About the F-22 software bug

About the F-22 software bug

[Pascal Obry]

   [Second attempt to post this message. Sorry if you reveived
    this multiple time, it seems this message never reached
    comp.lang.ada].


Just curious, does someone have information to share about this problem:

<<
While attempting its first overseas deployment to the Kadena Air Base in
Okinawa, Japan, on 11 February 2007, a group of six F-22 Raptors flying
from Hickam AFB, Hawaii, experienced multiple computer crashes
coincident with their crossing of the 180th meridian of longitude (the
International Date Line). The computer failures included at least
navigation (completely lost) and communication. The fighters were able
to return to Hawaii by following their tankers, something that might
have been problematic had the weather not been good. The error was fixed
within 48 hours, allowing a delayed deployment.[24]
>> >>
I know that the F-22 is 90% of Ada. Is there some public information
about this bug? Is that a design bug?

Thanks,
Pascal.

-- 

--|------------------------------------------------------
--| Pascal Obry                           Team-Ada Member
--| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE
--|------------------------------------------------------
--|    http://www.obry.net  -  http://v2p.fr.eu.org
--| "The best way to travel is by means of imagination"
--|
--| gpg --keyserver keys.gnupg.net --recv-key F949BD3B

Re: About the F-22 software bug

[Hibou57 (Yannick Duchêne)]

On 5 fév, 07:42, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
>
>         So far as I recall -- from some years ago -- it was an algorithm
> problem handling position information wrap-around from crossing, as
> mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
>         I didn't hear that they had to follow the tankers back -- was under
> the impression once they managed to cross back heading east a reboot of
> the navigation system started working again...
>
> --
>         Wulfraed         Dennis Lee Bieber               KD6MOG
>         wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/

Do you know what was the pattern of this conception error ?
You've said “ from some years ago ” : this was a known problem ?
Wasn't solved since so long ?

Re: About the F-22 software bug

[Martin]

On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
> On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...@obry.net>
> declaimed the following in comp.lang.ada:
>
> > I know that the F-22 is 90% of Ada. Is there some public information
> > about this bug? Is that a design bug?
>
>         So far as I recall -- from some years ago -- it was an algorithm
> problem handling position information wrap-around from crossing, as
> mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
>         I didn't hear that they had to follow the tankers back -- was under
> the impression once they managed to cross back heading east a reboot of
> the navigation system started working again...
>
> --
>         Wulfraed         Dennis Lee Bieber               KD6MOG
>         wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/

For some reason (that I don't get at all) lots of systems define long
as -180 <= x <= +180 degrees.

Having the potential to alias a position seems like a bad idea for a
start, so when I've been coding such systems up, I've always spent a
bit of time making it convert positions into the range -180 <= x <
+180 degrees and using a proper ADT.

I wonder if it was anything to do with that?...

Cheers
-- Martin

Re: About the F-22 software bug

[Ludovic Brenta]

Martin wrote on comp.lang.ada:
> On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
> > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...@obry.net>
> > declaimed the following in comp.lang.ada:
> > > I know that the F-22 is 90% of Ada. Is there some public information
> > > about this bug? Is that a design bug?
>
> >         So far as I recall -- from some years ago -- it was an algorithm
> > problem handling position information wrap-around from crossing, as
> > mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
> >         I didn't hear that they had to follow the tankers back -- was under
> > the impression once they managed to cross back heading east a reboot of
> > the navigation system started working again...
>
> > --
> >         Wulfraed         Dennis Lee Bieber               KD6MOG
> >         wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/
>
> For some reason (that I don't get at all) lots of systems define long
> as -180 <= x <= +180 degrees.
>
> Having the potential to alias a position seems like a bad idea for a
> start, so when I've been coding such systems up, I've always spent a
> bit of time making it convert positions into the range -180 <= x <
> +180 degrees and using a proper ADT.
>
> I wonder if it was anything to do with that?...

