dlaqr1 (l) - Linux Manuals

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

PURPOSE