kmcwaitingtime.h

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/*
 *            Copyright 2009-2026 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.
 *
 */
 
#pragma once
#ifndef VOTCA_XTP_KMCWAITINGTIME_H
#define VOTCA_XTP_KMCWAITINGTIME_H
 
// Standard includes
#include <memory>
#include <string>
#include <vector>
 
// Local VOTCA includes
#include "kmcrandom.h"
#include "kmcrates.h"
 
namespace votca {
namespace xtp {

class WaitingTimeStrategy {
 public:
  virtual ~WaitingTimeStrategy() = default;
  virtual std::string Name() const = 0;
  virtual void Prepare(const TimeDependentRates& rates) = 0;
  virtual double NextTime(Index site, double t, KMCRandom& random) const = 0;
  virtual Index ChooseHop(Index site, double t, KMCRandom& random) const = 0;
};

class ExponentialWaitingTime final : public WaitingTimeStrategy {
 public:
  std::string Name() const override { return "exponential"; }
  void Prepare(const TimeDependentRates& rates) override;
  double NextTime(Index site, double t, KMCRandom& random) const override;
  Index ChooseHop(Index site, double t, KMCRandom& random) const override;
 
 private:
  const ToFGraph* graph_ = nullptr;
  std::vector<double> escape_;
  std::vector<double> cumulative_;  // per edge, cumulative within its site
};

class ThinningWaitingTime final : public WaitingTimeStrategy {
 public:
  std::string Name() const override { return "thinning"; }
  void Prepare(const TimeDependentRates& rates) override;
  double NextTime(Index site, double t, KMCRandom& random) const override;
  Index ChooseHop(Index site, double t, KMCRandom& random) const override;
 
 private:
  const TimeDependentRates* rates_ = nullptr;
  std::vector<double> bound_escape_;
  std::vector<double> cumulative_;  // of the bounds
};

class IntegratedRateInversion final : public WaitingTimeStrategy {
 public:
  struct Settings {
    Index quadrature_points = 1000;  // per period, for Lambda_i
    Index interpolation_points = 100;
    double tolerance = 1e-14;  // relative, root search
  };
  explicit IntegratedRateInversion(const Settings& settings)
      : settings_(settings) {}
  std::string Name() const override { return "integrated-rate inversion"; }
  void Prepare(const TimeDependentRates& rates) override;
  double NextTime(Index site, double t, KMCRandom& random) const override;
  Index ChooseHop(Index site, double t, KMCRandom& random) const override;
 
 private:
  Settings settings_;
  const TimeDependentRates* rates_ = nullptr;
};

std::unique_ptr<WaitingTimeStrategy> MakeWaitingTimeStrategy(
    const std::string& name);
 
}  // namespace xtp
}  // namespace votca
 
#endif  // VOTCA_XTP_KMCWAITINGTIME_H