Random/gamma.hpp

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#pragma once
 
#include <algorithm>
#include <random>
#include <string>
 
#include "NumCpp/Core/Internal/Error.hpp"
#include "NumCpp/Core/Internal/StaticAsserts.hpp"
#include "NumCpp/Core/Shape.hpp"
#include "NumCpp/NdArray.hpp"
#include "NumCpp/Random/generator.hpp"
 
namespace nc::random
{
    namespace detail
    {
        //============================================================================
        // Method Description:
        template<typename dtype, typename GeneratorType = std::mt19937>
        dtype gamma(GeneratorType& generator, dtype inGammaShape, dtype inScaleValue = 1)
        {
            STATIC_ASSERT_ARITHMETIC(dtype);
 
            if (inGammaShape <= 0)
            {
                THROW_INVALID_ARGUMENT_ERROR("input gamma shape should be greater than zero.");
            }
 
            if (inScaleValue <= 0)
            {
                THROW_INVALID_ARGUMENT_ERROR("input scale should be greater than zero.");
            }
 
            std::gamma_distribution<dtype> dist(inGammaShape, inScaleValue);
            return dist(generator);
        }
 
        //============================================================================
        // Method Description:
        template<typename dtype, typename GeneratorType = std::mt19937>
        NdArray<dtype> gamma(GeneratorType& generator, const Shape& inShape, dtype inGammaShape, dtype inScaleValue = 1)
        {
            STATIC_ASSERT_ARITHMETIC(dtype);
 
            if (inGammaShape <= 0)
            {
                THROW_INVALID_ARGUMENT_ERROR("input gamma shape should be greater than zero.");
            }
 
            if (inScaleValue <= 0)
            {
                THROW_INVALID_ARGUMENT_ERROR("input scale should be greater than zero.");
            }
 
            NdArray<dtype> returnArray(inShape);
 
            std::gamma_distribution<dtype> dist(inGammaShape, inScaleValue);
 
            std::for_each(returnArray.begin(),
                          returnArray.end(),
                          [&generator, &dist](dtype& value) -> void { value = dist(generator); });
 
            return returnArray;
        }
    } // namespace detail
 
    //============================================================================
    // Method Description:
    template<typename dtype>
    dtype gamma(dtype inGammaShape, dtype inScaleValue = 1)
    {
        return detail::gamma(generator_, inGammaShape, inScaleValue);
    }
 
    //============================================================================
    // Method Description:
    template<typename dtype>
    NdArray<dtype> gamma(const Shape& inShape, dtype inGammaShape, dtype inScaleValue = 1)
    {
        return detail::gamma(generator_, inShape, inGammaShape, inScaleValue);
    }
} // namespace nc::random