TensorList.h

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// -                        Open3D: www.open3d.org                            -
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// The MIT License (MIT)
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// Copyright (c) 2018 www.open3d.org
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#pragma once

#include <cstddef>
#include <memory>
#include <string>

#include "open3d/core/Blob.h"
#include "open3d/core/Device.h"
#include "open3d/core/Dtype.h"
#include "open3d/core/ShapeUtil.h"
#include "open3d/core/SizeVector.h"
#include "open3d/core/Tensor.h"
#include "open3d/core/TensorKey.h"

namespace open3d {
namespace core {

class TensorList {
public:
    TensorList() : TensorList(SizeVector({}), Dtype::Float32) {}

    TensorList(const SizeVector& element_shape,
               Dtype dtype,
               const Device& device = Device("CPU:0"))
        : element_shape_(element_shape),
          size_(0),
          reserved_size_(ComputeReserveSize(0)),
          internal_tensor_(shape_util::Concat({reserved_size_}, element_shape_),
                           dtype,
                           device) {}

    TensorList(const std::vector<Tensor>& tensors)
        : TensorList(tensors.begin(), tensors.end()) {}

    TensorList(int64_t size,
               const SizeVector& element_shape,
               Dtype dtype,
               const Device& device = Device("CPU:0"))
        : element_shape_(element_shape),
          size_(size),
          reserved_size_(ComputeReserveSize(size)),
          internal_tensor_(shape_util::Concat({reserved_size_}, element_shape_),
                           dtype,
                           device) {}

    TensorList(const std::initializer_list<Tensor>& tensors)
        : TensorList(tensors.begin(), tensors.end()) {}

    template <class InputIterator>
    TensorList(InputIterator begin, InputIterator end) {
        int64_t size = std::distance(begin, end);
        if (size == 0) {
            utility::LogError(
                    "Empty input tensors cannot initialize a tensorlist.");
        }

        // Set size_ and reserved_size_.
        size_ = size;
        reserved_size_ = ComputeReserveSize(size_);

        // Check shape consistency and set element_shape_.
        element_shape_ = begin->GetShape();
        std::for_each(begin, end, [&](const Tensor& tensor) -> void {
            if (tensor.GetShape() != element_shape_) {
                utility::LogError(
                        "Tensors must have the same shape {}, but got {}.",
                        element_shape_, tensor.GetShape());
            }
        });

        // Check dtype consistency.
        Dtype dtype = begin->GetDtype();
        std::for_each(begin, end, [&](const Tensor& tensor) -> void {
            if (tensor.GetDtype() != dtype) {
                utility::LogError(
                        "Tensors must have the same dtype {}, but got {}.",
                        dtype.ToString(), tensor.GetDtype().ToString());
            }
        });

        // Check device consistency.
        Device device = begin->GetDevice();
        std::for_each(begin, end, [&](const Tensor& tensor) -> void {
            if (tensor.GetDevice() != device) {
                utility::LogError(
                        "Tensors must have the same device {}, but got {}.",
                        device.ToString(), tensor.GetDevice().ToString());
            }
        });

        // Construct internal tensor.
        internal_tensor_ =
                Tensor(shape_util::Concat({reserved_size_}, element_shape_),
                       dtype, device);
        size_t i = 0;
        for (auto iter = begin; iter != end; ++iter, ++i) {
            internal_tensor_[i] = *iter;
        }
    }

    static TensorList FromTensor(const Tensor& tensor, bool inplace = false);

    TensorList(const TensorList& other) = default;

    TensorList(TensorList&& other) = default;

    TensorList& operator=(const TensorList& other) & = default;

    TensorList& operator=(TensorList&& other) & = default;

    void CopyFrom(const TensorList& other);

    void ShallowCopyFrom(const TensorList& other);

    TensorList Copy() const;

    Tensor AsTensor() const;

    void Resize(int64_t new_size);

    void PushBack(const Tensor& tensor);

    void Extend(const TensorList& other);

    static TensorList Concatenate(const TensorList& a, const TensorList& b);

    TensorList operator+(const TensorList& other) const {
        return Concatenate(*this, other);
    }

    TensorList& operator+=(const TensorList& other) {
        Extend(other);
        return *this;
    }

    Tensor operator[](int64_t index) const;

    void Clear();

    std::string ToString() const;

    SizeVector GetElementShape() const { return element_shape_; }

    void AssertElementShape(const SizeVector& expected_element_shape) const {
        if (expected_element_shape != element_shape_) {
            utility::LogError(
                    "TensorList has element shape {}, but is expected to have "
                    "element shape {}.",
                    element_shape_, expected_element_shape);
        }
    }

    void AssertDevice(const Device& expected_device) const {
        if (GetDevice() != expected_device) {
            utility::LogError(
                    "TensorList has device {}, but is expected to be {}.",
                    GetDevice().ToString(), expected_device.ToString());
        }
    }

    Device GetDevice() const { return internal_tensor_.GetDevice(); }

    Dtype GetDtype() const { return internal_tensor_.GetDtype(); }

    int64_t GetSize() const { return size_; }

    int64_t GetReservedSize() const { return reserved_size_; }

    const Tensor& GetInternalTensor() const { return internal_tensor_; }

    bool IsResizable() const { return is_resizable_; }

protected:
    TensorList(const SizeVector element_shape,
               int64_t size,
               int64_t reserved_size,
               const Tensor& internal_tensor,
               bool is_resizable)
        : element_shape_(element_shape),
          size_(size),
          reserved_size_(reserved_size),
          internal_tensor_(internal_tensor),
          is_resizable_(is_resizable) {}

    void ResizeWithExpand(int64_t new_size);

    static int64_t ComputeReserveSize(int64_t size);

protected:
    SizeVector element_shape_;

    int64_t size_ = 0;

    int64_t reserved_size_ = 0;

    Tensor internal_tensor_;

    bool is_resizable_ = true;
};
}  // namespace core
}  // namespace open3d