jorgecarleitao edited a comment on pull request #9235:
URL: https://github.com/apache/arrow/pull/9235#issuecomment-763898758
I made a mistake in benchmarking and have to retract my statement. I am
really sorry for the noise. :(
I mistakenly updated the wrong part of the code before running the bench.
@mbrubeck , even though there is a small difference between the the two
extends in the benches that you added, when used in a non-trivial operation
(`arithmetic`), `collect` is about +65% slower than using
`extend_from_trusted_len_iter`.
This hints that the `extend_trusted_len_iter` does have a significant
benefit, if anything at helping the compiler optimize out some code.
what I am using for the final benches:
```bash
git checkout 7bb2f3c13f0e652b01e3fecbee0ae32ff094f3e6
cargo bench --bench arithmetic_kernels -- "add 512"
git checkout cdbbc6f9d81d37216dc158177405529988fa0279
cargo bench --bench arithmetic_kernels -- "add 512"
```
The difference in code is
```rust
let values = left
.values()
.iter()
.zip(right.values().iter())
.map(|(l, r)| op(*l, *r));
let mut buffer = MutableBuffer::new(0);
unsafe { buffer.extend_from_trusted_len_iter(values) };
```
to
```rust
let buffer = left
.values()
.iter()
.zip(right.values().iter())
.map(|(l, r)| op(*l, *r))
.collect();
```
IMO this is interesting by itself.
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