Zend: Optimize sorting single-element arrays

[LamentXU123]

Now, zend_array_sort() uses zend_array_sort_ex(), which unpacks packed arrays and temporarily increments the array refcount to protect against the comparator freeing the array.

Obviously this is useless for one-element arrays. Here, we can just use zend_hash_sort_ex instead for this case.

Some may ask what's the meaning to sort one-element array anyways. This can't be similar to what sorting zero-element array do, which is directly returning the empty array. Because the sorting functions have other things to do rather than just sort the elements.

<?php
$array = ['key' => 42];
sort($array);

var_dump($array);
// [0 => 42]

Here, we remain the original sort behavior for one-element array while making it faster because we are not actually sorting them

benchmark results:

After: 448.923 ms
Before: 905.807 ms
a roughly 50.4% enhancement in this specific case.

script:

<?php

const ITERATIONS = 20_000_000;
const RUNS = 7;

function run(int $iterations): float
{
    $array = [42];

    $start = hrtime(true);
    for ($i = 0; $i < $iterations; $i++) {
        sort($array, SORT_NUMERIC);
    }

    return (hrtime(true) - $start) / 1e6;
}

run(100_000); // Warmup

$times = [];
for ($run = 0; $run < RUNS; $run++) {
    $times[] = run(ITERATIONS);
}

sort($times, SORT_NUMERIC);
$median = $times[intdiv(RUNS, 2)];

printf(
    "single-element sort: %.3f ms (%d iterations, median of %d)\n",
    $median,
    ITERATIONS,
    RUNS,
);

[devnexen]

unless Gina beats me to it, I ll review a bit later seems good not entirely sure it s bug free

[devnexen]

I know it s performance oriented and with your last change it seems ok, but try to think of a test oriented regression, e.g. making sure a refactoring does not break it.

[LamentXU123]

Thanks !

[Girgias]

Is this really a case worth optimising? How often does one actually try to sort a single element array?

[LamentXU123]

Is this really a case worth optimising? How often does one actually try to sort a single element array?

It makes no sense to sort an empty array either. But we have a fast-path for it. Not mentioning sorting one-element array actually has some meaningful behaviors.

[Girgias]

Is this really a case worth optimising? How often does one actually try to sort a single element array?

It makes no sense to sort an empty array either. But we have a fast-path for it. Not mentioning sorting one-element array actually has some meaningful behaviors.

yeah I don't know why we are optimising empty arrays at least that should just be something the optimizer decides it can elide and not the function handling it...

[LamentXU123]

Is this really a case worth optimising? How often does one actually try to sort a single element array?

It makes no sense to sort an empty array either. But we have a fast-path for it. Not mentioning sorting one-element array actually has some meaningful behaviors.

yeah I don't know why we are optimising empty arrays at least that should just be something the optimizer decides it can elide and not the function handling it...

I think it is meaningful for these fast-path optimizations. It doesn't have downside anyways and AFAIK the parameters of sort is usually dynamic, in many cases it might be sorting empty or single arrays.

And yes, I think of migrating it to optimizer before. I am not familiar with it and I don't sure it can be smart enough to catch all cases. If it is this might be a good follow-up