On Sun, Aug 28, 2022 at 1:38 PM Henry Rich <[email protected]> wrote:
> OK, I guess you could have a workaround. The problem occurs only when
> there are no non-sparse entries, ...
Yes... for the algorithm I was working with, the "no sparse entries"
issue quickly disappears, so I was able to skip over that.
In other words, instead of
pritchard=: {{
spokes=. $.,1
primes=. i.0
while. y > #spokes do.
primes=. primes, p=. 2+(}.spokes) i.1 NB. find next prime
rim=. #spokes NB. "length" of "circumference" of wheel
spokes=. (y<.p*rim)$spokes NB. roll next larger wheel
spokes=. 0 ((#~ y>])_1+p*1+i.rim)} spokes NB. remove newly
recognized prime from wheel
end.
while. y > p*p do.
primes=. primes, p=. 2+(}.spokes) i.1 NB. find next prime
spokes=. 0 ((#~ y>])_1+p*1+i.rim)} spokes NB. scrub it out of wheel
end.
primes,1+}.,I.spokes
}}
I went with
pritchard=: {{
spokes=. $.6$4{.1
primes=. 2, p=.3
while. y > #spokes do.
primes=. primes, p=. 2+(}.spokes) i.1 NB. find next prime
rim=. #spokes NB. "length" of "circumference" of wheel
spokes=. (y<.p*rim)$spokes NB. roll next larger wheel
spokes=. 8 $.0 ((#~ y>])_1+p*1+i.rim)} spokes NB. remove newly
recognized prime from wheel
end.
while. y > p*p do.
primes=. primes, p=. 2+(}.spokes) i.1 NB. find next prime
spokes=. 0 ((#~ y>])_1+p*1+i.rim)} spokes NB. scrub it out of wheel
end.
primes,1+}.,I.spokes
}}
(on rosettacode...)
Thanks,
--
Raul
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