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Ruud H.G. van Tol on Sat, 26 Nov 2022 08:48:41 +0100
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- To: pari-dev@pari.math.u-bordeaux.fr
- Subject: 3^k performance
- From: "Ruud H.G. van Tol" <rvtol@isolution.nl>
- Date: Sat, 26 Nov 2022 08:47:39 +0100
- Delivery-date: Sat, 26 Nov 2022 08:48:41 +0100
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A022330_1(n)=1+n+sum(k=1,n,logint(3^k,2))
A022330_2(n)=my(t=1);1+n+sum(k=1,n,logint(t*=3,2))
? A022330_1(10^5)
cpu time = 8,322 ms, real time = 8,352 ms.
%15 = 7924941755
? A022330_2(10^5)
cpu time = 215 ms, real time = 217 ms.
%16 = 7924941755
So about a 40x difference.
Is that worthwhile to look into?
How to best approach that?
BTW, I learned the trick from
https://oeis.org/A071521
(Charles R Greathouse IV, 2018)
-- Ruud
P.S. And on pari-users I would probably have
also asked which sumnum it should use. :)