Problem with boost ublas matrix product

Question

I'm trying to use the ublas part of Boost but I'm not able to multiply matrices and assign the result to other matrices for some reason.

This works:

#include <boost/numeric/ublas/symmetric.hpp>
#include <boost/numeric/ublas/io.hpp>

using namespace boost::numeric::ublas;

typedef symmetric_matrix<int,lower> symatrix;

int main() {
  int N = 10;
  symatrix foo(N,N);
  for (int i = 0; i < N; i++)
    for(int j = 0; j <= i; j++) {
      foo(i,j) = i - j + 1;
    }
  symatrix goo(foo);
  //goo = prod(foo,foo);
  std::cout << prod(foo,foo)<< std::endl;

}

But if I uncomment the line goo = prod(foo,foo); or try something like:

symatrix goo = prod(foo,foo);

I get a runtime error I can't decipher.

Check failed in file /usr/include/boost/numeric/ublas/detail/matrix_assign.hpp at line 761:
detail::expression_type_check (m, cm)
terminate called after throwing an instance of 'boost::numeric::ublas::external_logic'
  what():  external logic
Aborted

How do I multiply matrices and assign the result?

I don't fully understand what is going on but I have found a few things out. Your code does work if I change the symatrix typedef into double type symmetric_matrix and int matrix. So it appears that the prod function does like your return type. — Joseph Lisee, May 02 '11 at 18:47

Joseph Lisee · Accepted Answer · 2011-05-02T18:55:00.667

2

You are not guaranteed to always get a symmetric matrix back when you multiply two symmetric matrices. So this error might be related to that, although I have no idea why the code works when I change your type to a symmetric_matrix type to a double.

edited May 02 '11 at 18:55

answered May 02 '11 at 18:38

Joseph Lisee

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That may be the problem. That's a shame though, cause the square of a symmetric matrix is also symmetric. Anyway, I should use a general matrix type. :( – Rafael S. Calsaverini May 03 '11 at 00:37

Problem with boost ublas matrix product

1 Answers1