如何快速实现并行映射 [英] How to implement a parallel map in swift
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问题描述
我有以下代码:-
extension Collection {
// EZSE : A parralelized map for collections, operation is non blocking
public func pmap<R>(_ each: (Self.Iterator.Element) -> R) -> [R?] {
let indices = indicesArray()
var res = [R?](repeating: nil, count: indices.count)
DispatchQueue.concurrentPerform(iterations: indices.count) { (index) in
let elementIndex = indices[index]
res[index] = each(self[elementIndex])
}
// Above code is non blocking so partial exec on most runs
return res
}
/// EZSE : Helper method to get an array of collection indices
private func indicesArray() -> [Self.Index] {
var indicesArray: [Self.Index] = []
var nextIndex = startIndex
while nextIndex != endIndex {
indicesArray.append(nextIndex)
nextIndex = index(after: nextIndex)
}
return indicesArray
}
}
在这里,在return语句res处,它通常在部分执行完成后返回.有意义的是,并发Perform是非阻塞的.我不确定如何继续等待.我应该使用调度组/期望之类的方法,还是有一些更简单,更优雅的方法?本质上,我正在寻找一种快速的等待通知抽象.
In here at the return statement res, it often returns with part of the execution completed. Makes sense, concurrent Perform is non blocking. I am unsure how to proceed to wait for it. Should I use something like a dispatch group/expectations or is there some simpler more elegant method? Essentially I am looking for a simple wait notify abstraction in swift.
推荐答案
您可以尝试执行以下操作:
You can try something like this:
// EZSE : A parralelized map for collections, operation is non blocking
public func pmap<R>(_ each: @escaping (Self.Iterator.Element) -> R) -> [R] {
let totalCount = indices.count
var res = ContiguousArray<R?>(repeating: nil, count: totalCount)
let queue = OperationQueue()
queue.maxConcurrentOperationCount = totalCount
let lock = NSRecursiveLock()
indices
.enumerated()
.forEach { index, elementIndex in
queue.addOperation {
let temp = each(self[elementIndex])
lock.lock()
res[index] = temp
lock.unlock()
}
}
queue.waitUntilAllOperationsAreFinished()
return res.map({ $0! })
}
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