I would have thought a longitude was really a mod 360, shifted by -180
for display purposes? For fractional degrees (i.e. minutes and
seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and
split in degrees, minutes and seconds when displaying.

--
Ludovic Brenta.

Re: About the F-22 software bug

[Martin]

On Feb 5, 8:52 am, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
> Martin wrote on comp.lang.ada:
>
>
>
> > On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
> > > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...@obry.net>
> > > declaimed the following in comp.lang.ada:
> > > > I know that the F-22 is 90% of Ada. Is there some public information
> > > > about this bug? Is that a design bug?
>
> > >         So far as I recall -- from some years ago -- it was an algorithm
> > > problem handling position information wrap-around from crossing, as
> > > mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
> > >         I didn't hear that they had to follow the tankers back -- was under
> > > the impression once they managed to cross back heading east a reboot of
> > > the navigation system started working again...
>
> > > --
> > >         Wulfraed         Dennis Lee Bieber               KD6MOG
> > >         wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/
>
> > For some reason (that I don't get at all) lots of systems define long
> > as -180 <= x <= +180 degrees.
>
> > Having the potential to alias a position seems like a bad idea for a
> > start, so when I've been coding such systems up, I've always spent a
> > bit of time making it convert positions into the range -180 <= x <
> > +180 degrees and using a proper ADT.
>
> > I wonder if it was anything to do with that?...
>
> I would have thought a longitude was really a mod 360, shifted by -180
> for display purposes? For fractional degrees (i.e. minutes and
> seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and
> split in degrees, minutes and seconds when displaying.
>
> --
> Ludovic Brenta.


No...it's -180 <= x <(=) +180...always - check any map / globe!!

Lat is always -90 <= x <= +90 deg - no doubt about that one :-)

Adding "shifts" would make understanding any problem very hard...

"So the position coming in is (+40, -100) but what's that inside the
code again????"

Cheers
-- Martin

Re: About the F-22 software bug

[Dmitry A. Kazakov]

On Fri, 5 Feb 2010 01:02:40 -0800 (PST), Martin wrote:

> On Feb 5, 8:52�am, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
>> Martin wrote on comp.lang.ada:
>>
>>
>>
>>> On Feb 5, 6:42�am, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
>>> > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...@obry.net>
>>> > declaimed the following in comp.lang.ada:
>>> > > I know that the F-22 is 90% of Ada. Is there some public information
>>> > > about this bug? Is that a design bug?
>>
>>> > � � � � So far as I recall -- from some years ago -- it was an algorithm
>>> > problem handling position information wrap-around from crossing, as
>>> > mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>>
>>> > � � � � I didn't hear that they had to follow the tankers back -- was under
>>> > the impression once they managed to cross back heading east a reboot of
>>> > the navigation system started working again...
>>
>>> > --
>>> > � � � � Wulfraed � � � � Dennis Lee Bieber � � � � � � � KD6MOG
>>> > � � � � wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/
>>
>>> For some reason (that I don't get at all) lots of systems define long
>>> as -180 <= x <= +180 degrees.
>>
>>> Having the potential to alias a position seems like a bad idea for a
>>> start, so when I've been coding such systems up, I've always spent a
>>> bit of time making it convert positions into the range -180 <= x <
>>> +180 degrees and using a proper ADT.
>>
>>> I wonder if it was anything to do with that?...
>>
>> I would have thought a longitude was really a mod 360, shifted by -180
>> for display purposes? For fractional degrees (i.e. minutes and
>> seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and
>> split in degrees, minutes and seconds when displaying.
>>
>> --
>> Ludovic Brenta.
> 
> No...it's -180 <= x <(=) +180...always - check any map / globe!!
> 
> Lat is always -90 <= x <= +90 deg - no doubt about that one :-)
> 
> Adding "shifts" would make understanding any problem very hard...

