DLAQR5(3)

NAME

SYNOPSIS

SUBROUTINE DLAQR5(
    WANTT, WANTZ, KACC22, N, KTOP, KBOT, NSHFTS, SR, SI, H, LDH, ILOZ, IHIZ, Z, LDZ, V, LDV, U, LDU, NV, WV, LDWV, NH, WH, LDWH )

INTEGER
    IHIZ, ILOZ, KACC22, KBOT, KTOP, LDH, LDU, LDV, LDWH, LDWV, LDZ, N, NH, NSHFTS, NV

LOGICAL
    WANTT, WANTZ

DOUBLE
    PRECISION H( LDH, * ), SI( * ), SR( * ), U( LDU, * ), V( LDV, * ), WH( LDWH, * ), WV( LDWV, * ), Z( LDZ, * )

DOUBLE
    PRECISION ZERO, ONE

PARAMETER
    ( ZERO = 0.0d0, ONE = 1.0d0 )

DOUBLE
    PRECISION ALPHA, BETA, H11, H12, H21, H22, REFSUM, SAFMAX, SAFMIN, SCL, SMLNUM, SWAP, TST1, TST2, ULP

INTEGER
    I, I2, I4, INCOL, J, J2, J4, JBOT, JCOL, JLEN, JROW, JTOP, K, K1, KDU, KMS, KNZ, KRCOL, KZS, M, M22, MBOT, MEND, MSTART, MTOP, NBMPS, NDCOL, NS, NU

LOGICAL
    ACCUM, BLK22, BMP22

DOUBLE
    PRECISION DLAMCH

EXTERNAL
    DLAMCH

INTRINSIC
    ABS, DBLE, MAX, MIN, MOD

DOUBLE
    PRECISION VT( 3 )

EXTERNAL
    DGEMM, DLABAD, DLACPY, DLAQR1, DLARFG, DLASET, DTRMM

IF( NSHFTS.LT.2 ) RETURN

IF( KTOP.GE.KBOT ) RETURN

DO  10 I = 1, NSHFTS - 2, 2

IF( SI( I ).NE.-SI( I+1 ) ) THEN

SWAP
    = SR( I )

SR( I ) = SR( I+1 )

SR( I+1 ) = SR( I+2 )

SR( I+2 ) = SWAP

SWAP
    = SI( I )

SI( I ) = SI( I+1 )

SI( I+1 ) = SI( I+2 )

SI( I+2 ) = SWAP

END IF

10  CONTINUE

NS  = NSHFTS - MOD( NSHFTS, 2 )

SAFMIN
    = DLAMCH( 'SAFE MINIMUM' )

SAFMAX
    = ONE / SAFMIN

CALL
    DLABAD( SAFMIN, SAFMAX )

ULP = DLAMCH( 'PRECISION' )

SMLNUM
    = SAFMIN*( DBLE( N ) / ULP )

ACCUM
    = ( KACC22.EQ.1 ) .OR. ( KACC22.EQ.2 )

BLK22
    = ( NS.GT.2 ) .AND. ( KACC22.EQ.2 )

IF( KTOP+2.LE.KBOT ) H( KTOP+2, KTOP ) = ZERO

NBMPS
    = NS / 2

KDU = 6*NBMPS - 3

DO  220 INCOL = 3*( 1-NBMPS ) + KTOP - 1, KBOT - 2, 3*NBMPS - 2

NDCOL
    = INCOL + KDU

IF( ACCUM ) CALL DLASET( 'ALL', KDU, KDU, ZERO, ONE, U, LDU )

DO  150 KRCOL = INCOL, MIN( INCOL+3*NBMPS-3, KBOT-2 )

MTOP
    = MAX( 1, ( ( KTOP-1 )-KRCOL+2 ) / 3+1 )

MBOT
    = MIN( NBMPS, ( KBOT-KRCOL ) / 3 )

M22 = MBOT + 1

BMP22
    = ( MBOT.LT.NBMPS ) .AND. ( KRCOL+3*( M22-1 ) ).EQ. ( KBOT-2 )

DO  20 M = MTOP, MBOT

K   = KRCOL + 3*( M-1 )

IF( K.EQ.KTOP-1 ) THEN

CALL
    DLAQR1( 3, H( KTOP, KTOP ), LDH, SR( 2*M-1 ), SI( 2*M-1 ), SR( 2*M ), SI( 2*M ), V( 1, M ) )

ALPHA
    = V( 1, M )

CALL
    DLARFG( 3, ALPHA, V( 2, M ), 1, V( 1, M ) )

ELSE

BETA
    = H( K+1, K )

