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79 lines
2.0 KiB
79 lines
2.0 KiB
// For licensing see accompanying LICENSE.md file.
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// Copyright (C) 2022 Apple Inc. All Rights Reserved.
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import Foundation
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/// A utility for timing events and tracking time statistics
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///
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/// Typical usage
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/// ```
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/// let timer: SampleTimer
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///
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/// for i in 0...<iterationCount {
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/// timer.start()
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/// doStuff()
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/// timer.stop()
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/// }
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///
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/// print(String(format: "mean: %.2f, var: %.2f",
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/// timer.mean, timer.variance))
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/// ```
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@available(iOS 16.2, macOS 13.1, *)
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public final class SampleTimer: Codable {
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var startTime: CFAbsoluteTime?
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var sum: Double = 0.0
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var sumOfSquares: Double = 0.0
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var count = 0
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var samples: [Double] = []
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public init() {}
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/// Start a sample, noting the current time
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public func start() {
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startTime = CFAbsoluteTimeGetCurrent()
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}
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// Stop a sample and record the elapsed time
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@discardableResult public func stop() -> Double {
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guard let startTime = startTime else {
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return 0
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}
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let elapsed = CFAbsoluteTimeGetCurrent() - startTime
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sum += elapsed
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sumOfSquares += elapsed * elapsed
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count += 1
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samples.append(elapsed)
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return elapsed
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}
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/// Mean of all sampled times
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public var mean: Double { sum / Double(count) }
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/// Variance of all sampled times
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public var variance: Double {
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guard count > 1 else {
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return 0.0
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}
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return sumOfSquares / Double(count - 1) - mean * mean
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}
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/// Standard deviation of all sampled times
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public var stdev: Double { variance.squareRoot() }
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/// Median of all sampled times
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public var median: Double {
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let sorted = samples.sorted()
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let (q, r) = sorted.count.quotientAndRemainder(dividingBy: 2)
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if r == 0 {
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return (sorted[q] + sorted[q - 1]) / 2.0
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} else {
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return Double(sorted[q])
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}
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}
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public var allSamples: [Double] {
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samples
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}
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}
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