More practical ways to speed up a program than by going from O(nlog n) to O(nlog log n). - Algorithmica / HN

Among the cool things that we will speed up:

• 2x faster GCD (compared to std::gcd)
• 8-15x faster binary search (compared to std::lower_bound)
• 5-10x faster segment trees (compared to Fenwick trees)
• 5x faster hash tables (compared to std::unordered_map)
• 2x faster popcount (compared to repeatedly calling popcnt)
• 2x faster parsing series of integers (compared to scanf)
• ?x faster sorting (compared to std::sort)
• 2x faster sum (compared to std::accumulate)
• 2-3x faster prefix sum (compared to naive implementation)
• 10x faster argmin (compared to naive implementation)
• 10x faster array searching (compared to std::find)
• 100x faster matrix multiplication (compared to “for-for-for”)
• optimal word-size integer factorization (~0.4ms per 60-bit integer)
• optimal Karatsuba Algorithm
• optimal FFT