Re: Euler problem #187

William James wrote:
>>
>> : PRIMES  ( -- n )
>>     FLAGS plimit 2/ 1 FILL
>>     3  EFLAG FLAGS DO

For speed, please run the outer loop only between FLAGS and
FLAGS+sqrt(plimit)/2. This is completely sufficient, as any non-prime is
already dividable by one number that's at most the square of plimit, so
after that, you'll never mark any new number as non-prime. This "small"
optimization improves the algorithm of sieve from O(n^1,5) to O(n), which
is a huge advantage if your n is 100 millions. The benchmark was never
optimized, since one idea of a benchmark is to run the same stupid thing,
and not change the rules.

> forprime( pr=2, sqrtint( top - 1 ),

Yes, that's the right end here.

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://www.jwdt.com/~paysan/