[boost] Bug in ublas?

From: George Katsirelos (gkatsi_at_[hidden])
Date: 2002-07-13 12:03:22

Hi,
The piece of code at the end of this mail produces unexpected output. 
Briefly, calling erase() on a sparse vector does weird things to the 
contents of that vector, even though the iterators still work (somewhat) 
correctly.

Note that after the call to d.erase(5), elements 2 and 3 do not appear 
in the output, even though they are there when iterating. Also note the 
0 == 0 that appears.
The compiler is gcc 3.1.
This seems like a bug or, if not, very counterintuitive behavior.

Thanks,
George

int main()
{
  using namespace boost::numerics;

  sparse_vector<double> d(10);

  d[2] = 3.;
  d[3] = 5.;
  d[7] = 10.;
  if(d[5] > 3.0 )
    std::cout << "will not be printed\n";
  std::cout << d << '\n';
  d.erase(5);
  std::cout << d << '\n';

  for( sparse_vector<double>::iterator i = d.begin(); i != d.end(); ++i ) {
    std::cout << i.index() << " == " << *i << '\n';
  }

  sparse_vector<double> d1(d);

  std::cout << d1 << '\n';

  for( sparse_vector<double>::iterator i = d1.begin(); i != d1.end(); 
++i ) {
    std::cout << i.index() << " == " << *i << '\n';
  }

  return 0;
}

The output is:
[10](0,0,3,5,0,0,0,10,0,0)
[10](0,0,0,0,0,0,0,10,0,0)
2 == 3
3 == 5
0 == 0
7 == 10
[10](0,0,0,0,0,0,0,10,0,0)
2 == 3
3 == 5
0 == 0
7 == 10