Thanks for your feedback. (Author here.) By my calculations (which I'll machine-check now with Maxima), the 30% and 70% speed-up claims are sound. First, let'

Thanks for your feedback. (Author here.) By my calculations (which I'll machine-check now with Maxima), the 30% and 70% speed-up claims are sound. First, let's fire up Maxima: $ maxima Maxima 5.30.0 http://maxima.sourceforge.net using Lisp SBCL 1.1.8-2.fc19 Distributed under the GNU Public License. See the file COPYING. Dedicated to the memory of William Schelter. The function bug_report() provides bug reporting information. Now let's calculate how much faster we made the row-copy code by unrolling its loop: (%i1) orig_loop_speed: (1*row) / (157*cycle)$ (%i2) unrolled_loop_speed: (1*row) / (120*cycle)$ (%i3) unrolling_speedup: unrolled_loop_speed / orig_loop_speed, numer; (%o3) 1.308333333333333 In other words, the unrolled-loop speed is 1.3 times the original-loop speed. That's 30% faster, right? Likewise, how much faster did shaving those 1200 cycles make the tile-copy code? (%i4) copy2_speed: (1*tile) / (2893*cycle)$ (%i5) copy3_speed: (1*tile) / (1689*cycle)$ (%i6) copy3_vs_2_speedup: copy3_speed / copy2_speed, numer; (%o6) 1.712847838957963 I'm willing to believe that I've screwed up here, but I can't see where. Can you show me? Thanks for your help!