67 lines
1.9 KiB
Swift
67 lines
1.9 KiB
Swift
//
|
|
// Collection.swift
|
|
//
|
|
//
|
|
// Created by MainasuK on 2021-12-7.
|
|
//
|
|
|
|
import Foundation
|
|
|
|
// https://gist.github.com/DougGregor/92a2e4f6e11f6d733fb5065e9d1c880f
|
|
extension Collection {
|
|
public func parallelMap<T>(
|
|
parallelism requestedParallelism: Int? = nil,
|
|
_ transform: @escaping (Element) async throws -> T
|
|
) async rethrows -> [T] {
|
|
let defaultParallelism = 2
|
|
let parallelism = requestedParallelism ?? defaultParallelism
|
|
|
|
let n = count
|
|
if n == 0 {
|
|
return []
|
|
}
|
|
return try await withThrowingTaskGroup(of: (Int, T).self, returning: [T].self) { group in
|
|
var result = [T?](repeatElement(nil, count: n))
|
|
|
|
var i = self.startIndex
|
|
var submitted = 0
|
|
|
|
func submitNext() async throws {
|
|
if i == self.endIndex { return }
|
|
|
|
group.addTask { [submitted, i] in
|
|
let value = try await transform(self[i])
|
|
return (submitted, value)
|
|
}
|
|
submitted += 1
|
|
formIndex(after: &i)
|
|
}
|
|
|
|
// submit first initial tasks
|
|
for _ in 0 ..< parallelism {
|
|
try await submitNext()
|
|
}
|
|
|
|
// as each task completes, submit a new task until we run out of work
|
|
while let (index, taskResult) = try await group.next() {
|
|
result[index] = taskResult
|
|
|
|
try Task.checkCancellation()
|
|
try await submitNext()
|
|
}
|
|
|
|
assert(result.count == n)
|
|
return Array(result.compactMap { $0 })
|
|
}
|
|
}
|
|
|
|
func parallelEach(
|
|
parallelism requestedParallelism: Int? = nil,
|
|
_ work: @escaping (Element) async throws -> Void
|
|
) async rethrows {
|
|
_ = try await parallelMap {
|
|
try await work($0)
|
|
}
|
|
}
|
|
}
|