standard: Optimize str_split() #20419
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Interestingly -0.17% Icount on symfony demo, wonder how much this is noisy / real. |
mvorisek
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Nov 7, 2025
| add_next_index_stringl(return_value, p, split_length); | ||
| p += split_length; | ||
| } | ||
| ZEND_HASH_FILL_PACKED(Z_ARRVAL_P(return_value)) { |
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can this also be applied to the multibyte version?
php-src/ext/mbstring/mbstring.c
Line 1641 in 5ab594c
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Yes, but it may be a bit more difficult.
Three optimizations:
- If the entire string is returned, we don't need to duplicate it.
- Use packed filling logic.
- Use fast construction of strings. This is useful when splitting
strings on length=1. In that case I get a 6x speedup in the code
below.
Bench:
```php
$x = str_repeat('A', 100);
for ($i = 0; $i < 1000000; $i++)
str_split($x, 10);
```
On an i7-4790:
```
Benchmark 1: ./sapi/cli/php x.php
Time (mean ± σ): 160.1 ms ± 6.4 ms [User: 157.3 ms, System: 1.8 ms]
Range (min … max): 155.6 ms … 184.7 ms 18 runs
Benchmark 2: ./sapi/cli/php_old x.php
Time (mean ± σ): 202.6 ms ± 4.0 ms [User: 199.1 ms, System: 1.9 ms]
Range (min … max): 197.4 ms … 209.2 ms 14 runs
Summary
./sapi/cli/php x.php ran
1.27 ± 0.06 times faster than ./sapi/cli/php_old x.php
```
The performance gain increases with smaller lengths.
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Three optimizations:
Bench:
On an i7-4790:
The performance gain increases with smaller lengths.