#pragma once
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// Defines the bloat16 type (brain floating-point). This representation uses
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// 1 bit for the sign, 8 bits for the exponent and 7 bits for the mantissa.
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#include <c10/macros/Macros.h>
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#include <cmath>
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#include <cstring>
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namespace c10 {
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namespace detail {
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inline C10_HOST_DEVICE float f32_from_bits(uint16_t src) {
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float res = 0;
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uint32_t tmp = src;
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tmp <<= 16;
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#ifdef __HIP_PLATFORM_HCC__
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float* tempRes;
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// We should be using memcpy in order to respect the strict aliasing rule
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// but it fails in the HIP environment.
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tempRes = reinterpret_cast<float*>(&tmp);
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res = *tempRes;
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#else
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std::memcpy(&res, &tmp, sizeof(tmp));
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#endif
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return res;
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}
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inline C10_HOST_DEVICE uint16_t bits_from_f32(float src) {
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uint32_t res = 0;
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#ifdef __HIP_PLATFORM_HCC__
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// We should be using memcpy in order to respect the strict aliasing rule
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// but it fails in the HIP environment.
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uint32_t* tempRes = reinterpret_cast<uint32_t*>(&src);
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res = *tempRes;
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#else
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std::memcpy(&res, &src, sizeof(res));
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#endif
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return res >> 16;
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}
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inline C10_HOST_DEVICE uint16_t round_to_nearest_even(float src) {
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if (std::isnan(src)) {
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return 0x7FC0;
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} else {
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union {
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uint32_t U32;
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float F32;
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};
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F32 = src;
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uint32_t rounding_bias = ((U32 >> 16) & 1) + 0x7FFF;
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return static_cast<uint16_t>((U32 + rounding_bias) >> 16);
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}
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}
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} // namespace detail
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struct alignas(2) BFloat16 {
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uint16_t x;
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// HIP wants __host__ __device__ tag, CUDA does not
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#ifdef __HIP_PLATFORM_HCC__
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C10_HOST_DEVICE BFloat16() = default;
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#else
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BFloat16() = default;
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#endif
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struct from_bits_t {};
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static constexpr from_bits_t from_bits() {
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return from_bits_t();
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}
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constexpr C10_HOST_DEVICE BFloat16(unsigned short bits, from_bits_t) : x(bits){};
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inline C10_HOST_DEVICE BFloat16(float value);
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inline C10_HOST_DEVICE operator float() const;
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};
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} // namespace c10
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#include <c10/util/BFloat16-inl.h>
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