V(  2, M ) = H( K+2, K )

V(  3, M ) = H( K+3, K )

CALL
    DLARFG( 3, BETA, V( 2, M ), 1, V( 1, M ) )

IF( V( 1, M ).NE.ZERO .AND. ( V( 3, M ).NE.ZERO .OR. ( H( K+3, K+1 ).EQ.ZERO .AND. H( K+3, K+2 ).EQ.ZERO ) ) ) THEN

H(  K+1, K ) = BETA

H(  K+2, K ) = ZERO

H(  K+3, K ) = ZERO

ELSE

CALL
    DLAQR1( 3, H( K+1, K+1 ), LDH, SR( 2*M-1 ), SI( 2*M-1 ), SR( 2*M ), SI( 2*M ), VT )

SCL = ABS( VT( 1 ) ) + ABS( VT( 2 ) ) + ABS( VT( 3 ) )

IF( SCL.NE.ZERO ) THEN

VT( 1 ) = VT( 1 ) / SCL

VT( 2 ) = VT( 2 ) / SCL

VT( 3 ) = VT( 3 ) / SCL

END IF

IF( ABS( H( K+1, K ) )*( ABS( VT( 2 ) )+ ABS( VT( 3 ) ) ).GT.ULP*ABS( VT( 1 ) )* ( ABS( H( K, K ) )+ABS( H( K+1, K+1 ) )+ABS( H( K+2, K+2 ) ) ) ) THEN

IF( V( 2, M ).EQ.ZERO .AND. V( 3, M ).EQ.ZERO ) THEN

V(  1, M ) = ZERO

ELSE

H(  K+1, K ) = BETA

H(  K+2, K ) = ZERO

H(  K+3, K ) = ZERO

END IF

ELSE

ALPHA
    = VT( 1 )

CALL
    DLARFG( 3, ALPHA, VT( 2 ), 1, VT( 1 ) )

REFSUM
    = H( K+1, K ) + H( K+2, K )*VT( 2 ) + H( K+3, K )*VT( 3 )

H(  K+1, K ) = H( K+1, K ) - VT( 1 )*REFSUM

H(  K+2, K ) = ZERO

H(  K+3, K ) = ZERO

V(  1, M ) = VT( 1 )

V(  2, M ) = VT( 2 )

V(  3, M ) = VT( 3 )

END IF

END IF

END IF

20  CONTINUE

K   = KRCOL + 3*( M22-1 )

IF( BMP22 ) THEN

IF( K.EQ.KTOP-1 ) THEN

CALL
    DLAQR1( 2, H( K+1, K+1 ), LDH, SR( 2*M22-1 ), SI( 2*M22-1 ), SR( 2*M22 ), SI( 2*M22 ), V( 1, M22 ) )

BETA
    = V( 1, M22 )

CALL
    DLARFG( 2, BETA, V( 2, M22 ), 1, V( 1, M22 ) )

ELSE

BETA
    = H( K+1, K )

V(  2, M22 ) = H( K+2, K )

CALL
    DLARFG( 2, BETA, V( 2, M22 ), 1, V( 1, M22 ) )

H(  K+1, K ) = BETA

H(  K+2, K ) = ZERO

END IF

ELSE

V(  1, M22 ) = ZERO

END IF

IF( ACCUM ) THEN

JBOT
    = MIN( NDCOL, KBOT )

ELSE
    IF( WANTT ) THEN

JBOT
    = N

ELSE

JBOT
    = KBOT

END IF

DO  40 J = MAX( KTOP, KRCOL ), JBOT

MEND
    = MIN( MBOT, ( J-KRCOL+2 ) / 3 )

DO  30 M = MTOP, MEND

K   = KRCOL + 3*( M-1 )

REFSUM
    = V( 1, M )*( H( K+1, J )+V( 2, M )* H( K+2, J )+V( 3, M )*H( K+3, J ) )

H(  K+1, J ) = H( K+1, J ) - REFSUM

H(  K+2, J ) = H( K+2, J ) - REFSUM*V( 2, M )

H(  K+3, J ) = H( K+3, J ) - REFSUM*V( 3, M )

30  CONTINUE

40  CONTINUE

IF( BMP22 ) THEN

K   = KRCOL + 3*( M22-1 )

DO  50 J = MAX( K+1, KTOP ), JBOT

REFSUM
    = V( 1, M22 )*( H( K+1, J )+V( 2, M22 )* H( K+2, J ) )

H(  K+1, J ) = H( K+1, J ) - REFSUM

H(  K+2, J ) = H( K+2, J ) - REFSUM*V( 2, M22 )

