Well yes, that's all true. The approach of alternating reads of blocks is slow only if you need to do it. If there's a diff in the first block (or so) then the

Well yes, that's all true. The approach of alternating reads of blocks is slow only if you need to do it. If there's a diff in the first block (or so) then there's not much to read. But it's a good example why there can't be one optimal strategy for finding duplicates. Depending on the data set composition, various implementations turn out the fastest. It depends heavily on where most the files differ (or not).