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 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
 #pragma once
 
 #include <stdint.h>
 #include <cmath>
 #include <cstring>
 #include <limits>
 
 namespace onnxruntime_float16 {
 
 namespace detail {
 
 enum class endian {
 #if defined(_WIN32)
   little = 0,
   big = 1,
   native = little,
 #elif defined(__GNUC__) || defined(__clang__)
   little = __ORDER_LITTLE_ENDIAN__,
   big = __ORDER_BIG_ENDIAN__,
   native = __BYTE_ORDER__,
 #else
 #error onnxruntime_float16::detail::endian is not implemented in this environment.
 #endif
 };
 
 static_assert(
     endian::native == endian::little || endian::native == endian::big,
     "Only little-endian or big-endian native byte orders are supported.");
 
 }  // namespace detail
 
 /// <summary>
 /// Shared implementation between public and internal classes. CRTP pattern.
 /// </summary>
 template <class Derived>
 struct Float16Impl {
  protected:
   /// <summary>
   /// Converts from float to uint16_t float16 representation
   /// </summary>
   /// <param name="v"></param>
   /// <returns></returns>
   constexpr static uint16_t ToUint16Impl(float v) noexcept;
 
   /// <summary>
   /// Converts float16 to float
   /// </summary>
   /// <returns>float representation of float16 value</returns>
   float ToFloatImpl() const noexcept;
 
   /// <summary>
   /// Creates an instance that represents absolute value.
   /// </summary>
   /// <returns>Absolute value</returns>
   uint16_t AbsImpl() const noexcept {
     return static_cast<uint16_t>(val & ~kSignMask);
   }
 
   /// <summary>
   /// Creates a new instance with the sign flipped.
   /// </summary>
   /// <returns>Flipped sign instance</returns>
   uint16_t NegateImpl() const noexcept {
     return IsNaN() ? val : static_cast<uint16_t>(val ^ kSignMask);
   }
 
  public:
   // uint16_t special values
   static constexpr uint16_t kSignMask = 0x8000U;
   static constexpr uint16_t kBiasedExponentMask = 0x7C00U;
   static constexpr uint16_t kPositiveInfinityBits = 0x7C00U;
   static constexpr uint16_t kNegativeInfinityBits = 0xFC00U;
   static constexpr uint16_t kPositiveQNaNBits = 0x7E00U;
   static constexpr uint16_t kNegativeQNaNBits = 0xFE00U;
   static constexpr uint16_t kEpsilonBits = 0x4170U;
   static constexpr uint16_t kMinValueBits = 0xFBFFU;  // Minimum normal number
   static constexpr uint16_t kMaxValueBits = 0x7BFFU;  // Largest normal number
   static constexpr uint16_t kOneBits = 0x3C00U;
   static constexpr uint16_t kMinusOneBits = 0xBC00U;
 
   uint16_t val{0};
 
   Float16Impl() = default;
 
   /// <summary>
   /// Checks if the value is negative
   /// </summary>
   /// <returns>true if negative</returns>
   bool IsNegative() const noexcept {
     return static_cast<int16_t>(val) < 0;
   }
 
   /// <summary>
   /// Tests if the value is NaN
   /// </summary>
   /// <returns>true if NaN</returns>
   bool IsNaN() const noexcept {
     return AbsImpl() > kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value is finite
   /// </summary>
   /// <returns>true if finite</returns>
   bool IsFinite() const noexcept {
     return AbsImpl() < kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value represents positive infinity.
   /// </summary>
   /// <returns>true if positive infinity</returns>
   bool IsPositiveInfinity() const noexcept {
     return val == kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value represents negative infinity
   /// </summary>
   /// <returns>true if negative infinity</returns>
   bool IsNegativeInfinity() const noexcept {
     return val == kNegativeInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value is either positive or negative infinity.
   /// </summary>
   /// <returns>True if absolute value is infinity</returns>
   bool IsInfinity() const noexcept {
     return AbsImpl() == kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value is NaN or zero. Useful for comparisons.
   /// </summary>
   /// <returns>True if NaN or zero.</returns>
   bool IsNaNOrZero() const noexcept {
     auto abs = AbsImpl();
     return (abs == 0 || abs > kPositiveInfinityBits);
   }
 
   /// <summary>
   /// Tests if the value is normal (not zero, subnormal, infinite, or NaN).
   /// </summary>
   /// <returns>True if so</returns>
   bool IsNormal() const noexcept {
     auto abs = AbsImpl();
     return (abs < kPositiveInfinityBits)           // is finite
            && (abs != 0)                           // is not zero
            && ((abs & kBiasedExponentMask) != 0);  // is not subnormal (has a non-zero exponent)
   }
 
