Python开源数学库numpy，很多底层实现采用C，有一定参考价值

eric2013

网站：https://github.com/numpy/numpy
文档：https://numpy.org/doc
源代码：https://github.com/numpy/numpy

源码中有很多以C实现的代码，有一定的参考性：



比如单精度浮点转半精度浮点

[C] 纯文本查看 复制代码

uint16_t numpy_floatbits_to_halfbits(uint32_t f) {
  uint16_t h_sgn = (uint16_t)((f & 0x80000000u) >> 16);
  uint32_t f_exp = f & 0x7f800000u;
  uint32_t f_sig = f & 0x007fffffu;
 
  // Exponent overflow/NaN converts to signed inf/NaN
  if (f_exp >= 0x47800000u) {
    if ((f_exp == 0x7f800000u) && (f_sig != 0)) {
      // NaN - propagate the flag in the significand...
      uint16_t ret = (uint16_t)(0x7c00u + (f_sig >> 13));
      ret += (ret == 0x7c00u); // ...but make sure it stays a NaN
      return h_sgn + ret;
    } else {
      // (overflow to) signed inf
      return (uint16_t)(h_sgn + 0x7c00u);
    }
  }
 
  // Exponent underflow converts to a subnormal half or signed zero
  if (f_exp <= 0x38000000u) {
    // Signed zeros, subnormal floats, and floats with small
    // exponents all convert to signed zero half-floats.
    if (f_exp < 0x33000000u) {
      return h_sgn;
    }
    // Make the subnormal significand
    f_exp >>= 23;
    f_sig += 0x00800000u;
    f_sig >>= (113 - f_exp);
    // Handle rounding by adding 1 to the bit beyond half precision
    //
    // If the last bit in the half significand is 0 (already even),
    // and the remaining bit pattern is 1000...0, then we do not add
    // one to the bit after the half significand. However, the
    // (113 - f_exp) shift can lose up to 11 bits, so the || checks
    // them in the original. In all other cases, we can just add one.
    if (((f_sig & 0x3fffu) != 0x1000u) || (f & 0x07ffu)) {
      f_sig += 0x1000u;
    }
    uint16_t h_sig = (uint16_t)(f_sig >> 13);
    // If the rounding causes a bit to spill into h_exp, it will
    // increment h_exp from zero to one and h_sig will be zero.
    // This is the correct result.
    return (uint16_t)(h_sgn + h_sig);
  }
 
  // Regular case with no overflow or underflow
  uint16_t h_exp = (uint16_t)((f_exp - 0x38000000u) >> 13);
  // Handle rounding by adding 1 to the bit beyond half precision
  //
  // If the last bit in the half significand is 0 (already even), and
  // the remaining bit pattern is 1000...0, then we do not add one to
  // the bit after the half significand. In all other cases, we do.
  if ((f_sig & 0x3fffu) != 0x1000u) {
      f_sig += 0x1000u;
  }
  uint16_t h_sig = (uint16_t)(f_sig >> 13);
  // If the rounding causes a bit to spill into h_exp, it will
  // increment h_exp by one and h_sig will be zero. This is the
  // correct result. h_exp may increment to 15, at greatest, in
  // which case the result overflows to a signed inf.
  return (uint16_t)(h_sgn + h_exp + h_sig);
}

我是黏黏虫

这个相当不错，感谢

我是黏黏虫

刚发现不错，感谢！

soyshell

做个标记，学习一下C语言的源码。

jackhbkarm

numpy库很有用，学习下怎么用C实现