create_diff_variable.h

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/*
 * Copyright 2021 MusicScience37 (Kenta Kabashima)
 *
 * 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
 
#include <Eigen/Core>
 
#include "num_collect/auto_diff/backward/variable.h"
#include "num_collect/base/concepts/real_scalar.h"
#include "num_collect/base/concepts/real_scalar_dense_vector.h"
#include "num_collect/base/exception.h"
#include "num_collect/base/index_type.h"
#include "num_collect/base/precondition.h"
#include "num_collect/logging/logging_macros.h"
#include "num_collect/util/assert.h"
 
namespace num_collect::auto_diff::backward {
 
template <base::concepts::real_scalar Scalar>
[[nodiscard]] inline auto create_diff_variable(const Scalar& value)
    -> variable<Scalar> {
    return variable<Scalar>(value, variable_tag());
}
 
template <base::concepts::real_scalar_dense_vector ValueVector>
using variable_vector_type =
    Eigen::Matrix<variable<typename ValueVector::Scalar>,
        ValueVector::RowsAtCompileTime, 1, Eigen::ColMajor,
        ValueVector::MaxRowsAtCompileTime, 1>;
 
namespace impl {
 
template <typename ValueVector>
class create_diff_variable_vector_functor {
public:
    using scalar_type = typename ValueVector::Scalar;
 
    using variable_type = variable<scalar_type>;
 
    using result_type =
        Eigen::Matrix<variable_type, ValueVector::RowsAtCompileTime, 1,
            Eigen::ColMajor, ValueVector::MaxRowsAtCompileTime, 1>;
 
    explicit create_diff_variable_vector_functor(const ValueVector& value_vec)
        : value_vec_(value_vec) {}
 
    [[nodiscard]] auto operator()(index_type row, index_type col) const
        -> variable_type {
        NUM_COLLECT_DEBUG_ASSERT(col == 0);
        return create_diff_variable<scalar_type>(value_vec_(row, col));
    }
 
private:
    const ValueVector& value_vec_;
};
 
}  // namespace impl
 
template <base::concepts::real_scalar_dense_vector ValueVector>
[[nodiscard]] inline auto create_diff_variable_vector(
    const Eigen::MatrixBase<ValueVector>& value_vec)
    -> Eigen::CwiseNullaryOp<
        impl::create_diff_variable_vector_functor<ValueVector>,
        typename impl::create_diff_variable_vector_functor<
            ValueVector>::result_type> {
    NUM_COLLECT_PRECONDITION(value_vec.cols() == 1,
        "create_diff_variable_vector function requires a vector as the "
        "argument.");
 
    using result_type = typename impl::create_diff_variable_vector_functor<
        ValueVector>::result_type;
    return result_type::NullaryExpr(value_vec.rows(), 1,
        impl::create_diff_variable_vector_functor<ValueVector>(
            value_vec.derived()));
}
 
}  // namespace num_collect::auto_diff::backward