feature gate functionality

.github/workflows/nalgebra-ci-build.yml

@@ -61,7 +61,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: test
-        run: cargo test --features arbitrary,rand,serde-serialize,sparse,debug,io,compare,libm,proptest-support,slow-tests,rkyv-safe-deser;
+        run: cargo test --features arbitrary,rand,serde-serialize,sparse,debug,io,compare,libm,proptest-support,slow-tests,rkyv-safe-deser,rayon;
   test-nalgebra-glm:
     runs-on: ubuntu-latest
     steps:

Cargo.toml

@@ -33,6 +33,7 @@ libm    = [ "simba/libm" ]
 libm-force = [ "simba/libm_force" ]
 macros = [ "nalgebra-macros" ]
 cuda   = [ "cust_core", "simba/cuda" ]
+rayon  = [ "dep:rayon" ]
 
 # Conversion
 convert-mint = [ "mint" ]
@@ -101,7 +102,7 @@ glam020        = { package = "glam", version = "0.20", optional = true }
 glam021        = { package = "glam", version = "0.21", optional = true }
 glam022        = { package = "glam", version = "0.22", optional = true }
 cust_core      = { version = "0.1", optional = true }
-rayon = "1.5" # TODO make this feature gated
+rayon          = { version = "1.5", optional = true }
 
 [dev-dependencies]
 serde_json = "1.0"

src/base/iter.rs

@@ -6,8 +6,6 @@ use std::iter::FusedIterator;
 use std::marker::PhantomData;
 use std::mem;
 
-use rayon::iter::plumbing::Producer;
-
 use crate::base::dimension::{Dim, U1};
 use crate::base::storage::{RawStorage, RawStorageMut};
 use crate::base::{Matrix, MatrixView, MatrixViewMut, Scalar};
@@ -365,34 +363,6 @@ impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> ExactSizeIterat
     }
 }
 
-impl<'a, T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> Producer for ColumnIter<'a, T, R, Cols, S>
-where
-    T: Send + Sync + Debug + PartialEq + Clone + 'static,
-    S: Sync,
-{
-    type Item = MatrixSlice<'a, T, R, U1, S::RStride, S::CStride>;
-    type IntoIter = ColumnIter<'a, T, R, Cols, S>;
-
-    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 = Self {
-            mat: self.mat,
-            range: self.range.start..(self.range.start + index),
-        };
-
-        let right = Self {
-            mat: self.mat,
-            range: (self.range.start + index)..self.range.end,
-        };
-        (left, right)
-    }
-
-    fn into_iter(self) -> Self::IntoIter {
-        self
-    }
-}
-
 /// An iterator through the mutable columns of a matrix.
 #[derive(Debug)]
 pub struct ColumnIterMut<'a, T, R: Dim, C: Dim, S: RawStorageMut<T, R, C>> {
@@ -469,12 +439,46 @@ impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> DoubleEndedI
     }
 }
 
-impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> Producer
+/// implementations for parallel iteration with rayon
+#[cfg(feature = "rayon")]
+mod parallel {
+    use super::*;
+    use rayon::iter::plumbing::Producer;
+
+    impl<'a, T, R: Dim, Cols: Dim, S: RawStorage<T, R, Cols>> Producer for ColumnIter<'a, T, R, Cols, S>
+    where
+        T: Send + Sync + Debug + PartialEq + Clone + 'static,
+        S: Sync,
+    {
+        type Item = MatrixSlice<'a, T, R, U1, S::RStride, S::CStride>;
+        type IntoIter = ColumnIter<'a, T, R, Cols, S>;
+
+        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 = Self {
+                mat: self.mat,
+                range: self.range.start..(self.range.start + index),
+            };
+
+            let right = Self {
+                mat: self.mat,
+                range: (self.range.start + index)..self.range.end,
+            };
+            (left, right)
+        }
+
+        fn into_iter(self) -> Self::IntoIter {
+            self
+        }
+    }
+
+    impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> Producer
         for ColumnIterMut<'a, T, R, C, S>
-where
+    where
         T: Send + Sync + Debug + PartialEq + Clone,
         S: Send + Sync,
-{
+    {
         type Item = MatrixSliceMut<'a, T, R, U1, S::RStride, S::CStride>;
         type IntoIter = ColumnIterMut<'a, T, R, C, S>;
 
@@ -499,9 +503,12 @@ where
             };
             (left, right)
         }
-}
+    }
 
-unsafe impl<'a, T: Scalar, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> Send
+    /// 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>
-{
+    {
+    }
 }

src/base/mod.rs

@@ -42,6 +42,7 @@ mod min_max;
 /// Mechanisms for working with values that may not be initialized.
 pub mod uninit;
 
+#[cfg(feature = "rayon")]
 pub mod par_iter;
 
 #[cfg(feature = "rkyv-serialize-no-std")]

tests/core/matrix.rs

@@ -1200,6 +1200,7 @@ fn column_iteration_double_ended() {
 }
 
 #[test]
+#[cfg(feature = "rayon")]
 fn parallel_column_iteration() {
     use nalgebra::dmatrix;
     use rayon::prelude::*;
@@ -1221,6 +1222,7 @@ fn parallel_column_iteration() {
 }
 
 #[test]
+#[cfg(feature = "rayon")]
 fn colum_iteration_mut_double_ended() {
     let dmat = nalgebra::dmatrix![
     13,14,15,16,17;
@@ -1239,6 +1241,7 @@ fn colum_iteration_mut_double_ended() {
 }
 
 #[test]
+#[cfg(feature = "rayon")]
 fn parallel_column_iteration_mut() {
     use rayon::prelude::*;
     let mut first = DMatrix::<f32>::zeros(400, 300);

tests/lib.rs

@@ -9,6 +9,10 @@ compile_error!(
      Example: `cargo test --features debug,compare,rand,macros`"
 );
 
+// make sure to test the parallel iterators for all builds that do not require no_std
+#[cfg(all(feature = "std", not(feature = "rayon")))]
+compile_error!("Please additionally enable the `rayon` feature to compile and run the tests");
+
 #[cfg(all(feature = "debug", feature = "compare", feature = "rand"))]
 #[macro_use]
 extern crate approx;