[Phpmyadmin-devel] Is PMA_STR_binarySearchInArr needed?

[Marc Delisle]

Piotr Przybylski a écrit :
> 2011/6/7 Marc Delisle <marc at infomarc.info>:
>> Piotr Przybylski a écrit :
>>> 2011/6/7 Marc Delisle <marc at infomarc.info>:
>>>> Piotr Przybylski a écrit :
>>>>> 2011/6/7 Marc Delisle <marc at infomarc.info>:
>>>>>> Rouslan Placella a écrit :
>>>>>>> On Tue, 2011-06-07 at 12:25 -0400, Marc Delisle wrote:
>>>>>>>> Marc Delisle a écrit :
>>>>>>>>> Piotr Przybylski a écrit :
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> For some time I was curious whether PMA_STR_binarySearchInArr is
>>>>>>>>>> needed at all, and my test showed that there are faster (sometimes
>>>>>>>>>> much faster) alternatives. Test for 100 000 iterations on PHP 5.3.4
>>>>>>>>>> (Windows, i5 2,53 GHz core):
>>>>>>>>>>
>>>>>>>>>> PMA_STR_binarySearchInArr:    2.6606s
>>>>>>>>>> array_search:     1.8936s
>>>>>>>>>> isset:            0.0102s
>>>>>>>>>> array_key_exists: 0.0934s
>>>>>>>>>>
>>>>>>>>>> Isset and array_key_exists require flipped array, but array_search is
>>>>>>>>>> a drop-in replacement that works faster, even though it does a linear
>>>>>>>>>> search. Code used to perform this test is at [1].
>>>>>>>>>>
>>>>>>>>>> [1] http://pastebin.com/cJmpmCPh
>>>>>>>>>>
>>>>>>>>> Piotr,
>>>>>>>>> I tested on a 64-bit Linux machine (running as a VM under ESX 4.1) under
>>>>>>>>> PHP 5.3.6-RC3 and got different results (for current master):
>>>>>>>>>
>>>>>>>>> Binary search:    0.6088
>>>>>>>>> array_search:     2.0246
>>>>>>>>> isset:            0.0068
>>>>>>>>> array_key_exists: 0.0176
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>> And on a similar VM running PHP 5.2.17:
>>>>>>>>
>>>>>>>> Binary search:    0.7197
>>>>>>>> array_search:     2.7731
>>>>>>>> isset:            0.0075
>>>>>>>> array_key_exists: 0.0178
>>>>>>>>
>>>>>>> My results look a lot like Marc's, too:
>>>>>>>
>>>>>>> PHP: 5.3.5
>>>>>>> PMA: Latest GIT
>>>>>>> OS:  Ubuntu Linux 11.04 - 64bit
>>>>>>> CPU: AMD Phenom II @ 3.95GHz
>>>>>>> RAM: DDR2 @ 1066MHz
>>>>>>>
>>>>>>> Binary search:    0.4967
>>>>>>> array_search:     1.5545
>>>>>>> isset:            0.0041
>>>>>>> array_key_exists: 0.0162
>>>>>>>
>>>>>>> Rouslan
>>>>>> isset() on a flipped array is the winner, but would require a logic
>>>>>> verification everywhere to be sure we flip a minimum of times.
>>>>>>
>>>>>> I also like the fact that we would no longer need to maintain a long
>>>>>> list of keywords in proper alpha order.
>>>>>>
>>>>> I was really counting on array_search results, but in this case I
>>>>> believe binary search is justified by code readability.
>>>>>
>>>> IMO the new form would be more readable.
>>>>
>>>> Current:
>>>>  PMA_STR_binarySearchInArr($d_cur_upper, $PMA_SQPdata_function_name,
>>>> $PMA_SQPdata_function_name_cnt)
>>>>
>>>> New:
>>>> isset($PMA_SQPdata_function_name_flipped[$d_cur_upper])
>>>>
>>> If we want to change this, I opt for:
>>> - isset in PMA_SQP_parse and do array_flip there
>>> - array_search in PMA_backquote - sometimes faster, worst case a few
>>> times slower, but much better that additional 43 KB of memory and
>>> array_flip in sqlparser.data.php
>>>
>> Ok for me.
>>
>> Did you find evidence that these arrays in their non-flipped form would
>> still be needed (apart from their usage in ./test) ?
>>
> 
> No, but I think it's better to leave their definitions as they are now
> - even though sorting would not be needed, they are currently easy to
> read and modify.
> 

OK.

-- 
Marc Delisle
http://infomarc.info