dft_tools/triqs/mc_tools/random_generator.hpp

/*******************************************************************************
 *
 * TRIQS: a Toolbox for Research in Interacting Quantum Systems
 *
 * Copyright (C) 2011-2014 by M. Ferrero, O. Parcollet
 *
 * TRIQS is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * TRIQS is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * TRIQS. If not, see <http://www.gnu.org/licenses/>.
 *
 ******************************************************************************/
#pragma once
#include <triqs/utility/first_include.hpp>
#include "../utility/exceptions.hpp"
#include "../utility/buffered_function.hpp"
#include "math.h"
#include <string>
#include <assert.h>
#include <type_traits>

namespace triqs {
namespace mc_tools {

  /// Return a list of the names of available generators, with separator sep
  std::string random_generator_names(std::string const & sep=" ");
  std::vector<std::string> random_generator_names_list();

 /**
  * Random generator, adapting the boost random generator.
  *
  * The name of the generator is given at construction, and its type is erased in this class.
  * For performance, the call to the generator is bufferized, with chunks of 1000 numbers.
  */
 class random_generator {
  utility::buffered_function<double> gen;
  std::string _name;

  public:
  /** Constructor
   *  @param RandomGeneratorName : Name of a boost generator e.g. mt19937, or "" (another Mersenne Twister).
   *  @param seed : The seed of the random generator
   */
  random_generator(std::string const& RandomGeneratorName, uint32_t seed_);

  random_generator() : random_generator("mt19937", 198) {}

  ///
  random_generator(random_generator const& p);

  random_generator(random_generator&&) = default;

  //
  random_generator & operator=(random_generator&&) = default;

  /// Name of the random generator
  std::string name() const { return _name; }

  /// Returns a integer in [0,i-1] with flat distribution
  template <typename T> typename std::enable_if<std::is_integral<T>::value, T>::type operator()(T i) {
   return (i == 1 ? 0 : T(floor(i * (gen()))));
  }

  /// Returns a double in [0,1[ with flat distribution
  double preview() { return gen.preview();} 

  double operator()() { return gen(); }

  /// Returns a double in [0,x[ with flat distribution
  double operator()(double x) { return x * (gen()); }

  /// Returns a double in [a,b[ with flat distribution
  double operator()(double a, double b) {
   assert(b > a);
   return a + (b - a) * (gen());
  }
 };
}
}