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Bug #79856 for() terribly poor performance
Submitted: 2020-07-14 07:36 UTC Modified: 2020-07-14 07:40 UTC
From: bugzilla77 at gmail dot com Assigned: beberlei (profile)
Status: Closed Package: Performance problem
PHP Version: 8.0.0alpha2 OS: Windows 10 Pro
Private report: No CVE-ID: None
 [2020-07-14 07:36 UTC] bugzilla77 at gmail dot com
Description:
------------
for() terribly poor performance

Test script:
---------------
// --- php

<?php
 $t=microtime(true);

 $s=0;
 for($i=0;$i<20000000;$i++){
  $s+=$i;
 }

 $t=microtime(true)-$t;

 print(($t*1000).'ms');
?>



// --- javascript

<script>
 t=new Date();

 s=0;
 for(i=0;i<20000000;i++){
  s+=i
 }

 t=new Date()-t;

 document.write(t+'ms');
</script>



// --- C#

using System;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {

            int t = Environment.TickCount;

            long s = 0;

            for (int i = 0; i < 20000000; i++)
            {
                s += i;
            }

            t = Environment.TickCount - t;

            Console.WriteLine(t+"ms");
            Console.ReadKey();
        }
    }
}

Expected result:
----------------
Performance at the level of other languages.

Actual result:
--------------
PHP 8.0alpha2: 343ms 
PHP 7.4: 461ms
javascript (Firefox 78.0.2): 58ms
C#: 16ms

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 [2020-07-14 07:40 UTC] beberlei@php.net
-Status: Open +Status: Closed -Assigned To: +Assigned To: beberlei
 [2020-07-14 07:40 UTC] beberlei@php.net
This is a bad comparison, because the result of the for loop can be calculated by the compiler in C# or an advanced JIT in case of Javascript.

PHP has opcache optimizations, but I don't believe there is one for this for loop construct. PHPs JIT is also in its infancy.

You should check instead calling a function that computes something inside the loop, for example a string operation.

I don't consider this a bug, because of the benchmark assumptions being questionable, so closing.
 
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