Feedback on LW1 EAR

[Uberto Barbini]

Hi Srikanth,

thanks for your illuminating reply.

Introducing ValueTypes on others projects I found another curious issue,
seems more a javac issue but not sure.
concurrentHashMap.computeIfPresent (and the other similar methods) raise an
error if the map is inside a ValueType. Other map methods (like the
commented code) works fine.


__ByValue public class UserAccounts {

    public final Map<String, Double> accounts = new ConcurrentHashMap<>();

    public void addReturnToUser(String userName, double amount){

//        Double prev = accounts.get(userName);
//        if ( prev != null) {
//            accounts.put(userName, amount + prev);
//        }
        accounts.computeIfPresent(userName, (String u, Double a) -> amount
+ a);
    }
...

(full code here
https://github.com/uberto/restApiCalculator/blob/valhalla/src/main/java/com/gamasoft/model/UserAccounts.java
)

---- Error
java.lang.IncompatibleClassChangeError: constant pool
com.gamasoft.model.UserAccounts$$Lambda$29/0x00000008000ba440 inconsistent
value type: com.gamasoft.model.UserAccounts

at
java.base/java.util.concurrent.ConcurrentHashMap.computeIfPresent(ConcurrentHashMap.java:1836)
at com.gamasoft.model.UserAccounts.addReturnToUser(UserAccounts.java:27)
at
com.gamasoft.model.CompoundInterestTest.addReturnToUserAccount(CompoundInterestTest.java:55)
...
Process finished with exit code 255






> In slightly longer term, we are also asking the question whether ==
> should simply be translated into the equals method call by javac where
> it can statically discern the operands to be values.
>

For what is worth, this solution sounds very attractive and promising to me.
Maybe the same could be extended to some other operands as well... :)))


> > 5) I saw that I can override toString() and call super.toString() to have
> > the standard Object behavior.
> This should have been rejected by javac. That it is not is a defect I
> would say.
>

Ok makes sense. I found being able to call on Object base methods is a bit
confusing.


Uberto







> Date: Mon, 20 Aug 2018 10:41:15 +0200
> From: Tobias Hartmann <tobias.hartmann at oracle.com>
> To: Uberto Barbini <uberto.gama at gmail.com>,
>         valhalla-dev at openjdk.java.net
> Subject: Re: Feedback on LW1 EAR
> Message-ID: <82c3335c-147a-bfdd-e24e-2598f25568ed at oracle.com>
> Content-Type: text/plain; charset=utf-8
>
> Hi Uberto,
>
> first of all, thanks a lot for trying out LW1 EA and for reporting these
> issues!
>
> The crash is a bug in the just-in-time (JIT) compiler when compiling the
> WatchV:equals method, I've
> filed [1] and will work on a fix.
>
> As a temporary workaround you can disable JIT compilation of the affected
> method via
> -XX:CompileCommand=exclude,"Knapsack\$WatchV::equals" or disable JIT
> compilation altogether by
> adding the -Xint command line flag (unfortunately, both options will slow
> down execution a lot but
> it should be good enough for non-performance testing).
>
> Thanks,
> Tobias
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8209687
>
>
> On 18.08.2018 12:40, Uberto Barbini wrote:
> > 5) I saw that I can override toString() and call super.toString() to have
> > the standard Object behavior. I wonder if there will be some kind of base
> > class for all ValueTypes or not.
> >
> >
> > Then I've tried to replace some immutable classes into Value Types use
> them
> > in my other projects.
> > The main hindrance has been the missing support for generics.
> > As workaround I've created a interface and based the collection on the
> > interface. It worked in a few projects but I had a Fatal Error on a
> simple
> > algorithm. I've tried to understand the exact problem but the same code
> > seems to work as standalone project... If it's something worth
> > investigating I can dig it more
> >
> >
> https://github.com/uberto/eopi/blob/ValhallaLW01/src/test/java/com/gamasoft/eopi/cap17_DynamicProgramming/KnapsackTest.java
> >
> >
> > #
> > # A fatal error has been detected by the Java Runtime Environment:
> > #
> > #  SIGSEGV (0xb) at pc=0x00007f08c3d648aa, pid=18399, tid=18426
> > #
> > # JRE version: OpenJDK Runtime Environment (11.0) (build
> > 11-lworldea+0-2018-07-30-1734349.david.simms.valhalla)
> > # Java VM: OpenJDK 64-Bit Server VM
> > (11-lworldea+0-2018-07-30-1734349.david.simms.valhalla, mixed mode,
> > compressed oops, g1 gc, linux-amd64)
> > # Problematic frame:
> > # V  [libjvm.so+0x4148aa]  AddPNode::Value(PhaseGVN*) const+0x7a
> > #
> > # No core dump will be written. Core dumps have been disabled. To enable
> > core dumping, try "ulimit -c unlimited" before starting Java again
> > #
> > # If you would like to submit a bug report, please visit:
> > #   http://bugreport.java.com/bugreport/crash.jsp
> > #
>
>
> End of valhalla-dev Digest, Vol 48, Issue 13
> ********************************************
>