[GitHub] [arrow] emkornfield commented on pull request #6985: ARROW-8413: [C++][Parquet] Refactor Generating validity bitmap for values column

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emkornfield commented on pull request #6985:
URL: https://github.com/apache/arrow/pull/6985#issuecomment-619488093


   @pitrou I think I addressed your comments.  One of them that went stale was the complexity for "AppendWord", I tried to remove parts that did not seem to affect performance on benchmarks for parquet column reading but I spent some time trying to maximize word level parallelism for the unaligned case, because I think at least for repeated fields I expect this case to be fairly common. 
   
   As a point of comparison using the AppendWord implementation I put in place for BigEndian shows much smaller improvements.  Really this should use CopyBitmap but I didn't want to start moving a move code then I needed to in bit_util.h for this PR. I opened 
    a [JIRA (ARROW-8595)](https://issues.apache.org/jira/browse/ARROW-8595) to track some improvements in that regard.
   
   If more comments are needed or you think there is a cleaner way of writing the code, I'm happy for input.
   
   @wesm do you want to look at the parquet specific logic/comments to make sure I captured them correctly?


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