ublas

问题 In the doc, they say We decided to use no operator overloading for ... They provide prod instead for these. But why? Is there any good reason? I like to do matrix * vector (as in most other languages). I like to understand why they did not overloaded this operator to understand why it might be a bad idea to just do it myself. Or aren't they any drawbacks if I overload it myself? 回答1: Probably, because op* in other languages, e.g. with Numpy in Python, will always be element-wise. In case that

问题 I'm a very noob at Boost::uBLAS. I have a function which take a ublas::matrix_expression<double> as input: namespace ublas = boost::numeric::ublas; void Func(const ublas::matrix_expression<double>& in, ublas::matrix_expression<double>& out); A caller is holding a row vector as ublas::vector<double> , and I want it to be passed to Func . Until now I have not found any way to do this. What is the best way, preferably without any temporary allocation? Thanks. 回答1: Well, there is an option to

问题 I simply want to traverse a matrix from start to finish touching upon every element. However, I see that there is no one iterator for boost matrix, rather there are two iterators, and I haven't been able to figure out how to make them work so that you can traverse the entire matrix typedef boost::numeric::ublas::matrix<float> matrix; matrix m1(3, 7); for (auto i = 0; i < m1.size1(); i++) { for (auto j = 0; j < m1.size2(); j++) { m1(i, j) = i + 1 + 0.1*j; } } for (auto itr1 = m1.begin1(); itr1

问题 I am trying to implement certain matrix operations but I am lost in the internals of ublas library. is there a resource such as tutorial or an example on how to implement new ublas matrix expressions? Thanks 回答1: Don't know if it'll help, but there's a wiki page on extending uBlas here. That expression template stuff really blows my mind. :) 回答2: My suggestion is to just template your new functions so you don't have to worry about matrix expressions or ublas internals. For example, if you

问题 I'm trying to read in a file that contains matrix data into a boost matrix. "" is already supposed to have operator overloads for this sort of thing and I can get it to write to a standard stream (cout). I don't know what's wrong with going the other way. I'm fairly new to C++, so I'm guessing I'm making an incorrect assumption regarding file streams, but it seemed like it made sense. Here are the web pages I'm going on: http://www.boost.org/doc/libs/1_51_0/boost/numeric/ublas/io.hpp http:/

问题 I am a newbie in C++ Boost uBLAS library so I have a noob question - how to transpose a matrix using this library? I could not find question here: http://www.boost.org/doc/libs/1_44_0/libs/numeric/ublas/doc/html/index.html 回答1: C = boost::numeric::ublas::trans(A); Documented (poorly) under Overview of Matrix and Vector Operations. 来源： https://stackoverflow.com/questions/4097153/how-to-transpose-matrix-using-ublas

问题 I am a newbie in C++ Boost uBLAS library so I have a noob question - how to transpose a matrix using this library? I could not find question here: http://www.boost.org/doc/libs/1_44_0/libs/numeric/ublas/doc/html/index.html 回答1: C = boost::numeric::ublas::trans(A); Documented (poorly) under Overview of Matrix and Vector Operations. 来源： https://stackoverflow.com/questions/4097153/how-to-transpose-matrix-using-ublas

问题 Is there a single-expression way to assign a scalar to all elements of a boost matrix or vector? I'm trying to find a more compact way of representing: boost::numeric::ublas::c_vector<float, N> v; for (size_t i=0; i<N; i++) { v[i] = myScalar; } The following do not work: boost::numeric::ublas::c_vector<float, N> v(myScalar, myScalar, ...and so on..., myScalar); boost::numeric::ublas::c_vector<float, N> v; v = myScalar; 回答1: Because the vector models a standard random access container you

问题 I understand that doing something like the following: auto&& x = Matrix1() + Matrix2() + Matrix3(); std::cout << x(2,3) << std::endl; Will cause a silent runtime error if the matrix operations use expression templates (such as boost::ublas). Is there any way of designing expression templates to prevent the compiler from compiling such code that may result in the use of expired temporaries at runtime? (I've attempted unsuccessfully to work around this issue, the attempt is here) 回答1: Is there