Ternary operator performance improvements View as Markdown

Hi,

As I already said, I don't see any technical issues with the patch.
I don't like it very mach, but it looks robust, and I don't object about it.

Thanks. Dmitry.

Hi,

I've already posted this patch and it has since been reviewed and improved.
I'm re-posting it for discussion before eventually commiting it.

The ternary operator always copies its second or third operand, which is very
slow compared to an if/else when the operand is an array for example:

$a = range(0,9);

// this takes 0.3 seconds here:

for ($i = 0; $i< 5000000; ++$i) {
if (true) {
$b = $a;
} else {
$b = $a;
}
}

// this takes 3.8 seconds:

for ($i = 0; $i< 5000000; ++$i) {
$b = true ? $a : $a;
}

I've tried to reduce the performance hit by avoiding the copy when possible
(patch attached).

Benchmark:

Without patch: (the numbers are the time taken to run the code a certain
amount of times)

$int = 0;
$ary = array(1,2,3,4,5,6,7,8,9);

true ? 1 : 0 0.124
true ? 1+0 : 0 0.109
true ? $ary : 0 2.020 !
true ? $int : 0 0.103
true ? ${'ary'} : 0 2.290 !
true ?: 0 0.091
1+0 ?: 0 0.086
$ary ?: 0 2.151 !
${'var'} ?: 0 2.317 !

With patch:

true ? 1 : 0 0.124
true ? 1+0 : 0 0.195
true ? $ary : 0 0.103
true ? $int : 0 0.089
true ? ${'ary'} : 0 0.103
true ?: 0 0.086
1+0 ?: 0 0.159
$cv ?: 0 0.090
${'var'} ?: 0 0.089

The array copying overhead is eliminated. There is however a slowdown in some
of the cases, but overall there is no completely unexpected performance hit as
it is the case currently.

What do you think ? Is there any objection ?

Best regards,

Seems like a good patch, +1 from me on inclusion into 5.4/HEAD.

Hi,

I've already posted this patch and it has since been reviewed and improved.
I'm re-posting it for discussion before eventually commiting it.

The ternary operator always copies its second or third operand, which is very
slow compared to an if/else when the operand is an array for example:

$a = range(0,9);

// this takes 0.3 seconds here:

for ($i = 0; $i < 5000000; ++$i) {
       if (true) {
               $b = $a;
       } else {
               $b = $a;
       }
}

// this takes 3.8 seconds:

for ($i = 0; $i < 5000000; ++$i) {
       $b = true ? $a : $a;
}

I've tried to reduce the performance hit by avoiding the copy when possible
(patch attached).

Benchmark:

Without patch: (the numbers are the time taken to run the code a certain
amount of times)

$int = 0;
$ary = array(1,2,3,4,5,6,7,8,9);

true ? 1 : 0        0.124
true ? 1+0 : 0      0.109
true ? $ary : 0     2.020 !
true ? $int : 0     0.103
true ? ${'ary'} : 0 2.290 !
true ?: 0           0.091
1+0 ?: 0            0.086
$ary ?: 0           2.151 !
${'var'} ?: 0       2.317 !

With patch:

true ? 1 : 0        0.124
true ? 1+0 : 0      0.195
true ? $ary : 0     0.103
true ? $int : 0     0.089
true ? ${'ary'} : 0 0.103
true ?: 0           0.086
1+0 ?: 0            0.159
$cv ?: 0            0.090
${'var'} ?: 0       0.089

The array copying overhead is eliminated. There is however a slowdown in some
of the cases, but overall there is no completely unexpected performance hit as
it is the case currently.

What do you think ? Is there any objection ?

Best regards,

Hi,

I've already posted this patch and it has since been reviewed and improved.
I'm re-posting it for discussion before eventually commiting it.

The ternary operator always copies its second or third operand, which is very
slow compared to an if/else when the operand is an array for example:

Is that why the following does not work as I expected:

$dbh = $how == 'r' ? (&$dbh_r) : (&$dbh_w);

$dbh is NOT a reference to $dbh_r or $dbh_w.

--
Alain Williams
Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer.
+44 (0) 787 668 0256 http://www.phcomp.co.uk/
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