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This pull request has been imported into Phabricator, and discussion and review of the diff will take place at https://reviews.facebook.net/D40473 |
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strtr() invoked with an array $replace_pairs as the second argument appears to perform much worse under HHVM than PHP5. PHP's implementation of multiple-string search was formerly quite naïve, and it was the subject of PHP bug 63893. In 2013, it was rewritten to utilize a clever and efficient algorithm for multi-pattern searching (Wu-Manber), and then further optimized. It looks like HHVM's implementation is based on the naive implementation PHP sported before PHP 5.4, which explains the poor performance. This patch ports over the strtr implementation in php 5.6.10. This implementation prefers the existing strtr_fast algorithm and falls back to wu-manber when there are too many patterns.
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@ebernhardson can you have a look at #6384 please? It seems likely this change is the cause of that crash. I'm going to spend some time later to confirm, but if it is, we'll have to revert it if you don't send a PR soonish to fix it. |
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#6395 is a proposed fix. |
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Addresses #5471
strtr() invoked with an array $replace_pairs as the second argument appears to
perform much worse under HHVM than PHP5.
PHP's implementation of multiple-string search was formerly quite naïve, and it
was the subject of PHP bug 63893. In 2013, it was rewritten to utilize a clever
and efficient algorithm for multi-pattern searching (Wu-Manber), and then
further optimized. It looks like HHVM's implementation is based on the naive
implementation PHP sported before PHP 5.4, which explains the poor performance.
This patch ports over the strtr implementation in php 5.6.10.