# _mm_atan2_pd, _mm256_atan2_pd

Calculates the inverse tangent of float64 variables x and y. Vector variant of atan2(x, y) function for a 128-bit/256-bit vector argument of float64 values.

## Syntax

extern __m128d _mm_atan2_pd(__m128d v1, __m128 v2);

extern __m256d _mm256_atan2_pd(__m256d v1, __m256 v2);

## Arguments

v1 | vector with float64 values
v2 | vector with float64 values

## Description

Calculates the arc tangent of corresponding float64 elements of vectors v1 and v2. The following is an illustration of the atan2 operation:

    Res[0]  = atan2(v1[0], v2[0])
    Res[1]  = atan2(v1[1], v2[1])
    Res[2]  = atan2(v1[2], v2[2])
    Res[15] = atan2(v1[15], v2[15])
    ...

### Note

This calculation is similar to calculating the arc tangent of `y / x`, except that the signs of both arguments are used to determine the quadrant of the result.

## Returns

Result of the bitwise operation.

### Note

Many routines in the Short Vector Math Library (SVML) are more optimized for Intel® microprocessors than for non-Intel microprocessors.

Parent topic: Intrinsics for Trigonometric Operations