   /// <summary>
   /// Tests if the value is subnormal (denormal).
   /// </summary>
   /// <returns>True if so</returns>
   bool IsSubnormal() const noexcept {
     auto abs = AbsImpl();
     return (abs < kPositiveInfinityBits)           // is finite
            && (abs != 0)                           // is not zero
            && ((abs & kBiasedExponentMask) == 0);  // is subnormal (has a zero exponent)
   }
 
   /// <summary>
   /// Creates an instance that represents absolute value.
   /// </summary>
   /// <returns>Absolute value</returns>
   Derived Abs() const noexcept { return Derived::FromBits(AbsImpl()); }
 
   /// <summary>
   /// Creates a new instance with the sign flipped.
   /// </summary>
   /// <returns>Flipped sign instance</returns>
   Derived Negate() const noexcept { return Derived::FromBits(NegateImpl()); }
 
   /// <summary>
   /// IEEE defines that positive and negative zero are equal, this gives us a quick equality check
   /// for two values by or'ing the private bits together and stripping the sign. They are both zero,
   /// and therefore equivalent, if the resulting value is still zero.
   /// </summary>
   /// <param name="lhs">first value</param>
   /// <param name="rhs">second value</param>
   /// <returns>True if both arguments represent zero</returns>
   static bool AreZero(const Float16Impl& lhs, const Float16Impl& rhs) noexcept {
     return static_cast<uint16_t>((lhs.val | rhs.val) & ~kSignMask) == 0;
   }
 
   bool operator==(const Float16Impl& rhs) const noexcept {
     if (IsNaN() || rhs.IsNaN()) {
       // IEEE defines that NaN is not equal to anything, including itself.
       return false;
     }
     return val == rhs.val;
   }
 
   bool operator!=(const Float16Impl& rhs) const noexcept { return !(*this == rhs); }
 
   bool operator<(const Float16Impl& rhs) const noexcept {
     if (IsNaN() || rhs.IsNaN()) {
       // IEEE defines that NaN is unordered with respect to everything, including itself.
       return false;
     }
 
     const bool left_is_negative = IsNegative();
     if (left_is_negative != rhs.IsNegative()) {
       // When the signs of left and right differ, we know that left is less than right if it is
       // the negative value. The exception to this is if both values are zero, in which case IEEE
       // says they should be equal, even if the signs differ.
       return left_is_negative && !AreZero(*this, rhs);
     }
     return (val != rhs.val) && ((val < rhs.val) ^ left_is_negative);
   }
 };
 
 // The following Float16_t conversions are based on the code from
 // Eigen library.
 
 // The conversion routines are Copyright (c) Fabian Giesen, 2016.
 // The original license follows:
 //
 // Copyright (c) Fabian Giesen, 2016
 // All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted.
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 namespace detail {
 union float32_bits {
   unsigned int u;
   float f;
 };
 }  // namespace detail
 
 template <class Derived>
 inline constexpr uint16_t Float16Impl<Derived>::ToUint16Impl(float v) noexcept {
   detail::float32_bits f{};
   f.f = v;
 
   constexpr detail::float32_bits f32infty = {255 << 23};
   constexpr detail::float32_bits f16max = {(127 + 16) << 23};
   constexpr detail::float32_bits denorm_magic = {((127 - 15) + (23 - 10) + 1) << 23};
   constexpr unsigned int sign_mask = 0x80000000u;
   uint16_t val = static_cast<uint16_t>(0x0u);
 
   unsigned int sign = f.u & sign_mask;
   f.u ^= sign;
 
   // NOTE all the integer compares in this function can be safely
   // compiled into signed compares since all operands are below
   // 0x80000000. Important if you want fast straight SSE2 code
   // (since there's no unsigned PCMPGTD).
 
   if (f.u >= f16max.u) {                         // result is Inf or NaN (all exponent bits set)
     val = (f.u > f32infty.u) ? 0x7e00 : 0x7c00;  // NaN->qNaN and Inf->Inf
   } else {                                       // (De)normalized number or zero
     if (f.u < (113 << 23)) {                     // resulting FP16 is subnormal or zero
       // use a magic value to align our 10 mantissa bits at the bottom of
       // the float. as long as FP addition is round-to-nearest-even this
       // just works.
       f.f += denorm_magic.f;
 
       // and one integer subtract of the bias later, we have our final float!
       val = static_cast<uint16_t>(f.u - denorm_magic.u);
     } else {
       unsigned int mant_odd = (f.u >> 13) & 1;  // resulting mantissa is odd
 
