On 11/25/2014 02:31 PM, Serhiy Storchaka wrote:
п'ятниця, 21-лис-2014 08:15:57 ви написали:
This looks very good indeed. As a matter of interest, is there any
particular reason you have used 2*b instead of b+b? Might b+b be faster
than b*2?
Yes, it is slightly faster, but the effect is indiscernible in total
time. But
there is not harm to use b+b.
Also, in various lines, you use //2. Would >>1 be quicker? On reflection,
perhaps you have had to use //2 because >>1 cannot be used in those
situations.
I thought this effect would be insignificant too. But actually it is
measurable
(about 10% for some input). Thanks, this optimization is worth to be
applied.
Unfortunately, for many values, the version of the function with >>1 is
slower. It's only when the argument is bigger than 10**40 that it's as
much as 1% faster. But it's true that for really large values, it's
quicker.
A quick test shows that 3.3 is about 20% faster for both these functions
than 2.7.
My oversight earlier was assuming a native type. Once you get into
"longs" which aren't supported by the processor, the shift will likely
become much faster than divide.
--
DaveA
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