version 1.19, 2018/05/29 07:18:01
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version 1.20, 2023/08/07 08:39:00
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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 DLATRS( UPLO, TRANS, DIAG, NORMIN, N, A, LDA, X, SCALE, |
SUBROUTINE DLATRS( UPLO, TRANS, DIAG, NORMIN, N, A, LDA, X, SCALE, |
$ CNORM, INFO ) |
$ CNORM, INFO ) |
* |
* |
* -- 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 .. |
CHARACTER DIAG, NORMIN, TRANS, UPLO |
CHARACTER DIAG, NORMIN, TRANS, UPLO |
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* .. External Functions .. |
* .. External Functions .. |
LOGICAL LSAME |
LOGICAL LSAME |
INTEGER IDAMAX |
INTEGER IDAMAX |
DOUBLE PRECISION DASUM, DDOT, DLAMCH |
DOUBLE PRECISION DASUM, DDOT, DLAMCH, DLANGE |
EXTERNAL LSAME, IDAMAX, DASUM, DDOT, DLAMCH |
EXTERNAL LSAME, IDAMAX, DASUM, DDOT, DLAMCH, DLANGE |
* .. |
* .. |
* .. External Subroutines .. |
* .. External Subroutines .. |
EXTERNAL DAXPY, DSCAL, DTRSV, XERBLA |
EXTERNAL DAXPY, DSCAL, DTRSV, XERBLA |
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* |
* |
* Quick return if possible |
* Quick return if possible |
* |
* |
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SCALE = ONE |
IF( N.EQ.0 ) |
IF( N.EQ.0 ) |
$ RETURN |
$ RETURN |
* |
* |
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* |
* |
SMLNUM = DLAMCH( 'Safe minimum' ) / DLAMCH( 'Precision' ) |
SMLNUM = DLAMCH( 'Safe minimum' ) / DLAMCH( 'Precision' ) |
BIGNUM = ONE / SMLNUM |
BIGNUM = ONE / SMLNUM |
SCALE = ONE |
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* |
* |
IF( LSAME( NORMIN, 'N' ) ) THEN |
IF( LSAME( NORMIN, 'N' ) ) THEN |
* |
* |
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IF( TMAX.LE.BIGNUM ) THEN |
IF( TMAX.LE.BIGNUM ) THEN |
TSCAL = ONE |
TSCAL = ONE |
ELSE |
ELSE |
TSCAL = ONE / ( SMLNUM*TMAX ) |
* |
CALL DSCAL( N, TSCAL, CNORM, 1 ) |
* Avoid NaN generation if entries in CNORM exceed the |
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* overflow threshold |
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* |
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IF( TMAX.LE.DLAMCH('Overflow') ) THEN |
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* Case 1: All entries in CNORM are valid floating-point numbers |
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TSCAL = ONE / ( SMLNUM*TMAX ) |
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CALL DSCAL( N, TSCAL, CNORM, 1 ) |
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ELSE |
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* Case 2: At least one column norm of A cannot be represented |
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* as floating-point number. Find the offdiagonal entry A( I, J ) |
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* with the largest absolute value. If this entry is not +/- Infinity, |
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* use this value as TSCAL. |
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TMAX = ZERO |
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IF( UPPER ) THEN |
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* |
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* A is upper triangular. |
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* |
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DO J = 2, N |
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TMAX = MAX( DLANGE( 'M', J-1, 1, A( 1, J ), 1, SUMJ ), |
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$ TMAX ) |
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END DO |
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ELSE |
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* |
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* A is lower triangular. |
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* |
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DO J = 1, N - 1 |
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TMAX = MAX( DLANGE( 'M', N-J, 1, A( J+1, J ), 1, |
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$ SUMJ ), TMAX ) |
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END DO |
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END IF |
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* |
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IF( TMAX.LE.DLAMCH('Overflow') ) THEN |
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TSCAL = ONE / ( SMLNUM*TMAX ) |
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DO J = 1, N |
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IF( CNORM( J ).LE.DLAMCH('Overflow') ) THEN |
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CNORM( J ) = CNORM( J )*TSCAL |
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ELSE |
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* Recompute the 1-norm without introducing Infinity |
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* in the summation |
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CNORM( J ) = ZERO |
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IF( UPPER ) THEN |
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DO I = 1, J - 1 |
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CNORM( J ) = CNORM( J ) + |
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$ TSCAL * ABS( A( I, J ) ) |
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END DO |
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ELSE |
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DO I = J + 1, N |
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CNORM( J ) = CNORM( J ) + |
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$ TSCAL * ABS( A( I, J ) ) |
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END DO |
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END IF |
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END IF |
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END DO |
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ELSE |
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* At least one entry of A is not a valid floating-point entry. |
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* Rely on TRSV to propagate Inf and NaN. |
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CALL DTRSV( UPLO, TRANS, DIAG, N, A, LDA, X, 1 ) |
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RETURN |
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END IF |
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END IF |
END IF |
END IF |
* |
* |
* Compute a bound on the computed solution vector to see if the |
* Compute a bound on the computed solution vector to see if the |