Time measurements

timeit.md

@@ -40,4 +40,8 @@ Measured on snehulak (Intel i5 5257U)
 - commit 8126213c7cd5: 24.4 s
 - commit 528d64b9fb6c (api change): 24 s
 - commit ac504e4195e5 (SAVE_MEMORY=1): 16.8 s
+- commit 6d90f293bca8 (small changes): 15.8 s
+- commit f5b43ca8ec1b (+ unroll loops): 14.8 s
+- commit f5b43ca8ec1b + OPTIMIZED_MAPPINGS: 13.7 s -- not much better
+  hence it stays off by default