Dandandan commented on code in PR #9542:
URL: https://github.com/apache/arrow-rs/pull/9542#discussion_r2927448171
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arrow-select/src/interleave.rs:
##########
@@ -154,13 +154,51 @@ fn interleave_primitive<T: ArrowPrimitiveType>(
data_type: &DataType,
) -> Result<ArrayRef, ArrowError> {
let interleaved = Interleave::<'_, PrimitiveArray<T>>::new(values,
indices);
+ let arrays = &interleaved.arrays;
+ let len = indices.len();
+
+ let mut output = Vec::with_capacity(len);
+ let dst: *mut T::Native = output.as_mut_ptr();
+ let mut base = 0;
+
+ // Process 8 elements at a time to issue multiple independent loads
+ // and increase memory-level parallelism for random access patterns.
+ let chunks = indices.chunks_exact(8);
+ let remainder = chunks.remainder();
+ for chunk in chunks {
+ let v0 = arrays[chunk[0].0].value(chunk[0].1);
Review Comment:
It just a loop unrolling constant - the higher the more code it will
generate inside the loop so it can hide more latency by running/pipelining the
instructions not depending on the loads.
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