computer language used to program Mars Lander

computer language used to program Mars Lander

[jhc0033]

Interesting article I came across on Slashdot:

http://developers.slashdot.org/developers/08/07/10/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation? I wonder also, do
they really mean C++ when they say C. In my experience, this is a
frequent, although disagreeable usage.

Re: computer language used to program Mars Lander

[jacob navia]

jhc0033@gmail.com wrote:
> Interesting article I came across on Slashdot:
> 
> http://developers.slashdot.org/developers/08/07/10/213211.shtml
> 
> They are using C at JPL to program Mars Lander and just about
> everything now! Not Ada. Anyone got an explanation? I wonder also, do
> they really mean C++ when they say C. In my experience, this is a
> frequent, although disagreeable usage.

They do not use even memory allocation. They use a subset of C

I am sure they do not use C++!


-- 
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique
http://www.cs.virginia.edu/~lcc-win32

Re: computer language used to program Mars Lander

[Maciej Sobczak]

On 14 Lip, 13:21, jacob navia <ja...@nospam.com> wrote:

> They do not use even memory allocation. They use a subset of C
>
> I am sure they do not use C++!

Why? I would expect some parts of C++ being used, no matter how much
constrained is the target environment.
In particular, C++ has better and more expressive type system,
destructors that can ensure proper execution of "exit" actions, better
support for encapsulation, etc. All these are real advantages as far
as safe and secure code is concerned and none of these require
additional run-time resources.

For example, would you like to have custom integer types with range
checking in this critical software? (Expected answer on this group is
"yes".) This is trivial in C++ and almost impossible in C. This alone
is already a reason to prefer C++ over C for such systems.

Now, why there is no Ada on Mars is another story - but don't worry
about what Martians will think: they will not see the source code
anyway. ;-)

--
Maciej Sobczak * www.msobczak.com * www.inspirel.com

Re: computer language used to program Mars Lander

[Nick Keighley]

On 14 Jul, 12:18, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
> Interesting article I came across on Slashdot:
>
> http://developers.slashdot.org/developers/08/07/10/213211.shtml
>
> They are using C at JPL to program Mars Lander and just about
> everything now! Not Ada. Anyone got an explanation? I wonder also, do
> they really mean C++ when they say C. In my experience, this is a
> frequent, although disagreeable usage.

contrary to popular expectations space probes are very
conservative in their use of technolgy. Processors are old
(and hence proven) memorys are small (less vulnerable to radiation).

Rememeber if there's a bug they can't just upgrade the software.
Well they can but it has to be mostly working for the download
to work.

These are essetially embedded systems and C is still popular
in that world.

I suspect its a damn sight easier to prove C correct than C++.

    a = b + c;

probably does what it says in C (assuming b and c have good values
and it doesn't overflow). In C++ there could be half a dozen
overloaded
operators in there.

--
Nick Keighley

I know not what I appear to the world, but to myself I seem to have
been
only like a boy playing on the sea-shore, and diverting myself in now
and
then finding a smoother pebble or a prettier shell, whilest the great
ocean of truth lay all undiscovered before me.
                    (Sir Issac Newton)

Re: computer language used to program Mars Lander

[Maciej Sobczak]

On 14 Lip, 13:49, Nick Keighley <nick_keighley_nos...@hotmail.com>
wrote:

> I suspect its a damn sight easier to prove C correct than C++.
>
>     a = b + c;
>
> probably does what it says in C (assuming b and c have good values
> and it doesn't overflow). In C++ there could be half a dozen
> overloaded
> operators in there.

Your reasoning is completely broken.
Let's try this one:

I suspect its a damn sight easier to prove C correct than Ada.

a = b + c;

probably does what it says in C. In Ada (substitute := for = ) there
could be half a dozen overloaded operators in there (and some
controlled operations as well).

Do you think that there are some monkeys in the project that randomly
overload operators? If yes, then Ada is equally vulnerable.

Another point: the operator + in C *is* overloaded and not only its
meaning, but also the generated object code differs depending on the
types of a and b. Yes, this is what overloading is all about and yes,
you can have serious errors in C because of that, especially when
combined with implicit conversions. What C++ or Ada can offer in this
area is at least to get rid of those implicit conversions. This is a
huge gain for proving correctness of the code.

--
Maciej Sobczak * www.msobczak.com * www.inspirel.com

Re: computer language used to program Mars Lander

[jhc0033]

On Jul 14, 4:49 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
wrote:

> contrary to popular expectations space probes are very
> conservative in their use of technolgy.

I disagree. Actually, the space industry will try anything and stick
with it until stuff explodes (Ariane rocket) or crashes into the wrong
celestial body because of faulty software. They did use Ada widely
before, and they even programmed some of their probes in Lisp. Seems
like C is the new fad there. Wait until they get bitten by macros and
dangling pointers.

Re: computer language used to program Mars Lander

[Brian]

<jhc0033@gmail.com> wrote in message 
news:807ef880-b2ac-4ac6-877c-21274e8ff4ab@d77g2000hsb.googlegroups.com...
> On Jul 14, 4:49 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
> wrote:
>
>> contrary to popular expectations space probes are very
>> conservative in their use of technolgy.
>
> I disagree. Actually, the space industry will try anything and stick
> with it until stuff explodes (Ariane rocket) or crashes into the wrong
> celestial body because of faulty software. They did use Ada widely
> before, and they even programmed some of their probes in Lisp. Seems
> like C is the new fad there. Wait until they get bitten by macros and
> dangling pointers.

And I disagree with your disagreement.  The Ariane rocket disaster is a good 
example of trying to migrate existing software on a "known" platform in 
response to a business situation.  Also, the crashes you refer to "because 
of faulty software" are examples of software that wasn't adequately tested 
before implementation in order to comply with non-changing, and 
non-changeable, mission requirements.  Celestial mechanics won't let you 
slip your ship date!

JPL, along with the rest of NASA has an extraordinary success record with 
their software.  It would be stunning in any kind of endeavor, but is 
especially so when you consider the kinds of missions, and the kinds of 
things that happen with their funding and manpower on a yearly basis.  Then, 
just to make the engineering problem a bit more interesting please remember 
that there isn't a lot of hardware that functions in that environment, and 
it's a few million miles from anybody who might be able to hit CTRL-ALT-DEL. 
With all this in mind, I think that these guys deserve a lot of respect.

So, why did they choose C for this application?  I wasn't there when the 
decision was made, but I'd suspect that it was the language that their 
coders were most familiar with, the language that had the right libraries 
for their application, and the language that they felt was most appropriate 
for this application.  In other words, good engineering judgment.

Give 'em their "props", okay?

Brian

Re: computer language used to program Mars Lander

[Michael Oswald]

jhc0033@gmail.com wrote:

> They did use Ada widely
> before, and they even programmed some of their probes in Lisp. 

Do you have some information on that? I mean, I work in the space 
business (although not directly on on-board software but rather mission 
control software and testing equipment) but I haven't heard of Lisp 
usage. Would definitely be a 'nice to know' for me.


lg,
Michael

Re: computer language used to program Mars Lander

[Larry Elmore]

Michael Oswald wrote:
> jhc0033@gmail.com wrote:
> 
>> They did use Ada widely
>> before, and they even programmed some of their probes in Lisp. 
> 
> Do you have some information on that? I mean, I work in the space 
> business (although not directly on on-board software but rather mission 
> control software and testing equipment) but I haven't heard of Lisp 
> usage. Would definitely be a 'nice to know' for me.

