_mm_dp_ps
Microsoft Specific
Emits the Streaming SIMD Extensions 4 (SSE4) instruction dpps. This instruction computes the dot product of single precision floating point values.
__m128 _mm_dp_ps(
__m128 a,
__m128 b,
const int mask
);
Parameters
[in] a
A 128-bit parameter that contains four 32-bit floating point values.[in] b
A 128-bit parameter that contains four 32-bit floating point values.[in] mask
A constant mask that determines which components will be multiplied and where to place the results.
Result value
A 128 bit parameter that contains the 32-bit results of the dot products.
The result can be expressed with the following equations:
tmp0 := (mask4 == 1) ? (a0 * b0) : +0.0
tmp1 := (mask5 == 1) ? (a1 * b1) : +0.0
tmp2 := (mask6 == 1) ? (a2 * b2) : +0.0
tmp3 := (mask7 == 1) ? (a3 * b3) : +0.0
tmp4 := tmp0 + tmp1 + tmp2 + tmp3
r0 := (mask0 == 1) ? tmp4 : +0.0
r1 := (mask1 == 1) ? tmp4 : +0.0
r2 := (mask2 == 1) ? tmp4 : +0.0
r3 := (mask3 == 1) ? tmp4 : +0.0
Requirements
Intrinsic |
Architecture |
|---|---|
_mm_dp_ps |
x86, x64 |
Header file <smmintrin.h>
Remarks
The immediate bits 4-7 of mask determine which of the corresponding source operand pairs are to be multiplied. Bits 0-3 determine whether the dot product result will be written. If a mask bit is 0, the corresponding product result or written value is +0.0.
r0-r3, a0-a3, and b0-b3are the sequentially ordered 32-bit components of return value r and parameters a and b, respectively. r0, a0, and b0 are the least significant 32 bits.
maski is bit i of parameter mask, where bit 0 is the least significant bit.
Before you use this intrinsic, software must ensure that the underlying processor supports the instruction.
Example
#include <stdio.h>
#include <smmintrin.h>
int main ()
{
__m128 a, b;
const int mask = 0x55;
a.m128_f32[0] = 1.5;
a.m128_f32[1] = 10.25;
a.m128_f32[2] = -11.0625;
a.m128_f32[3] = 81.0;
b.m128_f32[0] = -1.5;
b.m128_f32[1] = 3.125;
b.m128_f32[2] = -50.5;
b.m128_f32[3] = 100.0;
__m128 res = _mm_dp_ps(a, b, mask);
printf_s("Original a: %f\t%f\t%f\t%f\nOriginal b: %f\t%f\t%f\t%f\n",
a.m128_f32[0], a.m128_f32[1], a.m128_f32[2], a.m128_f32[3],
b.m128_f32[0], b.m128_f32[1], b.m128_f32[2], b.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: 1.500000 10.250000 -11.062500 81.000000
Original b: -1.500000 3.125000 -50.500000 100.000000
Result res: 556.406250 0.000000 556.406250 0.000000