ConcurrentSum1 performs sum concurrently.

ConcurrentSum2 performs sum concurrently.

ConcurrentSum3 uses coordination free sharding to perform more efficient computation.

ConcurrentSum4 is like ConcurrentSum3, but it reads file in sharded way too.

ParseInt is 3-4x times faster than strconv.ParseInt or Atoi.

Sum is a naive implementation and algorithm for summing integers from file.

Sum2 is sum with optimized the first latency + CPU bottleneck bytes.Split.

Sum2_scanner is a sum attempting using scanner.

Sum3 is a sum with optimized the second latency + CPU bottleneck: string conversion.

Sum4 is a sum with optimized the second latency + CPU bottleneck: ParseInt and string conversion.

Sum5 is like Sum4, but noticing that it takes time to even allocate 21 MB on heap (and read file to it).

Sum6 is like Sum4, but trying to use max 10 KB of mem without scanner and bulk read.

Sum7 is cached (cheating!) (: Read more in "Efficient Go"; Example 10-15.