NASA's Deep Space 1

Re: computer language used to program Mars Lander

[jhc0033]

On Jul 23, 7:43 am, Michael Oswald <muell...@gmx.net> wrote:
> I mean, I work in the space
> business (although not directly on on-board software but rather mission
> control software and testing equipment) but I haven't heard of Lisp
> usage. Would definitely be a 'nice to know' for me.

Probably because they weren't too successful. I personally think Lisp
is super-cool, but inappropriate for space (or any reliability-
sensitive work).

If I remember correctly, when they used Lisp in the probe, there was a
bug and they used Lisp's live patching and interactive debugging to
fix it, so they only missed their target by a quadrillion miles
instead of missing it by a gazillion miles.

On the other hand, the bug wouldn't have happened in the first place,
if they used a good static language. I'll let someone who knows better
fill in the details (that's why I added comp.lang.lisp to the groups)

Happy space exploration and exploitation!

Re: computer language used to program Mars Lander

[Stefan Scholl]

In comp.lang.lisp jhc0033@gmail.com <jhc0033@gmail.com> wrote:
> On the other hand, the bug wouldn't have happened in the first place,
> if they used a good static language.

Ariane 5? ;-)

Re: computer language used to program Mars Lander

[Grant Rettke]

> Ariane 5? ;-)

They should have used Eiffel ;)

Re: computer language used to program Mars Lander

[John Thingstad]

Pￜ Thu, 24 Jul 2008 08:59:11 +0200, skrev jhc0033@gmail.com  
<jhc0033@gmail.com>:

> On Jul 23, 7:43 am, Michael Oswald <muell...@gmx.net> wrote:
>> I mean, I work in the space
>> business (although not directly on on-board software but rather mission
>> control software and testing equipment) but I haven't heard of Lisp
>> usage. Would definitely be a 'nice to know' for me.
>
> Probably because they weren't too successful. I personally think Lisp
> is super-cool, but inappropriate for space (or any reliability-
> sensitive work).
>
> If I remember correctly, when they used Lisp in the probe, there was a
> bug and they used Lisp's live patching and interactive debugging to
> fix it, so they only missed their target by a quadrillion miles
> instead of missing it by a gazillion miles.
>
> On the other hand, the bug wouldn't have happened in the first place,
> if they used a good static language. I'll let someone who knows better
> fill in the details (that's why I added comp.lang.lisp to the groups)
>
> Happy space exploration and exploitation!

Mathematically verify it with ACL2! Way better than silly type checking.
Check that theprogram does what the spec sais.
(Which still only proves that it does what you say, not what you men.))

--------------
John Thingstad

Re: computer language used to program Mars Lander

[jhc0033]

On Jul 24, 12:39 am, "John Thingstad" <jpth...@online.no> wrote:

> Mathematically verify it with ACL2! Way better than silly type checking.
> Check that theprogram does what the spec sais.
> (Which still only proves that it does what you say, not what you men.))
>

Typo-prone people probably shouldn't use dynamically-typed languages!
BTW us, static folk, got Coq, which is probably better than ACL2: the
name "ACL2" sounds like they couldn't even get it right in the first
try.

Re: computer language used to program Mars Lander

[John Thingstad]

Pￜ Thu, 24 Jul 2008 09:51:55 +0200, skrev jhc0033@gmail.com  
<jhc0033@gmail.com>:

> On Jul 24, 12:39 am, "John Thingstad" <jpth...@online.no> wrote:
>
>> Mathematically verify it with ACL2! Way better than silly type checking.
>> Check that theprogram does what the spec sais.
>> (Which still only proves that it does what you say, not what you men.))
>>
>
> Typo-prone people probably shouldn't use dynamically-typed languages!
> BTW us, static folk, got Coq, which is probably better than ACL2: the
> name "ACL2" sounds like they couldn't even get it right in the first
> try.

Well the first post got tossed away by accident and the second was written  
in a hurry in aggravation.
Anyhow you are wrong. Since variables must be declared before they are  
used and also assigned a object typo's are get caught at compile time just  
like in a statically compiled language.

--------------
John Thingstad

Re: computer language used to program Mars Lander

[Brian]

<jhc0033@gmail.com> wrote in message 
news:76fc184b-bd62-4bd3-9ccf-8a6cd872c30b@v39g2000pro.googlegroups.com...
> On Jul 24, 12:39 am, "John Thingstad" <jpth...@online.no> wrote:
>
>> Mathematically verify it with ACL2! Way better than silly type checking.
>> Check that theprogram does what the spec sais.
>> (Which still only proves that it does what you say, not what you men.))
>>
>
> Typo-prone people probably shouldn't use dynamically-typed languages!
> BTW us, static folk, got Coq, which is probably better than ACL2: the
> name "ACL2" sounds like they couldn't even get it right in the first
> try.

You've "got Coq"???  And you're willing to talk about bad names?
*grin* 

Re: computer language used to program Mars Lander

[jhc0033]

On Jul 24, 1:39 pm, "Brian" <phaedrus...@hotmail.com> wrote:
> <jhc0...@gmail.com> wrote in message
>
> news:76fc184b-bd62-4bd3-9ccf-8a6cd872c30b@v39g2000pro.googlegroups.com...
>
> > On Jul 24, 12:39 am, "John Thingstad" <jpth...@online.no> wrote:
>
> >> Mathematically verify it with ACL2! Way better than silly type checking.
> >> Check that theprogram does what the spec sais.
> >> (Which still only proves that it does what you say, not what you men.))
>
> > Typo-prone people probably shouldn't use dynamically-typed languages!
> > BTW us, static folk, got Coq, which is probably better than ACL2: the
> > name "ACL2" sounds like they couldn't even get it right in the first
> > try.
>
> You've "got Coq"???  And you're willing to talk about bad names?
> *grin*

I think "Coq" conveys a feeling of confidence that a theorem prover
should. (Btw thanks for ruining the discussion with your low-brow
shtik)

Re: computer language used to program Mars Lander

[Brian]

<jhc0033@gmail.com> wrote in message 
news:6e2a8ce8-25e9-427b-9c67-3285ce73e398@j7g2000prm.googlegroups.com...
> On Jul 24, 1:39 pm, "Brian" <phaedrus...@hotmail.com> wrote:
>> <jhc0...@gmail.com> wrote in message
>>
>> news:76fc184b-bd62-4bd3-9ccf-8a6cd872c30b@v39g2000pro.googlegroups.com...
>>
>> > On Jul 24, 12:39 am, "John Thingstad" <jpth...@online.no> wrote:
>>
>> >> Mathematically verify it with ACL2! Way better than silly type 
>> >> checking.
>> >> Check that theprogram does what the spec sais.
>> >> (Which still only proves that it does what you say, not what you 
>> >> men.))
>>
>> > Typo-prone people probably shouldn't use dynamically-typed languages!
>> > BTW us, static folk, got Coq, which is probably better than ACL2: the
>> > name "ACL2" sounds like they couldn't even get it right in the first
>> > try.
>>
>> You've "got Coq"???  And you're willing to talk about bad names?
>> *grin*
>
> I think "Coq" conveys a feeling of confidence that a theorem prover
> should. (Btw thanks for ruining the discussion with your low-brow
> shtik)

After the ACL2 comment, it seemed appropriate.  I doubt if one comment 
"ruined" the discussion for anyone.  Well, anyone other than those whose 
craniums are firmly emplaced in their anal orifice...  (High-brow shtik is 
sooo much better!)

