Mars Rover Controlled By Java

[Michael Borgwardt]

Re: Mars Rover Controlled By Java

seemanta dutta wrote:[color=blue][color=green]
>>Why mention oxygen specifically?
>>The solar panels mentioned would have no
>>problem with the complete absence of oxygen.
>>[/color]
>
>
> My dear friend, planes need atmosphere not only for combustion but
> also for generating the required lift by its wings or copter blades or
> whatever.[/color]

So he is right: oxygen does not, specifically, matter.
[color=blue]
> A rarefied atmosphere would not be able to generate enough
> lift at a decent velocity like on earth. of course by increasing the
> velocity several times we can generate some lift, but that would be a
> totally wasteful use of energy.[/color]

Don't forget that the necessary lift is *also* much lower on Mars
since it has only one tenth the mass!

[mmeron@cars3.uchicago.edu]

Re: Mars Rover Controlled By Java

In article <bulei6$ipk4p$1 @ID-161931.news.uni-berlin.de>, Michael Borgwardt <brazil@brazi ls-animeland.de> writes:[color=blue]
>seemanta dutta wrote:[color=green][color=darkred]
>>>Why mention oxygen specifically?
>>>The solar panels mentioned would have no
>>>problem with the complete absence of oxygen.
>>>[/color]
>>
>>
>> My dear friend, planes need atmosphere not only for combustion but
>> also for generating the required lift by its wings or copter blades or
>> whatever.[/color]
>
>So he is right: oxygen does not, specifically, matter.
>[color=green]
>> A rarefied atmosphere would not be able to generate enough
>> lift at a decent velocity like on earth. of course by increasing the
>> velocity several times we can generate some lift, but that would be a
>> totally wasteful use of energy.[/color]
>
>Don't forget that the necessary lift is *also* much lower on Mars
>since it has only one tenth the mass!
>[/color]
Well, the gravity is not proporitonal to mass alone. It's radius is
smaller as well, so its gravity, on surface, is doen only by a factor
of 2 or so. Its atmospheric density, on the other hand, is down by
more than two orders of magnitude. So, the necessary lift is lower by
much less than the available lift.

Mati Meron | "When you argue with a fool,
meron@cars.uchi cago.edu | chances are he is doing just the same"

[Ken Hagan]

Re: Mars Rover Controlled By Java

Would it be *on-topic* to query the relevance of this to...

comp.arch
comp.distribute d
comp.lang.java
comp.lang.java. programmer
comp.object
comp.programmin g
comp.theory
sci.physics

I'm all for serendipity and all that, and I've learned all sorts
of things from off-topic threads, but I think the OP's claim (and
hence the official subject of the thread) was shot down with the
first or second reply and we've given aircraft and Java advocacy
a good run now.

[Bjorn-Ove.Heimsund@uib.no]

Re: Mars Rover Controlled By Java

In comp.arch Jan Panteltje <pNaonStpealmtj e@yahoo.com> wrote:[color=blue]
> Java is the worst thing that could happen to computing since the
> invention of the chuwing gum hard disk.
> It is slow, slow, slow, slow, SLOW, and not to mention slow.
> And on top of that it is slow.[/color]

I think most people have that impression either by playing with Java 1.0
(or listening to those who have), or by using Swing applications.

Newer Java versions and graphical applications using ie. SWT perform
the same as native C/Fortran applications. In fact, the new Hotspot
optimizer in 1.4 is quite good at numerical codes too. For some large
scale computations, my Java codes perform identical to Fortran codes,
with the added benefits of readability and maintainability , not to
mention trivial cross-platform deployment (from my desktop to the local
supercomputer, with excellent scalability).

I might add that Java w/Hotspot quite often outperforms vanilla C
codes, it's only when adding lots of optimization flags to the compiler
that the performance gap closes.

--
Bjørn-Ove Heimsund
Centre for Integrated Petroleum Research
University of Bergen, Norway

[Jan C. Vorbrüggen]

Re: Mars Rover Controlled By Java

> Newer Java versions and graphical applications using ie. SWT perform[color=blue]
> the same as native C/Fortran applications. In fact, the new Hotspot
> optimizer in 1.4 is quite good at numerical codes too.[/color]

While that is likely true, ...
[color=blue]
> For some large
> scale computations, my Java codes perform identical to Fortran codes,[/color]

Really? Even if you compile with optimization?
[color=blue]
> with the added benefits of readability and maintainability , not to
> mention trivial cross-platform deployment (from my desktop to the local
> supercomputer, with excellent scalability).[/color]

I consider a reasonably well-written F95 program to be very maintainable
and more portable than Java - if only for the fact that there's only one
F95 standard all compilers are written to, while there are several
incompatible (in various ways) Java "standards" around, not to mention
the different thread semantics of different implementations .
[color=blue]
> I might add that Java w/Hotspot quite often outperforms vanilla C
> codes, it's only when adding lots of optimization flags to the compiler
> that the performance gap closes.[/color]

For any modern compiler of a 3GL language, not compiling with (the equivalent
of) -fast is grossly negligent.