       // update exponent, rounding bias part 1
       // Equivalent to `f.u += ((unsigned int)(15 - 127) << 23) + 0xfff`, but
       // without arithmetic overflow.
       f.u += 0xc8000fffU;
       // rounding bias part 2
       f.u += mant_odd;
       // take the bits!
       val = static_cast<uint16_t>(f.u >> 13);
     }
   }
 
   val |= static_cast<uint16_t>(sign >> 16);
   return val;
 }
 
 template <class Derived>
 inline float Float16Impl<Derived>::ToFloatImpl() const noexcept {
   constexpr detail::float32_bits magic = {113 << 23};
   constexpr unsigned int shifted_exp = 0x7c00 << 13;  // exponent mask after shift
   detail::float32_bits o{};
 
   o.u = (val & 0x7fff) << 13;            // exponent/mantissa bits
   unsigned int exp = shifted_exp & o.u;  // just the exponent
   o.u += (127 - 15) << 23;               // exponent adjust
 
   // handle exponent special cases
   if (exp == shifted_exp) {   // Inf/NaN?
     o.u += (128 - 16) << 23;  // extra exp adjust
   } else if (exp == 0) {      // Zero/Denormal?
     o.u += 1 << 23;           // extra exp adjust
     o.f -= magic.f;           // re-normalize
   }
 
   // Attempt to workaround the Internal Compiler Error on ARM64
   // for bitwise | operator, including std::bitset
 #if (defined _MSC_VER) && (defined _M_ARM || defined _M_ARM64 || defined _M_ARM64EC)
   if (IsNegative()) {
     return -o.f;
   }
 #else
   // original code:
   o.u |= (val & 0x8000U) << 16U;  // sign bit
 #endif
   return o.f;
 }
 
 /// Shared implementation between public and internal classes. CRTP pattern.
 template <class Derived>
 struct BFloat16Impl {
  protected:
   /// <summary>
   /// Converts from float to uint16_t float16 representation
   /// </summary>
   /// <param name="v"></param>
   /// <returns></returns>
   static uint16_t ToUint16Impl(float v) noexcept;
 
   /// <summary>
   /// Converts bfloat16 to float
   /// </summary>
   /// <returns>float representation of bfloat16 value</returns>
   float ToFloatImpl() const noexcept;
 
   /// <summary>
   /// Creates an instance that represents absolute value.
   /// </summary>
   /// <returns>Absolute value</returns>
   uint16_t AbsImpl() const noexcept {
     return static_cast<uint16_t>(val & ~kSignMask);
   }
 
   /// <summary>
   /// Creates a new instance with the sign flipped.
   /// </summary>
   /// <returns>Flipped sign instance</returns>
   uint16_t NegateImpl() const noexcept {
     return IsNaN() ? val : static_cast<uint16_t>(val ^ kSignMask);
   }
 
  public:
   // uint16_t special values
   static constexpr uint16_t kSignMask = 0x8000U;
   static constexpr uint16_t kBiasedExponentMask = 0x7F80U;
   static constexpr uint16_t kPositiveInfinityBits = 0x7F80U;
   static constexpr uint16_t kNegativeInfinityBits = 0xFF80U;
   static constexpr uint16_t kPositiveQNaNBits = 0x7FC1U;
   static constexpr uint16_t kNegativeQNaNBits = 0xFFC1U;
   static constexpr uint16_t kSignaling_NaNBits = 0x7F80U;
   static constexpr uint16_t kEpsilonBits = 0x0080U;
   static constexpr uint16_t kMinValueBits = 0xFF7FU;
   static constexpr uint16_t kMaxValueBits = 0x7F7FU;
   static constexpr uint16_t kRoundToNearest = 0x7FFFU;
   static constexpr uint16_t kOneBits = 0x3F80U;
   static constexpr uint16_t kMinusOneBits = 0xBF80U;
 
   uint16_t val{0};
 
   BFloat16Impl() = default;
 
   /// <summary>
   /// Checks if the value is negative
   /// </summary>
   /// <returns>true if negative</returns>
   bool IsNegative() const noexcept {
     return static_cast<int16_t>(val) < 0;
   }
 
   /// <summary>
   /// Tests if the value is NaN
   /// </summary>
   /// <returns>true if NaN</returns>
   bool IsNaN() const noexcept {
     return AbsImpl() > kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value is finite
   /// </summary>
   /// <returns>true if finite</returns>
   bool IsFinite() const noexcept {
     return AbsImpl() < kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value represents positive infinity.
   /// </summary>
   /// <returns>true if positive infinity</returns>
   bool IsPositiveInfinity() const noexcept {
     return val == kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value represents negative infinity
   /// </summary>
   /// <returns>true if negative infinity</returns>
   bool IsNegativeInfinity() const noexcept {
     return val == kNegativeInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value is either positive or negative infinity.
   /// </summary>
   /// <returns>True if absolute value is infinity</returns>
   bool IsInfinity() const noexcept {
     return AbsImpl() == kPositiveInfinityBits;
   }
 
