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Added extern for CXX support . #21

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45 changes: 28 additions & 17 deletions bf16.h
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Original file line number Diff line number Diff line change
@@ -1,7 +1,14 @@
#ifndef BF16_h
#define BF16_h

#ifdef __cplusplus

#include <stdint.h>

extern "C" {

#endif

/**
* Converts brain16 to float32.
*
Expand Down Expand Up @@ -42,29 +49,33 @@
* @see IEEE 754-2008
*/
static inline float from_brain(uint16_t h) {
union {
float f;
uint32_t i;
} u;
u.i = (uint32_t)h << 16;
return u.f;
union {
float f;
uint32_t i;
} u;
u.i = (uint32_t)h << 16;
return u.f;
}

/**
* Converts float32 to brain16.
*/
static inline uint16_t to_brain(float s) {
uint16_t h;
union {
float f;
uint32_t i;
} u;
u.f = s;
if ((u.i & 0x7fffffff) > 0x7f800000) { /* nan */
h = (u.i >> 16) | 64; /* force to quiet */
return h;
}
return (u.i + (0x7fff + ((u.i >> 16) & 1))) >> 16;
uint16_t h;
union {
float f;
uint32_t i;
} u;
u.f = s;
if ((u.i & 0x7fffffff) > 0x7f800000) { /* nan */
h = (u.i >> 16) | 64; /* force to quiet */
return h;
}
return (u.i + (0x7fff + ((u.i >> 16) & 1))) >> 16;
}

#ifdef __cplusplus
}
#endif

#endif
110 changes: 58 additions & 52 deletions fp16.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,83 +8,89 @@
*
* The original code is MIT licensed. */

#include <stdint.h>
#include <math.h>
#include <stdint.h>

static inline float fp32_from_bits(uint32_t w) {
union {
uint32_t as_bits;
float as_value;
} fp32;
fp32.as_bits = w;
return fp32.as_value;
union {
uint32_t as_bits;
float as_value;
} fp32;
fp32.as_bits = w;
return fp32.as_value;
}

static inline uint32_t fp32_to_bits(float f) {
union {
float as_value;
uint32_t as_bits;
} fp32;
fp32.as_value = f;
return fp32.as_bits;
union {
float as_value;
uint32_t as_bits;
} fp32;
fp32.as_value = f;
return fp32.as_bits;
}

float from_half(uint16_t h) {
const uint32_t w = (uint32_t) h << 16;
const uint32_t sign = w & UINT32_C(0x80000000);
const uint32_t two_w = w + w;
const uint32_t w = (uint32_t)h << 16;
const uint32_t sign = w & UINT32_C(0x80000000);
const uint32_t two_w = w + w;

const uint32_t exp_offset = UINT32_C(0xE0) << 23;
#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) || defined(__GNUC__) && !defined(__STRICT_ANSI__)
const float exp_scale = 0x1.0p-112f;
const uint32_t exp_offset = UINT32_C(0xE0) << 23;
#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) || \
defined(__GNUC__) && !defined(__STRICT_ANSI__)
const float exp_scale = 0x1.0p-112f;
#else
const float exp_scale = fp32_from_bits(UINT32_C(0x7800000));
const float exp_scale = fp32_from_bits(UINT32_C(0x7800000));
#endif
const float normalized_value = fp32_from_bits((two_w >> 4) + exp_offset) * exp_scale;
const float normalized_value =
fp32_from_bits((two_w >> 4) + exp_offset) * exp_scale;

const uint32_t magic_mask = UINT32_C(126) << 23;
const float magic_bias = 0.5f;
const float denormalized_value = fp32_from_bits((two_w >> 17) | magic_mask) - magic_bias;
const uint32_t magic_mask = UINT32_C(126) << 23;
const float magic_bias = 0.5f;
const float denormalized_value =
fp32_from_bits((two_w >> 17) | magic_mask) - magic_bias;

