/home/docs/checkouts/readthedocs.org/user_builds/advanced-micro-devices-hip/checkouts/docs-5.0.2/include/hip/hip_bfloat16.h Source File

/home/docs/checkouts/readthedocs.org/user_builds/advanced-micro-devices-hip/checkouts/docs-5.0.2/include/hip/hip_bfloat16.h Source File#

HIP Runtime API Reference: /home/docs/checkouts/readthedocs.org/user_builds/advanced-micro-devices-hip/checkouts/docs-5.0.2/include/hip/hip_bfloat16.h Source File
Go to the documentation of this file.
 
#ifndef _HIP_BFLOAT16_H_
#define _HIP_BFLOAT16_H_
 
#if __cplusplus < 201103L || !defined(__HIPCC__)
 
// If this is a C compiler, C++ compiler below C++11, or a host-only compiler, we only
// include a minimal definition of hip_bfloat16
 
#include <stdint.h>
typedef struct
{
    uint16_t data;
} hip_bfloat16;
 
#else // __cplusplus < 201103L || !defined(__HIPCC__)
 
#include <cmath>
#include <cstddef>
#include <cstdint>
#include <hip/hip_runtime.h>
#include <ostream>
#include <type_traits>
 
struct hip_bfloat16
{
    uint16_t data;
 
    enum truncate_t
    {
        truncate
    };
 
    __host__ __device__ hip_bfloat16() = default;
 
    // round upper 16 bits of IEEE float to convert to bfloat16
    explicit __host__ __device__ hip_bfloat16(float f)
        : data(float_to_bfloat16(f))
    {
    }
 
    explicit __host__ __device__ hip_bfloat16(float f, truncate_t)
        : data(truncate_float_to_bfloat16(f))
    {
    }
 
    // zero extend lower 16 bits of bfloat16 to convert to IEEE float
    __host__ __device__ operator float() const
    {
        union
        {
            uint32_t int32;
            float    fp32;
        } u = {uint32_t(data) << 16};
        return u.fp32;
    }
 
    static  __host__ __device__ hip_bfloat16 round_to_bfloat16(float f)
    {
        hip_bfloat16 output;
        output.data = float_to_bfloat16(f);
        return output;
    }
 
    static  __host__ __device__ hip_bfloat16 round_to_bfloat16(float f, truncate_t)
    {
        hip_bfloat16 output;
        output.data = truncate_float_to_bfloat16(f);
        return output;
    }
 
private:
    static __host__ __device__ uint16_t float_to_bfloat16(float f)
    {
        union
        {
            float    fp32;
            uint32_t int32;
        } u = {f};
        if(~u.int32 & 0x7f800000)
        {
            // When the exponent bits are not all 1s, then the value is zero, normal,
            // or subnormal. We round the bfloat16 mantissa up by adding 0x7FFF, plus
            // 1 if the least significant bit of the bfloat16 mantissa is 1 (odd).
            // This causes the bfloat16's mantissa to be incremented by 1 if the 16
            // least significant bits of the float mantissa are greater than 0x8000,
            // or if they are equal to 0x8000 and the least significant bit of the
            // bfloat16 mantissa is 1 (odd). This causes it to be rounded to even when
            // the lower 16 bits are exactly 0x8000. If the bfloat16 mantissa already
            // has the value 0x7f, then incrementing it causes it to become 0x00 and
            // the exponent is incremented by one, which is the next higher FP value
            // to the unrounded bfloat16 value. When the bfloat16 value is subnormal
            // with an exponent of 0x00 and a mantissa of 0x7F, it may be rounded up
            // to a normal value with an exponent of 0x01 and a mantissa of 0x00.
            // When the bfloat16 value has an exponent of 0xFE and a mantissa of 0x7F,
            // incrementing it causes it to become an exponent of 0xFF and a mantissa
            // of 0x00, which is Inf, the next higher value to the unrounded value.
            u.int32 += 0x7fff + ((u.int32 >> 16) & 1); // Round to nearest, round to even
        }
        else if(u.int32 & 0xffff)
        {
            // When all of the exponent bits are 1, the value is Inf or NaN.
            // Inf is indicated by a zero mantissa. NaN is indicated by any nonzero
            // mantissa bit. Quiet NaN is indicated by the most significant mantissa
            // bit being 1. Signaling NaN is indicated by the most significant
            // mantissa bit being 0 but some other bit(s) being 1. If any of the
            // lower 16 bits of the mantissa are 1, we set the least significant bit
            // of the bfloat16 mantissa, in order to preserve signaling NaN in case
            // the bloat16's mantissa bits are all 0.
            u.int32 |= 0x10000; // Preserve signaling NaN
        }
        return uint16_t(u.int32 >> 16);
    }
 