Really, I find it's usually those who make tone, content or format comments 
that tend to bring down the discussion.  A little levity rarely hurts much, 
and I'm sure you'll get over it.

And btw, you're welcome.

Re: computer language used to program Mars Lander

[jhc0033]

On Jul 25, 1:29 pm, "Brian" <phaedrus...@hotmail.com> wrote:
> <jhc0...@gmail.com> wrote in message

> > I think "Coq" conveys a feeling of confidence that a theorem prover
> > should. (Btw thanks for ruining the discussion with your low-brow
> > shtik)
>
> ....

I wasn't trying to be serious. I mean, read the first sentence! Comedy
is hard.

Re: computer language used to program Mars Lander

[Brian]

<jhc0033@gmail.com> wrote in message 
news:12db33c8-1609-4447-8ad3-97b7b45d291b@q5g2000prf.googlegroups.com...
> On Jul 25, 1:29 pm, "Brian" <phaedrus...@hotmail.com> wrote:
>> <jhc0...@gmail.com> wrote in message
>
>> > I think "Coq" conveys a feeling of confidence that a theorem prover
>> > should. (Btw thanks for ruining the discussion with your low-brow
>> > shtik)
>>
>> ....
>
> I wasn't trying to be serious. I mean, read the first sentence! Comedy
> is hard.

Sorry, not only did I mis-read, I also missed the rimshot.
Goodnight Sheky!

You've all been a great audience.  Be sure to tip your waitresses!
We'll be here all week. 

Re: computer language used to program Mars Lander

[pls.mrjm]

jhc0033@gmail.com ha scritto:
> I personally think Lisp
> is super-cool, but inappropriate for space (or any reliability-
> sensitive work).

You got it, this is the best way of convincing: first the cookie, then
the shit!

BTW, what exactly are the super-cool things you noted?

:)

-PM

Re: computer language used to program Mars Lander

[Pascal J. Bourguignon]

"jhc0033@gmail.com" <jhc0033@gmail.com> writes:

> On Jul 23, 7:43 am, Michael Oswald <muell...@gmx.net> wrote:
>> I mean, I work in the space
>> business (although not directly on on-board software but rather mission
>> control software and testing equipment) but I haven't heard of Lisp
>> usage. Would definitely be a 'nice to know' for me.
>
> Probably because they weren't too successful. I personally think Lisp
> is super-cool, but inappropriate for space (or any reliability-
> sensitive work).
>
> If I remember correctly, when they used Lisp in the probe, there was a
> bug and they used Lisp's live patching and interactive debugging to
> fix it, so they only missed their target by a quadrillion miles
> instead of missing it by a gazillion miles.

It wasn't the purpose of the mission to hit the target, but to fly by.


> On the other hand, the bug wouldn't have happened in the first place,
> if they used a good static language. I'll let someone who knows better
> fill in the details (that's why I added comp.lang.lisp to the groups)
>
> Happy space exploration and exploitation!

http://en.wikipedia.org/wiki/Deep_Space_1

http://www.nasa.gov/lb/centers/ames/news/releases/1999/99_37AR.html
REMOTE AGENT EXPERIMENT MEETS ALL OBJECTIVES

http://web.archive.org/web/20010923215958/http://rax.arc.nasa.gov/

http://www.flownet.com/gat/jpl-lisp.html

Be sure to read the description of the bug:

http://web.archive.org/web/20061106012026/http://ic.arc.nasa.gov/publications/pdf/2000-0176.pdf

It has nothing to do with Lisp per se.  It could have occured with any
other programming language.  Now, the question is how do you correct a
dead-lock on a running system compiled from Ada code, 3 second-light
away, without rebooting it?  This is what lisp allowed for this space
probe, and what lisp allows also for running web servers.

-- 
__Pascal Bourguignon__

Re: computer language used to program Mars Lander

[Michael Oswald]

Pascal J. Bourguignon wrote:

> http://en.wikipedia.org/wiki/Deep_Space_1
> 
> http://www.nasa.gov/lb/centers/ames/news/releases/1999/99_37AR.html
> REMOTE AGENT EXPERIMENT MEETS ALL OBJECTIVES
> 
> http://web.archive.org/web/20010923215958/http://rax.arc.nasa.gov/
> 
> http://www.flownet.com/gat/jpl-lisp.html
> 
> Be sure to read the description of the bug:
> 
> http://web.archive.org/web/20061106012026/http://ic.arc.nasa.gov/publications/pdf/2000-0176.pdf
> 
> It has nothing to do with Lisp per se.  It could have occured with any
> other programming language.  Now, the question is how do you correct a
> dead-lock on a running system compiled from Ada code, 3 second-light
> away, without rebooting it?  This is what lisp allowed for this space
> probe, and what lisp allows also for running web servers.
> 

Thanks for the links!

Very interesting. It also makes sense to me to put Lisp into this Remote 
Agent unit (which doesn't seem to be very time critical and also doesn't 
deal with low level stuff but is rather on a high level).
So each language can play out it's strengths.

Re: computer language used to program Mars Lander

[Stefan Scholl]

In comp.lang.lisp Michael Oswald <muell_om@gmx.net> wrote:
> Very interesting. It also makes sense to me to put Lisp into this Remote 
> Agent unit (which doesn't seem to be very time critical and also doesn't 
> deal with low level stuff but is rather on a high level).
> So each language can play out it's strengths.

Subtle trolling. Gratuliere.


-- 
Web (en): http://www.no-spoon.de/ -*- Web (de): http://www.frell.de/

Re: computer language used to program Mars Lander

[Michael Oswald]

Stefan Scholl wrote:
> Subtle trolling. Gratuliere.

What's your problem?

Re: computer language used to program Mars Lander

[j.oke]

On 24 Lug, 08:59, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
> is super-cool

On 24 Lug, 08:59, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
> ... super-cool ...

What's the better language: hebrew or english?

Well, the first one is simple and perfect, and the second one goes all
for convenience (mixed to european history, which took origin from
latin, which took origin from greek, which took origin from egyptian,
which took origin from hebrew (and so the circle is finally closed
again)). <-- please note: we have to close 2 (two) parens here, which
seems to be a real problem to all the non-Lispers out there...

So what?

(The translation to coding slangs is left as an exercise to the reader
(no, the human one)). <-- yet another one!!

-JO

Re: computer language used to program Mars Lander

[Adam Beneschan]

On Jul 25, 2:19 pm, "j.oke" <java....@gmail.com> wrote:
> On 24 Lug, 08:59, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
>
> > is super-cool
>
> On 24 Lug, 08:59, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
>
> > ... super-cool ...
>
> What's the better language: hebrew or english?
>
> Well, the first one is simple and perfect, and the second one goes all
> for convenience (mixed to european history, which took origin from
> latin, which took origin from greek, which took origin from egyptian,
> which took origin from hebrew (and so the circle is finally closed
> again)).

Ummm, no.  I think you're talking about the *alphabet*, not the
language.  The English language is part of a large group of languages
called Indo-European, and Hebrew isn't part of this group (nor is
Egyptian).  Where this language originated is controversial; one
theory is somewhere northeast of the Black Sea.  I don't think you're
quite right about the alphabets, either; the Greek and Hebrew
alphabets are both more or less directly derived from the Phoenician
alphabet, and Egyptian hieroglyphics don't figure into it at all.

