gamedevlists-consoles

[GD-Consoles] PS2 floating point

[Research \(GameBrains\) <res...@ga...>]

Hello,
Our physics engine is experiencing some odd behavior on the PS2.  We =
traced it to our resting contact force calculation where sometimes it =
seems the result is not quite right, but it works fine on other =
platforms.  I don't know if it's an urban legend or what, but I have =
heard that the PS2 has some quirks with regard to floating point numbers =
and so I thought I would just ask and see if this is something I need to =
look at or not.  If so, what are the differences between the PS2 IEEE =
implementation and is there a doc describing them?
Thanks,
Brett

Re: [GD-Consoles] PS2 floating point

[Gareth W. <gw...@ra...>]

There are indeed subtle differences between the PS2 and the IEEE implementation.

Try the 'EE Core User's Manual' (2nd Edition), Page 77, Chapter 4
'Floating-Point Unit (FPU)', section 4.8 'IEEE 754 Compatability'

Cheers.

---
Gareth White - Engine Programmer - Ratbag Pty Ltd
Level 8, 63 Pirie Street, Adelaide, SA, Australia, 5000
Ph: +61 8 8223 5830, Fax: +61 8 8223 5746, Mob: 0403 942668
http://www.ratbaggames.com/

----- Original Message -----
From: "Research (GameBrains)" <res...@ga...>
To: <Gam...@li...>
Sent: Thursday, February 27, 2003 4:46 PM
Subject: [GD-Consoles] PS2 floating point


Hello,
Our physics engine is experiencing some odd behavior on the PS2.  We traced it
to our resting contact force calculation where sometimes it seems the result is
not quite right, but it works fine on other platforms.  I don't know if it's an
urban legend or what, but I have heard that the PS2 has some quirks with regard
to floating point numbers and so I thought I would just ask and see if this is
something I need to look at or not.  If so, what are the differences between the
PS2 IEEE implementation and is there a doc describing them?
Thanks,
Brett


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Re: [GD-Consoles] PS2 floating point

[Research \(GameBrains\) <res...@ga...>]

Gareth,
Found it! (moved to chapter 8 in 6th edition).  Thank you very much!
Brett

----- Original Message -----=20
From: "Gareth White" <gw...@ra...>
To: <res...@ga...>
Cc: <gam...@li...>
Sent: Thursday, February 27, 2003 2:49 PM
Subject: Re: [GD-Consoles] PS2 floating point


> There are indeed subtle differences between the PS2 and the IEEE =
implementation.
>=20
> Try the 'EE Core User's Manual' (2nd Edition), Page 77, Chapter 4
> 'Floating-Point Unit (FPU)', section 4.8 'IEEE 754 Compatability'
>=20
> Cheers.
>=20
> ---
> Gareth White - Engine Programmer - Ratbag Pty Ltd
> Level 8, 63 Pirie Street, Adelaide, SA, Australia, 5000
> Ph: +61 8 8223 5830, Fax: +61 8 8223 5746, Mob: 0403 942668
> http://www.ratbaggames.com/
>=20
> ----- Original Message -----
> From: "Research (GameBrains)" <res...@ga...>
> To: <Gam...@li...>
> Sent: Thursday, February 27, 2003 4:46 PM
> Subject: [GD-Consoles] PS2 floating point
>=20
>=20
> Hello,
> Our physics engine is experiencing some odd behavior on the PS2.  We =
traced it
> to our resting contact force calculation where sometimes it seems the =
result is
> not quite right, but it works fine on other platforms.  I don't know =
if it's an
> urban legend or what, but I have heard that the PS2 has some quirks =
with regard
> to floating point numbers and so I thought I would just ask and see if =
this is
> something I need to look at or not.  If so, what are the differences =
between the
> PS2 IEEE implementation and is there a doc describing them?
> Thanks,
> Brett
>=20
>=20
> -------------------------------------------------------
> This SF.net email is sponsored by: Scholarships for Techies!
> Can't afford IT training? All 2003 ictp students receive scholarships.
> Get hands-on training in Microsoft, Cisco, Sun, Linux/UNIX, and more.
> www.ictp.com/training/sourceforge.asp
> _______________________________________________
> Gamedevlists-consoles mailing list
> Gam...@li...
> https://lists.sourceforge.net/lists/listinfo/gamedevlists-consoles
> Archives:
> http://sourceforge.net/mailarchive/forum.php?forum_idU3
>=20
>=20
>=20
> -------------------------------------------------------
> This SF.net email is sponsored by: Scholarships for Techies!
> Can't afford IT training? All 2003 ictp students receive scholarships.
> Get hands-on training in Microsoft, Cisco, Sun, Linux/UNIX, and more.
> www.ictp.com/training/sourceforge.asp
> _______________________________________________
> Gamedevlists-consoles mailing list
> Gam...@li...
> https://lists.sourceforge.net/lists/listinfo/gamedevlists-consoles
> Archives:
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Re: [GD-Consoles] PS2 floating point

[J. G. <jg-...@jg...>]

Hi Brett,

Out of interest what was the problem with your implementation?  I found
that -fshort-double stopped some of the problems I was having with one
issue when I tested some float stuff a while ago.  However, if the code
is the problem then this would not solve that.

