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//! Parallel iterators for matrices compatible with rayon.
// only enables the `doc_cfg` feature when
// the `docsrs` configuration attribute is defined
#![cfg_attr(docsrs, feature(doc_cfg))]
use crate::{
iter::{ColumnIter, ColumnIterMut},
Dim, Matrix, MatrixView, MatrixViewMut, RawStorage, RawStorageMut, Scalar, U1,
};
use rayon::iter::plumbing::Producer;
use rayon::{iter::plumbing::bridge, prelude::*};
/// A rayon parallel iterator over the columns of a matrix. It is created
/// using the [`par_column_iter`] method of [`Matrix`].
///
/// *Only available if compiled with the feature `rayon`.*
/// [`par_column_iter`]: crate::Matrix::par_column_iter
/// [`Matrix`]: crate::Matrix
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
pub struct ParColumnIter<'a, T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> {
mat: &'a Matrix<T, R, Cols, S>,
}
impl<'a, T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> ParColumnIter<'a, T, R, Cols, S> {
/// Create a new parallel iterator for the given matrix.
fn new(matrix: &'a Matrix<T, R, Cols, S>) -> Self {
Self { mat: matrix }
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
impl<'a, T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> ParallelIterator
for ParColumnIter<'a, T, R, Cols, S>
where
T: Sync + Send + Scalar,
S: Sync,
{
type Item = MatrixView<'a, T, R, U1, S::RStride, S::CStride>;
fn drive_unindexed<Consumer>(self, consumer: Consumer) -> Consumer::Result
where
Consumer: rayon::iter::plumbing::UnindexedConsumer<Self::Item>,
{
bridge(self, consumer)
}
fn opt_len(&self) -> Option<usize> {
Some(self.mat.ncols())
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
/// *Only available if compiled with the feature `rayon`.*
impl<'a, T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> IndexedParallelIterator
for ParColumnIter<'a, T, R, Cols, S>
where
T: Send + Sync + Scalar,
S: Sync,
{
fn len(&self) -> usize {
self.mat.ncols()
}
fn drive<C: rayon::iter::plumbing::Consumer<Self::Item>>(self, consumer: C) -> C::Result {
bridge(self, consumer)
}
fn with_producer<CB: rayon::iter::plumbing::ProducerCallback<Self::Item>>(
self,
callback: CB,
) -> CB::Output {
let producer = ColumnProducer(ColumnIter::new(self.mat));
callback.callback(producer)
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
/// A rayon parallel iterator through the mutable columns of a matrix.
/// *Only available if compiled with the feature `rayon`.*
pub struct ParColumnIterMut<
'a,
T,
R: Dim,
Cols: Dim,
S: RawStorage<T, R, Cols> + RawStorageMut<T, R, Cols>,
> {
mat: &'a mut Matrix<T, R, Cols, S>,
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
/// *only available if compiled with the feature `rayon`*
impl<'a, T, R, Cols, S> ParColumnIterMut<'a, T, R, Cols, S>
where
R: Dim,
Cols: Dim,
S: RawStorage<T, R, Cols> + RawStorageMut<T, R, Cols>,
{
/// create a new parallel iterator for the given matrix.
fn new(mat: &'a mut Matrix<T, R, Cols, S>) -> Self {
Self { mat }
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
/// *Only available if compiled with the feature `rayon`*
impl<'a, T, R, Cols, S> ParallelIterator for ParColumnIterMut<'a, T, R, Cols, S>
where
R: Dim,
Cols: Dim,
S: RawStorage<T, R, Cols> + RawStorageMut<T, R, Cols>,
T: Send + Sync + Scalar,
S: Send + Sync,
{
type Item = MatrixViewMut<'a, T, R, U1, S::RStride, S::CStride>;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: rayon::iter::plumbing::UnindexedConsumer<Self::Item>,
{
bridge(self, consumer)
}
fn opt_len(&self) -> Option<usize> {
Some(self.mat.ncols())
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
/// *Only available if compiled with the feature `rayon`*
impl<'a, T, R, Cols, S> IndexedParallelIterator for ParColumnIterMut<'a, T, R, Cols, S>
where
R: Dim,
Cols: Dim,
S: RawStorage<T, R, Cols> + RawStorageMut<T, R, Cols>,
T: Send + Sync + Scalar,
S: Send + Sync,
{
fn drive<C: rayon::iter::plumbing::Consumer<Self::Item>>(self, consumer: C) -> C::Result {
bridge(self, consumer)
}
fn len(&self) -> usize {
self.mat.ncols()
}
fn with_producer<CB: rayon::iter::plumbing::ProducerCallback<Self::Item>>(
self,
callback: CB,
) -> CB::Output {
let producer = ColumnProducerMut(ColumnIterMut::new(self.mat));
callback.callback(producer)
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
/// # Parallel iterators using `rayon`
/// *Only available if compiled with the feature `rayon`*
impl<T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> Matrix<T, R, Cols, S>
where
T: Send + Sync + Scalar,
S: Sync,
{
/// Iterate through the columns of the matrix in parallel using rayon.
