withUnsafeMutableShapedBufferPointer(using:_:)

Declaration

mutating func withUnsafeMutableShapedBufferPointer<R>(using bufferLayout: MLShapedArrayBufferLayout, _ body: (inout UnsafeMutableBufferPointer<Scalar>, [Int], [Int]) throws -> R) rethrows -> R

Discussion

The storage contains the scalars according to buffer layout parameter. For example, the scalar at [x1, x2, ... xn] with strides [s1, s2, ... sn] is stored at ptr[x1 * s1 + x2 * s2 + ... + xn * sn]

Unlike withUnsafeMutableShapedBufferPointer(:), this function allows the caller to specify the buffer layout.

// Initialize 2x3 shaped array using an external data that lays out scalars in
// last-major order.
let data: [Int32] = [0, 3,
                     1, 4,
                     2, 5]
var array = MLShapedArray<Int32>(repeating: 0, shape: [2, 3])
array.withUnsafeMutableShapedBufferPointer(using: .lastMajorContiguous) { destinationPtr, _, _ in
    data.withUnsafeBufferPointer() { sourcePtr in
        destinationPtr.update(from: sourcePtr)
    }
}

print(array.strides) //  [1, 2]
print(array.scalars) // [0, 1, 2, 3, 4, 5])