From 64e1aec2941adc9bddcf1bca715b9ed8b83bf6f1 Mon Sep 17 00:00:00 2001
From: Magnus Ulimoen <flymagnus@gmail.com>
Date: Fri, 28 Feb 2020 22:26:18 +0100
Subject: [PATCH] simplify loop conditions

---
 sbp/src/operators/upwind4.rs | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/sbp/src/operators/upwind4.rs b/sbp/src/operators/upwind4.rs
index 83d5d8c..44d3b12 100644
--- a/sbp/src/operators/upwind4.rs
+++ b/sbp/src/operators/upwind4.rs
@@ -6,7 +6,7 @@ use ndarray::{s, ArrayView1, ArrayView2, ArrayViewMut1, ArrayViewMut2, Axis};
 #[derive(Debug)]
 pub struct Upwind4 {}
 
-/// Simdtype used in diff_simd_col
+/// Simdtype used in diff_simd_col and diff_simd_row
 #[cfg(feature = "f32")]
 type SimdT = packed_simd::f32x8;
 #[cfg(not(feature = "f32"))]
@@ -29,7 +29,7 @@ macro_rules! diff_simd_row_7_47 {
                 assert_eq!(prev.shape(), fut.shape());
                 assert!(prev.len_of(Axis(1)) >= 2 * $BLOCK.len());
                 assert!(prev.len() >= SimdT::lanes());
-                // The prev and fut array must have contigous last dimension
+                // The prev and fut array must have contiguous last dimension
                 assert_eq!(prev.strides()[1], 1);
                 assert_eq!(fut.strides()[1], 1);
 
@@ -44,7 +44,6 @@ macro_rules! diff_simd_row_7_47 {
                     let fut = unsafe {
                         slice::from_raw_parts_mut(fut.uget_mut((j, 0)) as *mut Float, nx)
                     };
-                    //let mut fut = fut.slice_mut(s![j, ..]);
 
                     let first_elems = unsafe { SimdT::from_slice_unaligned_unchecked(prev) };
                     let block = {
@@ -79,17 +78,11 @@ macro_rules! diff_simd_row_7_47 {
                             diag[0], diag[1], diag[2], diag[3], diag[4], diag[5], diag[6], 0.0,
                         )
                     };
-                    for (f, p) in fut
-                        .iter_mut()
-                        .skip(block.len())
-                        .zip(
-                            prev.windows(SimdT::lanes())
-                                .map(SimdT::from_slice_unaligned)
-                                .skip(1),
-                        )
-                        .take(nx - 2 * block.len())
-                    {
-                        *f = idx * (p * diag).sum();
+                    for i in 4..nx - 4 {
+                        unsafe {
+                            let prev = SimdT::from_slice_unaligned_unchecked(&prev[i - 3..]);
+                            *fut.get_unchecked_mut(i) = idx * (prev * diag).sum();
+                        }
                     }
 
                     let last_elems =
@@ -129,7 +122,7 @@ macro_rules! diff_simd_col_7_47 {
                 use std::slice;
                 assert_eq!(prev.shape(), fut.shape());
                 assert_eq!(prev.stride_of(Axis(0)), 1);
-                assert_eq!(prev.stride_of(Axis(0)), 1);
+                assert_eq!(fut.stride_of(Axis(0)), 1);
                 let ny = prev.len_of(Axis(0));
                 let nx = prev.len_of(Axis(1));
                 assert!(nx >= 2 * $BLOCK.len());