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1

0

I work on a codebase that uses Java 8.

I created a set of JMH-based benchmarks that give me a certain set of numbers, using Java 8.

I then ran those compiled classes with Java 9, 10, 11, and 12, and got other sets of numbers.

My question is, if I recompile those classes with corresponding compilerVersion, source, and target properties in the pom, should I expect to see any statistically significant changes in those numbers?

In other words, if I run the Java8-compiled classes with Java 9, will I expect to see any real differences in then numbers if I instead compile the classes first with Java 9, and and then run them with Java 9 (and same question for 10, 11, and 12)?

Note that I'm not asking about running Maven with a different version of Java (but I would do that also), I'm talking about changing the properties in the maven-compiler-plugin to represent that version.

I believe the answer to this question would be no, I should not expect any noticeable differences in the timings, as I believe that Java 8 compatible source code would compile to the same bytecode that the Java 9, 10, 11, and 12 compiler would produce.

java jmh

share|improve this question

asked Mar 24 at 19:54

David M. KarrDavid M. Karr

6,491951115

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Did you see statistically significant differences? I would expect the answer to be no, since the Java compiler is pretty "dumb": it produces equivalent bytecode with little or no optimization, so you will see little or no difference in the produced bytecode. All the smarts are in the JVM that you run that code on.
  
  – Andy Turner
  Mar 24 at 19:59
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Can you post your benchmarks? Or at least describe what they do?
  
  – Nestor Sokil
  Mar 24 at 20:02
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  You can of course test your beliefs by inspecting the bytecode produced by the different versions to see if there are any differences.
  
  – Andy Turner
  Mar 24 at 20:06
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Generally speaking, I think it is most possible, that there are such differences in runtime and the JVM executes your code differently. The bytecode is most likely the same (although the spec does not prohibit it from changing in a newer version), but a lot of stuff could have been changed in JIT.
  
  – Nestor Sokil
  Mar 24 at 20:20
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Without knowing the code, this is difficult to judge, there are major difference between Java 8 and Java 9 +, most notably the module system (though if your code was written for java 8 this shouldn't be a factor). However I do believe that java 9 also now uses UTF8 for String representation, which may be a factor with respect to bench marking?
  
  – Bill Naylor
  Mar 24 at 20:27
  
  

  
  
  
  

add a comment | 

1

0

I work on a codebase that uses Java 8.

I created a set of JMH-based benchmarks that give me a certain set of numbers, using Java 8.

I then ran those compiled classes with Java 9, 10, 11, and 12, and got other sets of numbers.

My question is, if I recompile those classes with corresponding compilerVersion, source, and target properties in the pom, should I expect to see any statistically significant changes in those numbers?

In other words, if I run the Java8-compiled classes with Java 9, will I expect to see any real differences in then numbers if I instead compile the classes first with Java 9, and and then run them with Java 9 (and same question for 10, 11, and 12)?

Note that I'm not asking about running Maven with a different version of Java (but I would do that also), I'm talking about changing the properties in the maven-compiler-plugin to represent that version.

I believe the answer to this question would be no, I should not expect any noticeable differences in the timings, as I believe that Java 8 compatible source code would compile to the same bytecode that the Java 9, 10, 11, and 12 compiler would produce.

java jmh

share|improve this question

asked Mar 24 at 19:54

David M. KarrDavid M. Karr

6,491951115

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Did you see statistically significant differences? I would expect the answer to be no, since the Java compiler is pretty "dumb": it produces equivalent bytecode with little or no optimization, so you will see little or no difference in the produced bytecode. All the smarts are in the JVM that you run that code on.
  
  – Andy Turner
  Mar 24 at 19:59
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Can you post your benchmarks? Or at least describe what they do?
  
  – Nestor Sokil
  Mar 24 at 20:02
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  You can of course test your beliefs by inspecting the bytecode produced by the different versions to see if there are any differences.
  
  – Andy Turner
  Mar 24 at 20:06
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Generally speaking, I think it is most possible, that there are such differences in runtime and the JVM executes your code differently. The bytecode is most likely the same (although the spec does not prohibit it from changing in a newer version), but a lot of stuff could have been changed in JIT.
  
  – Nestor Sokil
  Mar 24 at 20:20
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Without knowing the code, this is difficult to judge, there are major difference between Java 8 and Java 9 +, most notably the module system (though if your code was written for java 8 this shouldn't be a factor). However I do believe that java 9 also now uses UTF8 for String representation, which may be a factor with respect to bench marking?
  
  – Bill Naylor
  Mar 24 at 20:27
  
  

  
  
  
  

add a comment | 

I work on a codebase that uses Java 8.

I created a set of JMH-based benchmarks that give me a certain set of numbers, using Java 8.

I then ran those compiled classes with Java 9, 10, 11, and 12, and got other sets of numbers.

My question is, if I recompile those classes with corresponding compilerVersion, source, and target properties in the pom, should I expect to see any statistically significant changes in those numbers?

In other words, if I run the Java8-compiled classes with Java 9, will I expect to see any real differences in then numbers if I instead compile the classes first with Java 9, and and then run them with Java 9 (and same question for 10, 11, and 12)?

Note that I'm not asking about running Maven with a different version of Java (but I would do that also), I'm talking about changing the properties in the maven-compiler-plugin to represent that version.

I believe the answer to this question would be no, I should not expect any noticeable differences in the timings, as I believe that Java 8 compatible source code would compile to the same bytecode that the Java 9, 10, 11, and 12 compiler would produce.

java jmh

share|improve this question

asked Mar 24 at 19:54

David M. KarrDavid M. Karr

6,491951115

share|improve this question

asked Mar 24 at 19:54

David M. KarrDavid M. Karr

6,491951115

share|improve this question

asked Mar 24 at 19:54

David M. KarrDavid M. Karr

6,491951115

asked Mar 24 at 19:54

David M. KarrDavid M. Karr

6,491951115

asked Mar 24 at 19:54

David M. KarrDavid M. Karr

6,491951115