Conflict rules are not added in the solver based on the packages loaded in the
solver by require rules, instead of loading remote metadata for them. This has
2 benefits:
- it reduces the number of conflict rules in the solver in case of conflict
rules targetting packages which are not required
- it fixes the behavior of replaces, which is meant to conflict with all
versions of the replaced package, without introducing a performance
regression (this behavior was changed when optimizing composer in the past).
It is known that composer update takes a lot of memory: #5915, #5902,
I am playing with a profiler (@blackfireio) to make a demo in my local
PHP meetup (@phpvigo) and I found out a way to use less memory. These
are my first tests:
* Private project using PHP 5.6:
* Memory: from 1.31GB to 1.07GB
* Wall Time: from 2min 8s to 1min 33s
* symfony-demo using PHP 7.1 in my old mac book:
* Memory: from 667MB to 523MB
* Wall Time: from 5min 29s to 5min 28s
Not use an array inside conflict rules is this improvement main idea:
```php
<?php
//Memory 38MB
gc_collect_cycles();
gc_disable();
class Rule
{
public $literals;
public function __construct(array $literals)
{
$this->literals = $literals;
}
}
$rules = array();
$i = 0;
while ($i<80000){ //
$i++;
$array = array(-$i, $i);
$rule = new Rule($array);
$rules[] = $rule;
}
```
```php
<?php
//Memory 11.1MB
gc_collect_cycles();
gc_disable();
class Rule2Literals
{
public $literal1;
public $literal2;
public function __construct($literal1, $literal2)
{
$this->literal1 = $literal1;
$this->literal2 = $literal2;
}
}
$rules = array();
$i = 0;
while ($i<80000){ //
$i++;
$rule = new ConflictRule(-$i, $i);
$rules[] = $rule;
}
```
More info https://github.com/composer/composer/pull/6168
For each version of each package we create a conflict rule with each
other version. These are then added to the rule set and skipped if
duplicate so instead we can just generate them only once to begin with
and avoid unnecessary memory allocation and duplication lookups.
Gabriel Caruso
Christophe Coevoet
Markus Staab
Jordi Boggiano
Vladimir Reznichenko
rubenrua
Yanick Witschi
Steve Preston
Nils Adermann
Pascal Borreli