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From Robin Garner <Robin.Gar...@anu.edu.au>
Subject Re: half-baked idea? j2me
Date Wed, 02 Nov 2005 02:05:31 GMT
Rodrigo Kumpera wrote:

>On 11/1/05, Robin Garner <robin.garner@anu.edu.au> wrote:
>  
>
>>>On 11/1/05, Robin Garner <Robin.Garner@anu.edu.au> wrote:
>>>      
>>>
>>>>Rodrigo Kumpera wrote:
>>>>
>>>>        
>>>>
>>>>>AFAIK IKVM, sablevm and jamvm all run on portable devices.
>>>>>
>>>>>Developing a j2me jvm is not as easier as it seens, first, the
>>>>>footprint and execution performance must be really optimized, so
>>>>>expect a LOT of assembly coding.
>>>>>
>>>>>
>>>>>          
>>>>>
>>>>Back to the language wars again :)  This does not necessarily follow.
>>>>Try googling for the 'squawk' VM - they had a poster at OOPSLA last
>>>>week.  This is a java-in-java virtual machine targetted at embedded
>>>>devices.  The core VM runs in 80KB of memory.  Device drivers are all
>>>>written in Java.
>>>>
>>>>        
>>>>
>>>Robin,
>>>
>>>With a java-in-java VM even if you don't write directly in assembly
>>>you still need to generate machine code with java anyway, and that
>>>will look a lot like asm (JikesRVM baseline JITer for example). With
>>>C, for example, you can get away using just an interpreter.
>>>      
>>>
>>My mistake, obviously.  When you said "performance must be really
>>optimized, so expect a LOT of assembly coding", I assumed you were saying
>>that large chunks of the VM would need to be written in assembler in order
>>to get adequate performance.
>>
>>So what _was_ the point you were making ?
>>
>>cheers
>>
>>
>>    
>>
>
>I was just trying to say that a decent j2me VM is not as simple as
>David suggested. Not that C or Java would be more suited to implement
>it. As a matter of fact, I think that java-in-java VMs can be as good
>as C/C++ based JVMs or better.
>
>But one thing is hard to deny, a simple JVM, like bootJVM, is a lot
>easier to write in C than in java (not using an AOT compiler). And
>that was my point, C/C++ sounds to be the easy path to start with.
>  
>
Actually my colleagues at ANU and I were remarking last week that all 
the recent discussion on the Harmony list (configure scripts, packed 
structs etc etc) were close to being proof that Java was the easier way 
to go.

Another data point (FWIW) - joeq, excluding the compiler and the class 
library interface comes in at ~39,000 lines of code.  bootJVM is already 
over 50,000.  I know that KLOC is a pretty bogus measure of complexity, 
but it certainly says _something_.  And Joeq is a fully functioning VM.

cheers

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