> ... super-pedantic ...

                              -- Adam

Re: computer language used to program Mars Lander

[Joost Kremers]

Adam Beneschan wrote:
> the Greek and Hebrew
> alphabets are both more or less directly derived from the Phoenician
> alphabet, and Egyptian hieroglyphics don't figure into it at all.

actually, i believe the consensus is that the proto-semitic alphabet from
which the phoenician alphabet developed, was directly derived from egyptian
hieroglyphics.


-- 
Joost Kremers                                      joostkremers@yahoo.com
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)

Re: computer language used to program Mars Lander

[j.oke]

On 26 Lug, 00:34, Adam Beneschan <a...@irvine.com> wrote:
> no.

There's much more thought in it (between the lines) than it might seem
(at a first/fast/superficial glance), but I don't expect anybody to
waste too much hours on meditating on it.

;)

-JO

Re: computer language used to program Mars Lander

[j.oke]

On 26 Lug, 00:34, Adam Beneschan <a...@irvine.com> wrote:
> I think you're talking about the *alphabet*, not the
> language.

I wrote (and meant): history.

-JO

Re: computer language used to program Mars Lander

[Paul Hsieh]

On Jul 14, 4:49 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
wrote:
> On 14 Jul, 12:18, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
>
> > Interesting article I came across on Slashdot:
>
> >http://developers.slashdot.org/developers/08/07/10/213211.shtml
>
> > They are using C at JPL to program Mars Lander and just about
> > everything now! Not Ada. Anyone got an explanation? I wonder also, do
> > they really mean C++ when they say C. In my experience, this is a
> > frequent, although disagreeable usage.
>
> contrary to popular expectations space probes are very
> conservative in their use of technology. Processors are old
> (and hence proven) memories are small (less vulnerable to radiation).

Indeed.  Ada is used by the military, because they have much more
sophisticated hardware in tanks and fighter jets.  I would expect that
perhaps NASA also uses it for the space shuttle.

> Remember if there's a bug they can't just upgrade the software.

They both can and *DO* do this.  They typically use VxWorks as the
main operating system, which comes with a fairly powerful command
console that makes it practical to actually debug, upload bug fixes
and reboot the systems all remotely.

> Well they can but it has to be mostly working for the download
> to work.

Its in the OS they use (and didn't make themselves.)

> These are essentially embedded systems and C is still popular
> in that world.

The small memory footprint and VxWorks environment probably makes C a
very attractive language for the NASA guys.  If they used Ada, they
would be slower, have much larger memory requirements and have a very
hard time debugging problems remotely.

> I suspect its a damn sight easier to prove C correct than C++.

Well by definition, since every C bug can be mapped to a C++ bug
(except for certain implicit type conversion failures; but that can be
dealt with by requiring that the C code also be compilable with a C++
compiler.)

--
Paul Hsieh
http://www.pobox.com/~qed/
http://bstring.sf.net/

Re: computer language used to program Mars Lander

[Chris Thomasson]

"Paul Hsieh" <websnarf@gmail.com> wrote in message 
news:13a2f4f0-6ec1-4570-b6bf-1621cfb32db2@a2g2000prm.googlegroups.com...
On Jul 14, 4:49 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
wrote:
> > On 14 Jul, 12:18, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
> >
> > > Interesting article I came across on Slashdot:
> >
> > >http://developers.slashdot.org/developers/08/07/10/213211.shtml
> >
> > > They are using C at JPL to program Mars Lander and just about
> > > everything now! Not Ada. Anyone got an explanation? I wonder also, do
> > > they really mean C++ when they say C. In my experience, this is a
> > > frequent, although disagreeable usage.
> >
> > contrary to popular expectations space probes are very
> > conservative in their use of technology. Processors are old
> > (and hence proven) memories are small (less vulnerable to radiation).

> Indeed.  Ada is used by the military, because they have much more
> sophisticated hardware in tanks and fighter jets.

Is this a trolling attempt? Anyway, the military uses C++ for all critical
system software in state-of-the-art fighter-bombers because they have much
more sophisticated hardware:

http://www.research.att.com/~bs/JSF-AV-rules.pdf

http://www.ldra.co.uk/nologindownload.asp?id=52

:^/




> I would expect that
> perhaps NASA also uses it for the space shuttle.

[...] 

Re: computer language used to program Mars Lander

[Default User]

Chris Thomasson wrote:

> "Paul Hsieh" <websnarf@gmail.com> wrote in message
> news:13a2f4f0-6ec1-4570-b6bf-1621cfb32db2@a2g2000prm.googlegroups.com.

> > Indeed.  Ada is used by the military, because they have much more
> > sophisticated hardware in tanks and fighter jets.
> 
> Is this a trolling attempt? Anyway, the military uses C++ for all
> critical system software in state-of-the-art fighter-bombers because
> they have much more sophisticated hardware:

We did quite a bit of code for avionics flight systems for military
aircraft in C++. It ran on top of an RTOS and there were certain
restrictions in the programming. Dynamic memory was only allocated at
startup, for instance.



Brian

Re: computer language used to program Mars Lander

[Chris Thomasson]

"Default User" <defaultuserbr@yahoo.com> wrote in message 
news:6ea1d5F65269U1@mid.individual.net...
> Chris Thomasson wrote:
>
>> "Paul Hsieh" <websnarf@gmail.com> wrote in message
>> news:13a2f4f0-6ec1-4570-b6bf-1621cfb32db2@a2g2000prm.googlegroups.com.
>
>> > Indeed.  Ada is used by the military, because they have much more
>> > sophisticated hardware in tanks and fighter jets.
>>
>> Is this a trolling attempt? Anyway, the military uses C++ for all
>> critical system software in state-of-the-art fighter-bombers because
>> they have much more sophisticated hardware:
>
> We did quite a bit of code for avionics flight systems for military
> aircraft in C++. It ran on top of an RTOS and there were certain
> restrictions in the programming. Dynamic memory was only allocated at
> startup, for instance.

Sounds pretty smart to me. IMHO, its nice that C++ is flexible enough
to work well under some fairly harsh, but necessary restrictions. Also,
IMVHO, it does not really matter what programming language is used because
in the end its all up to the programmer to "get it right". Even an ADA-
based system could contain subtle logic bugs. That would be very bad if
one of those nasty bugs revealed a code-path which could open the bomb
bay doors, arm something and let it loose!

:^o 

Re: computer language used to program Mars Lander

[Gary Scott]

Chris Thomasson wrote:

> "Paul Hsieh" <websnarf@gmail.com> wrote in message 
> news:13a2f4f0-6ec1-4570-b6bf-1621cfb32db2@a2g2000prm.googlegroups.com...
> On Jul 14, 4:49 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
> wrote:
> 
>> > On 14 Jul, 12:18, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
>> >
>> > > Interesting article I came across on Slashdot:
>> >
>> > >http://developers.slashdot.org/developers/08/07/10/213211.shtml
>> >
>> > > They are using C at JPL to program Mars Lander and just about
>> > > everything now! Not Ada. Anyone got an explanation? I wonder also, do
>> > > they really mean C++ when they say C. In my experience, this is a
>> > > frequent, although disagreeable usage.
>> >
>> > contrary to popular expectations space probes are very
>> > conservative in their use of technology. Processors are old
>> > (and hence proven) memories are small (less vulnerable to radiation).
> 
> 
>> Indeed.  Ada is used by the military, because they have much more
>> sophisticated hardware in tanks and fighter jets.
> 
> 
> Is this a trolling attempt? Anyway, the military uses C++ for all critical
> system software in state-of-the-art fighter-bombers because they have much
> more sophisticated hardware:
> 
> http://www.research.att.com/~bs/JSF-AV-rules.pdf
> 
> http://www.ldra.co.uk/nologindownload.asp?id=52

It has very little to do with the "sophistication of the hardware".