JG

Research (GameBrains) wrote:
> Gareth,
> Found it! (moved to chapter 8 in 6th edition).  Thank you very much!
> Brett
> 
> ----- Original Message ----- 
> From: "Gareth White" <gw...@ra...>
> To: <res...@ga...>
> Cc: <gam...@li...>
> Sent: Thursday, February 27, 2003 2:49 PM
> Subject: Re: [GD-Consoles] PS2 floating point
> 
> 
>> There are indeed subtle differences between the PS2 and the IEEE implementation.
>> 
>> Try the 'EE Core User's Manual' (2nd Edition), Page 77, Chapter 4
>> 'Floating-Point Unit (FPU)', section 4.8 'IEEE 754 Compatability'
>> 
>> Cheers.
>> 
>> ---
>> Gareth White - Engine Programmer - Ratbag Pty Ltd
>> Level 8, 63 Pirie Street, Adelaide, SA, Australia, 5000
>> Ph: +61 8 8223 5830, Fax: +61 8 8223 5746, Mob: 0403 942668
>> http://www.ratbaggames.com/
>> 
>> ----- Original Message -----
>> From: "Research (GameBrains)" <res...@ga...>
>> To: <Gam...@li...>
>> Sent: Thursday, February 27, 2003 4:46 PM
>> Subject: [GD-Consoles] PS2 floating point
>> 
>> 
>> Hello,
>> Our physics engine is experiencing some odd behavior on the PS2.  We traced it
>> to our resting contact force calculation where sometimes it seems the result is
>> not quite right, but it works fine on other platforms.  I don't know if it's an
>> urban legend or what, but I have heard that the PS2 has some quirks with regard
>> to floating point numbers and so I thought I would just ask and see if this is
>> something I need to look at or not.  If so, what are the differences between the
>> PS2 IEEE implementation and is there a doc describing them?
>> Thanks,
>> Brett

Re: [GD-Consoles] PS2 floating point

[Research \(GameBrains\) <res...@ga...>]

We are still looking at the problem, but it seems that calculations =
resulting in small numbers are the problem.  On GameCube and PC the =
results are correct but on the PS2 it's not.  Still a good possibility =
that there is simply a bug in our code somewhere too :-)  The cool thing =
about multi-platform development is a lot of times different hardware =
and different compilers help you find bugs you would have never found =
otherwsie....
Cheers,
Brett

----- Original Message -----=20
From: "J. Grant" <jg-...@jg...>
To: <gam...@li...>
Sent: Thursday, February 27, 2003 10:33 PM
Subject: Re: [GD-Consoles] PS2 floating point


> Hi Brett,
>=20
> Out of interest what was the problem with your implementation?  I =
found
> that -fshort-double stopped some of the problems I was having with one
> issue when I tested some float stuff a while ago.  However, if the =
code
> is the problem then this would not solve that.
>=20
> JG
>=20
> Research (GameBrains) wrote:
> > Gareth,
> > Found it! (moved to chapter 8 in 6th edition).  Thank you very much!
> > Brett
> >=20
> > ----- Original Message -----=20
> > From: "Gareth White" <gw...@ra...>
> > To: <res...@ga...>
> > Cc: <gam...@li...>
> > Sent: Thursday, February 27, 2003 2:49 PM
> > Subject: Re: [GD-Consoles] PS2 floating point
> >=20
> >=20
> >> There are indeed subtle differences between the PS2 and the IEEE =
implementation.
> >>=20
> >> Try the 'EE Core User's Manual' (2nd Edition), Page 77, Chapter 4
> >> 'Floating-Point Unit (FPU)', section 4.8 'IEEE 754 Compatability'
> >>=20
> >> Cheers.
> >>=20
> >> ---
> >> Gareth White - Engine Programmer - Ratbag Pty Ltd
> >> Level 8, 63 Pirie Street, Adelaide, SA, Australia, 5000
> >> Ph: +61 8 8223 5830, Fax: +61 8 8223 5746, Mob: 0403 942668
> >> http://www.ratbaggames.com/
> >>=20
> >> ----- Original Message -----
> >> From: "Research (GameBrains)" <res...@ga...>
> >> To: <Gam...@li...>
> >> Sent: Thursday, February 27, 2003 4:46 PM
> >> Subject: [GD-Consoles] PS2 floating point
> >>=20
> >>=20
> >> Hello,
> >> Our physics engine is experiencing some odd behavior on the PS2.  =
We traced it
> >> to our resting contact force calculation where sometimes it seems =
the result is
> >> not quite right, but it works fine on other platforms.  I don't =
know if it's an
> >> urban legend or what, but I have heard that the PS2 has some quirks =
with regard
> >> to floating point numbers and so I thought I would just ask and see =
if this is
> >> something I need to look at or not.  If so, what are the =
differences between the
> >> PS2 IEEE implementation and is there a doc describing them?
> >> Thanks,
> >> Brett
>=20
>=20
>=20
>=20
> -------------------------------------------------------
> This sf.net email is sponsored by:ThinkGeek
> Welcome to geek heaven.
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