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lapack/SRC/dsyconv.f
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Julie e18d437924 Making LAPACK's code eternal... no more version and date in source files. 
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2021-03-25 10:16:58 -07:00

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*> \brief \b DSYCONV
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download DSYCONV + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dsyconv.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dsyconv.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dsyconv.f">
*> [TXT]</a>
*> \endhtmlonly
*
* Definition:
* ===========
*
* SUBROUTINE DSYCONV( UPLO, WAY, N, A, LDA, IPIV, E, INFO )
*
* .. Scalar Arguments ..
* CHARACTER UPLO, WAY
* INTEGER INFO, LDA, N
* ..
* .. Array Arguments ..
* INTEGER IPIV( * )
* DOUBLE PRECISION A( LDA, * ), E( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> DSYCONV convert A given by TRF into L and D and vice-versa.
*> Get Non-diag elements of D (returned in workspace) and
*> apply or reverse permutation done in TRF.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] UPLO
*> \verbatim
*> UPLO is CHARACTER*1
*> Specifies whether the details of the factorization are stored
*> as an upper or lower triangular matrix.
*> = 'U': Upper triangular, form is A = U*D*U**T;
*> = 'L': Lower triangular, form is A = L*D*L**T.
*> \endverbatim
*>
*> \param[in] WAY
*> \verbatim
*> WAY is CHARACTER*1
*> = 'C': Convert
*> = 'R': Revert
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The order of the matrix A. N >= 0.
*> \endverbatim
*>
*> \param[in,out] A
*> \verbatim
*> A is DOUBLE PRECISION array, dimension (LDA,N)
*> The block diagonal matrix D and the multipliers used to
*> obtain the factor U or L as computed by DSYTRF.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*> LDA is INTEGER
*> The leading dimension of the array A. LDA >= max(1,N).
*> \endverbatim
*>
*> \param[in] IPIV
*> \verbatim
*> IPIV is INTEGER array, dimension (N)
*> Details of the interchanges and the block structure of D
*> as determined by DSYTRF.
*> \endverbatim
*>
*> \param[out] E
*> \verbatim
*> E is DOUBLE PRECISION array, dimension (N)
*> E stores the supdiagonal/subdiagonal of the symmetric 1-by-1
*> or 2-by-2 block diagonal matrix D in LDLT.
*> \endverbatim
*>
*> \param[out] INFO
*> \verbatim
*> INFO is INTEGER
*> = 0: successful exit
*> < 0: if INFO = -i, the i-th argument had an illegal value
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup doubleSYcomputational
*
* =====================================================================
SUBROUTINE DSYCONV( UPLO, WAY, N, A, LDA, IPIV, E, INFO )
*
* -- LAPACK computational routine --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
* .. Scalar Arguments ..
CHARACTER UPLO, WAY
INTEGER INFO, LDA, N
* ..
* .. Array Arguments ..
INTEGER IPIV( * )
DOUBLE PRECISION A( LDA, * ), E( * )
* ..
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ZERO
PARAMETER ( ZERO = 0.0D+0 )
* ..
* .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
*
* .. External Subroutines ..
EXTERNAL XERBLA
* .. Local Scalars ..
LOGICAL UPPER, CONVERT
INTEGER I, IP, J
DOUBLE PRECISION TEMP
* ..
* .. Executable Statements ..
