Try keeping the loop over all primes and breaking when `a > maxp` where maxp is calculated once before the loop as `maxp = floor(Int,sqrt(n))`.
On Monday, August 22, 2016 at 4:58:30 PM UTC-4, Achu wrote: > > I have a simple piece of code that finds me 10001 prime numbers. > > function a() > pl=[2] > n=3 > ct=1 > while(ct<10001) > isnprime=true > for a in pl > if n%a==0 > isnprime=false > break > end > end > if isnprime > push!(pl,n) > ct+=1 > end > n+=2 > end > return pl > end > > When I tweaked the code to check only prime factors less than the sqrt of > the number, it slowed it down by a factor of 3. > > function a() > pl=[2] > n=3 > ct=1 > while(ct<10001) > isnprime=true > for a in pl[pl.<sqrt(n)] > if n%a==0 > isnprime=false > break > end > end > if isnprime > push!(pl,n) > ct+=1 > end > n+=2 > end > return pl > end > > Why is that? > >
