concatenation_layer.h

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// SPDX-License-Identifier: AGPL-3.0-only
// Copyright (C) 2026 Artificial Intelligence Techniques, S.L. and Roberto López González
 
#pragma once
 
#include "opennn/network/layers/layer.h"
#include "opennn/network/operators/operator.h"
 
namespace opennn
{
 
struct ConcatenationOperator : Operator
{
    vector<Index> input_channels;
 
    void forward_propagate(ForwardPropagation&, size_t, ForwardPropagationMode) override;
    void back_propagate(ForwardPropagation&, BackPropagation&, size_t) const override;
};
 
class Concatenation final : public Layer
{
public:
 
    Concatenation(const Shape& = {},
                  const vector<Index>& per_input_channels = {},
                  const string& = "concatenation_layer");
 
    Shape get_output_shape() const override;
 
    Index get_sources_number() const noexcept override { return ssize(concatenation.input_channels); }
 
    vector<TensorSpec> get_backward_specs(Index) const override;
 
    void set(const Shape&, const vector<Index>&, const string&);
    bool accepts_input_rank(Index rank) const override { return is_one_of(rank, 3); }
 
    void on_compute_dtype_changed() override
    {
        throw_if(get_compute_dtype() != Type::FP32,
                 "{} layer supports FP32 activations only; compile the network with Type::FP32.",
                 get_name());
    }
 
    void from_JSON(const JsonDocument&) override;
    void load_state_from_JSON(const JsonDocument&) override;
 
    void read_JSON_body(const Json*) override;
    void write_JSON_body(JsonWriter&) const override;
 
private:
 
    const Json* legacy_body(const JsonDocument&) const;
 
    ConcatenationOperator concatenation;
};
 
}