Microsoft Specific

Emits the Streaming SIMD Extensions 4 (SSE4) instruction roundss. This instruction rounds up a single precision floating point value.

__m128 _mm_ceil_ss( 
   __m128 a,
   __m128 b


  • [in] a
    A 128-bit parameter that contains four 32-bit floating point values.

  • [in] b
    A 128-bit parameter that contains a 32-bit floating point value in the low doubleword.

Return value

r0 := CEIL(b0)
r1 := a1
r2 := a2
r3 := a3





x86, x64

Header file <smmintrin.h>


The return value r and parameters a and b each consist of 128 bits. r0-r3, a0-a3, and b0-b3 are the sequentially ordered 32-bit components of these parameters, where r0, a0, and b0 denote the least significant 32 bits.

This function is implemented as a macro that invokes intrinsic _mm_round_ss with appropriate rounding control.

Before using this intrinsic, software must ensure that the processor supports the instruction.


#include <stdio.h>
#include <smmintrin.h>

int main () {
    __m128 a, b;

    a.m128_f32[3] = 10.25;
    a.m128_f32[2] = -6.5;
    a.m128_f32[1] = 16;
    a.m128_f32[0] = 0.125;
    b.m128_f32[3] = 0;
    b.m128_f32[2] = 0;
    b.m128_f32[1] = 0;
    b.m128_f32[0] = 625.5;

    __m128 res = _mm_ceil_ss( a, b );

    printf_s("Original a: %10f %10f %10f %10f\nOriginal b: %10f %10f %10f %10f\n",
                a.m128_f32[3], a.m128_f32[2], a.m128_f32[1], a.m128_f32[0],
                b.m128_f32[3], b.m128_f32[2], b.m128_f32[1], b.m128_f32[0]);

    printf_s("Result res: %10f %10f %10f %10f\n",
                res.m128_f32[3], res.m128_f32[2], res.m128_f32[1], res.m128_f32[0]);

    return 0;

Original a:  10.250000  -6.500000  16.000000   0.125000
Original b:   0.000000   0.000000   0.000000 625.500000
Result res:  10.250000  -6.500000  16.000000 626.000000

See Also


Compiler Intrinsics