    // Truncate instead of rounding, preserving SNaN
    static __host__ __device__ uint16_t truncate_float_to_bfloat16(float f)
    {
        union
        {
            float    fp32;
            uint32_t int32;
        } u = {f};
        return uint16_t(u.int32 >> 16) | (!(~u.int32 & 0x7f800000) && (u.int32 & 0xffff));
    }
};
 
typedef struct
{
    uint16_t data;
} hip_bfloat16_public;
 
static_assert(std::is_standard_layout<hip_bfloat16>{},
              "hip_bfloat16 is not a standard layout type, and thus is "
              "incompatible with C.");
 
static_assert(std::is_trivial<hip_bfloat16>{},
              "hip_bfloat16 is not a trivial type, and thus is "
              "incompatible with C.");
 
static_assert(sizeof(hip_bfloat16) == sizeof(hip_bfloat16_public)
                  && offsetof(hip_bfloat16, data) == offsetof(hip_bfloat16_public, data),
              "internal hip_bfloat16 does not match public hip_bfloat16");
 
inline std::ostream& operator<<(std::ostream& os, const hip_bfloat16& bf16)
{
    return os << float(bf16);
}
inline __host__ __device__ hip_bfloat16 operator+(hip_bfloat16 a)
{
    return a;
}
inline __host__ __device__ hip_bfloat16 operator-(hip_bfloat16 a)
{
    a.data ^= 0x8000;
    return a;
}
inline __host__ __device__ hip_bfloat16 operator+(hip_bfloat16 a, hip_bfloat16 b)
{
    return hip_bfloat16(float(a) + float(b));
}
inline __host__ __device__ hip_bfloat16 operator-(hip_bfloat16 a, hip_bfloat16 b)
{
    return hip_bfloat16(float(a) - float(b));
}
inline __host__ __device__ hip_bfloat16 operator*(hip_bfloat16 a, hip_bfloat16 b)
{
    return hip_bfloat16(float(a) * float(b));
}
inline __host__ __device__ hip_bfloat16 operator/(hip_bfloat16 a, hip_bfloat16 b)
{
    return hip_bfloat16(float(a) / float(b));
}
inline __host__ __device__ bool operator<(hip_bfloat16 a, hip_bfloat16 b)
{
    return float(a) < float(b);
}
inline __host__ __device__ bool operator==(hip_bfloat16 a, hip_bfloat16 b)
{
    return float(a) == float(b);
}
inline __host__ __device__ bool operator>(hip_bfloat16 a, hip_bfloat16 b)
{
    return b < a;
}
inline __host__ __device__ bool operator<=(hip_bfloat16 a, hip_bfloat16 b)
{
    return !(a > b);
}
inline __host__ __device__ bool operator!=(hip_bfloat16 a, hip_bfloat16 b)
{
    return !(a == b);
}
inline __host__ __device__ bool operator>=(hip_bfloat16 a, hip_bfloat16 b)
{
    return !(a < b);
}
inline __host__ __device__ hip_bfloat16& operator+=(hip_bfloat16& a, hip_bfloat16 b)
{
    return a = a + b;
}
inline __host__ __device__ hip_bfloat16& operator-=(hip_bfloat16& a, hip_bfloat16 b)
{
    return a = a - b;
}
inline __host__ __device__ hip_bfloat16& operator*=(hip_bfloat16& a, hip_bfloat16 b)
{
    return a = a * b;
}
inline __host__ __device__ hip_bfloat16& operator/=(hip_bfloat16& a, hip_bfloat16 b)
{
    return a = a / b;
}
inline __host__ __device__ hip_bfloat16& operator++(hip_bfloat16& a)
{
    return a += hip_bfloat16(1.0f);
}
inline __host__ __device__ hip_bfloat16& operator--(hip_bfloat16& a)
{
    return a -= hip_bfloat16(1.0f);
}
inline __host__ __device__ hip_bfloat16 operator++(hip_bfloat16& a, int)
{
    hip_bfloat16 orig = a;
    ++a;
    return orig;
}
inline __host__ __device__ hip_bfloat16 operator--(hip_bfloat16& a, int)
{
    hip_bfloat16 orig = a;
    --a;
    return orig;
}
 
namespace std
{
    constexpr __host__ __device__ bool isinf(hip_bfloat16 a)
    {
        return !(~a.data & 0x7f80) && !(a.data & 0x7f);
    }
    constexpr __host__ __device__ bool isnan(hip_bfloat16 a)
    {
        return !(~a.data & 0x7f80) && +(a.data & 0x7f);
    }
    constexpr __host__ __device__ bool iszero(hip_bfloat16 a)
    {
        return !(a.data & 0x7fff);
    }
}
 
#endif // __cplusplus < 201103L || !defined(__HIPCC__)
 
#endif // _HIP_BFLOAT16_H_