MLCompute_MNIST_Utilities.swift

// Load in memory and split is not performant
private func getFileLine(filePath: String, process: (String) -> Void) {
    guard let filePointer:UnsafeMutablePointer<FILE> = fopen(filePath,"r") else {
        preconditionFailure("Could not open file at \(filePath)")
    }

    defer {
        fclose(filePointer)
    }

    var lineByteArrayPointer: UnsafeMutablePointer<CChar>? = nil
    var lineCap: Int = 0

    while getline(&lineByteArrayPointer, &lineCap, filePointer) > 0 {
        let line = String.init(cString:lineByteArrayPointer!).trimmingCharacters(in: .whitespacesAndNewlines)

        process(line)
    }
}

private func oneHotEncoding(_ number: Int, length: Int = 10) -> [Float] {
    guard number < length else {
        fatalError("wrong ordinal vs encoding length")
    }

    var array = Array<Float>(repeating: 0.0, count: length)
    array[number] = 1.0
    return array
}

private func oneHotDecoding(_ encoding: [Float]) -> Int {
    var value: Int = 0

    for i in 0..<encoding.count {
        if encoding[i] == 1 {
            value = i
            break
        }
    }

    return value
}

private func argmaxDecoding(_ encoding: [Float]) -> Int {
    var max: Float = 0
    var pos: Int = 0

    for i in 0..<encoding.count {
        if encoding[i] > max {
            max = encoding[i]
            pos = i
        }
    }

    return pos
}