const uint32_t denormalized_cutoff = UINT32_C(1) << 27;
const uint32_t result = sign |
(two_w < denormalized_cutoff ? fp32_to_bits(denormalized_value) : fp32_to_bits(normalized_value));
return fp32_from_bits(result);
const uint32_t denormalized_cutoff = UINT32_C(1) << 27;
const uint32_t result =
sign | (two_w < denormalized_cutoff ? fp32_to_bits(denormalized_value)
: fp32_to_bits(normalized_value));
return fp32_from_bits(result);
}

uint16_t to_half(float f) {
#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) || defined(__GNUC__) && !defined(__STRICT_ANSI__)
const float scale_to_inf = 0x1.0p+112f;
const float scale_to_zero = 0x1.0p-110f;
#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) || \
defined(__GNUC__) && !defined(__STRICT_ANSI__)
const float scale_to_inf = 0x1.0p+112f;
const float scale_to_zero = 0x1.0p-110f;
#else
const float scale_to_inf = fp32_from_bits(UINT32_C(0x77800000));
const float scale_to_zero = fp32_from_bits(UINT32_C(0x08800000));
const float scale_to_inf = fp32_from_bits(UINT32_C(0x77800000));
const float scale_to_zero = fp32_from_bits(UINT32_C(0x08800000));
#endif
float base = (fabsf(f) * scale_to_inf) * scale_to_zero;
float base = (fabsf(f) * scale_to_inf) * scale_to_zero;

const uint32_t w = fp32_to_bits(f);
const uint32_t shl1_w = w + w;
const uint32_t sign = w & UINT32_C(0x80000000);
uint32_t bias = shl1_w & UINT32_C(0xFF000000);
if (bias < UINT32_C(0x71000000)) {
bias = UINT32_C(0x71000000);
}
const uint32_t w = fp32_to_bits(f);
const uint32_t shl1_w = w + w;
const uint32_t sign = w & UINT32_C(0x80000000);
uint32_t bias = shl1_w & UINT32_C(0xFF000000);
if (bias < UINT32_C(0x71000000)) {
bias = UINT32_C(0x71000000);
}

base = fp32_from_bits((bias >> 1) + UINT32_C(0x07800000)) + base;
const uint32_t bits = fp32_to_bits(base);
const uint32_t exp_bits = (bits >> 13) & UINT32_C(0x00007C00);
const uint32_t mantissa_bits = bits & UINT32_C(0x00000FFF);
const uint32_t nonsign = exp_bits + mantissa_bits;
return (sign >> 16) | (shl1_w > UINT32_C(0xFF000000) ? UINT16_C(0x7E00) : nonsign);
base = fp32_from_bits((bias >> 1) + UINT32_C(0x07800000)) + base;
const uint32_t bits = fp32_to_bits(base);
const uint32_t exp_bits = (bits >> 13) & UINT32_C(0x00007C00);
const uint32_t mantissa_bits = bits & UINT32_C(0x00000FFF);
const uint32_t nonsign = exp_bits + mantissa_bits;
return (sign >> 16) |
(shl1_w > UINT32_C(0xFF000000) ? UINT16_C(0x7E00) : nonsign);
}

#ifdef TEST_MAIN
#include <stdio.h>
int main(void) {
float f = 1.2345;
uint16_t half = to_half(f);
float f2 = from_half(half);
printf("%f %f\n", f, f2);
return 0;
float f = 1.2345;
uint16_t half = to_half(f);
float f2 = from_half(half);
printf("%f %f\n", f, f2);
return 0;
}
#endif
11 changes: 11 additions & 0 deletions fp16.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,17 @@

#ifndef FP16_h
#define FP16_h

#ifdef __cplusplus
#include <cstdint>
extern "C" {
#endif

float from_half(uint16_t h);
uint16_t to_half(float f);

#ifdef __cplusplus
}
#endif

#endif
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