50  CONTINUE

END IF

IF( ACCUM ) THEN

JTOP
    = MAX( KTOP, INCOL )

ELSE
    IF( WANTT ) THEN

JTOP
    = 1

ELSE

JTOP
    = KTOP

END IF

DO  90 M = MTOP, MBOT

IF( V( 1, M ).NE.ZERO ) THEN

K   = KRCOL + 3*( M-1 )

DO  60 J = JTOP, MIN( KBOT, K+3 )

REFSUM
    = V( 1, M )*( H( J, K+1 )+V( 2, M )* H( J, K+2 )+V( 3, M )*H( J, K+3 ) )

H(  J, K+1 ) = H( J, K+1 ) - REFSUM

H(  J, K+2 ) = H( J, K+2 ) - REFSUM*V( 2, M )

H(  J, K+3 ) = H( J, K+3 ) - REFSUM*V( 3, M )

60  CONTINUE

IF( ACCUM ) THEN

KMS = K - INCOL

DO  70 J = MAX( 1, KTOP-INCOL ), KDU

REFSUM
    = V( 1, M )*( U( J, KMS+1 )+V( 2, M )* U( J, KMS+2 )+V( 3, M )*U( J, KMS+3 ) )

U(  J, KMS+1 ) = U( J, KMS+1 ) - REFSUM

U(  J, KMS+2 ) = U( J, KMS+2 ) - REFSUM*V( 2, M )

U(  J, KMS+3 ) = U( J, KMS+3 ) - REFSUM*V( 3, M )

70  CONTINUE

ELSE
    IF( WANTZ ) THEN

DO  80 J = ILOZ, IHIZ

REFSUM
    = V( 1, M )*( Z( J, K+1 )+V( 2, M )* Z( J, K+2 )+V( 3, M )*Z( J, K+3 ) )

Z(  J, K+1 ) = Z( J, K+1 ) - REFSUM

Z(  J, K+2 ) = Z( J, K+2 ) - REFSUM*V( 2, M )

Z(  J, K+3 ) = Z( J, K+3 ) - REFSUM*V( 3, M )

80  CONTINUE

END IF

END IF

90  CONTINUE

K   = KRCOL + 3*( M22-1 )

IF( BMP22 .AND. ( V( 1, M22 ).NE.ZERO ) ) THEN

DO  100 J = JTOP, MIN( KBOT, K+3 )

REFSUM
    = V( 1, M22 )*( H( J, K+1 )+V( 2, M22 )* H( J, K+2 ) )

H(  J, K+1 ) = H( J, K+1 ) - REFSUM

H(  J, K+2 ) = H( J, K+2 ) - REFSUM*V( 2, M22 )

100 CONTINUE

IF( ACCUM ) THEN

KMS = K - INCOL

DO  110 J = MAX( 1, KTOP-INCOL ), KDU

REFSUM
    = V( 1, M22 )*( U( J, KMS+1 )+V( 2, M22 )* U( J, KMS+2 ) )

U(  J, KMS+1 ) = U( J, KMS+1 ) - REFSUM

U(  J, KMS+2 ) = U( J, KMS+2 ) - REFSUM*V( 2, M22 )

110 CONTINUE

ELSE
    IF( WANTZ ) THEN

DO  120 J = ILOZ, IHIZ

REFSUM
    = V( 1, M22 )*( Z( J, K+1 )+V( 2, M22 )* Z( J, K+2 ) )

Z(  J, K+1 ) = Z( J, K+1 ) - REFSUM

Z(  J, K+2 ) = Z( J, K+2 ) - REFSUM*V( 2, M22 )

120 CONTINUE

END IF

END IF

MSTART
    = MTOP

IF( KRCOL+3*( MSTART-1 ).LT.KTOP ) MSTART = MSTART + 1

MEND
    = MBOT

IF( BMP22 ) MEND = MEND + 1

IF( KRCOL.EQ.KBOT-2 ) MEND = MEND + 1

DO  130 M = MSTART, MEND

K   = MIN( KBOT-1, KRCOL+3*( M-1 ) )

IF( H( K+1, K ).NE.ZERO ) THEN

TST1
    = ABS( H( K, K ) ) + ABS( H( K+1, K+1 ) )

IF( TST1.EQ.ZERO ) THEN

IF( K.GE.KTOP+1 ) TST1 = TST1 + ABS( H( K, K-1 ) )

IF( K.GE.KTOP+2 ) TST1 = TST1 + ABS( H( K, K-2 ) )

IF( K.GE.KTOP+3 ) TST1 = TST1 + ABS( H( K, K-3 ) )