/// This iterates over *immutable* references to the columns of the matrix,
/// if *mutable* access to the columns is required, use [`par_column_iter_mut`]
/// instead.
///
/// # Example
/// Using parallel column iterators to calculate the sum of the maximum
/// elements in each column:
/// ```
/// use nalgebra::{dmatrix, DMatrix};
/// use rayon::prelude::*;
///
/// let matrix : DMatrix<f64> = dmatrix![1.0, 0.0, 5.0;
/// 2.0, 4.0, 1.0;
/// 3.0, 2.0, 2.0;
/// ];
/// let sum_of_max :f64 = matrix
/// .par_column_iter()
/// .map(|col| col.max())
/// .sum();
///
/// assert_eq!(sum_of_max,3.0 + 4.0 + 5.0);
///
/// ```
///
/// [`par_column_iter_mut`]: crate::Matrix::par_column_iter_mut
pub fn par_column_iter(&self) -> ParColumnIter<'_, T, R, Cols, S> {
ParColumnIter::new(self)
}
/// Mutably iterate through the columns of this matrix in parallel using rayon.
/// Allows mutable access to the columns in parallel using mutable references.
/// If mutable access to the columns is not required rather use [`par_column_iter`]
/// instead.
///
/// # Example
/// Normalize each column of a matrix with respect to its own maximum value.
///
/// ```
/// use nalgebra::{dmatrix, DMatrix};
/// use rayon::prelude::*;
///
/// let mut matrix : DMatrix<f64> = dmatrix![
/// 2.0, 4.0, 6.0;
/// 1.0, 2.0, 3.0;
/// ];
/// matrix.par_column_iter_mut().for_each(|mut col| col /= col.max());
///
/// assert_eq!(matrix, dmatrix![1.0, 1.0, 1.0; 0.5, 0.5, 0.5]);
/// ```
///
/// [`par_column_iter`]: crate::Matrix::par_column_iter
pub fn par_column_iter_mut(&mut self) -> ParColumnIterMut<'_, T, R, Cols, S>
where
S: RawStorageMut<T, R, Cols>,
{
ParColumnIterMut::new(self)
}
}
/// A private helper newtype that wraps the `ColumnIter` and implements
/// the rayon `Producer` trait. It's just here so we don't have to make the
/// rayon trait part of the public interface of the `ColumnIter`.
struct ColumnProducer<'a, T, R: Dim, C: Dim, S: RawStorage<T, R, C>>(ColumnIter<'a, T, R, C, S>);
#[cfg_attr(doc_cfg, doc(cfg(feature = "rayon")))]
/// *only available if compiled with the feature `rayon`*
impl<'a, T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> Producer
for ColumnProducer<'a, T, R, Cols, S>
where
T: Send + Sync + Scalar,
S: Sync,
{
type Item = MatrixView<'a, T, R, U1, S::RStride, S::CStride>;
type IntoIter = ColumnIter<'a, T, R, Cols, S>;
#[inline]
fn into_iter(self) -> Self::IntoIter {
self.0
}
#[inline]
fn split_at(self, index: usize) -> (Self, Self) {
// The index is relative to the size of this current iterator.
// It will always start at zero so it serves as an offset.
let (left_iter, right_iter) = self.0.split_at(index);
(Self(left_iter), Self(right_iter))
}
}
/// See `ColumnProducer`. A private wrapper newtype that keeps the Producer
/// implementation private
struct ColumnProducerMut<'a, T, R: Dim, C: Dim, S: RawStorageMut<T, R, C>>(
ColumnIterMut<'a, T, R, C, S>,
);
impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> Producer
for ColumnProducerMut<'a, T, R, C, S>
where
T: Send + Sync + Scalar,
S: Send + Sync,
{
type Item = MatrixViewMut<'a, T, R, U1, S::RStride, S::CStride>;
type IntoIter = ColumnIterMut<'a, T, R, C, S>;
fn into_iter(self) -> Self::IntoIter {
self.0
}
fn split_at(self, index: usize) -> (Self, Self) {
// The index is relative to the size of this current iterator
// it will always start at zero so it serves as an offset.
let (left_iter, right_iter) = self.0.split_at(index);
(Self(left_iter), Self(right_iter))
}
}
/// this implementation is safe because we are enforcing exclusive access
/// to the columns through the active range of the iterator
unsafe impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> Send
for ColumnIterMut<'a, T, R, C, S>
{
}