Skip to content

Optimization_1x4_8

Jump to bottom
Jianyu Huang edited this page Aug 2, 2016 · 3 revisions

Copy the contents of file MMult_1x4_7.c into a file named MMult_1x4_8.c and change the contents:

|| from || to || ||<^> -Include(HowToOptimizeGemm/Details/MMult_1x4_7)- ||<^> -Include(HowToOptimizeGemm/Details/MMult_1x4_8)- ||

Change the first lines in the makefile to {{{ OLD := MMult_1x4_7 NEW := MMult_1x4_8
}}}

  • make run {{{ octave:3> PlotAll % this will create the plot }}}

This time the performance graph will look something like

ImageLink(http://www.cs.utexas.edu/users/rvdg/HowToOptimizeGemm/Graphs/compare_MMult-1x4-7_MMult-1x4-8.png,http://www.cs.utexas.edu/users/rvdg/HowToOptimizeGemm/Graphs/compare_MMult-1x4-7_MMult-1x4-8.png,width=40%)

We now unrolled the loop by four. Interestingly enough, this decreases performance slightly. What this probably means is that by adding the optimization, we confused the compiler, which therefore could not do an optimization that it did before.

Clone this wiki locally