random.h

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/*
 * Copyright 2009-2020 The VOTCA Development Team (http://www.votca.org)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
 
#ifndef VOTCA_TOOLS_RANDOM_H
#define VOTCA_TOOLS_RANDOM_H
 
// Standard includes
#include <random>
 
// Local VOTCA includes
#include "types.h"
 
namespace votca {
namespace tools {
 
class Random {
 public:
  void init(Index seed) {
    if (seed < 0) {
      throw std::runtime_error("seed integer must be positive.");
    }
    mt_ = std::mt19937(unsigned(seed));
  }
  // draws a random double from [0,1)
  double rand_uniform() { return distribution_(mt_); }
  // sets maxint for a uniform integer distribution [0,maxint]
  void setMaxInt(Index maxint) {
    int_distribution_ = std::uniform_int_distribution<Index>{0, maxint};
  }
  // draws from a uniform integer distribution [0,maxint]
  Index rand_uniform_int() { return int_distribution_(mt_); }
 
 private:
  std::mt19937 mt_;
  std::uniform_real_distribution<double> distribution_{0.0, 1.0};
  std::uniform_int_distribution<Index> int_distribution_;
};
 
}  // namespace tools
}  // namespace votca
 
#endif  // VOTCA_TOOLS_RANDOM_H