Cintu07 commented on PR #10995:
URL: https://github.com/apache/arrow-rs/pull/10995#issuecomment-5556790460
i ran it on my machine too, aarch64.
different rows moved for me. your +22% row came out +1.8%. instead by char
(non-ascii, prefix) was +11.7%.
so i ran the same branch again against the same baseline, no code change at
all
between the two runs:
by char (non-ascii, prefix) +53%
by char (non-ascii, tail) +31%
by char (ascii, prefix) -3.7% improved
by char (ascii, tail) -2.3% improved
same code both times. so this bench can swing 50% on my box by itself.
the row that runs the new branches is start = 1, length = str_len - 1. run
one was
+0.06% at p 0.96, run two -1.35% at p 0.22. it did not move either time.
my laptop is noisier than your runner, sure. but every by char row goes
through
substring_by_char_impl and the diff never touches that function, so those
cannot be
my change.
if you would rather not have the extra branch in the loop at all, i can move
the
checks out. start and length do not change per row, they only need checking
once.
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