> 
> :^/
> 
> 
> 
> 
>> I would expect that
>> perhaps NASA also uses it for the space shuttle.
> 
> 
> [...]


-- 

Gary Scott
mailto:garylscott@sbcglobal dot net

Fortran Library:  http://www.fortranlib.com

Support the Original G95 Project:  http://www.g95.org
-OR-
Support the GNU GFortran Project:  http://gcc.gnu.org/fortran/index.html

If you want to do the impossible, don't hire an expert because he knows 
it can't be done.

-- Henry Ford

Re: computer language used to program Mars Lander

[Chris Thomasson]

"Gary Scott" <garylscott@sbcglobal.net> wrote in message 
news:d4Rfk.33338$ZE5.20098@nlpi061.nbdc.sbc.com...
> Chris Thomasson wrote:
>
>> "Paul Hsieh" <websnarf@gmail.com> wrote in message 
>> news:13a2f4f0-6ec1-4570-b6bf-1621cfb32db2@a2g2000prm.googlegroups.com...
>> On Jul 14, 4:49 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
>> wrote:
>>
>>> > On 14 Jul, 12:18, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
>>> >
>>> > > Interesting article I came across on Slashdot:
>>> >
>>> > >http://developers.slashdot.org/developers/08/07/10/213211.shtml
>>> >
>>> > > They are using C at JPL to program Mars Lander and just about
>>> > > everything now! Not Ada. Anyone got an explanation? I wonder also, 
>>> > > do
>>> > > they really mean C++ when they say C. In my experience, this is a
>>> > > frequent, although disagreeable usage.
>>> >
>>> > contrary to popular expectations space probes are very
>>> > conservative in their use of technology. Processors are old
>>> > (and hence proven) memories are small (less vulnerable to radiation).
>>
>>
>>> Indeed.  Ada is used by the military, because they have much more
>>> sophisticated hardware in tanks and fighter jets.
>>
>>
>> Is this a trolling attempt? Anyway, the military uses C++ for all 
>> critical
>> system software in state-of-the-art fighter-bombers because they have 
>> much
>> more sophisticated hardware:
>>
>> http://www.research.att.com/~bs/JSF-AV-rules.pdf
>>
>> http://www.ldra.co.uk/nologindownload.asp?id=52
>
> It has very little to do with the "sophistication of the hardware".
[...]

Yeah, I was "trying" to be sarcastic.

:^( 

Re: computer language used to program Mars Lander

[Colin Paul Gloster]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: TEXT/PLAIN; charset=UTF-8, Size: 8734 bytes --]

On Thu, 17 Jul 2008, Paul Hsieh wrote:

|-------------------------------------------------------------------------|
|"On Jul 14, 4:49 am, Nick Keighley <nick_keighley_nos...@hotmail.com>    |
|wrote:                                                                   |
|> On 14 Jul, 12:18, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:       |
|>                                                                        |
|> > Interesting article I came across on Slashdot:                       |
|>                                                                        |
|> >http://developers.slashdot.org/developers/08/07/10/213211.shtml       |
|>                                                                        |
|> > They are using C at JPL to program Mars Lander and just about        |
|> > everything now! Not Ada. Anyone got an explanation? I wonder also, do|
|> > they really mean C++ when they say C. In my experience, this is a    |
|> > frequent, although disagreeable usage.                               |
|>                                                                        |
|> contrary to popular expectations space probes are very                 |
|> conservative in their use of technology. Processors are old            |
|> (and hence proven) [..]                                                |
|                                                                         |
|Indeed."                                                                 |
|-------------------------------------------------------------------------|

Agreed.

|-------------------------------------------------------------------------|
|" memories are small"                                                    |
|-------------------------------------------------------------------------|

Agreed (in the sense that they do not have many binary digits).

|-------------------------------------------------------------------------|
|" (less vulnerable to radiation)."                                       |
|-------------------------------------------------------------------------|

Memories used in space probes are less vulnerable to radiation than
normal memories, but this is not because of the centimeters cubed
used. 

On Page 12 of
HTTP://AMS.Aeroflex.com/ProductFiles/DataSheets/4MSRAM/ut8r512x8.pdf
, dimensions of 0.575 inches by 0.910 inches by (0.117-0.013) inches
(approximately 14.6 millimeters by 23.1 mm by 2.6 mm approximately
equal to 877 mm cubed) are shown for an astronautical four megabit
SRAM excluding the legs, whereas we can see from
WWW.IDT.com/?genID=71V416L&source=products_genericPart_71V416L
and
WWW.IDT.com/?app=packaging&packageID=BE48&mktseg=IDT
that dimensions closer to 9 mm by 9 mm by 1.2 mm (97.2 mm cubed) are
available for four megabits of Terran SRAM.

Of course, a problem with radiation is more likely to happen to (2 x
877) mm cubed of 2 x 4 Mbits of SRAM than to 1 x 877 mm cubed of 1 x 4
Mbits of SRAM.

|-------------------------------------------------------------------------|
|"  Ada [..]                                                              |
|[..]                                                                     |
|[..]  I would expect that                                                |
|perhaps NASA also uses it for the space shuttle."                        |
|-------------------------------------------------------------------------|

I have heard that a language which is used only for the Space Shuttles
was used instead.

|-------------------------------------------------------------------------|
|> Remember if there's a bug they can't just upgrade the software.        |
|                                                                         |
|They both can and *DO* do this."                                         |
|-------------------------------------------------------------------------|

They can upgrade the software. They can not do this easily, so Nick
Keighley's assertion "they can't just upgrade the software" is
correct. Were the probe on the Moon, there would be a latency 

|-------------------------------------------------------------------------|
|"  They typically use VxWorks as the                                     |
|main operating system,"                                                  |
|-------------------------------------------------------------------------|

Actually before the rovers launched in circa 2003, NASA used to not
use VxWorks. A port of VxWorks to a processor which had not been
supported before was specifically written for that mission. This is in
contrast to the often conservative nature of responsible astronautical
engineers, but NASA has shown itself to be reckless on a number of
occasions.

|-------------------------------------------------------------------------|
|" which comes with a fairly powerful command                             |
|console that makes it practical to actually debug, upload bug fixes      |
|and reboot the systems all remotely.                                     |
|                                                                         |
|> Well they can but it has to be mostly working for the download         |
|> to work.                                                               |
|                                                                         |
|Its in the OS they use (and didn't make themselves.)"                    |
|-------------------------------------------------------------------------|

Were the probe on the Moon, the latency would be a few seconds
long. Latencies for other destinations would be much worse. If Mars
was at its closest to the Sun (i.e. at 1.381 Astronomical Units (A.U.s)) and
were Earth between the Sun and Mars, then there would be a distance of
approximately 0.381 A.U.s equal to circa 500 light seconds multiplied
by 0.381 equals 190.5 light seconds equals over three light minutes
between the Earthling operators and the probe. Between the time an
operator typed ps to list the processes and the time the telecommand
was received over three minutes later, plenty of terminal problems
could have ended the mission.

