Function

vDSP_vmsa(_:_:_:_:_:_:_:_:)

Multiplies the sum of two single-precision vectors by a single-precision scalar value.

Declaration

func vDSP_vmsa(_ __A: UnsafePointer<Float>, _ __IA: vDSP_Stride, _ __B: UnsafePointer<Float>, _ __IB: vDSP_Stride, _ __C: UnsafePointer<Float>, _ __D: UnsafeMutablePointer<Float>, _ __ID: vDSP_Stride, _ __N: vDSP_Length)

Parameters

__A: Single-precision real input vector.
__IA: Stride for A.
__B: Single-precision real input vector.
__IB: Stride for B.
__C: Single-precision real input scalar.
__D: Single-precision real output vector.
__ID: Stride for D.
__N: The number of elements to process.

Discussion

This function calculates the products of the first N elements of A and B, adds each product to the scalar value C, and writes the result to D:

A diagram showing the operation of the vDSP_vmsa function. There are five rows. The top two rows represents the first two inputs, vector A and vector B. The third row represents the intermediate result of the first two inputs. The forth row represents the third input, scalar C. The bottom row represents the output, vector D. The diagram has connecting lines from the inputs to the output vector indicating the relationships between the inputs and output.

The operation is:

 for (n = 0; n < N; ++n)
    D[n] = A[n] * B[n] + C;

The following code shows an example of using vDSP_vmsa(_:_:_:_:_:_:_:_:):

let stride = vDSP_Stride(1)

let a: [Float] = [10, 20, 30, 40, 50]
let b: [Float] = [ 1,  2,  3,  4,  5]

var c: Float = 2

let n = vDSP_Length(a.count)

var d = [Float](repeating: 0,
                count: a.count)

vDSP_vmsa(a, stride,
          b, stride,
          &c,
          &d, stride,
          n)

// Prints "[12.0, 42.0, 92.0, 162.0, 252.0]"
print(d)

vDSP_vmsa(_:_:_:_:_:_:_:_:)

Declaration

Parameters

Discussion

See Also

Ternary (Vector-Vector-Scalar) Multiply-Add Operations