version 1.19, 2020/05/21 21:45:59
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version 1.20, 2023/08/07 08:38:55
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*> \author Univ. of Colorado Denver |
*> \author Univ. of Colorado Denver |
*> \author NAG Ltd. |
*> \author NAG Ltd. |
* |
* |
*> \date December 2016 |
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* |
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*> \ingroup doubleOTHERauxiliary |
*> \ingroup doubleOTHERauxiliary |
* |
* |
*> \par Further Details: |
*> \par Further Details: |
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* ===================================================================== |
* ===================================================================== |
SUBROUTINE DLANV2( A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN ) |
SUBROUTINE DLANV2( A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN ) |
* |
* |
* -- LAPACK auxiliary routine (version 3.7.0) -- |
* -- LAPACK auxiliary 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..-- |
* December 2016 |
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* |
* |
* .. Scalar Arguments .. |
* .. Scalar Arguments .. |
DOUBLE PRECISION A, B, C, CS, D, RT1I, RT1R, RT2I, RT2R, SN |
DOUBLE PRECISION A, B, C, CS, D, RT1I, RT1R, RT2I, RT2R, SN |
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* ===================================================================== |
* ===================================================================== |
* |
* |
* .. Parameters .. |
* .. Parameters .. |
DOUBLE PRECISION ZERO, HALF, ONE |
DOUBLE PRECISION ZERO, HALF, ONE, TWO |
PARAMETER ( ZERO = 0.0D+0, HALF = 0.5D+0, ONE = 1.0D+0 ) |
PARAMETER ( ZERO = 0.0D+0, HALF = 0.5D+0, ONE = 1.0D+0, |
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$ TWO = 2.0D0 ) |
DOUBLE PRECISION MULTPL |
DOUBLE PRECISION MULTPL |
PARAMETER ( MULTPL = 4.0D+0 ) |
PARAMETER ( MULTPL = 4.0D+0 ) |
* .. |
* .. |
* .. Local Scalars .. |
* .. Local Scalars .. |
DOUBLE PRECISION AA, BB, BCMAX, BCMIS, CC, CS1, DD, EPS, P, SAB, |
DOUBLE PRECISION AA, BB, BCMAX, BCMIS, CC, CS1, DD, EPS, P, SAB, |
$ SAC, SCALE, SIGMA, SN1, TAU, TEMP, Z |
$ SAC, SCALE, SIGMA, SN1, TAU, TEMP, Z, SAFMIN, |
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$ SAFMN2, SAFMX2 |
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INTEGER COUNT |
* .. |
* .. |
* .. External Functions .. |
* .. External Functions .. |
DOUBLE PRECISION DLAMCH, DLAPY2 |
DOUBLE PRECISION DLAMCH, DLAPY2 |
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* .. |
* .. |
* .. Executable Statements .. |
* .. Executable Statements .. |
* |
* |
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SAFMIN = DLAMCH( 'S' ) |
EPS = DLAMCH( 'P' ) |
EPS = DLAMCH( 'P' ) |
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SAFMN2 = DLAMCH( 'B' )**INT( LOG( SAFMIN / EPS ) / |
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$ LOG( DLAMCH( 'B' ) ) / TWO ) |
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SAFMX2 = ONE / SAFMN2 |
IF( C.EQ.ZERO ) THEN |
IF( C.EQ.ZERO ) THEN |
CS = ONE |
CS = ONE |
SN = ZERO |
SN = ZERO |
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* Complex eigenvalues, or real (almost) equal eigenvalues. |
* Complex eigenvalues, or real (almost) equal eigenvalues. |
* Make diagonal elements equal. |
* Make diagonal elements equal. |
* |
* |
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COUNT = 0 |
SIGMA = B + C |
SIGMA = B + C |
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10 CONTINUE |
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COUNT = COUNT + 1 |
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SCALE = MAX( ABS(TEMP), ABS(SIGMA) ) |
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IF( SCALE.GE.SAFMX2 ) THEN |
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SIGMA = SIGMA * SAFMN2 |
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TEMP = TEMP * SAFMN2 |
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IF (COUNT .LE. 20) |
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$ GOTO 10 |
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END IF |
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IF( SCALE.LE.SAFMN2 ) THEN |
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SIGMA = SIGMA * SAFMX2 |
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TEMP = TEMP * SAFMX2 |
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IF (COUNT .LE. 20) |
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$ GOTO 10 |
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END IF |
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P = HALF*TEMP |
TAU = DLAPY2( SIGMA, TEMP ) |
TAU = DLAPY2( SIGMA, TEMP ) |
CS = SQRT( HALF*( ONE+ABS( SIGMA ) / TAU ) ) |
CS = SQRT( HALF*( ONE+ABS( SIGMA ) / TAU ) ) |
SN = -( P / ( TAU*CS ) )*SIGN( ONE, SIGMA ) |
SN = -( P / ( TAU*CS ) )*SIGN( ONE, SIGMA ) |