If you have software on the probe which is sorting ten numbers while
you are uploading a patch to the sorting algorithhm, and pausing or
terminating the current sorting is unacceptable (it might not actually
be buggy, perhaps it merely needs an adjustment), then does VxWorks
know that the only safe times to install the patch are between one
run's final iteration and the next run's next iteration. VxWorks can
not possibly know that without being told. This is independent of
operating system and language.

Are you aware that well-maintained unmanned spacecraft are not
rebooted even when software is being patched while most of the rest of
the software is still being run?

|-------------------------------------------------------------------------|
|"[..]                                                                    |
|                                                                         |
|The small memory footprint and VxWorks environment probably makes C a    |
|very attractive language for the NASA guys.  If they used Ada, they      |
|would be slower, have much larger memory requirements and have a very    |
|hard time debugging problems remotely.                                   |
|                                                                         |
|[..]"                                                                    |
|-------------------------------------------------------------------------|

How is C on VxWorks faster than Ada? It is not clear to me whether you
believe that C on VxWorks makes the speed of light faster or whether
it teleports Mars to be situated closer to Earth.

Please explain the speeds of less than two microseconds without
VxWorks and over eight seconds with VxWorks in Table 1 of
"The Ravenscar Tasking Profile - Experience Report"
by Brian Dobbing and George Romanski in the PDF file hyperlinked to
from
HTTP://Portal.ACM.org/citation.cfm?id=329607.334733&coll=Portal&dl=GUIDE&CFID=37194600&CFTOKEN=70659176

VxWorks consumes "36KB" according to
WWW.Windriver.com/products/product-notes/Platform-for-Network-Equipment-ve-Note.pdf
whereas the Ada runtime overhead for Aonix ObjectRaven was claimed to
be less than five kilobytes in Table 2. Please explain how Ada using
less than five kilobytes is a "much larger memory" requirement than C
using 36KB.

Please show me something in your post about Ada which is not nonsense.

Sincerely,
Colin Paul Gloster

Re: computer language used to program Mars Lander

[Dmitry A. Kazakov]

On Fri, 18 Jul 2008 19:02:58 +0100, Colin Paul Gloster wrote:

> On Thu, 17 Jul 2008, Paul Hsieh wrote:
> 
>|The small memory footprint and VxWorks environment probably makes C a    
>|very attractive language for the NASA guys.  If they used Ada, they      
>|would be slower, have much larger memory requirements and have a very    
>|hard time debugging problems remotely.                                   
> 
> How is C on VxWorks faster than Ada?

As a part of religious experience, I guess...

Actually some VxWorks guys, who are aware of Ada, tried to convince us that
our project on VxWorks should use C, rather than Ada, because "C is
faster."

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: computer language used to program Mars Lander

[Pascal Obry]

Paul,

> The small memory footprint and VxWorks environment probably makes C a
> very attractive language for the NASA guys.  If they used Ada, they
> would be slower, have much larger memory requirements and have a very
> hard time debugging problems remotely.

That's just good-old-wrong-assumption made by lot of people. Ada is 
slower? I see nothing slow in Ada which is a language. Does a language 
has speed now?

More seriously, some benchmarks have shown that some Ada compiler have 
been generating faster code than C compiler on a given application. And 
of course, some other benchmarks have shown the opposite.

The memory requirement for Ada is wrong too. Using a zero-foot-print 
runtime you have zero memory requirement from the runtime.

>> I suspect its a damn sight easier to prove C correct than C++.

Still lot easier to prove Ada correct. And in any case on critical 
applications there is no Ada nor C but some subset that makes the 
languages safer (e.g. SPARK for Ada or MISRA-C for C).

Please let's try to at least have constructive criticisms.

Thanks.
Pascal.

-- 

--|------------------------------------------------------
--| Pascal Obry                           Team-Ada Member
--| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE
--|------------------------------------------------------
--|              http://www.obry.net
--| "The best way to travel is by means of imagination"
--|
--| gpg --keyserver wwwkeys.pgp.net --recv-key C1082595

Re: computer language used to program Mars Lander

[Gautier]

Paul Hsieh:

> The small memory footprint and VxWorks environment probably makes C a
> very attractive language for the NASA guys.  If they used Ada, they
> would be slower,

Oooh... This is a misconception that comes from the time of 
non-optimizing compilers for PC's - around 20 years ago. At that time a 
i++ was faster than a i:= i + 1, sure. But it was long long time ago. 
Never heard of GCC ?...
_________________________________________________________
Gautier's Ada programming -- http://sf.net/users/gdemont/

NB: For a direct answer, e-mail address on the Web site!

Re: computer language used to program Mars Lander

[jacob navia]

Gautier wrote:
> Paul Hsieh:
> 
>> The small memory footprint and VxWorks environment probably makes C a
>> very attractive language for the NASA guys.  If they used Ada, they
>> would be slower,
> 
> Oooh... This is a misconception that comes from the time of 
> non-optimizing compilers for PC's - around 20 years ago. At that time a 
> i++ was faster than a i:= i + 1, sure. But it was long long time ago. 
> Never heard of GCC ?...
> _________________________________________________________
> Gautier's Ada programming -- http://sf.net/users/gdemont/
> 
> NB: For a direct answer, e-mail address on the Web site!

Do you have any data to prove that ADA is faster than C?
Or that has a smaller memory footprint?



-- 
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique
http://www.cs.virginia.edu/~lcc-win32

Re: computer language used to program Mars Lander

[Georg Bauhaus]

jacob navia wrote:

> Do you have any data to prove that ADA is faster than C?
> Or that has a smaller memory footprint?

Oh, not that again. ;-) I'm sure that Jacob, being a compiler writer,
is perfectly aware of how and when some +1 on a variable in either
language can and will be mapped to the same instruction(s). Etc.

Earlier, Keith Thompson said the wonderful words,
"This was cross-posted to comp.lang.ada and comp.lang.c.  I suggest we
all refuse to take the bait and *not* start a cross-language flame
war."


-- 
Georg Bauhaus
Y A Time Drain  http://www.9toX.de

Re: computer language used to program Mars Lander

[Gary Scott]

jacob navia wrote:
> Gautier wrote:
> 
>> Paul Hsieh:
>>
>>> The small memory footprint and VxWorks environment probably makes C a
>>> very attractive language for the NASA guys.  If they used Ada, they
>>> would be slower,
>>
>>
>> Oooh... This is a misconception that comes from the time of 
>> non-optimizing compilers for PC's - around 20 years ago. At that time 
>> a i++ was faster than a i:= i + 1, sure. But it was long long time 
>> ago. Never heard of GCC ?...
>> _________________________________________________________
>> Gautier's Ada programming -- http://sf.net/users/gdemont/
>>
>> NB: For a direct answer, e-mail address on the Web site!
> 
> 
> Do you have any data to prove that ADA is faster than C?

There should in general be no difference other than that there may be 
some constructs that are harder for the compiler writer to figure out 
how to optimize in one language versus the other.  Probably works both ways.

