Craig White created GROOVY-8019:
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Summary: Strange performance issue using if(true) versus if(1==1)
Key: GROOVY-8019
URL: https://issues.apache.org/jira/browse/GROOVY-8019
Project: Groovy
Issue Type: Bug
Affects Versions: 2.4.7, 2.4.4
Environment: Groovy Script Engine in a Java app running on Windows 7
and Windows Server 2012
Reporter: Craig White
While using a Groovy script we came across a strange performance anomaly.
Having the bulk of our script wrapped in an if( true ){} statement as opposed
to an if( 1==1 ){} statement severely degrades performance of the inner part
of the script. Multi-threaded performance is most severely affected. There
appeared to be much more contention running the same script on a 48 core box
with the "if(true)". (took about 100x longer to run 48 copies of these
scripts on their own threads).
The curious aspect of this, is that the 'if' statement is not in the nested
loops, but somehow has negatively affected the compilation / optimization /
byte-code.
Running a Single copy of this script on a 8 core i7 shows quite a performance
hit too... (5000ms vs. 200ms)
The (effective) code to run the script is as follows...
compiledScript = ((Compilable)engine).compile(scriptString);
result = compiledScript.eval(bindings);
Here's the script...
// $script_engine_name=groovy
long sum = 0;
double m = 1;
if( true ) {
System.err.println( "START");
long t0 = System.currentTimeMillis();
for( int j=0; j<1000; j++ ) {
for( int i=0; i<100000; i++ ) {
sum = sum + i;
m = m*i;
}
}
long t1 = System.currentTimeMillis();
System.err.println( "END - " + (t1-t0)+"ms");
}
System.err.println( "Done: "+sum+" "+m );
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