IF( K.LE.KBOT-2 ) TST1 = TST1 + ABS( H( K+2, K+1 ) )

IF( K.LE.KBOT-3 ) TST1 = TST1 + ABS( H( K+3, K+1 ) )

IF( K.LE.KBOT-4 ) TST1 = TST1 + ABS( H( K+4, K+1 ) )

END IF

IF( ABS( H( K+1, K ) ).LE.MAX( SMLNUM, ULP*TST1 ) ) THEN

H12 = MAX( ABS( H( K+1, K ) ), ABS( H( K, K+1 ) ) )

H21 = MIN( ABS( H( K+1, K ) ), ABS( H( K, K+1 ) ) )

H11 = MAX( ABS( H( K+1, K+1 ) ), ABS( H( K, K )-H( K+1, K+1 ) ) )

H22 = MIN( ABS( H( K+1, K+1 ) ), ABS( H( K, K )-H( K+1, K+1 ) ) )

SCL = H11 + H12

TST2
    = H22*( H11 / SCL )

IF( TST2.EQ.ZERO .OR. H21*( H12 / SCL ).LE. MAX( SMLNUM, ULP*TST2 ) )H( K+1, K ) = ZERO

END IF

END IF

130 CONTINUE

MEND
    = MIN( NBMPS, ( KBOT-KRCOL-1 ) / 3 )

DO  140 M = MTOP, MEND

K   = KRCOL + 3*( M-1 )

REFSUM
    = V( 1, M )*V( 3, M )*H( K+4, K+3 )

H(  K+4, K+1 ) = -REFSUM

H(  K+4, K+2 ) = -REFSUM*V( 2, M )

H(  K+4, K+3 ) = H( K+4, K+3 ) - REFSUM*V( 3, M )

140 CONTINUE

150 CONTINUE

IF( ACCUM ) THEN

IF( WANTT ) THEN

JTOP
    = 1

JBOT
    = N

ELSE

JTOP
    = KTOP

JBOT
    = KBOT

END IF

IF( ( .NOT.BLK22 ) .OR. ( INCOL.LT.KTOP ) .OR. ( NDCOL.GT.KBOT ) .OR. ( NS.LE.2 ) ) THEN

K1  = MAX( 1, KTOP-INCOL )

NU  = ( KDU-MAX( 0, NDCOL-KBOT ) ) - K1 + 1

DO  160 JCOL = MIN( NDCOL, KBOT ) + 1, JBOT, NH

JLEN
    = MIN( NH, JBOT-JCOL+1 )

CALL
    DGEMM( 'C', 'N', NU, JLEN, NU, ONE, U( K1, K1 ), LDU, H( INCOL+K1, JCOL ), LDH, ZERO, WH, LDWH )

CALL
    DLACPY( 'ALL', NU, JLEN, WH, LDWH, H( INCOL+K1, JCOL ), LDH )

160 CONTINUE

DO  170 JROW = JTOP, MAX( KTOP, INCOL ) - 1, NV

JLEN
    = MIN( NV, MAX( KTOP, INCOL )-JROW )

CALL
    DGEMM( 'N', 'N', JLEN, NU, NU, ONE, H( JROW, INCOL+K1 ), LDH, U( K1, K1 ), LDU, ZERO, WV, LDWV )

CALL
    DLACPY( 'ALL', JLEN, NU, WV, LDWV, H( JROW, INCOL+K1 ), LDH )

170 CONTINUE

IF( WANTZ ) THEN

DO  180 JROW = ILOZ, IHIZ, NV

JLEN
    = MIN( NV, IHIZ-JROW+1 )

CALL
    DGEMM( 'N', 'N', JLEN, NU, NU, ONE, Z( JROW, INCOL+K1 ), LDZ, U( K1, K1 ), LDU, ZERO, WV, LDWV )

CALL
    DLACPY( 'ALL', JLEN, NU, WV, LDWV, Z( JROW, INCOL+K1 ), LDZ )

180 CONTINUE

END IF

ELSE

I2  = ( KDU+1 ) / 2

I4  = KDU

J2  = I4 - I2

J4  = KDU

KZS = ( J4-J2 ) - ( NS+1 )

KNZ = NS + 1

DO  190 JCOL = MIN( NDCOL, KBOT ) + 1, JBOT, NH

JLEN
    = MIN( NH, JBOT-JCOL+1 )

CALL
    DLACPY( 'ALL', KNZ, JLEN, H( INCOL+1+J2, JCOL ), LDH, WH( KZS+1, 1 ), LDWH )

