Dictionary in Swift with Mutable Array how does the value work very slowly? How to optimize or build correctly?

Question

I am trying to build a data structure in Swift that maps an integer to an array of objects (a dictionary with an int key and a key as a value). The objects are extremely small and they simply wrap UIColor and Int. I have two implementations that use a Swift array as the type of the value of a dictionary, while the other uses NSMutableArray as the type of the value. My C object code is very fast, but my Swift code is very slow. Ideally, I would not want to use NSMutableArray and would like to save it as a Swift array. For this, I write an algorithm and performance, I noticed some overhead with objC_msgSend. Can someone help me optimize my Swift code? Am I doing something wrong or is it just a byproduct of a quick treatment array like value types? If so, I would like to understandwhy is the value type in this case so slow, what are my parameters, and how can this scenario scale in the future? Below I posted a code snippet and the resulting criteria:

Array quick code:

let numColors = colorCount(filter: filter, colorInfoCount: colorInfo.count)
var colorCountsArray: [Int] = [Int]()
var countToColorMap: [Int:[CountedColor]] = [Int:[CountedColor]](minimumCapacity: capacity)
var topColors = [CountedColor]()

var startTime = CACurrentMediaTime()
for (color, colorCount) in colorInfo {
    colorCountsArray.append(colorCount)
    if countToColorMap[colorCount] != nil {
        countToColorMap[colorCount]?.append(CountedColor(color: color, colorCount: colorCount))
    } else {
        countToColorMap[colorCount] = [CountedColor(color: color, colorCount: colorCount)]
    }
}
var endTime = CACurrentMediaTime()
print("Time after mapping: \(endTime - startTime)")

Fast performance:

Time after mapping: 45.0881789259997

NSMutableArray Code:

let numColors = colorCount(filter: filter, colorInfoCount: colorInfo.count)
var colorCountsArray: [Int] = [Int]()
var countToColorMap: [Int:NSMutableArray] = [Int:NSMutableArray](minimumCapacity: capacity)
var topColors = [CountedColor]()


var startTime = CACurrentMediaTime()
for (color, colorCount) in colorInfo {
    colorCountsArray.append(colorCount)
    if countToColorMap[colorCount] != nil {
        countToColorMap[colorCount]?.add(CountedColor(color: color, colorCount: colorCount))
    } else {
        countToColorMap[colorCount] = NSMutableArray(object: CountedColor(color: color, colorCount: colorCount))
    }
}
var endTime = CACurrentMediaTime()
print("Time after mapping: \(endTime - startTime)")

NSMutableArray Performance:

Time after mapping: 0.367132211999888

The colorInfo object is a dictionary that maps UIColor objects to an integer representing an account. The code, in fact, is inverse, displays this by matching an integer with a UIColor array (its array, because several colors can have the same number). ColorInfo contains 60,000 character pairs UIColor, Int.

Answer 1

Copying to recording is a difficult thing, and you need to think carefully about how many things share the structure you are trying to change. The culprit is here.

countToColorMap[colorCount]?.append(CountedColor(color: color as! UIColor, colorCount: colorCount))

, . "" ( append), --.

, , . ? . :

if countToColorMap[colorCount] != nil {
    countToColorMap[colorCount]?.append(CountedColor(color: color as! UIColor, colorCount: colorCount))
} else {
    countToColorMap[colorCount] = [CountedColor(color: color as! UIColor, colorCount: colorCount)]
}

:

Elapsed Time: 74.2517465990022
53217

:

var countForColor = countToColorMap.removeValue(forKey: colorCount) ?? []
countForColor.append(CountedColor(color: color as! UIColor, colorCount: colorCount))
countToColorMap[colorCount] = countForColor

:

Elapsed Time: 0.370953808000195
53217

Answer 2

- , 4.2

var countToColorMap = [Int: [CountedColor]]()

for (color, colorCount) in colorInfo {
    countToColorMap[colorCount, default: [CountedColor]()].append(CountedColor(color: color as! UIColor, colorCount: colorCount))
}