On 10 Jul 2004 10:58:14 GMT, Derrick Steed
wrote:

Martin Gregorie wrote:
Simple answer: follow the NOTAMplot lead and write desktop soaring
software in Java so we can all have copies regardless of which OS we
run.


Like all simple answers, it's wrong: Java is portable because of the JVM
(Java Virtual Machine), this is a java processor which runs in software on
the host machine.

I know that and its not as slow as you may think. This is said from
the perspective of doing Java development on a 133 MHz PC. What IS
very slow and uses cycles like crazy is loading classes from JAR
files: not only do you have to search the file, but you need to expand
it first. Once an application has all its classes loaded it actually
runs pretty fast.

A properly designed and implemented VM isn't slow - in the good old
days of COBOL and mainframes I used a 4GL, Filetab. It was
implemented, like Perl, as a compile-and-go script with the result run
in a VM. That executed as fast as a well-written COBOL program and
faster than a badly written one.

As many people have learned to their cost, you pay for
this abstraction in compute cycles (lots of them!) - thus Java is SLOW.
Unless you know of a source of very high speed PDA's which can also support
LARGE amounts of RAM, then this one is a dead duck. You'll need both to
support the kind of functions you now find in the PDA flight director
systems on offer: e.g. moving map, support for different projections, etc.

Errm, I did say DESKTOP applications.

They are all written in C++ anyway, and that is the architypal portable
language which also has the required performance even on PDA's,

and is noticeably less efficient in cycles burnt than plain ANSI C.

so why not
port SeeYou (or whatever) to a Linux PDA?

I'd settle for ports to a plain Linux desktop - as I said, I wasn't
talking about PDA software. However, if Java is practical on a Palm,
which it is, then it should fly on an Intel-based PDA unless WinCE
really sucks in the efficiency department.


--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :