vDSP_vpythgD

Declaration

extern void vDSP_vpythgD(const double *__A, vDSP_Stride __IA, const double *__B, vDSP_Stride __IB, const double *__C, vDSP_Stride __IC, const double *__D, vDSP_Stride __ID, double *__E, vDSP_Stride __IE, vDSP_Length __N);

Parameters

• __A:

  A vector that contains the first values of the first set of legs of the triangles.

• __IA:

  The distance between the elements in the input vector A.

• __B:

  A vector that contains the second values of the first set of legs of the triangles.

• __IB:

  The distance between the elements in the input vector B.

• __C:

  A vector that contains the first values of the second set of legs of the triangles.

• __IC:

  The distance between the elements in the input vector C.

• __D:

  A vector that contains the second values of the second set of legs of the triangles.

• __ID:

  The distance between the elements in the input vector D.

• __E:

  A vector that receives the result of the calculation.

• __IE:

  The distance between the elements in the output vector E.

• __N:

  The number of elements to process.

Discussion

This function calculates the length of the hypotenuse of n number of triangles, where n is the number of elements in the supplied vectors. The differences between corresponding elements of vectors x0 and x1 and vectors y0 and y1 define the lengths of the two legs of each triangle.

The functions use the following operation:

for (n = 0; n < N; ++n)
    E[n] = sqrt((A[n]-B[n])**2 + (C[n]-D[n])**2);

For example, the following code calculates the hypotenuse of four Pythagorean triples:

    let stride = 1
    
    let a: [Double] = [3, 6, 5, 9]
    let b: [Double] = [0, 0, 0, 0]
    
    let c: [Double] = [0, 0, 0, 0]
    let d: [Double] = [4, 8, 12, 12]
    
    let hypotenuses = [Double](
        unsafeUninitializedCapacity: a.count) {
            buffer, initializedCount in
            
            vDSP_vpythgD(
                a, stride,
                b, stride,
                c, stride,
                d, stride,
                buffer.baseAddress!, stride,
                vDSP_Length(a.count)
            )
            
            initializedCount = a.count
        }
    
    // Prints "[5.0, 10.0, 13.0, 15.0]".
    print(hypotenuses)

See Also

Vector Pythagorean computation

• vDSP_vpythg