Microsoft Specific

Emits the Streaming SIMD Extensions 4 (SSE4) instruction roundps. This instruction rounds the parameter down.

__m128 _mm_floor_ps( 
   __m128 a


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

Return value

The result can be expressed with the following equations:

r0 := FLOOR(a0)
r1 := FLOOR(a1)
r2 := FLOOR(a2)
r3 := FLOOR(a3)





x86, x64

Header file <smmintrin.h>


r0-r3 and a0-a3 are the sequentially ordered 32-bit components of return value r and parameter a. r0 and a0 denote the least significant 32 bits.

This function is implemented as a macro that invokes _mm_round_ps.

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


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

int main ()
    __m128 a;

    a.m128_f32[0] = 0.0625;
    a.m128_f32[1] = -3.25;
    a.m128_f32[2] = 100.125;
    a.m128_f32[3] = -0.5;

    __m128 res = _mm_floor_ps(a);

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

    return 0;
Original a: 0.062500    -3.250000       100.125000      -0.500000
Result res: 0.000000    -4.000000       100.000000      -1.000000

See Also


Compiler Intrinsics