I really do not know how to solve it and need help to get through my work. Can anyone with kindness help me? ---------- 转发邮件信息 ---------- 发件人："fmingu <fmingu@163.com>" 发送日期：2010-03-29 09:02:29 收件人：boost-users@lists.boost.org 主题： Re:Re: [Boost-users] A question on the preciseness of the double used in MTL. Can anyone with kindness help me? 在2010-03-29 08:28:13，"Steven Watanabe" <watanabesj@gmail.com> 写道：

AMDG

fmingu wrote:

...

I am using MTL(Matrix Template Library) for Matrix computing in Dev-C++ 4.9.8.0 and updated the gcc version from 3.2 to 4.4.1 by installing tdm-mingw-1.908.0-4.4.1-2 and the boost version is 1.37.0. The system is Windows xp The sample code is :

#include <boost/numeric/mtl/mtl.hpp>

#include "boost/random/normal_distribution.hpp"

#include <boost/random.hpp>

#include <boost/random/uniform_real.hpp>

int main(int argc, char* argv[])

{

using namespace mtl; using namespace mtl::matrix;

const unsigned n= 5;

dense2D<double> A(n, n), B(n, n);

morton_dense<double, doppled_64_row_mask> C(n, n), D(n, n);

dense2D<double> F(n, n), E(n, n);

hessian_setup(A, 3.0); hessian_setup(B, 1.0);

hessian_setup(C, 2.0); hessian_setup(D, 11.0);

B(1,1)=9.9999;

..........................

std::cout << "The matrices are: B=\n" << B <<"\n";

std::cout << "The result is " <<1.0/3.0 <<"\n";

…………………….

But the result is shown that B(1,1) is 10, and 1.0/3.0 is 0.33.

How can I get the highest precision of the type double and dense2D<double> for scientific computation?

The same question occurred in random number generation in boost random library.

Use std::setprecision to print more digits.

In Christ, Steven Watanabe

I rewrote the program following your advice but std::cout << "The matrices are: B=\n" << std::setprecision(5)<<B<<"\n"; do not show any changes while the code: std::cout << "The result is " << std::setprecision(10)<<1.0/3.0 <<"\n"; worked well. How can I do now? Thanks a lot.