Speed Impact experiment on GCJ

Andrew Haley aph@redhat.com
Thu Feb 16 15:17:00 GMT 2006


Rui Wang writes:
 > >
 > >REMARK: Obviously, the JIT discovers that the loop is not 
 > >really a loop sometime during the first iterations and decides 
 > >to optimize pretty hard...
 > 
 > -sh-2.05b$ cat jresult.d 
 > 200.0   23     
 > 300.0   9       
 > 400.0   0       
 > 500.0   1       
 > 600.0   0      
 > 700.0   1       
 > 1000.0  1       
 > 2000.0  2      
 > 5000.0  4       
 > 10000.0 6       
 > 20000.0 12      
 > 30000.0 13      
 > 
 > >gcj at -O3:
 > >
 > >[thhal@localhost gcjtest]$ time ./client task.test servers.d result.d
 > >
 > >real    0m1.469s
 > >user    0m1.265s
 > >sys     0m0.202s
 > >
 > >200.0   184
 > >300.0   276
 > >400.0   346
 > >500.0   442
 > -sh-2.05b$ cat result.d
 > 200.0   1      
 > 300.0   0      
 > 400.0   0       
 > 500.0   0      
 > 600.0   0       
 > 700.0   0      
 > 1000.0  0      
 > 2000.0  0       
 > 5000.0  1   
 > 10000.0 1      
 > 20000.0 1     
 > 30000.0 3      
 > 
 > There are two possible reasons: 
 > 1. different gcj version ( I am using 4.2.0, and yours is 4.0.0),
 > but I doubt this is the problem.

It is.

 > 2. you didn't put -O3 while compiling the bytecode to object file. If
 > you try it
 > With -O3, it will actually make a huge difference. But I don't know why
 > through, would somebody 
 > On this maillist mind to answer this question?

gcj -v --help

Andrew.



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