   /// <summary>
   /// Tests if the value is NaN or zero. Useful for comparisons.
   /// </summary>
   /// <returns>True if NaN or zero.</returns>
   bool IsNaNOrZero() const noexcept {
     auto abs = AbsImpl();
     return (abs == 0 || abs > kPositiveInfinityBits);
   }
 
   /// <summary>
   /// Tests if the value is normal (not zero, subnormal, infinite, or NaN).
   /// </summary>
   /// <returns>True if so</returns>
   bool IsNormal() const noexcept {
     auto abs = AbsImpl();
     return (abs < kPositiveInfinityBits)           // is finite
            && (abs != 0)                           // is not zero
            && ((abs & kBiasedExponentMask) != 0);  // is not subnormal (has a non-zero exponent)
   }
 
   /// <summary>
   /// Tests if the value is subnormal (denormal).
   /// </summary>
   /// <returns>True if so</returns>
   bool IsSubnormal() const noexcept {
     auto abs = AbsImpl();
     return (abs < kPositiveInfinityBits)           // is finite
            && (abs != 0)                           // is not zero
            && ((abs & kBiasedExponentMask) == 0);  // is subnormal (has a zero exponent)
   }
 
   /// <summary>
   /// Creates an instance that represents absolute value.
   /// </summary>
   /// <returns>Absolute value</returns>
   Derived Abs() const noexcept { return Derived::FromBits(AbsImpl()); }
 
   /// <summary>
   /// Creates a new instance with the sign flipped.
   /// </summary>
   /// <returns>Flipped sign instance</returns>
   Derived Negate() const noexcept { return Derived::FromBits(NegateImpl()); }
 
   /// <summary>
   /// IEEE defines that positive and negative zero are equal, this gives us a quick equality check
   /// for two values by or'ing the private bits together and stripping the sign. They are both zero,
   /// and therefore equivalent, if the resulting value is still zero.
   /// </summary>
   /// <param name="lhs">first value</param>
   /// <param name="rhs">second value</param>
   /// <returns>True if both arguments represent zero</returns>
   static bool AreZero(const BFloat16Impl& lhs, const BFloat16Impl& rhs) noexcept {
     // IEEE defines that positive and negative zero are equal, this gives us a quick equality check
     // for two values by or'ing the private bits together and stripping the sign. They are both zero,
     // and therefore equivalent, if the resulting value is still zero.
     return static_cast<uint16_t>((lhs.val | rhs.val) & ~kSignMask) == 0;
   }
 };
 
 template <class Derived>
 inline uint16_t BFloat16Impl<Derived>::ToUint16Impl(float v) noexcept {
   uint16_t result;
   if (std::isnan(v)) {
     result = kPositiveQNaNBits;
   } else {
     auto get_msb_half = [](float fl) {
       uint16_t result;
 #ifdef __cpp_if_constexpr
       if constexpr (detail::endian::native == detail::endian::little) {
 #else
       if (detail::endian::native == detail::endian::little) {
 #endif
         std::memcpy(&result, reinterpret_cast<char*>(&fl) + sizeof(uint16_t), sizeof(uint16_t));
       } else {
         std::memcpy(&result, &fl, sizeof(uint16_t));
       }
       return result;
     };
 
     uint16_t upper_bits = get_msb_half(v);
     union {
       uint32_t U32;
       float F32;
     };
     F32 = v;
     U32 += (upper_bits & 1) + kRoundToNearest;
     result = get_msb_half(F32);
   }
   return result;
 }
 
 template <class Derived>
 inline float BFloat16Impl<Derived>::ToFloatImpl() const noexcept {
   if (IsNaN()) {
     return std::numeric_limits<float>::quiet_NaN();
   }
   float result;
   char* const first = reinterpret_cast<char*>(&result);
   char* const second = first + sizeof(uint16_t);
 #ifdef __cpp_if_constexpr
   if constexpr (detail::endian::native == detail::endian::little) {
 #else
   if (detail::endian::native == detail::endian::little) {
 #endif
     std::memset(first, 0, sizeof(uint16_t));
     std::memcpy(second, &val, sizeof(uint16_t));
   } else {
     std::memcpy(first, &val, sizeof(uint16_t));
     std::memset(second, 0, sizeof(uint16_t));
   }
   return result;
 }
 
 }  // namespace onnxruntime_float16

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