> Or that has a smaller memory footprint?
> 
> 
> 


-- 

Gary Scott
mailto:garylscott@sbcglobal dot net

Fortran Library:  http://www.fortranlib.com

Support the Original G95 Project:  http://www.g95.org
-OR-
Support the GNU GFortran Project:  http://gcc.gnu.org/fortran/index.html

If you want to do the impossible, don't hire an expert because he knows 
it can't be done.

-- Henry Ford

Re: computer language used to program Mars Lander

[Richard Tobin]

In article <4880f2ed$1_6@news.bluewin.ch>,
Gautier  <gautier@fakeaddress.nil> wrote:

>Oooh... This is a misconception that comes from the time of 
>non-optimizing compilers for PC's - around 20 years ago. At that time a 
>i++ was faster than a i:= i + 1, sure.

I'd have been very disappointed with a compiler that did that 20 years ago.

>Never heard of GCC ?...

Why yes, we were using it 20 years ago!

-- Richard
-- 
Please remember to mention me / in tapes you leave behind.

Re: computer language used to program Mars Lander

[Jean-Pierre Rosen]

Gautier a �crit :
> Paul Hsieh:
> 
>> The small memory footprint and VxWorks environment probably makes C a
>> very attractive language for the NASA guys.  If they used Ada, they
>> would be slower,
> 
> Oooh... This is a misconception that comes from the time of 
> non-optimizing compilers for PC's - around 20 years ago. At that time a 
> i++ was faster than a i:= i + 1, sure. But it was long long time ago. 
> Never heard of GCC ?...

When I started working on a (Pascal) compiler, this optimization was the 
first one I introduced in the compiler, because it was the easiest one 
to do. And it was 30 years ago...

-- 
---------------------------------------------------------
            J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr

Re: computer language used to program Mars Lander

[Nick Keighley]

On 22 Jul, 09:39, Jean-Pierre Rosen <ro...@adalog.fr> wrote:
> Gautier a écrit :

<snip>

> > [this] comes from the time of
> > non-optimizing compilers for PC's - around 20 years ago. At that time a
> > i++ was faster than a i:= i + 1, sure. But it was long long time ago.
> > Never heard of GCC ?...
>
> When I started working on a (Pascal) compiler, this optimization was the
> first one I introduced in the compiler, because it was the easiest one
> to do. And it was 30 years ago...

Pascal has a ++ operator?

--
Nick Keighley

Re: computer language used to program Mars Lander

[Richard]

Nick Keighley <nick_keighley_nospam@hotmail.com> writes:

> On 22 Jul, 09:39, Jean-Pierre Rosen <ro...@adalog.fr> wrote:
>> Gautier a écrit :
>
> <snip>
>
>> > [this] comes from the time of
>> > non-optimizing compilers for PC's - around 20 years ago. At that time a
>> > i++ was faster than a i:= i + 1, sure. But it was long long time ago.
>> > Never heard of GCC ?...
>>
>> When I started working on a (Pascal) compiler, this optimization was the
>> first one I introduced in the compiler, because it was the easiest one
>> to do. And it was 30 years ago...
>
> Pascal has a ++ operator?

It was probably added as lesson 2 in an under graduate compiler course.

Re: computer language used to program Mars Lander

[Jean-Pierre Rosen]

Nick Keighley a �crit :
> On 22 Jul, 09:39, Jean-Pierre Rosen <ro...@adalog.fr> wrote:
>> Gautier a �crit :
> 
> <snip>
> 
>>> [this] comes from the time of
>>> non-optimizing compilers for PC's - around 20 years ago. At that time a
>>> i++ was faster than a i:= i + 1, sure. But it was long long time ago.
>>> Never heard of GCC ?...
>> When I started working on a (Pascal) compiler, this optimization was the
>> first one I introduced in the compiler, because it was the easiest one
>> to do. And it was 30 years ago...
> 
> Pascal has a ++ operator?
> 
No, I was refering to optimizing I := I+1 into a single "Inc" machine 
instruction.

-- 
---------------------------------------------------------
            J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr

Re: computer language used to program Mars Lander

[CBFalconer]

Jean-Pierre Rosen wrote:
> Nick Keighley a �crit :
>> Jean-Pierre Rosen <ro...@adalog.fr> wrote:
>>> Gautier a �crit :
>>
>> <snip>
>>
>>>> [this] comes from the time of non-optimizing compilers for PC's
>>>> - around 20 years ago. At that time a i++ was faster than a
>>>> i:= i + 1, sure. But it was long long time ago.
>>>>
>>>> Never heard of GCC ?...
>>>
>>> When I started working on a (Pascal) compiler, this optimization
>>> was the first one I introduced in the compiler, because it was
>>> the easiest one to do. And it was 30 years ago...
>>
>> Pascal has a ++ operator?
>
> No, I was refering to optimizing I := I+1 into a single "Inc"
> machine instruction.

ISO Standard Pascal has no 'inc' instruction.  Some non-standard
abortions do.  However those abortions also omit critical portions
of the standard, such as f^ and the put and get functions.  There
is more.

-- 
 [mail]: Chuck F (cbfalconer at maineline dot net) 
 [page]: <http://cbfalconer.home.att.net>
            Try the download section.

Re: computer language used to program Mars Lander

[Jean-Pierre Rosen]

CBFalconer a �crit :
>> No, I was refering to optimizing I := I+1 into a single "Inc"
>> machine instruction.
> 
> ISO Standard Pascal has no 'inc' instruction.  Some non-standard
> abortions do.  However those abortions also omit critical portions
> of the standard, such as f^ and the put and get functions.  There
> is more.
> 
Please read again, I was refering to the Inc /machine instruction/ that 
we had for our target at that time (an IRIS-80, a french machine derived 
from XDS-Sigma7).

-- 
---------------------------------------------------------
            J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr

Re: computer language used to program Mars Lander

[CBFalconer]

Jean-Pierre Rosen wrote:
> CBFalconer a �crit :
>
>>> No, I was refering to optimizing I := I+1 into a single "Inc"
>>> machine instruction.
>>
>> ISO Standard Pascal has no 'inc' instruction.  Some non-standard
>> abortions do.  However those abortions also omit critical portions
>> of the standard, such as f^ and the put and get functions.  There
>> is more.
>
> Please read again, I was refering to the Inc /machine instruction/
> that we had for our target at that time (an IRIS-80, a french
> machine derived from XDS-Sigma7).

Fair enough.  No further discussion needed, since it was OT in the
first place, and only caused by my righteous irritation :-) at the
destruction of Pascal by bad approximations.

-- 
 [mail]: Chuck F (cbfalconer at maineline dot net) 
 [page]: <http://cbfalconer.home.att.net>
            Try the download section.

Re: computer language used to program Mars Lander

[Antoninus Twink]

On 22 Jul 2008 at 21:11, CBFalconer wrote:
> ISO Standard Pascal has no 'inc' instruction.  Some non-standard
> abortions do.  However those abortions also omit critical portions
> of the standard, such as f^ and the put and get functions.  There
> is more.

By the "standards" you insist on holding the rest of the world to,
you're way "off-topic". Try comp.lang.pascal or
alt.bullshit.cbf-dribblings.