*
INFO = 0
UPPER = LSAME( UPLO, 'U' )
CONVERT = LSAME( WAY, 'C' )
IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
INFO = -1
ELSE IF( .NOT.CONVERT .AND. .NOT.LSAME( WAY, 'R' ) ) THEN
INFO = -2
ELSE IF( N.LT.0 ) THEN
INFO = -3
ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
INFO = -5
END IF
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'DSYCONV', -INFO )
RETURN
END IF
*
* Quick return if possible
*
IF( N.EQ.0 )
$ RETURN
*
IF( UPPER ) THEN
*
* A is UPPER
*
* Convert A (A is upper)
*
* Convert VALUE
*
IF ( CONVERT ) THEN
I=N
E(1)=ZERO
DO WHILE ( I .GT. 1 )
IF( IPIV(I) .LT. 0 ) THEN
E(I)=A(I-1,I)
E(I-1)=ZERO
A(I-1,I)=ZERO
I=I-1
ELSE
E(I)=ZERO
ENDIF
I=I-1
END DO
*
* Convert PERMUTATIONS
*
I=N
DO WHILE ( I .GE. 1 )
IF( IPIV(I) .GT. 0) THEN
IP=IPIV(I)
IF( I .LT. N) THEN
DO 12 J= I+1,N
TEMP=A(IP,J)
A(IP,J)=A(I,J)
A(I,J)=TEMP
12 CONTINUE
ENDIF
ELSE
IP=-IPIV(I)
IF( I .LT. N) THEN
DO 13 J= I+1,N
TEMP=A(IP,J)
A(IP,J)=A(I-1,J)
A(I-1,J)=TEMP
13 CONTINUE
ENDIF
I=I-1
ENDIF
I=I-1
END DO
ELSE
*
* Revert A (A is upper)
*
*
* Revert PERMUTATIONS
*
I=1
DO WHILE ( I .LE. N )
IF( IPIV(I) .GT. 0 ) THEN
IP=IPIV(I)
IF( I .LT. N) THEN
DO J= I+1,N
TEMP=A(IP,J)
A(IP,J)=A(I,J)
A(I,J)=TEMP
END DO
ENDIF
ELSE
IP=-IPIV(I)
I=I+1
IF( I .LT. N) THEN
DO J= I+1,N
TEMP=A(IP,J)
A(IP,J)=A(I-1,J)
A(I-1,J)=TEMP
END DO
ENDIF
ENDIF
I=I+1
END DO
*
* Revert VALUE
*
I=N
DO WHILE ( I .GT. 1 )
IF( IPIV(I) .LT. 0 ) THEN
A(I-1,I)=E(I)
I=I-1
ENDIF
I=I-1
END DO
END IF
ELSE
*
* A is LOWER
*
IF ( CONVERT ) THEN
*
* Convert A (A is lower)
*
*
* Convert VALUE
*
I=1
E(N)=ZERO
DO WHILE ( I .LE. N )
IF( I.LT.N .AND. IPIV(I) .LT. 0 ) THEN
E(I)=A(I+1,I)
E(I+1)=ZERO
A(I+1,I)=ZERO
I=I+1
ELSE
E(I)=ZERO
ENDIF
I=I+1
END DO
*
* Convert PERMUTATIONS
*
I=1
DO WHILE ( I .LE. N )
IF( IPIV(I) .GT. 0 ) THEN
IP=IPIV(I)
IF (I .GT. 1) THEN
DO 22 J= 1,I-1
TEMP=A(IP,J)
A(IP,J)=A(I,J)
A(I,J)=TEMP
22 CONTINUE
ENDIF
ELSE
IP=-IPIV(I)
IF (I .GT. 1) THEN
DO 23 J= 1,I-1
TEMP=A(IP,J)
A(IP,J)=A(I+1,J)
A(I+1,J)=TEMP
23 CONTINUE
ENDIF
I=I+1
ENDIF
I=I+1
END DO
ELSE
*
* Revert A (A is lower)
*
*
* Revert PERMUTATIONS
*
I=N
DO WHILE ( I .GE. 1 )
IF( IPIV(I) .GT. 0 ) THEN
IP=IPIV(I)
IF (I .GT. 1) THEN
DO J= 1,I-1
TEMP=A(I,J)
A(I,J)=A(IP,J)
A(IP,J)=TEMP
END DO
ENDIF
ELSE
IP=-IPIV(I)
I=I-1
IF (I .GT. 1) THEN
DO J= 1,I-1
TEMP=A(I+1,J)
A(I+1,J)=A(IP,J)
A(IP,J)=TEMP
END DO
ENDIF
ENDIF
I=I-1
END DO
*
* Revert VALUE
*
I=1
DO WHILE ( I .LE. N-1 )
IF( IPIV(I) .LT. 0 ) THEN
A(I+1,I)=E(I)
I=I+1
ENDIF
I=I+1
END DO
END IF
END IF
RETURN
*
* End of DSYCONV
*
END
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