Re: "everybody in the control room is using Java"

[Ole-Hjalmar Kristensen <ole-hjalmar.kristensen@substitute_employer_here.com>]

>>>>> "DL" == Dmytry Lavrov <dmytrylavrov@fsmail.net> writes:

    DL> "Martin Dowie" <martin.dowie@btopenworld.com> wrote in message news:<bu9o60$h6v$1@sparta.btinternet.com>...
    >> "Hyman Rosen" <hyrosen@mail.com> wrote in message
    >> news:1074275354.853176@master.nyc.kbcfp.com...
    >> > <http://news.com.com/2100-1007_3-5142220.html?tag=nefd_top>
    >> 
    >> Yeah, not the real thing though!..
    >> 
    >> http://www.ghs.com/news/230811j.html

    DL> http://www.cobalt.com/aboutsun/media/features/mars.html

    DL> http://www.linuxdevices.com/news/NS3674252711.html

    DL> Interesting thing, that so called "java technology" ."It's  powers the
    DL> rover from earth" :)

    DL> Major problem in mars missions is probably programs portability and
    DL> execution with as much as possible limited access to hardware(no
    DL> access to things like ports,legs,cameras,trusters,fans,etc) ,like java
    DL> applets on my PC where i don't want it to have any access to my
    DL> hardware except framebuffer memory ?

    DL> Question:

    DL> I just can't believe _at_all_ that realtime java will _always_ meet
    DL> deadline,expecially that someone has proved that.

    DL> Should be assumed that worsest possible GC(garbage collection)
    DL> operations could happen between deadlines.That's mean,i think,normally
    DL> load of processor should be not more than several precents,because
    DL> processor should be fast enough to do GC.If there's JIT like
    DL> compiler,situation are even worse,it's should be assumed that all
    DL> commands are interpreted,not compiled! Or someone should do very
    DL> pricely analysis.... and it's possible that there will be something
    DL> wrong with it itself,so it's should be checked....

Don't know about the compiler, but real time garbage collection is
essentially a solved problem, provided you do not allocate such large
objects that the time to move a single object breaks your schedule.
Look in the book "Garbage Collection" by Lin and Jones, or do a Google
serach for Henry G. Baker (who now is a venture capitalist it seems) 
to read his papers. 

    DL> Program should use not more than,say, 1/100th of time(assuming that GC
    DL> lag 100 times more pricely than normal allocation,and that lag could
    DL> happen constantly  ),and run at <1/20 speed(interpretation)....damn
    DL> inefficient ,because it's better to have slower and more reliable
    DL> processors than ,hehe,p4 . Is there any tools for SPECIFIC java
    DL> platform that will calculate maximal execution time _accurately_? It's
    DL> should be very hard to make that tool that it will not assume GC lags
    DL> always like i'm doing.

    DL> Also,there's no doubling for software if there's same runtime in both
    DL> rovers.

-- 
   C++: The power, elegance and simplicity of a hand grenade.