/usr/include/boost/math/tools/solve.hpp is in libboost1.49-dev 1.49.0-3.2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 | // (C) Copyright John Maddock 2006.
// Use, modification and distribution are subject to the
// Boost Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_MATH_TOOLS_SOLVE_HPP
#define BOOST_MATH_TOOLS_SOLVE_HPP
#ifdef _MSC_VER
#pragma once
#endif
#include <boost/config.hpp>
#include <boost/assert.hpp>
#ifdef BOOST_MSVC
#pragma warning(push)
#pragma warning(disable:4996 4267 4244)
#endif
#include <boost/numeric/ublas/lu.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/vector.hpp>
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
namespace boost{ namespace math{ namespace tools{
//
// Find x such that Ax = b
//
// Caution: this uses undocumented, and untested ublas code,
// however short of writing our own LU-decompostion code
// it's the only game in town.
//
template <class T>
boost::numeric::ublas::vector<T> solve(
const boost::numeric::ublas::matrix<T>& A_,
const boost::numeric::ublas::vector<T>& b_)
{
//BOOST_ASSERT(A_.size() == b_.size());
boost::numeric::ublas::matrix<T> A(A_);
boost::numeric::ublas::vector<T> b(b_);
boost::numeric::ublas::permutation_matrix<> piv(b.size());
lu_factorize(A, piv);
lu_substitute(A, piv, b);
//
// iterate to reduce error:
//
boost::numeric::ublas::vector<T> delta(b.size());
for(unsigned i = 0; i < 1; ++i)
{
noalias(delta) = prod(A_, b);
delta -= b_;
lu_substitute(A, piv, delta);
b -= delta;
T max_error = 0;
for(unsigned i = 0; i < delta.size(); ++i)
{
T err = fabs(delta[i] / b[i]);
if(err > max_error)
max_error = err;
}
//std::cout << "Max change in LU error correction: " << max_error << std::endl;
}
return b;
}
}}} // namespaces
#endif // BOOST_MATH_TOOLS_SOLVE_HPP
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