Jan

[Bjorn-Ove.Heimsund@uib.no]

Re: Mars Rover Controlled By Java

In comp.arch Jan C. Vorbrüggen <jvorbrueggen@m ediasec.de> wrote:[color=blue][color=green]
>> For some large
>> scale computations, my Java codes perform identical to Fortran codes,[/color]
>
> Really? Even if you compile with optimization?[/color]

Yes, but I might add that the things I do are not easily vectorizable
(sparse matrix calculations). For dense array computations, a good
compiler can do fancy unrolling tricks and other things which is not
(yet) available in Java nor in Hotspot.
[color=blue][color=green]
>> with the added benefits of readability and maintainability , not to
>> mention trivial cross-platform deployment (from my desktop to the local
>> supercomputer, with excellent scalability).[/color]
>
> I consider a reasonably well-written F95 program to be very maintainable
> and more portable than Java - if only for the fact that there's only one
> F95 standard all compilers are written to, while there are several[/color]

It's very easy to create unmaintainable code in any language, Java is no
exception. It's just that Java doesn't have a 40 year legacy baggage,
and encourages good design practices. Java seems to be well recieved
in some computer science institutes as well, especially as an
introduction to OO programming.

On the portability side, I have had issues porting some F95 codes
between compilers, both of which had different ideas how the standard
were to be interpreted (and the compilers were quite new too). F77
compiles nicely, though.
[color=blue]
> incompatible (in various ways) Java "standards" around, not to mention
> the different thread semantics of different implementations .[/color]

Since Java 1.2, I have yet to encounter any issues with thread
implementations , be it on AIX, Solaris, Linux or Windows. There are
of course some more issues relating to thread local storage and
caching, but the semantics of this is being worked out (for Java 1.5)
[color=blue][color=green]
>> I might add that Java w/Hotspot quite often outperforms vanilla C
>> codes, it's only when adding lots of optimization flags to the compiler
>> that the performance gap closes.[/color]
>
> For any modern compiler of a 3GL language, not compiling with (the equivalent
> of) -fast is grossly negligent.[/color]

Agreed. But many folks around here run their codes compiled with
"f77 -g" (not that I do that, of course :-)

--
Bjørn-Ove Heimsund
Centre for Integrated Petroleum Research
University of Bergen, Norway

[Alan Balmer]

Re: Mars Rover Controlled By Java

On Wed, 21 Jan 2004 10:11:07 -0000, "Ken Hagan"
<K.Hagan@thermo teknix.co.uk> wrote:
[color=blue]
>Would it be *on-topic* to query the relevance of this to...
>
>comp.arch
>comp.distribut ed
>comp.lang.ja va
>comp.lang.java .programmer
>comp.object
>comp.programmi ng
>comp.theory
>sci.physics
>
>I'm all for serendipity and all that, and I've learned all sorts
>of things from off-topic threads, but I think the OP's claim (and
>hence the official subject of the thread) was shot down with the
>first or second reply and we've given aircraft and Java advocacy
>a good run now.
>[/color]
In unmoderated groups, threads don't have "official" subjects, and
thread drift will be with us forever. Messages do have topicality,
however, and the comparison and qualification of programming
languages, and specifically Java, would seem to be topical in at least
two of the above groups. I will volunteer to trim the cross-post list,
however.

As for your question, yes. Topicality is always on-topic.

--
Al Balmer
Balmer Consulting
removebalmercon sultingthis@att .net

[Programmer Dude]

Re: Mars Rover Controlled By Java

seemanta dutta wrote:
[color=blue]
> of course by increasing the velocity several times we can generate
> some lift, but that would be a totally wasteful use of energy.[/color]

One can also increase wing area. This is, e.g., why 747s can land
so amazingly slowly for such a big bird.

--
|_ CJSonnack <Chris@Sonnack. com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ _______________ ____| Call: 1-800-DEV-NULL |
|______________ _______________ _______________ _|_____________ __________|

[Programmer Dude]

Re: Mars Rover Controlled By Java

seemanta dutta wrote:
[color=blue]
> of course by increasing the velocity several times we can generate
> some lift, but that would be a totally wasteful use of energy.[/color]

One can also increase wing area. This is, e.g., why 747s can land
so amazingly slowly for such a big bird.

