On 04/29/2016 02:23 PM, C Bergström wrote:
Dear lazyweb,
I'm working on optimizing for a non-x86 target processor and left no
choice but to start writing optimized math functions.
So far I've compared
glibc
Sun solaris open sourced code
NetBSD mathlib (Which originated from Sun circa 1993)
netlib
{REDACTED-vendor-name} modified version of netlib
Surprisingly, glibc does a pretty respectable job in terms of
accuracy, but alas it's certainly not the fastest.
------------
One of the faster versions tested sometimes incorrectly
rounds for medium size and larger arguments, i.e. the least
significant bit differs from the other versions.
---
sin(6e5) =
bfcb40318b8c1728 vs
bfcb40318b8c1727 =
-0.212896531236929975605676 (REDACTED-vendor-name) vs
-0.212896531236929947850101 (nearest) vs
-0.212896531236929960235352 (higher precision) ...
-------
Question: Is the above acceptable to your scientific codes in general?
Is this the sort of problem John Gustafson's Unums was meant to eliminate?
http://www.johngustafson.net/unums.html
Unfortunately, that seems to be the best (only?) page on the Internet
about Unums, other than his Wikipedia entry:
https://en.wikipedia.org/wiki/John_Gustafson_(scientist)#Unums
--
Prentice
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