Bug #64633 [Com]: microtime regression - resolution reduced to 64 ticks per second

Edit report at https://bugs.php.net/bug.php?id=64633&edit=1 ID: 64633 Comment by: yaro2000 at yandex dot ru Reported by: phpbugs at musiclogistics dot net Summary: microtime regression - resolution reduced to 64 ticks per second Status: Assigned Type: Bug Package: Date/time related Operating System: Windows 7 PHP Version: 5.4.14 Assigned To: pajoye Block user comment: N Private report: N New Comment: 5.4.09 - OK, 5.4.10 - OK ... 5.4.14 - BUG, 5.4.15 - BUG Why? Previous Comments: ------------------------------------------------------------------------ [2013-07-31 07:19:11] martin dot hason at gmail dot com The same problem occurs in PHP 5.5.1 too! Please fix this bug. ------------------------------------------------------------------------ [2013-06-16 04:02:52] yaro at opti dot su The same problem occurs in PHP 5.4.15 too! Why developers ignore such an important issue? ------------------------------------------------------------------------ [2013-04-12 14:22:32] phpbugs at musiclogistics dot net @ab@php.net: You are right: While usleep() only works in 1/64 second increments on my machine (640 loops of "usleep(1)" take about 10 seconds), this is not related to PHP 5.4.14. It's the same on 5.4.13 and probably a limitation of Windows' multitasking. ------------------------------------------------------------------------ [2013-04-12 11:29:36] pajoye@php.net We should use performance counters instead, which brings a much higher precision at less cost. ------------------------------------------------------------------------ [2013-04-12 11:25:47] ab@php.net This is a tradeoff one has to make, precision vs. accuracy. That's very depending on the hardware. While on one system using the performance timer it would work as expected, on another it's still more accurate time with a very variable precision. That's where you could see in your snippet currentTimeMs() - $startTimeMs < 0. That is much more weird than possibly having a worse resolution, say currentTimeMs() - $startTimeMs == 0. Heres' an interesting reading about this http://blogs.msdn.com/b/oldnewthing/archive/2005/09/02/459952.aspx . The goal of the latest fix is to remove the random results. Also this will work in most cases as normally a script doesn't consist on just two subsequent microtime calls. Starting with win8 there is a much better API, but it of course doesn't help here. I'm not sure it should be touched, will look how to improve it without getting to the old erroneous behaviour. Maybe reimplement the performance timer part and make an ini option to let user decide if the performance timer should be used. As we really cannot foresee every hardware bugs. Btw. usleep() isn't affected by that, it uses the waitable timer which has a better resolution. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=64633 -- Edit this bug report at https://bugs.php.net/bug.php?id=64633&edit=1