natural_anthropogenic_kernel.hpp

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/*
 * PoPS model - disperal kernel combining natural and anthropogenic dispersals
 *
 * Copyright (C) 2015-2020 by the authors.
 *
 * Authors: Vaclav Petras (wenzeslaus gmail com)
 *
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */
 
#ifndef POPS_NATURAL_ANTHROPOGENIC_KERNEL_HPP
#define POPS_NATURAL_ANTHROPOGENIC_KERNEL_HPP
 
#include "kernel_types.hpp"
 
#include <tuple>
#include <random>
#include <type_traits>
 
namespace pops {
 
template<typename NaturalKernelType, typename AnthropogenicKernelType>
class NaturalAnthropogenicDispersalKernel
{
protected:
    bool use_anthropogenic_kernel_;
    NaturalKernelType natural_kernel_;
    AnthropogenicKernelType anthropogenic_kernel_;
    std::bernoulli_distribution bernoulli_distribution;
 
public:
    NaturalAnthropogenicDispersalKernel(
        const NaturalKernelType& natural_kernel,
        const AnthropogenicKernelType& anthropogenic_kernel,
        bool use_anthropogenic_kernel,
        double percent_natural_dispersal)
        : use_anthropogenic_kernel_(use_anthropogenic_kernel),
          // Here we initialize all distributions,
          // although we won't use all of them.
          natural_kernel_(natural_kernel),
          anthropogenic_kernel_(anthropogenic_kernel),
          // use bernoulli distribution to act as the sampling with prob(gamma,1-gamma)
          bernoulli_distribution(percent_natural_dispersal)
    {}
 
    template<typename Generator>
    std::tuple<int, int> operator()(Generator& generator, int row, int col)
    {
        // switch in between the supported kernels
        if (!use_anthropogenic_kernel_
            || !anthropogenic_kernel_.is_cell_eligible(row, col)
            || bernoulli_distribution(generator)) {
            return natural_kernel_(generator, row, col);
        }
        return anthropogenic_kernel_(generator, row, col);
    }
 
    static bool supports_kernel(const DispersalKernelType type)
    {
        if (std::is_same<NaturalKernelType, AnthropogenicKernelType>::value) {
            return NaturalKernelType::supports_kernel(type);
        }
        else {
            return NaturalKernelType::supports_kernel(type)
                   || AnthropogenicKernelType::supports_kernel(type);
        }
    }
};
 
}  // namespace pops
 
#endif  // POPS_NATURAL_ANTHROPOGENIC_KERNEL_HPP