forums.silverfrost.com Forum Index forums.silverfrost.com
Welcome to the Silverfrost forums
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Complex*32

 
Post new topic   Reply to topic    forums.silverfrost.com Forum Index -> Support
View previous topic :: View next topic  
Author Message
MarkJordan



Joined: 18 Jan 2006
Posts: 11

PostPosted: Mon Apr 20, 2020 3:48 pm    Post subject: Complex*32 Reply with quote

I know I can get to complex*20 - 18 digit precision.
Is there any support for higher precision?
Back to top
View user's profile Send private message
PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 7916
Location: Salford, UK

PostPosted: Mon Apr 20, 2020 4:51 pm    Post subject: Reply with quote

complex*20 is available with FTN95 but only for Win32. Higher precision is not supported.
Back to top
View user's profile Send private message AIM Address
John-Silver



Joined: 30 Jul 2013
Posts: 1520
Location: Aerospace Valley

PostPosted: Mon Apr 20, 2020 8:43 pm    Post subject: Reply with quote

is there a technical reason why it's not available in x64 ?
_________________
''Computers (HAL and MARVIN excepted) are incredibly rigid. They question nothing. Especially input data.Human beings are incredibly trusting of computers and don't check input data. Together cocking up even the simplest calculation ... Smile "
Back to top
View user's profile Send private message
PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 7916
Location: Salford, UK

PostPosted: Mon Apr 20, 2020 9:36 pm    Post subject: Reply with quote

The hardware does not provide it.
Back to top
View user's profile Send private message AIM Address
JohnCampbell



Joined: 16 Feb 2006
Posts: 2554
Location: Sydney

PostPosted: Tue Apr 21, 2020 2:51 am    Post subject: Reply with quote

Paul,

Is there a more extensive explanation ?
Is a 8087 - 80 bit hardware supported in Win32 or is it emulated in 32-bit ?
If it is available from Win32, why can't it be accessed from x64 ?

I did have a use for 80 bit use in eigenvector "filtering" (Gram-Schmidt Orthogonalization), where I was calculating a tri-product of 2 eigenvectors and mass vector. I thought I proved that 80-bit filtering was better than 64-bit, although I gave that away with the 64-bit conversion. One of those projects on the to-do list. Might get a Covid bump up the list !

John
Back to top
View user's profile Send private message
PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 7916
Location: Salford, UK

PostPosted: Tue Apr 21, 2020 7:57 am    Post subject: Reply with quote

John

There will be but I don't have the experience and knowledge to give it.

With my limited understanding, if I wanted 80 bit reals in a 64 bit executable then I would set up a pipe to a 32 bit executable running in the background that would access the FPU. As I understand it, if there is a direct way to get to the FPU then Microsoft do not support it.
Back to top
View user's profile Send private message AIM Address
Robert



Joined: 29 Nov 2006
Posts: 444
Location: Manchester

PostPosted: Tue Apr 21, 2020 6:31 pm    Post subject: Reply with quote

I think the hardware does provide it but it is difficult to use in x64. 80-bit reals use the FP stack model whereas efficient x64 code uses SSE instructions. 80-bit reals are not supported in .NET either
Back to top
View user's profile Send private message Visit poster's website
JohnCampbell



Joined: 16 Feb 2006
Posts: 2554
Location: Sydney

PostPosted: Wed Apr 22, 2020 4:16 am    Post subject: Reply with quote

It has been a puzzle to me to know if there is still an "80-bit 8087" like FPU on modern processors. Certainly we are encouraged to use SSE or AVX instructions due to their efficiency. But if an 80-bit hardware computation existed for, say dot_product_80, it can in theory improve the accuracy, without resorting to a much slower higher precision emulation library.
It is only recently that FTN95 has provided access to SSE and AVX, so haven't we been mostly using 64-bit calculations, without the extra bits that 80-bit registers provide, at no performance cost?

I do have a dot_product_kahan (...), although only used it in test examples.

I never had a FE modelling job where 80 bit made a real difference. Not sure why, as in theory it could, although all the arrays were real*8. I did these tests many years ago.
Back to top
View user's profile Send private message
Robert



Joined: 29 Nov 2006
Posts: 444
Location: Manchester

PostPosted: Wed Apr 22, 2020 10:14 am    Post subject: Reply with quote

FTN95 x64 has always used the SSE instructions for floating point arithmetic.
Back to top
View user's profile Send private message Visit poster's website
JohnCampbell



Joined: 16 Feb 2006
Posts: 2554
Location: Sydney

PostPosted: Tue May 19, 2020 10:00 am    Post subject: Re: Reply with quote

Robert wrote:
FTN95 x64 has always used the SSE instructions for floating point arithmetic.

Robert, when you say "SSE instructions", do you mean 64-bit (as opposed to 80-bit) ?
I understand FTN95 /OPT does not incorporate any SSE or AVX register/vector instructions for FP calculations.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    forums.silverfrost.com Forum Index -> Support All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group