Optimization_1x4_6

Copy the contents of file MMult_1x4_5.c into a file named MMult_1x4_6.c and change the contents:

|| from || to || ||<^> -Include(HowToOptimizeGemm/Details/MMult_1x4_5)- ||<^> -Include(HowToOptimizeGemm/Details/MMult_1x4_6)- ||

Change the first lines in the makefile to {{{ OLD := MMult_1x4_5 NEW := MMult_1x4_6
}}}

• 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-1x4-5_MMult-1x4-6.png,http://www.cs.utexas.edu/users/rvdg/HowToOptimizeGemm/Graphs/compare_MMult-1x4-5_MMult-1x4-6.png,width=40%)

Now we start seeing a performance benefit. We accumulate the updates to the current 1x4 row of C in registers and we place the element A( p, 0 ) in a register, to reduce traffic between cache and registers.