make core-intrinsics cfg'ed

sbp/src/lib.rs

@@ -1,4 +1,4 @@
-#![feature(core_intrinsics)]
+#![cfg_attr(feature = "fast-float", feature(core_intrinsics))]
 #![feature(array_windows)]
 #![feature(array_chunks)]
 

sbp/src/operators/algos.rs

@@ -353,6 +353,12 @@ mod fastfloat {
             Self(f)
         }
     }
+    impl From<FastFloat> for Float {
+        #[inline(always)]
+        fn from(f: FastFloat) -> Self {
+            f.0
+        }
+    }
 }
 #[cfg(feature = "fast-float")]
 use fastfloat::FastFloat;
@@ -838,14 +844,17 @@ pub(crate) fn diff_op_col_simd(
 }
 
 #[inline(always)]
-fn product_fast<'a>(
-    u: impl Iterator<Item = &'a Float>,
-    v: impl Iterator<Item = &'a Float>,
-) -> Float {
-    use std::intrinsics::{fadd_fast, fmul_fast};
-    u.zip(v).fold(0.0, |acc, (&u, &v)| unsafe {
-        // We do not care about the order of multiplication nor addition
-        fadd_fast(acc, fmul_fast(u, v))
+fn dotproduct<'a>(u: impl Iterator<Item = &'a Float>, v: impl Iterator<Item = &'a Float>) -> Float {
+    u.zip(v).fold(0.0, |acc, (&u, &v)| {
+        #[cfg(feature = "fast-float")]
+        unsafe {
+            // We do not care about the order of multiplication nor addition
+            (FastFloat::from(acc) + FastFloat::from(u) * FastFloat::from(v)).into()
+        }
+        #[cfg(not(feature = "fast-float"))]
+        {
+            acc + u * v
+        }
     })
 }
 
@@ -1043,7 +1052,7 @@ pub(crate) fn diff_op_row(
             assert!(prev.len() >= 2 * block.len());
 
             for (bl, f) in block.iter().zip(fut.iter_mut()) {
-                let diff = product_fast(bl.iter(), prev[..bl.len()].iter());
+                let diff = dotproduct(bl.iter(), prev[..bl.len()].iter());
                 *f = diff * idx;
             }
 
@@ -1057,12 +1066,12 @@ pub(crate) fn diff_op_row(
                 .zip(fut.iter_mut().skip(block.len()))
                 .take(nx - 2 * block.len())
             {
-                let diff = product_fast(diag.iter(), window.iter());
+                let diff = dotproduct(diag.iter(), window.iter());
                 *f = diff * idx;
             }
 
             for (bl, f) in block.iter().zip(fut.iter_mut().rev()) {
-                let diff = product_fast(bl.iter(), prev.iter().rev());
+                let diff = dotproduct(bl.iter(), prev.iter().rev());
 
                 *f = idx
                     * if symmetry == Symmetry::Symmetric {