unsupported/Eigen/MPRealSupport

// This file is part of a joint effort between Eigen, a lightweight C++ template library
// for linear algebra, and MPFR C++, a C++ interface to MPFR library (http://www.holoborodko.com/pavel/)
//
// Copyright (C) 2010 Pavel Holoborodko <pavel@holoborodko.com>
// Copyright (C) 2010 Konstantin Holoborodko <konstantin@holoborodko.com>
// Copyright (C) 2010 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// 
// Contributors:
// Brian Gladman, Helmut Jarausch, Fokko Beekhof, Ulrich Mutze, Heinz van Saanen, Pere Constans

#ifndef EIGEN_MPREALSUPPORT_MODULE_H
#define EIGEN_MPREALSUPPORT_MODULE_H

#include <ctime>
#include <mpreal.h>
#include <Eigen/Core>

namespace Eigen {
  
  /** \ingroup Unsupported_modules
    * \defgroup MPRealSupport_Module MPFRC++ Support module
    *
    * \code
    * #include <Eigen/MPRealSupport>
    * \endcode
    *
    * This module provides support for multi precision floating point numbers
    * via the <a href="http://www.holoborodko.com/pavel/mpfr">MPFR C++</a>
    * library which itself is built upon <a href="http://www.mpfr.org/">MPFR</a>/<a href="http://gmplib.org/">GMP</a>.
    *
    * You can find a copy of MPFR C++ that is known to be compatible in the unsupported/test/mpreal folder.
    *
    * Here is an example:
    *
\code
#include <iostream>
#include <Eigen/MPRealSupport>
#include <Eigen/LU>
using namespace mpfr;
using namespace Eigen;
int main()
{
  // set precision to 256 bits (double has only 53 bits)
  mpreal::set_default_prec(256);
  // Declare matrix and vector types with multi-precision scalar type
  typedef Matrix<mpreal,Dynamic,Dynamic>  MatrixXmp;
  typedef Matrix<mpreal,Dynamic,1>        VectorXmp;

  MatrixXmp A = MatrixXmp::Random(100,100);
  VectorXmp b = VectorXmp::Random(100);

  // Solve Ax=b using LU
  VectorXmp x = A.lu().solve(b);
  std::cout << "relative error: " << (A*x - b).norm() / b.norm() << std::endl;
  return 0;
}
\endcode
    *
    */

  template<> struct NumTraits<mpfr::mpreal>
    : GenericNumTraits<mpfr::mpreal>
  {
    enum {
      IsInteger = 0,
      IsSigned = 1,
      IsComplex = 0,
      RequireInitialization = 1,
      ReadCost = 10,
      AddCost = 10,
      MulCost = 40
    };

    typedef mpfr::mpreal Real;
    typedef mpfr::mpreal NonInteger;

    inline static mpfr::mpreal highest() { return  mpfr::mpreal_max(mpfr::mpreal::get_default_prec()); }
    inline static mpfr::mpreal lowest()  { return -mpfr::mpreal_max(mpfr::mpreal::get_default_prec()); }

    inline static Real epsilon()
    {
      return mpfr::machine_epsilon(mpfr::mpreal::get_default_prec());
    }
    inline static Real dummy_precision()
    {
      unsigned int weak_prec = ((mpfr::mpreal::get_default_prec()-1)*90)/100;
      return mpfr::machine_epsilon(weak_prec);
    }
  };

namespace internal {

  template<> mpfr::mpreal random<mpfr::mpreal>()
  {
#if (MPFR_VERSION >= MPFR_VERSION_NUM(3,0,0))
    static gmp_randstate_t state;
    static bool isFirstTime = true;

    if(isFirstTime)
    {
      gmp_randinit_default(state);
      gmp_randseed_ui(state,(unsigned)time(NULL));
      isFirstTime = false;
    }

    return mpfr::urandom(state)*2-1;
#else
    return mpfr::mpreal(random<double>());
#endif
  }

  template<> mpfr::mpreal random<mpfr::mpreal>(const mpfr::mpreal& a, const mpfr::mpreal& b)
  {
    return a + (b-a) * random<mpfr::mpreal>();
  }

  bool isMuchSmallerThan(const mpfr::mpreal& a, const mpfr::mpreal& b, const mpfr::mpreal& prec)
  {
    return mpfr::abs(a) <= mpfr::abs(b) * prec;
  }

  inline bool isApprox(const mpfr::mpreal& a, const mpfr::mpreal& b, const mpfr::mpreal& prec)
  {
    return mpfr::abs(a - b) <= (mpfr::min)(mpfr::abs(a), mpfr::abs(b)) * prec;
  }

  inline bool isApproxOrLessThan(const mpfr::mpreal& a, const mpfr::mpreal& b, const mpfr::mpreal& prec)
  {
    return a <= b || isApprox(a, b, prec);
  }
  
  template<> inline long double cast<mpfr::mpreal,long double>(const mpfr::mpreal& x)
  { return x.toLDouble(); }
  template<> inline double cast<mpfr::mpreal,double>(const mpfr::mpreal& x)
  { return x.toDouble(); }
  template<> inline long cast<mpfr::mpreal,long>(const mpfr::mpreal& x)
  { return x.toLong(); }
  template<> inline int cast<mpfr::mpreal,int>(const mpfr::mpreal& x)
  { return int(x.toLong()); }

} // end namespace internal
}

#endif // EIGEN_MPREALSUPPORT_MODULE_H