--
|_ CJSonnack <Chris@Sonnack. com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ _______________ ____| Call: 1-800-DEV-NULL |
|______________ _______________ _______________ _|_____________ __________|

[Michael N. Christoff]

Re: Mars Rover Controlled By Java

>[color=blue]
> The code on the rover wasn't specified, but it's most likely C/C++ as
> that is the primary development language for Wind River VxWorks. I'm
> not even sure if that OS has Java support, though even if it did it
> would be a BAD choice. Java is NOT designed with real-time operating
> systems in mind. It's a fine language for what it is, but it's not
> really a suitable choice for this application. Ada might actually be
> the best choice, as this is the sort of thing that language was
> designed for, but C/C++ is a good alternative that is widely supported
> and well known.
>[/color]

Seems like Java may well be used on the actual rover in the future:

Jim Sculley wrote:
<quote>
In any event this entire discussion has ignored the Realtime
Specification for Java, implementations of which are being used in
mission critical apps, such as control systems for a future Mars rover:

http://www.opengroup.org/rtforum/uploads/40/2930/OpenGroup_Golden_Gate_May01

-v05.pdf

Jim S.
</quote>



l8r, Mike N. Christoff

[Michael N. Christoff]

Re: Mars Rover Controlled By Java

>[color=blue]
> The code on the rover wasn't specified, but it's most likely C/C++ as
> that is the primary development language for Wind River VxWorks. I'm
> not even sure if that OS has Java support, though even if it did it
> would be a BAD choice. Java is NOT designed with real-time operating
> systems in mind. It's a fine language for what it is, but it's not
> really a suitable choice for this application. Ada might actually be
> the best choice, as this is the sort of thing that language was
> designed for, but C/C++ is a good alternative that is widely supported
> and well known.
>[/color]

Seems like Java may well be used on the actual rover in the future:

Jim Sculley wrote:
<quote>
In any event this entire discussion has ignored the Realtime
Specification for Java, implementations of which are being used in
mission critical apps, such as control systems for a future Mars rover:

http://www.opengroup.org/rtforum/uploads/40/2930/OpenGroup_Golden_Gate_May01

-v05.pdf

Jim S.
</quote>



l8r, Mike N. Christoff

[Richard Maine]

Re: Mars Rover Controlled By Java

Jan C. Vorbrüggen <jvorbrueggen@m ediasec.de> writes:
[color=blue]
> For any modern compiler of a 3GL language, not compiling with (the equivalent
> of) -fast is grossly negligent.[/color]

A few years ago, I was asked to help with improving the performance of
a major production code here. The author of the code didn't even
know how to turn on the optimizer. I mean turning on the optimizer
at all, even with a simple -O, much less experimenting with the other
settings. I was a bit shocked that they felt the need to call for
help and hadn't even tried that. This was from a supposedly
professional full-time programmer and was in a code that had gone
through all the formal development process (for what little that
was actually worth :-() and was in production use.

But then, I found plenty of other problems also. I suppose it
figures. :-(

It was a Fortran code, but the major problems didn't have much to
do with the language. If you are sufficiently clueless, you can
manage to express that cluelessness in any language.

--
Richard Maine | Good judgment comes from experience;
email: my first.last at org.domain | experience comes from bad judgment.
org: nasa, domain: gov | -- Mark Twain

[Richard Maine]

Re: Mars Rover Controlled By Java

Jan C. Vorbrüggen <jvorbrueggen@m ediasec.de> writes:
[color=blue]
> For any modern compiler of a 3GL language, not compiling with (the equivalent
> of) -fast is grossly negligent.[/color]

A few years ago, I was asked to help with improving the performance of
a major production code here. The author of the code didn't even
know how to turn on the optimizer. I mean turning on the optimizer
at all, even with a simple -O, much less experimenting with the other
settings. I was a bit shocked that they felt the need to call for
help and hadn't even tried that. This was from a supposedly
professional full-time programmer and was in a code that had gone
through all the formal development process (for what little that
was actually worth :-() and was in production use.

But then, I found plenty of other problems also. I suppose it
figures. :-(

It was a Fortran code, but the major problems didn't have much to
do with the language. If you are sufficiently clueless, you can
manage to express that cluelessness in any language.

--
Richard Maine | Good judgment comes from experience;
email: my first.last at org.domain | experience comes from bad judgment.
org: nasa, domain: gov | -- Mark Twain

[Ashlie Benjamin Hocking]

Re: Mars Rover Controlled By Java

Richard Maine <nospam@see.sig nature> writes:[color=blue]
>If you are sufficiently clueless, you can manage to express that
>cluelessness in any language.[/color]

I think this is a quote worthy of a .sig file. (I'm assuming this is a
Richard Maine original?)

---------------------------------------------------------------------
| "Good and evil both increase at compound
Ben Hocking, Grad Student | interest. That is why the little
hocking@cs.virg inia.edu | decisions you and I make every day are of
| such infinite importance." - C. S. Lewis
---------------------------------------------------------------------

[Ashlie Benjamin Hocking]

Re: Mars Rover Controlled By Java

Richard Maine <nospam@see.sig nature> writes:[color=blue]
>If you are sufficiently clueless, you can manage to express that
>cluelessness in any language.[/color]

I think this is a quote worthy of a .sig file. (I'm assuming this is a
Richard Maine original?)

---------------------------------------------------------------------
| "Good and evil both increase at compound
Ben Hocking, Grad Student | interest. That is why the little
hocking@cs.virg inia.edu | decisions you and I make every day are of
| such infinite importance." - C. S. Lewis
---------------------------------------------------------------------