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Sources/PenguinParallel/NonblockingThreadPool/NonBlockingSpinningState.swift
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| // Copyright 2020 Penguin Authors | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
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| // TODO: once some version of atomics lands in Swift, refactor this to make it much nicer! | ||
|
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| /// A helper that packs the spinning state of the `NonBlockingThreadPool` into 64 bits. | ||
| internal struct NonBlockingSpinningState { | ||
| var underlying: UInt64 | ||
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| init(_ underlying: UInt64) { self.underlying = underlying } | ||
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| /// The number of spinning worker threads. | ||
| var spinningCount: UInt64 { | ||
| get { | ||
| underlying & Self.spinningCountMask | ||
| } | ||
| set { | ||
| assert(newValue < Self.spinningCountMask, "new value: \(newValue)") | ||
| underlying = (underlying & ~Self.spinningCountMask) | newValue | ||
| } | ||
| } | ||
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| /// Number of non-notifying submissions into the pool. | ||
| var noNotifyCount: UInt64 { | ||
| (underlying & Self.noNotifyCountMask) >> Self.noNotifyCountShift | ||
| } | ||
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| /// True iff a task has been submitted to the pool without notifying the thread pool's `condition`. | ||
| var hasNoNotifyTask: Bool { | ||
| (underlying & Self.noNotifyCountMask) != 0 | ||
| } | ||
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| /// Returns a new state with the the non-notifying count incremented by one. | ||
| func incrementingNoNotifyCount() -> Self { | ||
| Self(underlying + Self.noNotifyCountIncrement) | ||
| } | ||
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| /// Decrements the non-notifying count by one. | ||
| mutating func decrementNoNotifyCount() { | ||
| underlying -= Self.noNotifyCountIncrement | ||
| } | ||
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| /// Returns a new state with the spinning count incremented by one. | ||
| func incrementingSpinningCount() -> Self { | ||
| Self(underlying + 1) | ||
| } | ||
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| /// Returns a new state with the spinning count decremented by one. | ||
| func decrementingSpinningCount() -> Self { | ||
| Self(underlying - 1) | ||
| } | ||
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| static let spinningCountBits: UInt64 = 32 | ||
| static let spinningCountMask: UInt64 = (1 << spinningCountBits) - 1 | ||
| static let noNotifyCountBits: UInt64 = 32 | ||
| static let noNotifyCountShift: UInt64 = 32 | ||
| static let noNotifyCountMask: UInt64 = ((1 << noNotifyCountBits) - 1) << noNotifyCountShift | ||
| static let noNotifyCountIncrement: UInt64 = (1 << noNotifyCountShift) | ||
| } | ||
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| extension NonBlockingSpinningState: CustomStringConvertible { | ||
| public var description: String { | ||
| "NonblockingSpinningState(spinningCount: \(spinningCount), noNotifyCount: \(noNotifyCount))" | ||
| } | ||
| } |
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59
Sources/PenguinParallel/NonblockingThreadPool/NumberOperations.swift
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| // Copyright 2020 Penguin Authors | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
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| /// Returns the positive integers that are coprime with `n`. | ||
| /// | ||
| /// Two numbers are co-prime if their GCD is 1. | ||
| internal func positiveCoprimes(_ n: Int) -> [Int] { | ||
| var coprimes = [Int]() | ||
| for i in 1...n { | ||
| var a = i | ||
| var b = n | ||
| // If GCD(a, b) == 1, then a and b are coprimes. | ||
| while b != 0 { | ||
| let tmp = a | ||
| a = b | ||
| b = tmp % b | ||
| } | ||
| if a == 1 { coprimes.append(i) } | ||
| } | ||
| return coprimes | ||
| } | ||
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| /// Returns a value deterministically selected from `0..<size`. | ||
| /// | ||
| /// This is a faster variation than computing `x % size`. For additional context, please see: | ||
| /// https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction | ||
| internal func fastFit(_ lhs: Int, into size: Int) -> Int { | ||
| let l = UInt32(lhs) | ||
| let r = UInt32(size) | ||
| return Int(l.multipliedFullWidth(by: r).high) | ||
| } | ||
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| /// Fast pseudorandom number generator using [permuted congruential | ||
| /// generators](https://www.pcg-random.org/). | ||
| internal struct PCGRandomNumberGenerator: RandomNumberGenerator { | ||
| var state: UInt64 | ||
| static var stream: UInt64 { 0xda3e_39cb_94b9_5bdb } | ||
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| mutating func next() -> UInt32 { | ||
| let current = state | ||
| // Update the internal state | ||
| state = current &* 6_364_136_223_846_793_005 &+ Self.stream | ||
| // Calculate output function (XSH-RS scheme), uses old state for max ILP. | ||
| let base = (current ^ (current >> 22)) | ||
| let shift = Int(22 + (current >> 61)) | ||
| return UInt32(truncatingIfNeeded: base >> shift) | ||
| } | ||
| } |