计时函数与float32 float16 int8 数据转换

个人整理常用

部分来自 ncnn

计时函数

// window 平台
#include <windows.h>double get_current_time()
{LARGE_INTEGER freq; // 频率LARGE_INTEGER pc;   // 计数QueryPerformanceFrequency(&freq);QueryPerformanceCounter(&pc);return pc.QuadPart * 1000.0 / freq.QuadPart; // us
}// android 平台 ios linux 等
#include <sys/time.h>double get_current_time()
{struct timeval tv;gettimeofday(&tv, NULL);return tv.tv_sec * 1000.0 + tv.tv_usec / 1000.0;
}

float32 float16 int8 数据转换

// convert float to half precision floating point
static unsigned short float32_to_float16(float value)
{// 1 : 8 : 23union{unsigned int u;float f;} tmp;tmp.f = value;// 1 : 8 : 23unsigned short sign = (tmp.u & 0x80000000) >> 31;unsigned short exponent = (tmp.u & 0x7F800000) >> 23;unsigned int significand = tmp.u & 0x7FFFFF;//     fprintf(stderr, "%d %d %d\n", sign, exponent, significand);// 1 : 5 : 10unsigned short fp16;if (exponent == 0){// zero or denormal, always underflowfp16 = (sign << 15) | (0x00 << 10) | 0x00;}else if (exponent == 0xFF){// infinity or NaNfp16 = (sign << 15) | (0x1F << 10) | (significand ? 0x200 : 0x00);}else{// normalizedshort newexp = exponent + (- 127 + 15);if (newexp >= 31){// overflow, return infinityfp16 = (sign << 15) | (0x1F << 10) | 0x00;}else if (newexp <= 0){// underflowif (newexp >= -10){// denormal half-precisionunsigned short sig = (significand | 0x800000) >> (14 - newexp);fp16 = (sign << 15) | (0x00 << 10) | sig;}else{// underflowfp16 = (sign << 15) | (0x00 << 10) | 0x00;}}else{fp16 = (sign << 15) | (newexp << 10) | (significand >> 13);}}return fp16;
}// convert half precision floating point to float
static float float16_to_float32(unsigned short value)
{// 1 : 5 : 10unsigned short sign = (value & 0x8000) >> 15;unsigned short exponent = (value & 0x7c00) >> 10;unsigned short significand = value & 0x03FF;//     fprintf(stderr, "%d %d %d\n", sign, exponent, significand);// 1 : 8 : 23union{unsigned int u;float f;} tmp;if (exponent == 0){if (significand == 0){// zerotmp.u = (sign << 31);}else{// denormalexponent = 0;// find non-zero bitwhile ((significand & 0x200) == 0){significand <<= 1;exponent++;}significand <<= 1;significand &= 0x3FF;tmp.u = (sign << 31) | ((-exponent + (-15 + 127)) << 23) | (significand << 13);}}else if (exponent == 0x1F){// infinity or NaNtmp.u = (sign << 31) | (0xFF << 23) | (significand << 13);}else{// normalizedtmp.u = (sign << 31) | ((exponent + (-15 + 127)) << 23) | (significand << 13);}return tmp.f;
}// round to nearest
static signed char float32_to_int8(float value)
{float tmp;if (value >= 0.f) tmp = value + 0.5;else tmp = value - 0.5;if (tmp > 127)return 127;if (tmp < -128)return -128;return tmp;
}