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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,160 @@ | ||
| use rand_core::CryptoRngCore; | ||
|
|
||
| #[cfg(feature = "multicore")] | ||
| use rayon::iter::{ParallelBridge, ParallelIterator}; | ||
|
|
||
| use crate::SieveFactory; | ||
|
|
||
| /// Sieves through the results of `sieve_factory` and returns the first item for which `predicate` is `true`. | ||
| /// | ||
| /// If `sieve_factory` signals that no more results can be created, returns `None`. | ||
| pub fn sieve_and_find<R, S>( | ||
| rng: &mut R, | ||
| sieve_factory: S, | ||
| predicate: impl Fn(&mut R, &S::Item) -> bool, | ||
| ) -> Option<S::Item> | ||
| where | ||
| S: SieveFactory, | ||
| R: CryptoRngCore, | ||
| { | ||
| // We could use `SieveIterator` here, but it requires cloning the `rng`. | ||
| // Unlike the parallel version, it is avoidable here. | ||
|
|
||
| let mut sieve_factory = sieve_factory; | ||
| let mut sieve = sieve_factory.make_sieve(rng, None)?; | ||
|
|
||
| loop { | ||
| if let Some(value) = sieve.find(|num| predicate(rng, num)) { | ||
| return Some(value); | ||
| } | ||
| if let Some(new_sieve) = sieve_factory.make_sieve(rng, Some(&sieve)) { | ||
| sieve = new_sieve; | ||
| } else { | ||
| return None; | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Sieves through the results of `sieve_factory` using a thread pool with `threadcount` threads, | ||
| /// and returns the first item for which `predicate` is `true`. | ||
| /// | ||
| /// If `sieve_factory` signals that no more results can be created, returns `None`. | ||
| #[cfg(feature = "multicore")] | ||
| pub fn par_sieve_and_find<R, S, F>(rng: &mut R, sieve_factory: S, predicate: F, threadcount: usize) -> Option<S::Item> | ||
| where | ||
| R: CryptoRngCore + Clone + Send + Sync, | ||
| S: Send + Sync + SieveFactory, | ||
| S::Sieve: Send, | ||
| S::Item: Send, | ||
| F: Sync + Fn(&mut R, &S::Item) -> bool, | ||
| { | ||
| let threadpool = rayon::ThreadPoolBuilder::new() | ||
| .num_threads(threadcount) | ||
| .build() | ||
| .expect("If the platform can spawn threads, then this call will work."); | ||
|
|
||
| let mut iter_rng = rng.clone(); | ||
| let iter = SieveIterator::new(&mut iter_rng, sieve_factory)?; | ||
|
|
||
| threadpool.install(|| { | ||
| iter.par_bridge().find_any(|c| { | ||
| let mut rng = rng.clone(); | ||
| predicate(&mut rng, c) | ||
| }) | ||
| }) | ||
| } | ||
|
|
||
| /// A structure that chains the creation of sieves, returning the results from one until it is exhausted, | ||
| /// and then creating a new one. | ||
| #[derive(Debug)] | ||
| pub struct SieveIterator<'a, R: CryptoRngCore, S: SieveFactory> { | ||
| sieve_factory: S, | ||
| sieve: S::Sieve, | ||
| rng: &'a mut R, | ||
| } | ||
|
|
||
| impl<'a, R: CryptoRngCore, S: SieveFactory> SieveIterator<'a, R, S> { | ||
| /// Creates a new chained iterator producing results from sieves returned from `sieve_factory`. | ||
| pub fn new(rng: &'a mut R, sieve_factory: S) -> Option<Self> { | ||
| let mut sieve_factory = sieve_factory; | ||
| let sieve = sieve_factory.make_sieve(rng, None)?; | ||
| Some(Self { | ||
| sieve_factory, | ||
| rng, | ||
| sieve, | ||
| }) | ||
| } | ||
| } | ||
|
|
||
| impl<R: CryptoRngCore, S: SieveFactory> Iterator for SieveIterator<'_, R, S> { | ||
| type Item = S::Item; | ||
|
|
||
| fn next(&mut self) -> Option<Self::Item> { | ||
| loop { | ||
| if let Some(result) = self.sieve.next() { | ||
| return Some(result); | ||
| } | ||
|
|
||
| self.sieve = self.sieve_factory.make_sieve(self.rng, Some(&self.sieve))?; | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use rand_core::{CryptoRngCore, OsRng}; | ||
|
|
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| use super::sieve_and_find; | ||
| use crate::SieveFactory; | ||
|
|
||
| #[cfg(feature = "multicore")] | ||
| use super::par_sieve_and_find; | ||
|
|
||
| #[test] | ||
| fn test_exhaustable_sieve_factory() { | ||
| // Test the logic handling the case of the sieve factory not being able to produce new sieves. | ||
| struct TestSieveFactory { | ||
| count: usize, | ||
| } | ||
|
|
||
| impl SieveFactory for TestSieveFactory { | ||
| type Item = usize; | ||
| type Sieve = core::ops::Range<usize>; | ||
|
|
||
| fn make_sieve( | ||
| &mut self, | ||
| _rng: &mut impl CryptoRngCore, | ||
| previous_sieve: Option<&Self::Sieve>, | ||
| ) -> Option<Self::Sieve> { | ||
| self.count += 1; | ||
| if previous_sieve.is_none() { | ||
| Some(self.count * 10..(self.count * 10 + 2)) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
| } | ||
|
|
||
| let factory = TestSieveFactory { count: 0 }; | ||
| let result = sieve_and_find(&mut OsRng, factory, |_rng, num| *num == 11); | ||
| assert!(result.is_some()); | ||
|
|
||
| #[cfg(feature = "multicore")] | ||
| { | ||
| let factory = TestSieveFactory { count: 0 }; | ||
| let result = par_sieve_and_find(&mut OsRng, factory, |_rng, num| *num == 11, 1); | ||
| assert!(result.is_some()); | ||
| } | ||
|
|
||
| let factory = TestSieveFactory { count: 0 }; | ||
| let result = sieve_and_find(&mut OsRng, factory, |_rng, num| *num == 20); | ||
| assert!(result.is_none()); | ||
|
|
||
| #[cfg(feature = "multicore")] | ||
| { | ||
| let factory = TestSieveFactory { count: 0 }; | ||
| let result = par_sieve_and_find(&mut OsRng, factory, |_rng, num| *num == 20, 1); | ||
| assert!(result.is_none()); | ||
| } | ||
| } | ||
| } |
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