Re: question on the patch FastString
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- Subject: Re: question on the patch FastString
- From: 云风 Cloud Wu <cloudwu@...>
- Date: 2020年5月26日 12:54:09 +0800
Philippe Verdy <verdyp@gmail.com> 于2020年5月26日周二 上午1:18写道：
> And as I said, Mersenne primes are not the best primes for the constant factor: it is only a workaround solution for very small devices that don't have a fast multiplication of two integers. you should use a prime that has alternates the highest number of sequences of 1 and sequences of 0 (ideally a binary number of the form "101010...101" and only if it is a prime.
> * 0b1010_1010_1010_1011 = 0xAAAB = 43691 : IT IS A PRIME ! (see https://primes.utm.edu/lists/small/10000.txt)
Is the form "...011011" a better choice ? It has more "1" in the
binary number, and the longest number of sequences of 1 is two. I
think the form "011" means 2 times of addition.
0b1011011011011011 =わ 0xB6Db = 46811 : It is a prime , too.