Function

vDSP_dotpr_s8_24(_:_:_:_:_:_:)

Calculates the dot product of a fixed-point 8.24 format vector.

Declaration

func vDSP_dotpr_s8_24(_ __A: UnsafePointer<Int32>, _ __IA: vDSP_Stride, _ __B: UnsafePointer<Int32>, _ __IB: vDSP_Stride, _ __C: UnsafeMutablePointer<Int32>, _ __N: vDSP_Length)

Parameters

__A

Single-precision fixed-point input vector A.

__IA

The stride within vector A.

__B

Single-precision fixed-point input vector B.

__IB

The stride within vector B.

__C

Pointer to an allocated variable of type int; on return, it contains the dot product.

__N

The number of elements.

Discussion

The functions in this group calculate the dot product of two vectors, using the following operation:

C[0] = sum(A[n] * B[n], 0 <= n < N);

The following example shows how you calculate the luminosity of a color using the Rec. 709 luma coefficients for the color-to-grayscale conversion. Array a defines the color, 0xDa70D6, and array b defines the coefficients:

let a: [Float] = [0xDA, 0x70, 0xD6]
let b: [Float] = [0.2126, 0.7152, 0.0722]

Passing these values to vDSP_dotpr(_:_:_:_:_:_:) calculates the luminosity and writes the result to c:

let n = vDSP_Length(a.count)
var c: Float = .nan

let stride = vDSP_Stride(1)

vDSP_dotpr(a, stride,
           b, stride,
           &c,
           n)

print(c)    // Prints "141.9"

See Also

Dot Product Calculation

static func dot<U>(U, U) -> Double

Returns the double-precision dot product of two vectors.

static func dot<U>(U, U) -> Float

Returns the single-precision dot product of two vectors.

Beta Software

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