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New algorithms for computing Givens rotations #631

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Merged
merged 10 commits into from
Nov 9, 2022
Merged

New algorithms for computing Givens rotations #631

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2495f1c
Solves a precision bug in clartg
weslleyspereira Oct 15, 2021
b89b15b
Removes one line from clartg
weslleyspereira Oct 18, 2021
ac11f62
Several changes to reduce the computation error
weslleyspereira Oct 26, 2021
4320882
Starting to modify zlartg
weslleyspereira Oct 28, 2021
37a1a1e
Fix all other Givens rotation routines
weslleyspereira Nov 3, 2021
a49a659
Merge branch 'fix-precision-in-clartgf90-2' of github.com:weslleysper…
weslleyspereira Nov 3, 2021
2904d87
Algorithm precise and with no bias in the error
weslleyspereira Nov 23, 2021
95b6e84
Updates Givens rotations with preciser algorithms
weslleyspereira Dec 10, 2021
cdc8f33
Fix documentation thanks to @vladimir-ch
weslleyspereira Dec 13, 2021
c362fff
Minor changes
weslleyspereira Dec 13, 2021
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11 changes: 10 additions & 1 deletion SRC/clartg.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -187,7 +187,11 @@ subroutine CLARTG( f, g, c, s, r )
d = sqrt( f2 )*sqrt( h2 )
end if
p = 1 / d
c = f2*p
if( f2 > safmin * g2 ) then
c = 1 / sqrt( one + g2/f2 )
else
c = f2*p
end if
s = conjg( g )*( f*p )
r = f*( h2*p )
else
Expand Down Expand Up @@ -224,6 +228,11 @@ subroutine CLARTG( f, g, c, s, r )
d = sqrt( f2 )*sqrt( h2 )
end if
p = 1 / d
if( f2 > safmin * g2 ) then
c = (1 / sqrt( one + g2/f2 )) * w
else
c = ( f2*p )*w
end if
c = ( f2*p )*w
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@langou langou Oct 16, 2021 •
edited
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@weslleyspereira: I think you want to remove line 236.
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@weslleyspereira weslleyspereira Oct 18, 2021

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Yes. I forgot it. Thanks!
s = conjg( gs )*( fs*p )
r = ( fs*( h2*p ) )*u
Expand Down