Unroll by 4 as a dumb heuristic more often.

Author: chriselrod

src/modeling/determinestrategy.jl

@@ -264,13 +264,11 @@ function unroll_no_reductions(ls, order, vloopsym)
     # heuristic guess
     # roundpow2(min(4, round(Int, (compute_rt + load_rt + 1) / compute_rt)))
     memory_rt = load_rt + store_rt
-    # @show memory_rt, load_rt, store_rt, compute_rt, compute_l
-    
-    u = if compute_rt > memory_rt
+    u = if compute_rt ≤ 1
+        4
+    elseif compute_rt > memory_rt
         clamp(round(Int, compute_l / compute_rt), 1, 4)
         # max(1, VectorizationBase.nextpow2( min( 4, round(Int, 8 / compute_rt) ) ))
-    elseif iszero(compute_rt)
-        4
     elseif iszero(load_rt)
         iszero(store_rt) ? 4 : max(1, min(4, round(Int, 2compute_rt / store_rt)))
     else