174 lines
4.8 KiB
Fortran
174 lines
4.8 KiB
Fortran
*> \brief \b DLAT2S converts a double-precision triangular matrix to a single-precision triangular matrix.
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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*> \htmlonly
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*> Download DLAT2S + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlat2s.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlat2s.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlat2s.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE DLAT2S( UPLO, N, A, LDA, SA, LDSA, INFO )
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*
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* .. Scalar Arguments ..
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* CHARACTER UPLO
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* INTEGER INFO, LDA, LDSA, N
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* ..
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* .. Array Arguments ..
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* REAL SA( LDSA, * )
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* DOUBLE PRECISION A( LDA, * )
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> DLAT2S converts a DOUBLE PRECISION triangular matrix, SA, to a SINGLE
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*> PRECISION triangular matrix, A.
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*>
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*> RMAX is the overflow for the SINGLE PRECISION arithmetic
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*> DLAS2S checks that all the entries of A are between -RMAX and
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*> RMAX. If not the conversion is aborted and a flag is raised.
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*>
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*> This is an auxiliary routine so there is no argument checking.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] UPLO
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*> \verbatim
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*> UPLO is CHARACTER*1
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*> = 'U': A is upper triangular;
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*> = 'L': A is lower triangular.
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*> \endverbatim
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*>
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> The number of rows and columns of the matrix A. N >= 0.
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*> \endverbatim
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*>
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*> \param[in] A
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*> \verbatim
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*> A is DOUBLE PRECISION array, dimension (LDA,N)
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*> On entry, the N-by-N triangular coefficient matrix A.
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*> \endverbatim
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*>
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*> \param[in] LDA
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*> \verbatim
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*> LDA is INTEGER
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*> The leading dimension of the array A. LDA >= max(1,N).
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*> \endverbatim
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*>
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*> \param[out] SA
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*> \verbatim
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*> SA is REAL array, dimension (LDSA,N)
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*> Only the UPLO part of SA is referenced. On exit, if INFO=0,
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*> the N-by-N coefficient matrix SA; if INFO>0, the content of
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*> the UPLO part of SA is unspecified.
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*> \endverbatim
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*>
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*> \param[in] LDSA
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*> \verbatim
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*> LDSA is INTEGER
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*> The leading dimension of the array SA. LDSA >= max(1,M).
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*> \endverbatim
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*>
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*> \param[out] INFO
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*> \verbatim
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*> INFO is INTEGER
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*> = 0: successful exit.
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*> = 1: an entry of the matrix A is greater than the SINGLE
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*> PRECISION overflow threshold, in this case, the content
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*> of the UPLO part of SA in exit is unspecified.
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \ingroup doubleOTHERauxiliary
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*
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* =====================================================================
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SUBROUTINE DLAT2S( UPLO, N, A, LDA, SA, LDSA, INFO )
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*
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* -- LAPACK auxiliary routine --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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*
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* .. Scalar Arguments ..
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CHARACTER UPLO
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INTEGER INFO, LDA, LDSA, N
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* ..
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* .. Array Arguments ..
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REAL SA( LDSA, * )
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DOUBLE PRECISION A( LDA, * )
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I, J
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DOUBLE PRECISION RMAX
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LOGICAL UPPER
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* ..
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* .. External Functions ..
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REAL SLAMCH
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LOGICAL LSAME
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EXTERNAL SLAMCH, LSAME
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC REAL
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* ..
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* .. Executable Statements ..
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*
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RMAX = SLAMCH( 'O' )
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UPPER = LSAME( UPLO, 'U' )
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IF( UPPER ) THEN
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DO 20 J = 1, N
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DO 10 I = 1, J
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IF( ( A( I, J ).LT.-RMAX ) .OR. ( A( I, J ).GT.RMAX ) )
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$ THEN
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INFO = 1
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GO TO 50
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END IF
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SA( I, J ) = REAL( A( I, J ) )
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10 CONTINUE
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20 CONTINUE
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ELSE
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DO 40 J = 1, N
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DO 30 I = J, N
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IF( ( A( I, J ).LT.-RMAX ) .OR. ( A( I, J ).GT.RMAX ) )
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$ THEN
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INFO = 1
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GO TO 50
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END IF
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SA( I, J ) = REAL( A( I, J ) )
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30 CONTINUE
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40 CONTINUE
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END IF
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50 CONTINUE
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*
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RETURN
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*
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* End of DLAT2S
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*
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END
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