[GitHub] [arrow] cyb70289 commented on a diff in pull request #13393: ARROW-16849: [C++][compute] Replace If-Else branch with bitwise operators in aggregate_basic_internal

[GitBox <gi...@apache.org>]

cyb70289 commented on code in PR #13393:
URL: https://github.com/apache/arrow/pull/13393#discussion_r899939657


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cpp/src/arrow/compute/kernels/aggregate_basic_internal.h:
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@@ -186,11 +186,8 @@ struct MeanImpl : public SumImpl<ArrowType, SimdLevel> {
       // Round the decimal result based on the remainder
       remainder.Abs();
       if (remainder * 2 >= this->count) {
-        if (this->sum >= 0) {
-          quotient += 1;
-        } else {
-          quotient -= 1;
-        }
+        auto flag = this->sum >= 0;
+        quotient = quotient + (1 & flag) - (1 & (!flag));

Review Comment:
   My gut feeling is compiler should be able to do necessary optimization of this code pattern. It may be better to keep current more readable code.
   Do you have benchmark result? Or can you write a short test code and compare the machine code on godblot?



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