ContinuousClock. This Swift 5.9 class is a stopwatch: it can measure the time required for a block of code to run. We can then print or compare the elapsed times.
With a closure, we specify a block of code that we want to time. The measure function then returns a Duration that we can write to the console.
Example. This program uses the ContinuousClock as a stopwatch, and it measures a function 2 times. It changes the number of iterations passed to the function.
Step 1 We create a new clock. On this instance of ContinuousClock, we can call methods like measure.
Step 2 Use call measure and use a closure argument. In the closure, we call the test() function and specify 10000 iterations.
Step 3 We call measure again, but this time we specify slightly different code within the closure—we use 20000 iterations.
Step 4 It is possible to compare the Duration returned by measure against another Duration.
func test(iterations: Int) {
// Run some slow computations.
let items = ["bird", "frog", "dog", "cat"]
var sum = 0
for _ in 0...iterations {
for item in items {
sum += item.count
}
}
if sum == 0 {
print("Error")
}
}
// Step 1: create a new clock.
let clock = ContinuousClock()
// Step 2: call measure with a closure, and specify the iterations.
let elapsed = clock.measure {
test(iterations: 10000)
}
print(elapsed)
// Step 3: call measure with a closure, using even more iterations.
let elapsed2 = clock.measure {
test(iterations: 20000)
}
print(elapsed2)
// Step 4: we can compare the elapsed time Durations.
if elapsed < elapsed2 {
print("First version was faster")
}0.0049672 seconds
0.0095812 seconds
First version was faster
Benchmarking. One way to learn how to write highly-efficient Swift code is to perform many micro-benchmarks of code. With ContinuousClock, this can be done without any complicated arithmetic.
It would be possible to use ContinuousClock to measure runtime performance, and then write this information to a file for later analysis. This could help diagnose sporadic slowdowns.
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