And shift does not solve the problem anyway, if that existed. The potential
problem is that the angle is not a real number. It could be represented by
one, but then the operations like +, -, *, /, =, /= must be replaced and
ones like <, >, <=, >= disallowed. With that done the value +180 would do
no harm, because -180 = +180 in terms of proper ADT operations. You simply
would not be able to distinguish them (without tricks like
Unchecked_Conversion).

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

Re: About the F-22 software bug

[Martin]

On Feb 5, 10:31 am, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:
> On Fri, 5 Feb 2010 01:02:40 -0800 (PST), Martin wrote:
> > On Feb 5, 8:52 am, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
> >> Martin wrote on comp.lang.ada:
>
> >>> On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
> >>> > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...@obry.net>
> >>> > declaimed the following in comp.lang.ada:
> >>> > > I know that the F-22 is 90% of Ada. Is there some public information
> >>> > > about this bug? Is that a design bug?
>
> >>> >         So far as I recall -- from some years ago -- it was an algorithm
> >>> > problem handling position information wrap-around from crossing, as
> >>> > mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
> >>> >         I didn't hear that they had to follow the tankers back -- was under
> >>> > the impression once they managed to cross back heading east a reboot of
> >>> > the navigation system started working again...
>
> >>> > --
> >>> >         Wulfraed         Dennis Lee Bieber               KD6MOG
> >>> >         wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/
>
> >>> For some reason (that I don't get at all) lots of systems define long
> >>> as -180 <= x <= +180 degrees.
>
> >>> Having the potential to alias a position seems like a bad idea for a
> >>> start, so when I've been coding such systems up, I've always spent a
> >>> bit of time making it convert positions into the range -180 <= x <
> >>> +180 degrees and using a proper ADT.
>
> >>> I wonder if it was anything to do with that?...
>
> >> I would have thought a longitude was really a mod 360, shifted by -180
> >> for display purposes? For fractional degrees (i.e. minutes and
> >> seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and
> >> split in degrees, minutes and seconds when displaying.
>
> >> --
> >> Ludovic Brenta.
>
> > No...it's -180 <= x <(=) +180...always - check any map / globe!!
>
> > Lat is always -90 <= x <= +90 deg - no doubt about that one :-)
>
> > Adding "shifts" would make understanding any problem very hard...
>
> And shift does not solve the problem anyway, if that existed. The potential
> problem is that the angle is not a real number. It could be represented by
> one, but then the operations like +, -, *, /, =, /= must be replaced and
> ones like <, >, <=, >= disallowed. With that done the value +180 would do
> no harm, because -180 = +180 in terms of proper ADT operations. You simply
> would not be able to distinguish them (without tricks like
> Unchecked_Conversion).
>
> --
> Regards,
> Dmitry A. Kazakovhttp://www.dmitry-kazakov.de

Yup, instead you end up with functions like "Is_Between (Anlge, First,
Last : Longitude) return Boolean"

Although because have 'clever' construct functions "Longitude (From :
Float)" that always put things in the 'correct' range (-180 <= x <
180), we could allow "=" (and "/=").

Cheers
-- Martin

Re: About the F-22 software bug

[Hibou57 (Yannick Duchêne)]

On 5 fév, 11:31, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:
> And shift does not solve the problem anyway, if that existed. The potential
> problem is that the angle is not a real number. It could be represented by
> one, but then the operations like +, -, *, /, =, /= must be replaced and
> ones like <, >, <=, >= disallowed.

I would have thought for reals, operations like +, -, *, /, <, >, /=
changed and =, <=, >= disallowed
Is there something I don't understand ?

Re: About the F-22 software bug

[Dmitry A. Kazakov]

On Fri, 5 Feb 2010 08:50:31 -0800 (PST), Hibou57 (Yannick Duch�ne) wrote:

> On 5 f�v, 11:31, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
>> And shift does not solve the problem anyway, if that existed. The potential
>> problem is that the angle is not a real number. It could be represented by
>> one, but then the operations like +, -, *, /, =, /= must be replaced and
>> ones like <, >, <=, >= disallowed.
> 
> I would have thought for reals, operations like +, -, *, /, <, >, /=
> changed and =, <=, >= disallowed
> Is there something I don't understand ?

