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From Gerry Steele <gerry.ste...@gmail.com>
Subject Re: Backward compatibility
Date Wed, 11 May 2005 22:22:12 GMT
I'm a big fan of the Apache foundation but this is one product I'm not too 
sure is such a good idea as of yet for reasons several:

>> Deprecated or non deprecated, we want Harmony to pass the TCK, so
> >> whatever the TCK wants us to do, we'll do it.


I hope you understand what sticking to the TCK entails. When it comes to 
implementing GUI stuff for instance, your platform will have to fully copy 
the official JVM's Swing/AWT widgets and all other details in order for the 
automation and robot driven tests to pass. The JCK testbase for tiger is 
immense. To get it setup and run is a skill on its own. To get it to pass 
all tests takes a serious am mount of tweaking and a noteable knowledge of 
the javatest harness. It will require implementations on things as extensive 
as CORBA and RMI. We would need passive agents, tname servers etc.

Also, when running the TCK bear in mind that you'll have to run the harness 
with the Sun VM.

I'm not sure about the particular extent of the testsuite provided with the 
TCK you guys are talking about (if there is interest can find out more), but 
the JCK, which is basically a TCK for the entire J2SE jre and jdk will be 
going on impossible to pass for an alternative implmentation as everything 
is written with the Sun JDK/JRE in mind and test cases are adapted in ways 
that will create an infinite unpredictable series of problems when trying to 
adapt your code.

Another reason is that I'm not quite sure I see the point. It will take 4-5 
years or more to even come close to a product like tiger. Sun are already 
working heavily on mustang and dolphin (to a lesser degree on the latter). 
As well as this, sun research have many projects looking at the future of 
the Java VM such as the Barcelona project which will drastically change the 
implementation of the JVM. For instance to make it more network orientated 
or to improve resource sharing.

The latter things (which are yet to see real sun implementation) might be 
something you guys might then want to take advantage of in order to leverage 
a selling point of Harmony. Without something like that it's just another 
attempt at a VM that will be playing catch-up forever.

Also, don't forget about quality. Sun put a serious amount of money and 
manpower into ensuring the quality and compatibility of the JVM. A lot of 
corporations depend on this. They have a regular update release cycle. For 
instance we are currently working on 1.3.1_16, 1.4.2_09, 5.0_04 & 5.0_05.

In a project of this size some of the the test suites take several days to 
run. Some take many many hours of man power. For excessive thoroughness 
there also manual JCK and regression test suites. Which, trust me, will not 
be performed by someone who isn't being paid for it. Things like this don't 
fit well with the community model. 

Another worry I have is that the effort here might be better redirect to 
some other project. We already have Java. Even if harmony does make it to a 
useable release people will still prefer to use the Sun VM. It will be the 
platform people build on and it will be the one they trust.

I'll be very interested in how this turns out. 

Regards,
Gerry

1) speed
> 
> 2) portability (java is claimed to run 'everywhere', but in fact, it
> runs only on a few operating systems, even fewer for 1.5)
> 
> 3) configurability (I might want to tune it differently and, for
> example, choose different thread/GC models)
> 
> 4) implementation stategy (in macosx, multiple JVMs share 80% of their
> memory, and some of Swing is native, therefore feels like the rest of
> the OS and it's hardware accelerated)
> 
> 5) internal modularity (we want diversity of implementation to drive
> innovation in the VM space, both in and out companies and universities)
> 
> And, last but not least, if Sun or other vendors that already have JVM
> want to stop paying for all that development on their and want to start
> sharing the development costs with the java ecosystem in general and
> with a clear warranty that we will not try to pollute the stream we all
> drink from, therefore want to contribute some of their code to Harmony,
> we will welcome them with open arms.
> 
> --
> Stefano.
> 
> 


-- 
Gerry Steele

x74521/+353-1-8199 521
http://blogs.sun.com/roller/page/gerrys
[gerry.steele@sun.com OR gerry.steele@gmail.com]

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