pitrou commented on code in PR #48549:
URL: https://github.com/apache/arrow/pull/48549#discussion_r2630368777
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cpp/src/arrow/util/rle_encoding_internal.h:
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@@ -377,6 +394,19 @@ class BitPackedRunDecoder {
return steps;
}
+ /// Get a batch of values and count how many equal match_value
+ /// Note: For bit-packed runs, we use std::count after GetBatch since it's
+ /// highly optimized by the compiler. The fused approach is only beneficial
+ /// for RLE runs where counting is O(1).
+ [[nodiscard]] rle_size_t GetBatchWithCount(value_type* out, rle_size_t
batch_size,
+ rle_size_t value_bit_width,
+ value_type match_value, int64_t*
out_count) {
+ const auto steps = GetBatch(out, batch_size, value_bit_width);
+ // std::count is highly optimized (SIMD) by modern compilers
+ *out_count += std::count(out, out + steps, match_value);
Review Comment:
The typical batch size for levels is probably small, so it would fit at
least in L2 cache and perhaps L1. Not sure it's worth trying to do it while
decoding.
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