CALL
    DLASET( 'ALL', KZS, JLEN, ZERO, ZERO, WH, LDWH )

CALL
    DTRMM( 'L', 'U', 'C', 'N', KNZ, JLEN, ONE, U( J2+1, 1+KZS ), LDU, WH( KZS+1, 1 ), LDWH )

CALL
    DGEMM( 'C', 'N', I2, JLEN, J2, ONE, U, LDU, H( INCOL+1, JCOL ), LDH, ONE, WH, LDWH )

CALL
    DLACPY( 'ALL', J2, JLEN, H( INCOL+1, JCOL ), LDH, WH( I2+1, 1 ), LDWH )

CALL
    DTRMM( 'L', 'L', 'C', 'N', J2, JLEN, ONE, U( 1, I2+1 ), LDU, WH( I2+1, 1 ), LDWH )

CALL
    DGEMM( 'C', 'N', I4-I2, JLEN, J4-J2, ONE, U( J2+1, I2+1 ), LDU, H( INCOL+1+J2, JCOL ), LDH, ONE, WH( I2+1, 1 ), LDWH )

CALL
    DLACPY( 'ALL', KDU, JLEN, WH, LDWH, H( INCOL+1, JCOL ), LDH )

190 CONTINUE

DO  200 JROW = JTOP, MAX( INCOL, KTOP ) - 1, NV

JLEN
    = MIN( NV, MAX( INCOL, KTOP )-JROW )

CALL
    DLACPY( 'ALL', JLEN, KNZ, H( JROW, INCOL+1+J2 ), LDH, WV( 1, 1+KZS ), LDWV )

CALL
    DLASET( 'ALL', JLEN, KZS, ZERO, ZERO, WV, LDWV )

CALL
    DTRMM( 'R', 'U', 'N', 'N', JLEN, KNZ, ONE, U( J2+1, 1+KZS ), LDU, WV( 1, 1+KZS ), LDWV )

CALL
    DGEMM( 'N', 'N', JLEN, I2, J2, ONE, H( JROW, INCOL+1 ), LDH, U, LDU, ONE, WV, LDWV )

CALL
    DLACPY( 'ALL', JLEN, J2, H( JROW, INCOL+1 ), LDH, WV( 1, 1+I2 ), LDWV )

CALL
    DTRMM( 'R', 'L', 'N', 'N', JLEN, I4-I2, ONE, U( 1, I2+1 ), LDU, WV( 1, 1+I2 ), LDWV )

CALL
    DGEMM( 'N', 'N', JLEN, I4-I2, J4-J2, ONE, H( JROW, INCOL+1+J2 ), LDH, U( J2+1, I2+1 ), LDU, ONE, WV( 1, 1+I2 ), LDWV )

CALL
    DLACPY( 'ALL', JLEN, KDU, WV, LDWV, H( JROW, INCOL+1 ), LDH )

200 CONTINUE

IF( WANTZ ) THEN

DO  210 JROW = ILOZ, IHIZ, NV

JLEN
    = MIN( NV, IHIZ-JROW+1 )

CALL
    DLACPY( 'ALL', JLEN, KNZ, Z( JROW, INCOL+1+J2 ), LDZ, WV( 1, 1+KZS ), LDWV )

CALL
    DLASET( 'ALL', JLEN, KZS, ZERO, ZERO, WV, LDWV )

CALL
    DTRMM( 'R', 'U', 'N', 'N', JLEN, KNZ, ONE, U( J2+1, 1+KZS ), LDU, WV( 1, 1+KZS ), LDWV )

CALL
    DGEMM( 'N', 'N', JLEN, I2, J2, ONE, Z( JROW, INCOL+1 ), LDZ, U, LDU, ONE, WV, LDWV )

CALL
    DLACPY( 'ALL', JLEN, J2, Z( JROW, INCOL+1 ), LDZ, WV( 1, 1+I2 ), LDWV )

CALL
    DTRMM( 'R', 'L', 'N', 'N', JLEN, I4-I2, ONE, U( 1, I2+1 ), LDU, WV( 1, 1+I2 ), LDWV )

CALL
    DGEMM( 'N', 'N', JLEN, I4-I2, J4-J2, ONE, Z( JROW, INCOL+1+J2 ), LDZ, U( J2+1, I2+1 ), LDU, ONE, WV( 1, 1+I2 ), LDWV )

CALL
    DLACPY( 'ALL', JLEN, KDU, WV, LDWV, Z( JROW, INCOL+1 ), LDZ )

210 CONTINUE

END IF

END IF

END IF

220 CONTINUE

END

PURPOSE