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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2024 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
public extension Collection where Index == Int {
/// Partition the elements of the collection into `numberOfBatches` roughly equally sized batches.
///
/// Elements are assigned to the batches round-robin. This ensures that elements that are close to each other in the
/// original collection end up in different batches. This is important because eg. test files will live close to each
/// other in the file system and test scanning wants to scan them in different batches so we don't end up with one
/// batch only containing source files and the other only containing test files.
func partition(intoNumberOfBatches numberOfBatches: Int) -> [[Element]] {
var batches: [[Element]] = Array(
repeating: {
var batch: [Element] = []
batch.reserveCapacity(self.count / numberOfBatches)
return batch
}(),
count: numberOfBatches
)
for (index, element) in self.enumerated() {
batches[index % numberOfBatches].append(element)
}
return batches.filter { !$0.isEmpty }
}
/// Partition the collection into batches that have a maximum size of `batchSize`.
///
/// The last batch will contain the remainder elements.
func partition(intoBatchesOfSize batchSize: Int) -> [[Element]] {
var batches: [[Element]] = []
batches.reserveCapacity(self.count / batchSize)
var lastIndex = self.startIndex
for index in stride(from: self.startIndex, to: self.endIndex, by: batchSize).dropFirst() + [self.endIndex] {
batches.append(Array(self[lastIndex..<index]))
lastIndex = index
}
return batches
}
}
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