From e7734fb80cac5dd1f7c9845d5530d80b664a9f3e Mon Sep 17 00:00:00 2001 From: misterg Date: Tue, 2 Jan 2018 14:42:09 -0500 Subject: [PATCH] OSS Sync, cl 163329677 --- googletest/samples/prime_tables.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/googletest/samples/prime_tables.h b/googletest/samples/prime_tables.h index 92ce16a0..55a3b44e 100644 --- a/googletest/samples/prime_tables.h +++ b/googletest/samples/prime_tables.h @@ -103,11 +103,15 @@ class PreCalculatedPrimeTable : public PrimeTable { ::std::fill(is_prime_, is_prime_ + is_prime_size_, true); is_prime_[0] = is_prime_[1] = false; - for (int i = 2; i <= max; i++) { + // Checks every candidate for prime number (we know that 2 is the only even + // prime). + for (int i = 2; i*i <= max; i += i%2+1) { if (!is_prime_[i]) continue; // Marks all multiples of i (except i itself) as non-prime. - for (int j = 2*i; j <= max; j += i) { + // We are starting here from i-th multiplier, because all smaller + // complex numbers were already marked. + for (int j = i*i; j <= max; j += i) { is_prime_[j] = false; } }