arrayperf-swift2.2.swift

// 2.2 (xcode 7.3), built with optimizations
final class ArrayPerfTests: XCTestCase {
    let source = 0..<300_000
    // otherwise, compiler would be able to optimize these loops by inlining.
    var map: (Int) -> String = { i in "\(i)" }

    // 118 ms (15% STDEV)
    func testRepeatedValue() {
        measureBlock {
            var array = Array(count: self.source.count, repeatedValue: "")
            for i in self.source {
                array[i] = self.map(i)
            }
        }
    }

    // 129 ms (22% STDEV)
    func testForLoop() {
        measureBlock {
            var array = [String]()
            array.reserveCapacity(self.source.count)
            for i in self.source {
                array.append(self.map(i))
            }
        }
    }

    // 116 ms (4% STDEV)
    func testMap() {
        measureBlock {
            let array = self.source.map(self.map)
        }
    }

    // 85 ms (5% STDEV)
    func testPointer() {
        measureBlock {
            let pointer = UnsafeMutablePointer<String>.alloc(self.source.count)
            for i in self.source {
                pointer.advancedBy(i).initialize(self.map(i))
            }
            let array = Array(UnsafeBufferPointer(start: pointer, count: self.source.count))
        }
    }
}

arrayperf-swift3.swift

// 3.0-preview-1 (xcode 8 beta 1), built with optimizations
final class ArrayPerfTests: XCTestCase {
    let source = 0..<300_000
    // otherwise, compiler would be able to optimize these loops by inlining.
    var map: (Int) -> String = { i in "\(i)" }

    // 120 ms (3% STDEV)
    func testRepeatedValue() {
        measure {
            var array = Array(repeating: "", count: self.source.count)
            for i in self.source {
                array[i] = self.map(i)
            }
        }
    }

    // 124 ms (4% STDEV)
    func testForLoop() {
        measure {
            var array = [String]()
            array.reserveCapacity(self.source.count)
            for i in self.source {
                array.append(self.map(i))
            }
        }
    }

    // 122 ms (3% STDEV)
    func testMap() {
        measure {
            let array = self.source.map(self.map)
        }
    }

    // 79 ms (3% STDEV)
    func testPointer() {
        measure {
            let pointer = UnsafeMutablePointer<String>.init(allocatingCapacity: self.source.count)
            for i in self.source {
                pointer.advanced(by: i).initialize(with: self.map(i))
            }
            let array = Array(UnsafeBufferPointer(start: pointer, count: self.source.count))
        }
    }
}