On Dec 6, 2013, at 7:36 AM, Jarno Rajahalme <jrajaha...@nicira.com> wrote: > On Dec 5, 2013, at 4:44 PM, Ben Pfaff <b...@nicira.com> wrote: >> How did you measure the benefit of inlining? > > With a standalone C program running different variants (original, inlined, > different algorithm) over
I should mention that I linked with a stripped down version of lib/util.c, keeping the interesting parts, and more importantly, keeping them in a different compilation unit, like we do with OVS. Jarno > randomized data of 10000 u64s about 100000 times and timing each algorithm > with clock_gettime(CLOCK_THREAD_CPUTIME_ID). Compiled for 32 or 64 bits with > -m32 or without, and for i7 with -march=native -mtune=native. I used -O2 as > we compile OVS with -O2, too. > > The alternate algorithm computes the popcount in parallel for the 64 bits (so > it is equally fast for both 32 and 64 bits), while the recalculated array > requires double the work for 64 bits, compared to 32 bits. But on the other > hand, the array lookup is still faster for 32 bits. > > Jarno > > >
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