version 1.9, 2011/11/21 22:19:35
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version 1.18, 2023/08/07 08:38:59
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*> \brief \b DLASQ6 |
*> \brief \b DLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr. |
* |
* |
* =========== DOCUMENTATION =========== |
* =========== DOCUMENTATION =========== |
* |
* |
* Online html documentation available at |
* Online html documentation available at |
* http://www.netlib.org/lapack/explore-html/ |
* http://www.netlib.org/lapack/explore-html/ |
* |
* |
*> \htmlonly |
*> \htmlonly |
*> Download DLASQ6 + dependencies |
*> Download DLASQ6 + dependencies |
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlasq6.f"> |
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlasq6.f"> |
*> [TGZ]</a> |
*> [TGZ]</a> |
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlasq6.f"> |
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlasq6.f"> |
*> [ZIP]</a> |
*> [ZIP]</a> |
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlasq6.f"> |
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlasq6.f"> |
*> [TXT]</a> |
*> [TXT]</a> |
*> \endhtmlonly |
*> \endhtmlonly |
* |
* |
* Definition: |
* Definition: |
* =========== |
* =========== |
* |
* |
* SUBROUTINE DLASQ6( I0, N0, Z, PP, DMIN, DMIN1, DMIN2, DN, |
* SUBROUTINE DLASQ6( I0, N0, Z, PP, DMIN, DMIN1, DMIN2, DN, |
* DNM1, DNM2 ) |
* DNM1, DNM2 ) |
* |
* |
* .. Scalar Arguments .. |
* .. Scalar Arguments .. |
* INTEGER I0, N0, PP |
* INTEGER I0, N0, PP |
* DOUBLE PRECISION DMIN, DMIN1, DMIN2, DN, DNM1, DNM2 |
* DOUBLE PRECISION DMIN, DMIN1, DMIN2, DN, DNM1, DNM2 |
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* .. Array Arguments .. |
* .. Array Arguments .. |
* DOUBLE PRECISION Z( * ) |
* DOUBLE PRECISION Z( * ) |
* .. |
* .. |
* |
* |
* |
* |
*> \par Purpose: |
*> \par Purpose: |
* ============= |
* ============= |
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* Authors: |
* Authors: |
* ======== |
* ======== |
* |
* |
*> \author Univ. of Tennessee |
*> \author Univ. of Tennessee |
*> \author Univ. of California Berkeley |
*> \author Univ. of California Berkeley |
*> \author Univ. of Colorado Denver |
*> \author Univ. of Colorado Denver |
*> \author NAG Ltd. |
*> \author NAG Ltd. |
* |
|
*> \date November 2011 |
|
* |
* |
*> \ingroup auxOTHERcomputational |
*> \ingroup auxOTHERcomputational |
* |
* |
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SUBROUTINE DLASQ6( I0, N0, Z, PP, DMIN, DMIN1, DMIN2, DN, |
SUBROUTINE DLASQ6( I0, N0, Z, PP, DMIN, DMIN1, DMIN2, DN, |
$ DNM1, DNM2 ) |
$ DNM1, DNM2 ) |
* |
* |
* -- LAPACK computational routine (version 3.4.0) -- |
* -- LAPACK computational routine -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* November 2011 |
|
* |
* |
* .. Scalar Arguments .. |
* .. Scalar Arguments .. |
INTEGER I0, N0, PP |
INTEGER I0, N0, PP |
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* |
* |
SAFMIN = DLAMCH( 'Safe minimum' ) |
SAFMIN = DLAMCH( 'Safe minimum' ) |
J4 = 4*I0 + PP - 3 |
J4 = 4*I0 + PP - 3 |
EMIN = Z( J4+4 ) |
EMIN = Z( J4+4 ) |
D = Z( J4 ) |
D = Z( J4 ) |
DMIN = D |
DMIN = D |
* |
* |
IF( PP.EQ.0 ) THEN |
IF( PP.EQ.0 ) THEN |
DO 10 J4 = 4*I0, 4*( N0-3 ), 4 |
DO 10 J4 = 4*I0, 4*( N0-3 ), 4 |
Z( J4-2 ) = D + Z( J4-1 ) |
Z( J4-2 ) = D + Z( J4-1 ) |
IF( Z( J4-2 ).EQ.ZERO ) THEN |
IF( Z( J4-2 ).EQ.ZERO ) THEN |
Z( J4 ) = ZERO |
Z( J4 ) = ZERO |
D = Z( J4+1 ) |
D = Z( J4+1 ) |
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TEMP = Z( J4+1 ) / Z( J4-2 ) |
TEMP = Z( J4+1 ) / Z( J4-2 ) |
Z( J4 ) = Z( J4-1 )*TEMP |
Z( J4 ) = Z( J4-1 )*TEMP |
D = D*TEMP |
D = D*TEMP |
ELSE |
ELSE |
Z( J4 ) = Z( J4+1 )*( Z( J4-1 ) / Z( J4-2 ) ) |
Z( J4 ) = Z( J4+1 )*( Z( J4-1 ) / Z( J4-2 ) ) |
D = Z( J4+1 )*( D / Z( J4-2 ) ) |
D = Z( J4+1 )*( D / Z( J4-2 ) ) |
END IF |
END IF |
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10 CONTINUE |
10 CONTINUE |
ELSE |
ELSE |
DO 20 J4 = 4*I0, 4*( N0-3 ), 4 |
DO 20 J4 = 4*I0, 4*( N0-3 ), 4 |
Z( J4-3 ) = D + Z( J4 ) |
Z( J4-3 ) = D + Z( J4 ) |
IF( Z( J4-3 ).EQ.ZERO ) THEN |
IF( Z( J4-3 ).EQ.ZERO ) THEN |
Z( J4-1 ) = ZERO |
Z( J4-1 ) = ZERO |
D = Z( J4+2 ) |
D = Z( J4+2 ) |
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TEMP = Z( J4+2 ) / Z( J4-3 ) |
TEMP = Z( J4+2 ) / Z( J4-3 ) |
Z( J4-1 ) = Z( J4 )*TEMP |
Z( J4-1 ) = Z( J4 )*TEMP |
D = D*TEMP |
D = D*TEMP |
ELSE |
ELSE |
Z( J4-1 ) = Z( J4+2 )*( Z( J4 ) / Z( J4-3 ) ) |
Z( J4-1 ) = Z( J4+2 )*( Z( J4 ) / Z( J4-3 ) ) |
D = Z( J4+2 )*( D / Z( J4-3 ) ) |
D = Z( J4+2 )*( D / Z( J4-3 ) ) |
END IF |
END IF |
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20 CONTINUE |
20 CONTINUE |
END IF |
END IF |
* |
* |
* Unroll last two steps. |
* Unroll last two steps. |
* |
* |
DNM2 = D |
DNM2 = D |
DMIN2 = DMIN |
DMIN2 = DMIN |