Github user StephanEwen commented on the pull request:
https://github.com/apache/flink/pull/973#issuecomment-127256237
The minus operation is not really evaluated in isolation. It is part of the
processor instruction pipeline at that point (see superscalar execution
architectures). It will most likely be computed in flight with other
instructions without adding overhead, because the pipeline's throughput is at
that point not limited by the ALU. Judging the cost or an isolated operation
does not work any more on modern processors.
The processing time is in almost all cases dominated stalls in the pipeline
doe to fetching variables from memory.
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