Merge pull request #350 from bluss/bounds-check-elim

 Tweak bounds checked indexing code (Index, IndexMut)

Author: bluss

examples/bounds_check_elim.rs

@@ -0,0 +1,103 @@
+#![crate_type="lib"]
+
+// Test cases for bounds check elimination
+
+extern crate ndarray;
+
+use ndarray::prelude::*;
+
+/*
+pub fn testslice(a: &[f64]) -> f64 {
+    let mut sum = 0.;
+    for i in 0..a.len() {
+        sum += a[i];
+    }
+    sum
+}
+
+pub fn testvec(a: &Vec<f64>) -> f64 {
+    let mut sum = 0.;
+    for i in 0..a.len() {
+        sum += a[i];
+    }
+    sum
+}
+
+pub fn testvec_as_slice(a: &Vec<f64>) -> f64 {
+    let a = a.as_slice();
+    let mut sum = 0.;
+    for i in 0..a.len() {
+        sum += a[i];
+    }
+    sum
+}
+*/
+
+#[no_mangle]
+pub fn test1d_single(a: &Array1<f64>, i: usize) -> f64 {
+    if i < a.len() { a[i] } else { 0. }
+}
+
+#[no_mangle]
+pub fn test1d_single_mut(a: &mut Array1<f64>, i: usize) -> f64 {
+    if i < a.len() { *&mut a[i] } else { 0. }
+}
+
+#[no_mangle]
+pub fn test1d_len_of(a: &Array1<f64>) -> f64 {
+    let a = &*a;
+    let mut sum = 0.;
+    for i in 0..a.len_of(Axis(0)) {
+        sum += a[i];
+    }
+    sum
+}
+
+#[no_mangle]
+pub fn test1d_range(a: &Array1<f64>) -> f64 {
+    let mut sum = 0.;
+    for i in 0..a.len() {
+        sum += a[i];
+    }
+    sum
+}
+
+#[no_mangle]
+pub fn test1d_while(a: &Array1<f64>) -> f64 {
+    let mut sum = 0.;
+    let mut i = 0;
+    while i < a.len() {
+        sum += a[i];
+        i += 1;
+    }
+    sum
+}
+
+#[no_mangle]
+pub fn test2d_ranges(a: &Array2<f64>) -> f64 {
+    let mut sum = 0.;
+    for i in 0..a.rows() {
+        for j in 0..a.cols() {
+            sum += a[[i, j]];
+        }
+    }
+    sum
+}
+
+#[no_mangle]
+pub fn test2d_whiles(a: &Array2<f64>) -> f64 {
+    let mut sum = 0.;
+    let mut i = 0;
+    while i < a.rows() {
+        let mut j = 0;
+        while j < a.cols() {
+            sum += a[[i, j]];
+            j += 1;
+        }
+        i += 1;
+    }
+    sum
+}
+
+fn main() {
+}

src/arraytraits.rs

@@ -69,7 +69,10 @@ impl<S, D, I> Index<I> for ArrayBase<S, D>
     #[inline]
     fn index(&self, index: I) -> &S::Elem {
         debug_bounds_check!(self, index);
-        self.get(index).unwrap_or_else(|| array_out_of_bounds())
+        unsafe {
+            &*self.ptr.offset(index.index_checked(&self.dim, &self.strides)
+                                   .unwrap_or_else(|| array_out_of_bounds()))
+        }
     }
 }
 
@@ -84,7 +87,10 @@ impl<S, D, I> IndexMut<I> for ArrayBase<S, D>
     #[inline]
     fn index_mut(&mut self, index: I) -> &mut S::Elem {
         debug_bounds_check!(self, index);
-        self.get_mut(index).unwrap_or_else(|| array_out_of_bounds())
+        unsafe {
+            &mut *self.as_mut_ptr().offset(index.index_checked(&self.dim, &self.strides)
+                                                .unwrap_or_else(|| array_out_of_bounds()))
+        }
     }
 }
 

tests/array.rs

@@ -219,6 +219,41 @@ fn test_cow()
     assert_eq!(before[3], 1);
 }
 
+#[test]
+fn test_cow_shrink()
+{
+    // A test for clone-on-write in the case that
+    // mutation shrinks the array and gives it different strides
+    //
+    let mut mat = RcArray::zeros((2, 3));
+    //mat.islice(s![.., ..;2]);
+    mat[[0, 0]] = 1;
+    let n = mat.clone();
+    mat[[0, 1]] = 2;
+    mat[[0, 2]] = 3;
+    mat[[1, 0]] = 4;
+    mat[[1, 1]] = 5;
+    mat[[1, 2]] = 6;
+    assert_eq!(mat[[0, 0]], 1);
+    assert_eq!(mat[[0, 1]], 2);
+    assert_eq!(n[[0, 0]], 1);
+    assert_eq!(n[[0, 1]], 0);
+    assert_eq!(n.get((0, 1)), Some(&0));
+    // small has non-C strides this way
+    let mut small = mat.reshape(6);
+    small.islice(s![4..;-1]);
+    assert_eq!(small[0], 6);
+    assert_eq!(small[1], 5);
+    let before = small.clone();
+    // mutation
+    // small gets back C strides in CoW.
+    small[1] = 9;
+    assert_eq!(small[0], 6);
+    assert_eq!(small[1], 9);
+    assert_eq!(before[0], 6);
+    assert_eq!(before[1], 5);
+}
+
 #[test]
 fn test_sub()
 {