HaoYang670 commented on issue #1400:
URL: https://github.com/apache/arrow-rs/issues/1400#issuecomment-1059882916
Strongly agree with you @jhorstmann. `fold` seems to copy all elements in
the array, and `reduce` just takes the references. If the code is rewritten as
```rust
if null_count == 0 {
// optimized path for arrays without null values
m.iter()
.copied()
.reduce(|acc, item| if cmp(&acc, &item) { item } else { acc })
```
and I can get the benchmark result:
```console
min 512 time: [833.73 ns 834.34 ns 835.06 ns]
change: [-0.2047% -0.0757% +0.0383%] (p = 0.24 >
0.05)
No change in performance detected.
Found 5 outliers among 100 measurements (5.00%)
4 (4.00%) high mild
1 (1.00%) high severe
```
, which is same as `fold`.
But wait! Which one is faster in this context, copy or reference? On my
desktop, I can get 50% performance improvement by using reference. However, you
said `fold` was faster on your laptop. Is it a little weird?
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