Rounds off double-precision floating point values to nearest upper/lower integer depending on rounding mode. The corresponding Intel® AVX instruction isVROUNDPD.


extern __m256d _mm256_round_pd(__m256d a, int iRoundMode);



float64 vector


A hexadecimal value dependent on rounding mode:

  • For rounding off to upper integer, the value is 0x0A
  • For rounding off to lower integer, the value is 0x09


Rounds off the elements of a float64 vector a to the nearest upper/lower integer value. Two shortcuts, in the form of #defines, are used to achieve these two separate operations:

#define _mm256_ceil_pd(a)   _mm256_round_pd((a), 0x0A)
#define _mm256_floor_pd(a)  _mm256_round_pd((a), 0x09)

These #defines tell the preprocessor to replace all instances of _mm256_ceil_pd(a) with _mm256_round_pd((a), 0x0A) and all instances of _mm256_floor_pd(a) with _mm256_round_pd((a), 0x09).

For example, if you write the following:

__m256 a, b;
a = _mm256_ceil_pd(b);

the preprocessor will modify it to:

a = _mm256_round_pd(b, 0x0a);

The Precision Floating Point Exception is signaled according to the (immediate operand) iRoundMode value.


Result of the rounding off operation as a vector with double-precision floating point values.

Para obtener información más completa sobre las optimizaciones del compilador, consulte nuestro Aviso de optimización.