Re: computer language used to program Mars Lander

[Chris Dollin]

Nick Keighley wrote:

> On 22 Jul, 09:39, Jean-Pierre Rosen <ro...@adalog.fr> wrote:
>> Gautier a �crit :
> 
> <snip>
> 
>> > [this] comes from the time of
>> > non-optimizing compilers for PC's - around 20 years ago. At that time a
>> > i++ was faster than a i:= i + 1, sure. But it was long long time ago.
>> > Never heard of GCC ?...
>>
>> When I started working on a (Pascal) compiler, this optimization was the
>> first one I introduced in the compiler, because it was the easiest one
>> to do. And it was 30 years ago...
> 
> Pascal has a ++ operator?

No, but it has an opportunity to optimise `i := i + 1;` to the same code
as a C compiler might have compiled `i++` into.

-- 
'It changed the future .. and it changed us.'               /Babylon 5/

Hewlett-Packard Limited registered office:                Cain Road,
Bracknell,
registered no: 690597 England                                    Berks RG12
1HN

Re: computer language used to program Mars Lander

[Walter Banks]

Nick Keighley wrote:

> Pascal has a ++ operator?

inc(x);

w..

Re: computer language used to program Mars Lander

[george.priv]

On Jul 14, 7:18 am, "jhc0...@gmail.com" <jhc0...@gmail.com> wrote:
> Interesting article I came across on Slashdot:
>
> http://developers.slashdot.org/developers/08/07/10/213211.shtml
>
> They are using C at JPL to program Mars Lander and just about
> everything now! Not Ada. Anyone got an explanation? I wonder also, do
> they really mean C++ when they say C. In my experience, this is a
> frequent, although disagreeable usage.

As pointed out it was subset of C and the size of the software is
relatively small by todays standards if it all fits in 128M (no VM
AFAIK).

The specifics of this project differs from earthly "life safety" type
of applications. If probe software fails, watchdog will reboot it into
the safe mode. There it will sit waiting the instructions/patches from
home.  Therefore, a critical part is a bootstrap and communication
module.  The rest is allowed to fail and can be fixed.

George

Re: computer language used to program Mars Lander

[Keith Thompson]

"jhc0033@gmail.com" <jhc0033@gmail.com> writes:
> Interesting article I came across on Slashdot:
>
> http://developers.slashdot.org/developers/08/07/10/213211.shtml
>
> They are using C at JPL to program Mars Lander and just about
> everything now! Not Ada. Anyone got an explanation? I wonder also, do
> they really mean C++ when they say C. In my experience, this is a
> frequent, although disagreeable usage.

This was cross-posted to comp.lang.ada and comp.lang.c.  I suggest we
all refuse to take the bait and *not* start a cross-language flame
war.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Nokia
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Re: computer language used to program Mars Lander

[CBFalconer]

Keith Thompson wrote:
> "jhc0033@gmail.com" <jhc0033@gmail.com> writes:
>
>> Interesting article I came across on Slashdot:
>>
>> http://developers.slashdot.org/developers/08/07/10/213211.shtml
>>
>> They are using C at JPL to program Mars Lander and just about
>> everything now! Not Ada. Anyone got an explanation? I wonder
>> also, do they really mean C++ when they say C. In my experience,
>> this is a frequent, although disagreeable usage.
> 
> This was cross-posted to comp.lang.ada and comp.lang.c.  I
> suggest we all refuse to take the bait and *not* start a
> cross-language flame war.

It has nothing to do with wars.  It is simply an illustration that
proves that it is _possible_ to generate accurate code with C.  It
is also possible with assembly language.  However, doing so
requires good programmers with plenty of experience.  You can get
equal quality from poorer programmers with less experience by using
Ada.  I leave it to you what you will get with experienced good
programmers and Ada.

-- 
 [mail]: Chuck F (cbfalconer at maineline dot net) 
 [page]: <http://cbfalconer.home.att.net>
            Try the download section.

Re: computer language used to program Mars Lander

[Stephen Leake]

"jhc0033@gmail.com" <jhc0033@gmail.com> writes:

> Interesting article I came across on Slashdot:
>
> http://developers.slashdot.org/developers/08/07/10/213211.shtml
>
> They are using C at JPL to program Mars Lander and just about
> everything now! Not Ada. Anyone got an explanation? 

They are comfortable with their current tools, and simply refuse to
consider others.

I run into that attitude all the time. Even when they are considering
adding tools like static analyzers, they won't consider changing
languages. It's extremely frustrating!

In the short run, sticking with what you know is safe. In the long
run, it is a significant loss of productivity. JPL and many, many
other places are sticking with the safe route.

-- 
-- Stephe

Re: computer language used to program Mars Lander

[Georg Bauhaus]

Stephen Leake schrieb:

> In the short run, sticking with what you know is safe. In the long
> run, it is a significant loss of productivity. JPL and many, many
> other places are sticking with the safe route.


Leon Festinger (1957): A Theory of Congnitive Dissonance.


--
Georg Bauhaus
Y A Time Drain  http://www.9toX.de

Re: computer language used to program Mars Lander

[Phaedrus]

"Stephen Leake" <Stephe.Leake@nasa.gov> wrote in message 
news:uvdz7uzeu.fsf@nasa.gov...
> "jhc0033@gmail.com" <jhc0033@gmail.com> writes:
>
>> Interesting article I came across on Slashdot:
>>
>> http://developers.slashdot.org/developers/08/07/10/213211.shtml
>>
>> They are using C at JPL to program Mars Lander and just about
>> everything now! Not Ada. Anyone got an explanation?
>
> They are comfortable with their current tools, and simply refuse to
> consider others.
>
> I run into that attitude all the time. Even when they are considering
> adding tools like static analyzers, they won't consider changing
> languages. It's extremely frustrating!
>
> In the short run, sticking with what you know is safe. In the long
> run, it is a significant loss of productivity. JPL and many, many
> other places are sticking with the safe route.
>
> -- 
> -- Stephe

Actually, JPL did try Ada for a few projects.  In the late early '90s they 
got the contract from the Army to work on the All Source Analysis System 
(ASAS), a very large project.  Also, unless my memory fails me they also did 
some (if not all) of the Cassini software in Ada, and I believe they did 
other projects in Ada, too.  While Cassini (being a relatively small, well 
contained project) went well, ASAS was another thing altogether.

The problem isn't that they won't try Ada, the problem is that when they 
did, they didn't get the results they wanted.  Remember back when Ada was 
the buzzword to have on your resume?  That was when they tried Ada, and some 
of the contractors they hired to "show them the way" weren't even sure how 
to spell Ada, much less get anything done in it.  (A VERY high priced 
contractor on ASAS admitted to me that he had never even seen Ada code 
before being hired for his "expert" knowledge.  Amazingly, they never caught 
on, even after he went on to greener pastures they were still raving about 
him!)

Sadly, these blunders and others don't get remembered as "how NOT to manage 
a software project", they get filed under "Ada sucks".   We need to convince 
them to give her another chance.

--Brian 

Re: computer language used to program Mars Lander

[christoph.grein]

On 16 Jul., 01:35, "Phaedrus" <phaedrus...@hotmail.com> wrote:
> Sadly, these blunders and others don't get remembered as "how NOT to manage
> a software project", they get filed under "Ada sucks".   We need to convince
> them to give her another chance.

I remember a guy appearing at Ada Europe conference in Toulouse
speaking about a project they started in Ada. They had no clear idea
what to do, didn't really know the language, had no strategy, they
really muddled along - and of course failed miserably. Then he
continued with saying, OK, we redid the project now that we knew what
and how to do, and we used C and it was a success. We will never again
use Ada.

(A fool with a good tool is still a fool.)