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Date: Thu, 15 Nov 2007 14:21:43 -0800 (PST)
From: "Maksim Ananjev (JIRA)" <jira@apache.org>
To: commits@harmony.apache.org
Subject: [jira] Commented: (HARMONY-5090) [drlvm][jit][opt]operator strength
 reduction
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    [ https://issues.apache.org/jira/browse/HARMONY-5090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12542902 ] 

Maksim Ananjev commented on HARMONY-5090:
-----------------------------------------

I used this:

public static void test(){
		
                Stopwatch sw = new Stopwatch();
		int sum = 0;
		int bigsum = 0;
		sw.start();
	
		for(int j=0; j<100000; j++){
			for (int i=0; i<100000; i++){
				i++;
				int temp = 10*i;
				sum +=temp;
			}
			bigsum+=sum;
		}
		
	    double time = sw.read();	
	    System.out.println(bigsum);
	    System.out.println(time);
}

The boost is 2x -4x depending on underlying system and hardware.
   

> [drlvm][jit][opt]operator strength reduction
> --------------------------------------------
>
>                 Key: HARMONY-5090
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5090
>             Project: Harmony
>          Issue Type: New Feature
>          Components: DRLVM
>         Environment: Hope it works everywhere
>            Reporter: Maksim Ananjev
>            Priority: Minor
>         Attachments: HARMONY-5090.patch
>
>
> Operator Strength Reduction is an optimization that reformulates costly operations in terms of less expensive ones.
> The simplest possible example is the following:
> before:
> int sum = 0;
> for(int i=0; i<10;i++){
> int temp = i * 10;
> sum+=temp
> }
> after:
> int sum = 0;
> for(int j=0; j<100; j+=10){
> sum+=j
> } 

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