block that contains the array‘s data) so there isn't need for multiple index calculations (consider also

问题 I'm trying to write some dimension-independent code for a template class in c++, using a boost::multi_array (though if other containers/data structures are better at this, I'd be happy to hear about it). Given a dimension, I would like to iterate over the full range of every other dimension, returning a 1d view along the selected dimension. This is fairly straightforward, or at least it appears to be from the boost documentation. What I can't figure out how to do is iterate the selected

问题 I am pretty new to C++ with Boost. I want an object of class "world" to have an array named "chunk" of type "octreenode". Previously I had an ordinary one-dimensional array, and this worked fine. Now I'm trying to move to using a 3D array with Boost's multi_array functionality, and I'm really not sure what I'm doing wrong. Simplified code: class world { public: typedef boost::multi_array<octreenode, 3> planetchunkarray; // a boost_multi for chunks typedef planetchunkarray::index index;

问题 The following code gives a segmentation fault: #include <iostream> #include <fstream> #include "binItr.h" #include <boost/multi_array.hpp> using namespace std; int main(){ const char * xifile = "results/feretxiG1155V0P5T231K10.bin"; const uint pSize = 5; const uint T = 231; ifstream xiFileId(xifile, ios::binary); typedef boost::multi_array<uint, 2> array_type; array_type xi(boost::extents[T][pSize + 1]); //the ii_t class in the following line is taken from http://stackoverflow.com/questions

问题 The following code gives a segmentation fault: #include <iostream> #include <fstream> #include "binItr.h" #include <boost/multi_array.hpp> using namespace std; int main(){ const char * xifile = "results/feretxiG1155V0P5T231K10.bin"; const uint pSize = 5; const uint T = 231; ifstream xiFileId(xifile, ios::binary); typedef boost::multi_array<uint, 2> array_type; array_type xi(boost::extents[T][pSize + 1]); //the ii_t class in the following line is taken from http://stackoverflow.com/questions

问题 What i need is to create a class that can hold boost::multi_array of same type but with different dimentions assume there are one or more such arrays of Double boost::multi_array<double, 2> array_2d; //2D array boost::multi_array<double, 3> array_3d; //4D array boost::multi_array<double, 4> array_4d; //5D array etc... i need a container class that can hold all of the above types that is able to deference the correct type later when needed something like GenericArray<double> arr; arr.IsEmpty()

问题 I have been looking into the boost::multi_array library in search of an iterator that allows you to traverse the whole multi_array in a single for loop. I don't think there is any such iterator in that library. (The iterators that are found there let you traverse a single dimension of the multi_array) Am I wrong? If not, is there any library that defines such an iterator? Entering into details, I'd like to write something like: boost::multi_array< double, 3 > ma(boost::extents[3][4][2]); for(

问题 I am trying to store a boost::indices in a variable. From what I can gather, this produces an index_gen type. However, index_gen seems to be templated in boost::detail , but the template parameters are not exposed to multi_array::index_gen , and they seem to default to <0,0> , which produces the error you'll see below: I have tried the following: #include "boost/multi_array.hpp" int main() { typedef boost::multi_array<double, 3> array_type; using IndexType = boost::array<array_type::index, 3>

问题 This discussion has let to another question. It seems that index_gen in multi_array (a.k.a. boost::multi_array::index_gen ) is set to boost::detail::multi_array::index_gen<0,0> , where I would have expected it to be boost::detail::multi_array::index_gen<Dim,Dim> where Dim is the template parameter of multi_array . Can anyone explain why this <0,0> type is used instead? 来源： https://stackoverflow.com/questions/35633531/why-is-index-gen-in-multi-array-a-boostdetailmulti-arrayindex-gen0-0