#18829 [Opn]: array_pop, array_shift, array_push... functions very slow with large arrays

ID: 18829 User updated by: jean-charles.rogez@devoteam.com Reported By: jean-charles.rogez@devoteam.com Status: Open Bug Type: Arrays related Operating System: Linux RedHat 7.1 PHP Version: 4.2.2 New Comment: In perl : @a = (1, 2, 3); shift(@a); print "$a[0], $a[1]"; Result : 2, 3 This is correct. I don't know how the shift function is implemented in perl, but i think arrays are not reindexed like in PHP, else it shouldn't be so fast. Previous Comments: ------------------------------------------------------------------------ [2002-08-12 09:18:55] rodif_bl@php.net The problem wasn't just array_shift it was array_shift and array_pop. array_shift is whats causing the slowness now but way its implemented now I really don't think it can get much faster. Basically when you shift of the top of the array it needs to re-index the entire array meaning if you have 10,000 records it needs to loop thru all 10,000 changing the index. If the function didn't need to do this it wouldn't take nearly as long. Does it work this way in perl or python. $a = array(1,2); array_shift($a); echo $a[0]; ------------------------------------------------------------------------ [2002-08-12 04:25:03] jean-charles.rogez@devoteam.com Same results than you. The script takes approximately 4 minutes on my P4 1.5Ghz with the latest CVS (before it was 87m...). After correction of the array_shift function, PHP should be in the same time than Perl or Python. ------------------------------------------------------------------------ [2002-08-10 05:39:19] edink@php.net I did some testing on your function and it seems that array_shift is to blame. If I avoid using that function, the execution time drop down to few seconds. To cut down the problem: $size = 5000; $Li1 = array(); $Li1 = array_pad($Li1, $size, 0); $Li2 = array(); while ($Li1) { $Li2[] = array_shift($Li1); } This takes 1.8 s on my P3 933 MHz. If I increase $size to 10000 it takes 16 s. The rest of array functions seem to be working fine. ------------------------------------------------------------------------ [2002-08-09 12:59:50] rodif_bl@php.net I ran current cvs and it was alot faster but still not fast enough. with your example with 50 itterations 4m55.514s 1 itteration was about 5 seconds this is running on 1.2 p3 ------------------------------------------------------------------------ [2002-08-09 09:03:01] rodif_bl@php.net This bug has been fixed in CVS. You can grab a snapshot of the CVS version at http://snaps.php.net/. In case this was a documentation problem, the fix will show up soon at http://www.php.net/manual/. In case this was a PHP.net website problem, the change will show up on the PHP.net site and on the mirror sites. Thank you for the report, and for helping us make PHP better. I recently fixed the speed for array_shift and array_pop. I\'ll look at array_push see if there is anything good there. Try current CVS and tell me if the speed increased for you. ------------------------------------------------------------------------ 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 http://bugs.php.net/18829 -- Edit this bug report at http://bugs.php.net/?id=18829&edit=1