diff --git a/src/dimension/mod.rs b/src/dimension/mod.rs
index 28d2e9b2c..212197fed 100644
--- a/src/dimension/mod.rs
+++ b/src/dimension/mod.rs
@@ -139,6 +139,14 @@ pub fn can_index_slice_not_custom<A, D: Dimension>(data: &[A], dim: &D) -> Resul
 ///    also implies that the length of any individual axis does not exceed
 ///    `isize::MAX`.)
 pub fn max_abs_offset_check_overflow<A, D>(dim: &D, strides: &D) -> Result<usize, ShapeError>
+where
+    D: Dimension,
+{
+    max_abs_offset_check_overflow_impl(mem::size_of::<A>(), dim, strides)
+}
+
+fn max_abs_offset_check_overflow_impl<D>(elem_size: usize, dim: &D, strides: &D)
+    -> Result<usize, ShapeError>
 where
     D: Dimension,
 {
@@ -168,7 +176,7 @@ where
     // Determine absolute difference in units of bytes between least and
     // greatest address accessible by moving along all axes
     let max_offset_bytes = max_offset
-        .checked_mul(mem::size_of::<A>())
+        .checked_mul(elem_size)
         .ok_or_else(|| from_kind(ErrorKind::Overflow))?;
     // Condition 2b.
     if max_offset_bytes > isize::MAX as usize {
@@ -216,13 +224,21 @@ pub fn can_index_slice<A, D: Dimension>(
 ) -> Result<(), ShapeError> {
     // Check conditions 1 and 2 and calculate `max_offset`.
     let max_offset = max_abs_offset_check_overflow::<A, _>(dim, strides)?;
+    can_index_slice_impl(max_offset, data.len(), dim, strides)
+}
 
+fn can_index_slice_impl<D: Dimension>(
+    max_offset: usize,
+    data_len: usize,
+    dim: &D,
+    strides: &D,
+) -> Result<(), ShapeError> {
     // Check condition 4.
     let is_empty = dim.slice().iter().any(|&d| d == 0);
-    if is_empty && max_offset > data.len() {
+    if is_empty && max_offset > data_len {
         return Err(from_kind(ErrorKind::OutOfBounds));
     }
-    if !is_empty && max_offset >= data.len() {
+    if !is_empty && max_offset >= data_len {
         return Err(from_kind(ErrorKind::OutOfBounds));
     }
 
diff --git a/src/iterators/mod.rs b/src/iterators/mod.rs
index 091119361..621c141ff 100644
--- a/src/iterators/mod.rs
+++ b/src/iterators/mod.rs
@@ -79,15 +79,18 @@ impl<A, D: Dimension> Iterator for Baseiter<A, D> {
         let ndim = self.dim.ndim();
         debug_assert_ne!(ndim, 0);
         let mut accum = init;
-        while let Some(mut index) = self.index.clone() {
+        while let Some(mut index) = self.index {
             let stride = self.strides.last_elem() as isize;
             let elem_index = index.last_elem();
             let len = self.dim.last_elem();
             let offset = D::stride_offset(&index, &self.strides);
             unsafe {
                 let row_ptr = self.ptr.offset(offset);
-                for i in 0..(len - elem_index) {
+                let mut i = 0;
+                let i_end = len - elem_index;
+                while i < i_end {
                     accum = g(accum, row_ptr.offset(i as isize * stride));
+                    i += 1;
                 }
             }
             index.set_last_elem(len - 1);
diff --git a/src/zip/mod.rs b/src/zip/mod.rs
index 2b6612b54..c23791f62 100644
--- a/src/zip/mod.rs
+++ b/src/zip/mod.rs
@@ -723,7 +723,7 @@ where
         }
     }
 
-    fn apply_core_contiguous<F, Acc>(&mut self, mut acc: Acc, mut function: F) -> FoldWhile<Acc>
+    fn apply_core_contiguous<F, Acc>(&mut self, acc: Acc, mut function: F) -> FoldWhile<Acc>
     where
         F: FnMut(Acc, P::Item) -> FoldWhile<Acc>,
         P: ZippableTuple<Dim = D>,
@@ -732,15 +732,35 @@ where
         let size = self.dimension.size();
         let ptrs = self.parts.as_ptr();
         let inner_strides = self.parts.contiguous_stride();
-        for i in 0..size {
-            unsafe {
-                let ptr_i = ptrs.stride_offset(inner_strides, i);
-                acc = fold_while![function(acc, self.parts.as_ref(ptr_i))];
-            }
+        unsafe {
+            self.inner(acc, ptrs, inner_strides, size, &mut function)
+        }
+    }
+
+    /// The innermost loop of the Zip apply methods
+    ///
+    /// Run the fold while operation on a stretch of elements with constant strides
+    ///
+    /// `ptr`: base pointer for the first element in this stretch
+    /// `strides`: strides for the elements in this stretch
+    /// `len`: number of elements
+    /// `function`: closure
+    unsafe fn inner<F, Acc>(&self, mut acc: Acc, ptr: P::Ptr, strides: P::Stride,
+                            len: usize, function: &mut F) -> FoldWhile<Acc>
+    where
+        F: FnMut(Acc, P::Item) -> FoldWhile<Acc>,
+        P: ZippableTuple
+    {
+        let mut i = 0;
+        while i < len {
+            let p = ptr.stride_offset(strides, i);
+            acc = fold_while!(function(acc, self.parts.as_ref(p)));
+            i += 1;
         }
         FoldWhile::Continue(acc)
     }
 
+
     fn apply_core_strided<F, Acc>(&mut self, acc: Acc, function: F) -> FoldWhile<Acc>
     where
         F: FnMut(Acc, P::Item) -> FoldWhile<Acc>,
@@ -773,15 +793,11 @@ where
         while let Some(index) = index_ {
             unsafe {
                 let ptr = self.parts.uget_ptr(&index);
-                for i in 0..inner_len {
-                    let p = ptr.stride_offset(inner_strides, i);
-                    acc = fold_while!(function(acc, self.parts.as_ref(p)));
-                }
+                acc = fold_while![self.inner(acc, ptr, inner_strides, inner_len, &mut function)];
             }
 
             index_ = self.dimension.next_for(index);
         }
-        self.dimension[unroll_axis] = inner_len;
         FoldWhile::Continue(acc)
     }
 
@@ -801,10 +817,7 @@ where
             loop {
                 unsafe {
                     let ptr = self.parts.uget_ptr(&index);
-                    for i in 0..inner_len {
-                        let p = ptr.stride_offset(inner_strides, i);
-                        acc = fold_while!(function(acc, self.parts.as_ref(p)));
-                    }
+                    acc = fold_while![self.inner(acc, ptr, inner_strides, inner_len, &mut function)];
                 }
 
                 if !self.dimension.next_for_f(&mut index) {
@@ -812,7 +825,6 @@ where
                 }
             }
         }
-        self.dimension[unroll_axis] = inner_len;
         FoldWhile::Continue(acc)
     }