Program Listing for File Device.h

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#pragma once

#include <c10/core/DeviceType.h>
#include <c10/macros/Export.h>
#include <c10/util/Exception.h>

#include <cstddef>
#include <cstdint>
#include <functional>
#include <iosfwd>
#include <string>

namespace c10 {

using DeviceIndex = int8_t;

struct C10_API Device final {
  using Type = DeviceType;

  /* implicit */ Device(DeviceType type, DeviceIndex index = -1)
      : type_(type), index_(index) {
    validate();
  }

  /* implicit */ Device(const std::string& device_string);

  bool operator==(const Device& other) const noexcept {
    return this->type_ == other.type_ && this->index_ == other.index_;
  }

  bool operator!=(const Device& other) const noexcept {
    return !(*this == other);
  }

  void set_index(DeviceIndex index) {
    index_ = index;
  }

  DeviceType type() const noexcept {
    return type_;
  }

  DeviceIndex index() const noexcept {
    return index_;
  }

  bool has_index() const noexcept {
    return index_ != -1;
  }

  bool is_cuda() const noexcept {
    return type_ == DeviceType::CUDA;
  }

  bool is_privateuseone() const noexcept {
    return type_ == DeviceType::PrivateUse1;
  }

  bool is_mps() const noexcept {
    return type_ == DeviceType::MPS;
  }

  bool is_hip() const noexcept {
    return type_ == DeviceType::HIP;
  }

  bool is_ve() const noexcept {
    return type_ == DeviceType::VE;
  }

  bool is_xpu() const noexcept {
    return type_ == DeviceType::XPU;
  }

  bool is_ipu() const noexcept {
    return type_ == DeviceType::IPU;
  }

  bool is_xla() const noexcept {
    return type_ == DeviceType::XLA;
  }

  bool is_mtia() const noexcept {
    return type_ == DeviceType::MTIA;
  }

  bool is_hpu() const noexcept {
    return type_ == DeviceType::HPU;
  }

  bool is_lazy() const noexcept {
    return type_ == DeviceType::Lazy;
  }

  bool is_vulkan() const noexcept {
    return type_ == DeviceType::Vulkan;
  }

  bool is_metal() const noexcept {
    return type_ == DeviceType::Metal;
  }

  bool is_maia() const noexcept {
    return type_ == DeviceType::MAIA;
  }

  bool is_meta() const noexcept {
    return type_ == DeviceType::Meta;
  }

  bool is_cpu() const noexcept {
    return type_ == DeviceType::CPU;
  }

  bool supports_as_strided() const noexcept {
    return type_ != DeviceType::IPU && type_ != DeviceType::XLA &&
        type_ != DeviceType::Lazy && type_ != DeviceType::MTIA;
  }

  std::string str() const;

 private:
  DeviceType type_;
  DeviceIndex index_ = -1;
  void validate() {
    // Removing these checks in release builds noticeably improves
    // performance in micro-benchmarks.
    // This is safe to do, because backends that use the DeviceIndex
    // have a later check when we actually try to switch to that device.
    TORCH_INTERNAL_ASSERT_DEBUG_ONLY(
        index_ >= -1,
        "Device index must be -1 or non-negative, got ",
        static_cast<int>(index_));
    TORCH_INTERNAL_ASSERT_DEBUG_ONLY(
        !is_cpu() || index_ <= 0,
        "CPU device index must be -1 or zero, got ",
        static_cast<int>(index_));
  }
};

C10_API std::ostream& operator<<(std::ostream& stream, const Device& device);

} // namespace c10

namespace std {
template <>
struct hash<c10::Device> {
  size_t operator()(c10::Device d) const noexcept {
    // Are you here because this static assert failed?  Make sure you ensure
    // that the bitmasking code below is updated accordingly!
    static_assert(sizeof(c10::DeviceType) == 1, "DeviceType is not 8-bit");
    static_assert(sizeof(c10::DeviceIndex) == 1, "DeviceIndex is not 8-bit");
    // Note [Hazard when concatenating signed integers]
    // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    // We must first convert to a same-sized unsigned type, before promoting to
    // the result type, to prevent sign extension when any of the values is -1.
    // If sign extension occurs, you'll clobber all of the values in the MSB
    // half of the resulting integer.
    //
    // Technically, by C/C++ integer promotion rules, we only need one of the
    // uint32_t casts to the result type, but we put in both for explicitness's
    // sake.
    uint32_t bits = static_cast<uint32_t>(static_cast<uint8_t>(d.type()))
            << 16 |
        static_cast<uint32_t>(static_cast<uint8_t>(d.index()));
    return std::hash<uint32_t>{}(bits);
  }
};
} // namespace std