Function

vDSP_maxmgviD(_:_:_:_:_:)

Calculates the maximum magnitude and corresponding index in a double-precision vector.

Declaration

func vDSP_maxmgviD(_ __A: UnsafePointer<Double>, _ __IA: vDSP_Stride, _ __C: UnsafeMutablePointer<Double>, _ __I: UnsafeMutablePointer<vDSP_Length>, _ __N: vDSP_Length)

Parameters

__A

Double-precision real input vector.

__I

Stride for A.

__C

Output scalar.

__IC

Output scalar index.

__N

The number of elements to process. If N is zero (0), this function returns -INFINITY in C, and the value in IC is undefined.

Discussion

This function calculates the maximum magnitude and corresonding index of the first N elements of A and writes the result to C:

A diagram showing the operation of the vDSP_maxmgvi function. There are three rows. The top row represents the input, vector A. The second row represents the maximum magnitude value operation. The bottom row represents the output, vector C. The diagram has connecting lines from the input vectors to the operation and from the operation to the output vector indicating the relationships between the input and output.

The index is the actual array index, not the pre-stride index. If vector A contains more than one instance of the maximum value, IC contains the index of the first instance.

The operation is:

*C = -INFINITY;
for (n = 0; n < N; ++n)
{
    if (*C < |A[n * I]|)
    {
        *C = |A[n * I]|;
        *IC = n * I;
    }
}

See Also

Maximum Calculation

static func maximum<U>(U) -> Double

Returns the maximum element in a double-precision vector.

static func maximum<U>(U) -> Float

Returns the maximum element in a single-precision vector.

static func maximumMagnitude<U>(U) -> Double

Returns the maximum magnitude element in a double-precision vector.

static func maximumMagnitude<U>(U) -> Float

Returns the maximum magnitude element in a single-precision vector.

static func indexOfMaximum<U>(U) -> (UInt, Double)

Returns the maximum element, and its index, in a double-precision vector.

static func indexOfMaximum<U>(U) -> (UInt, Float)

Returns the maximum element, and its index, in a signal-precision vector.

static func indexOfMaximumMagnitude<U>(U) -> (UInt, Double)

Returns the maximum magnitude element, and its index, in a double-precision vector.

static func indexOfMaximumMagnitude<U>(U) -> (UInt, Float)

Returns the maximum magnitude element, and its index, in a single-precision vector.

func vDSP_maxmgv(UnsafePointer<Float>, vDSP_Stride, UnsafeMutablePointer<Float>, vDSP_Length)

Calculates the maximum magnitude in a single-precision vector.

func vDSP_maxmgvi(UnsafePointer<Float>, vDSP_Stride, UnsafeMutablePointer<Float>, UnsafeMutablePointer<vDSP_Length>, vDSP_Length)

Calculates the maximum magnitude and corresponding index in a single-precision vector.