You can compare angles, but cannot order them, at least while keeping
transitivity of ">":

   a > b /\ b > c  =>  a > c

Also a combination of operations like yours is impossible:

   a /= b  <=>  not (a = b)

through the law of excluded middle (if not in the intuitionistic logic).
Then:

   a > b \/ a = b  <=>  a >= b

So ">" and "/=" would carry the rest with.

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

Re: About the F-22 software bug

[Martin]

On Feb 5, 4:50 pm, Hibou57 (Yannick Duchêne)
<yannick_duch...@yahoo.fr> wrote:
> On 5 fév, 11:31, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
>
> > And shift does not solve the problem anyway, if that existed. The potential
> > problem is that the angle is not a real number. It could be represented by
> > one, but then the operations like +, -, *, /, =, /= must be replaced and
> > ones like <, >, <=, >= disallowed.
>
> I would have thought for reals, operations like +, -, *, /, <, >, /=
> changed and =, <=, >= disallowed
> Is there something I don't understand ?

Longitude is cyclical - < and > only 'work' if there is a hard-stop at
each end.

You can make up some rules that might work for a project, e.g. 2
points are only ever compared using the shortest route between them
(and not the route that goes [almost] round the earth!) but it isn't
really an honest abstraction.

Cheers
-- Martin

Re: About the F-22 software bug

[Phil Clayton]

On Feb 5, 9:02 am, Martin <martin.do...@btopenworld.com> wrote:
> On Feb 5, 8:52 am, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
>
>
>
> > Martin wrote on comp.lang.ada:
>
> > > On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
> > > > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...@obry.net>
> > > > declaimed the following in comp.lang.ada:
> > > > > I know that the F-22 is 90% of Ada. Is there some public information
> > > > > about this bug? Is that a design bug?
>
> > > >         So far as I recall -- from some years ago -- it was an algorithm
> > > > problem handling position information wrap-around from crossing, as
> > > > mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
> > > >         I didn't hear that they had to follow the tankers back -- was under
> > > > the impression once they managed to cross back heading east a reboot of
> > > > the navigation system started working again...
>
> > > > --
> > > >         Wulfraed         Dennis Lee Bieber               KD6MOG
> > > >         wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/
>
> > > For some reason (that I don't get at all) lots of systems define long
> > > as -180 <= x <= +180 degrees.
>
> > > Having the potential to alias a position seems like a bad idea for a
> > > start, so when I've been coding such systems up, I've always spent a
> > > bit of time making it convert positions into the range -180 <= x <
> > > +180 degrees and using a proper ADT.
>
> > > I wonder if it was anything to do with that?...
>
> > I would have thought a longitude was really a mod 360, shifted by -180
> > for display purposes? For fractional degrees (i.e. minutes and
> > seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and
> > split in degrees, minutes and seconds when displaying.
>
> > --
> > Ludovic Brenta.
>
> No...it's -180 <= x <(=) +180...always - check any map / globe!!
>
> Lat is always -90 <= x <= +90 deg - no doubt about that one :-)
>
> Adding "shifts" would make understanding any problem very hard...
>
> "So the position coming in is (+40, -100) but what's that inside the
> code again????"

Interesting to see that 'cyclic fixed point types' are under
discussion:

http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai05s/ai05-0175-1.txt?rev=1.2

http://www.ada-auth.org/ai-files/minutes/min-0911.html#AI175

Phil

Re: About the F-22 software bug

[sjw]

On Feb 5, 11:39 pm, Phil Clayton <phil.clay...@lineone.net> wrote:

> Interesting to see that 'cyclic fixed point types' are under
> discussion:
>
> http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai05s/ai05-0175-1.txt?rev=1.2
>
> http://www.ada-auth.org/ai-files/minutes/min-0911.html#AI175

Interesting that those discussions are in terms of cyclic *fixed
point* types.

