Better sizehint for primes

JuliaLang · May 12, 2016 · 7f07a50 · 7f07a50
1 parent 9c2a233
commit 7f07a50
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Showing 2 changed files with 4 additions and 1 deletion.
diff --git a/base/primes.jl b/base/primes.jl
@@ -83,7 +83,7 @@ function primes(lo::Int, hi::Int)
     lo ≤ 3 ≤ hi && push!(list, 3)
     lo ≤ 5 ≤ hi && push!(list, 5)
     hi < 7 && return list
-    sizehint!(list, floor(Int, hi / log(hi)))
+    sizehint!(list, floor(Int, max(hi,0) / log(max(hi,2)) - max(lo,0) / log(max(lo,2))))
     sieve = _primesmask(max(7, lo), hi)
     lwi = wheel_index(lo - 1)
     @inbounds for i = 1:length(sieve)   # don't use eachindex here

diff --git a/test/numbers.jl b/test/numbers.jl
@@ -2253,6 +2253,9 @@ for T in [Int,BigInt], n = [1:1000;1000000]
         @test s[k] == primesmask(k, k)[1]
     end
 end
+let i = rand(1:2^(3*WORD_SIZE÷4))
+    @test primes(i,i+1476) == filter(isprime, i:i + 1476) == filter(isprime, big(i:i + 1476))
+end
 
 @test !isprime(1000000003)
 @test !isprime(1000000005)