dlaqr1(l) - Linux man page
Name
Synopsis
- SUBROUTINE DLAQR1(
N, H, LDH, SR1, SI1, SR2, SI2, V )
DOUBLE
PRECISION SI1, SI2, SR1, SR2
INTEGER
LDH, N
DOUBLE
PRECISION H( LDH, * ), V( * )
DOUBLE
PRECISION ZERO
PARAMETER
( ZERO = 0.0d0 )
DOUBLE
PRECISION H21S, H31S, S
INTRINSIC
ABS
IF(
N.EQ.2 ) THEN
S
= ABS( H( 1, 1 )-SR2 ) + ABS( SI2 ) + ABS( H( 2, 1 ) )
IF(
S.EQ.ZERO ) THEN
V(
1 ) = ZERO
V(
2 ) = ZERO
ELSE
H21S
= H( 2, 1 ) / S
V(
1 ) = H21S*H( 1, 2 ) + ( H( 1, 1 )-SR1 )* ( ( H( 1, 1 )-SR2 ) / S ) - SI1*( SI2 / S )
V(
2 ) = H21S*( H( 1, 1 )+H( 2, 2 )-SR1-SR2 )
END
IF
ELSE
S
= ABS( H( 1, 1 )-SR2 ) + ABS( SI2 ) + ABS( H( 2, 1 ) ) + ABS( H( 3, 1 ) )
IF(
S.EQ.ZERO ) THEN
V(
1 ) = ZERO
V(
2 ) = ZERO
V(
3 ) = ZERO
ELSE
H21S
= H( 2, 1 ) / S
H31S
= H( 3, 1 ) / S
V(
1 ) = ( H( 1, 1 )-SR1 )*( ( H( 1, 1 )-SR2 ) / S ) - SI1*( SI2 / S ) + H( 1, 2 )*H21S + H( 1, 3 )*H31S
V(
2 ) = H21S*( H( 1, 1 )+H( 2, 2 )-SR1-SR2 ) + H( 2, 3 )*H31S
V(
3 ) = H31S*( H( 1, 1 )+H( 3, 3 )-SR1-SR2 ) + H21S*H( 3, 2 )
END
IF
END
IF
END