Re: IEEE 754 mode for Java

It is really weird that your results do not match. Prior Java 17 the "strictfp" keyword could be used to force the JVM to not cheat a little. But since Java 17 it is the default and the keyword does nothing anymore (https://openjdk.org/jeps/306). So the results should be portable now.

In case you are using DoubleSummaryStatistics in your code, GWT emulation uses Kahan summation to compensate for rounding errors but I think Java uses the same algorithm. However JavaDoc of DoubleSummaryStatistics.getSum() leaves room to have different implementations and error compensations. It explicitly says that the output may vary for the same input.

-- J.

Craig Mitchell schrieb am Montag, 12. Mai 2025 um 15:45:15 UTC+2:

The results from GWTTestCase match JavaScript!

It's rather slow though.  Running the same test in these envs:

• Java: 184ms.
• JavaScript (Chrome): 3.5 seconds.
• GWTTestCase: 5.8 minutes.

On Wednesday, 30 April 2025 at 3:39:57 pm UTC+10 Craig Mitchell wrote:

> I meant that IntelliJ run configuration for JUnit has an option forkmode and I am pretty sure the maven plugin also has an option for JVM forking. For example you can configure that every test method should run in a forked VM in IntelliJ. By default it doesn't do that. 

Ah, cool, thanks.  I see that option now.

With it on, I get different results again.  Different to maven, different to no fork, and different to JavaScript.

And if I run it through Maven with "mvn test -DforkCount=1 -DreuseForks=false", I get results that are completely different again.

They are still consistent though.  Ie: Running it multiple times, always gets the same results.

On Tuesday, 29 April 2025 at 8:34:25 pm UTC+10 Jens wrote:

> Maybe the result slightly changes if JVM decides to optimize a hot code path in case the JVM is reused. You might want to check how maven and your intellij run configuration are configured in terms of JVM forking.

IntelliJ seems to add the options:

-Dkotlinx.coroutines.debug.enable.creation.stack.trace=false -Ddebugger.agent.enable.coroutines=true -Dkotlinx.coroutines.debug.enable.flows.stack.trace=true -Dkotlinx.coroutines.debug.enable.mutable.state.flows.stack.trace=true -Dfile.encoding=UTF-8 -Dsun.stdout.encoding=UTF-8 -Dsun.stderr.encoding=UTF-8

So I added those to MAVEN_OPTS, but it didn't seem to make any difference.  I also tried adding @NotThreadSafe to my test suite, again no difference.

I meant that IntelliJ run configuration for JUnit has an option forkmode and I am pretty sure the maven plugin also has an option for JVM forking. For example you can configure that every test method should run in a forked VM in IntelliJ. By default it doesn't do that. 

-- J.

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