Re: [ublas] Return type of 'mean_square'

Subject: Re: [ublas] Return type of 'mean_square'
From: Marco Guazzone (marco.guazzone_at_[hidden])
Date: 2015-08-18 11:14:34

Don't know enough detail about the mean_square function, but what if
AE::value_type is a long double?

Maybe you could use type deduction like the following:

   typename ublas::promote_traits<typename AE::value_type,double>::promote_type

I've written the following example:

--- [snip] ---
#include <boost/numeric/ublas/traits.hpp>
#include <iostream>

void foo(long double x)
{
    (void)x;
    std::cout << "LONG DOUBLE" << std::endl;
}
void foo(double x)
{
    (void)x;
    std::cout << "DOUBLE" << std::endl;
}

int main()
{
    namespace ublas = boost::numeric::ublas;

    std::cout << "long double vs. double -> ";
    ublas::promote_traits<long double,double>::promote_type ld_d = 0;
    foo(ld_d);
    std::cout << std::endl;

    std::cout << "int vs. double -> ";
    ublas::promote_traits<int,double>::promote_type i_d = 0;
    foo(i_d);
    std::cout << std::endl;

    std::cout << "long vs. double -> ";
    ublas::promote_traits<long,double>::promote_type l_d = 0;
    foo(l_d);
    std::cout << std::endl;
}
--- [/snip] ---

I've compiled on my machine (Linux 64bit with GCC 5.1.1 20150618 (Red
Hat 5.1.1-4)) with flags "-Wall -Wextra -ansi -pedantic", and the
result is:

long double vs. double -> LONG DOUBLE

int vs. double -> DOUBLE

long vs. double -> DOUBLE

Marco

On Tue, Aug 18, 2015 at 4:35 PM, Nasos Iliopoulos <nasos_i_at_[hidden]> wrote:
> I was debating this myself. I think converting to double is a good idea.
>
> -Nasos
>
> you cast the type do double before.
>
>
> On 08/10/2015 11:40 AM, Joaquim Duran Comas wrote:
>
> Hello,
>
> Few days ago, I patched the function 'mean_square' for vectors and matrices.
> Currently, the current return type of the function is AE::value_type. To get
> better accuracy, is it better return double type than AE::value_type
> (specially if it is an integuer)?
>
> Joaquim Duran
>
>
>
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