From: Siep Korteling <s.korteling@...>
Date: 2007-11-06T20:14:56+09:00
Subject: sieve.rb sample

the sieve of Erathotenes sample (sieve.rb) in Ruby 1.9 looks like this:


max = Integer(ARGV.shift || 100)
sieve = []
for i in 2 .. max
  sieve[i] = i
end

for i in 2 .. Math.sqrt(max)
  next unless sieve[i]
  (i*i).step(max, i) do |j|
    sieve[j] = nil
  end
end
puts sieve.compact.join(", ")


Is Math.sqrt(max) calculated every loop?
....
m=Math.sqrt(max)
for i in 2 .. m
....

runs about 20% faster on my machine.
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