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Posted to dev@orc.apache.org by GitBox <gi...@apache.org> on 2021/06/09 13:42:30 UTC

[GitHub] [orc] belugabehr edited a comment on pull request #714: ORC-812: Simplify getClosestBufferSize in Writer

belugabehr edited a comment on pull request #714:
URL: https://github.com/apache/orc/pull/714#issuecomment-857703731


   Hey @pgaref You'll have to pull out pen-and-paper and play with it :)
   
   `<< 1` simply doubles the value.  We're not interested in doubling, we're interesting in finding the next power of 2. 
   
   `3  << 1 = 6 (not power of 2)`
   `3 - 1 = 2 = 0x02 = 2 is highest one bit  ===>  2 * 2 = 4` ✔️ 
   
   
   Consider a value of `2`:
   `Integer.highestOneBit(size) = 0x02 ====> 2 * 2 = 4` ❌ (The nearest power of 2 is 2)


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