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Ublas : |
From: Vyacheslav E. Andrejev (vandrejev_at_[hidden])
Date: 2005-02-25 02:21:57
Hello All
vector_norm_2::apply has a little bug when compiled with BOOST_UBLAS_SCALED_NORM
defined. If first component of vector is zero, returned result will be division
zero by zero (Quiet NaN). I suggest following modification of code (from
boost/numeric/ublas/functional.hpp, lines 435-463):
template<class E>
static BOOST_UBLAS_INLINE
result_type apply (const vector_expression<E> &e) {
#ifndef BOOST_UBLAS_SCALED_NORM
real_type t = real_type ();
size_type size (e ().size ());
for (size_type i = 0; i < size; ++ i) {
real_type u (type_traits<value_type>::norm_2 (e () (i)));
t += u * u;
}
return type_traits<real_type>::sqrt (t);
#else
real_type scale = real_type ();
real_type sum_squares (1);
size_type size (e ().size ());
for (size_type i = 0; i < size; ++ i) {
real_type u (type_traits<value_type>::norm_2 (e () (i)));
if (0 == u) continue;
if (scale < u) {
real_type v (scale / u);
sum_squares = sum_squares * v * v + real_type (1);
scale = u;
} else {
real_type v (u / scale);
sum_squares += v * v;
}
}
return scale * type_traits<real_type>::sqrt (sum_squares);
#endif
}
-- Vyacheslav E. Andrejev System Architect, Excelsior, LLC