I agree that at the boundary you need to handle cyclic fixed point.
Back in the day, the Ferranti name for these was 'standard angle
format'; the F1600 series was a 24-bit machine, and the most
significant bit typically represented -180 degrees. Overflow was
represented by an optional check, so wrap-round was as easy as pie.

But why (on a machine with any sort of floating-point capability)
would you want to preserve this anywhere other than at the boundary?

On my present system, angles are stored in radians. Handling wrap-
round (and sometimes we need to deal with a range -2pi .. 2pi) was not
properly dignified with library support from the start, but we've
achieved a generic which lets you normalise an angle to -pi <= a < pi
or to 0 <= b < 2pi or to -2pi <= c < 2pi with minimal pain. We don't
need to worry about latitude!

Re: About the F-22 software bug

[Martin]

On Feb 6, 12:12 pm, sjw <simon.j.wri...@mac.com> wrote:
> I agree that at the boundary you need to handle cyclic fixed point.
> Back in the day, the Ferranti name for these was 'standard angle
> format'; the F1600 series was a 24-bit machine, and the most
> significant bit typically represented -180 degrees. Overflow was
> represented by an optional check, so wrap-round was as easy as pie.

SAF16 and SAF32 still in use today!! ;-)

Cheers
-- Martin

Re: About the F-22 software bug

[jonathan]

On Feb 4, 6:46 pm, Pascal Obry <pas...@obry.net> wrote:
> Just curious, does someone have information to share about this problem:
>
> <<
> While attempting its first overseas deployment to the Kadena Air Base in
> Okinawa, Japan, on 11 February 2007, a group of six F-22 Raptors flying
> from Hickam AFB, Hawaii, experienced multiple computer crashes
> coincident with their crossing of the 180th meridian of longitude (the
> International Date Line).

I did another quick web search ... this was the best
I could find:

http://www.murdoconline.net/archives/4595.html/comment-page-1#comment-324995

quote:

  ... it should be noted that they did test the code in a
  simulator, and it worked fine. But the simulator did not
  use the actual GINS [GPS Inertial Navigation System]
  hardware (because the simulator does not actually move,
  so a GPS receiver would be useless to simulate movement).
  The GINS hardware was tested separately and also did not
  show an anomoly...

By the way, if you want an awesome display of some
real F-22 software in action, there are several youtube
videos around. I googled: F-22 youtube Supermanouverability.
All I can think of watching these is what the programmers have
go through to make these things happen. To me its seriously
scary ... complexity quite possibly on par with that of
in-flight entertainment systems;-)

Jonathan

Re: About the F-22 software bug

[Pascal Obry]

Le 06/02/2010 16:30, jonathan a �crit :
> On Feb 4, 6:46 pm, Pascal Obry <pas...@obry.net> wrote:
>> Just curious, does someone have information to share about this problem:
>>
>> <<
>> While attempting its first overseas deployment to the Kadena Air Base in
>> Okinawa, Japan, on 11 February 2007, a group of six F-22 Raptors flying
>> from Hickam AFB, Hawaii, experienced multiple computer crashes
>> coincident with their crossing of the 180th meridian of longitude (the
>> International Date Line).
> 
> I did another quick web search ... this was the best
> I could find:
> 
> http://www.murdoconline.net/archives/4595.html/comment-page-1#comment-324995

Thanks to all for your feedbacks.

Pascal.

-- 

--|------------------------------------------------------
--| Pascal Obry                           Team-Ada Member
--| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE
--|------------------------------------------------------
--|    http://www.obry.net  -  http://v2p.fr.eu.org
--| "The best way to travel is by means of imagination"
--|
--| gpg --keyserver keys.gnupg.net --recv-key F949BD3B