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364 lines
8.8 KiB
364 lines
8.8 KiB
2 years ago
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*> \brief \b SSYCONV
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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 SSYCONV + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ssyconv.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/ssyconv.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/ssyconv.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 SSYCONV( UPLO, WAY, N, A, LDA, IPIV, E, INFO )
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*
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* .. Scalar Arguments ..
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* CHARACTER UPLO, WAY
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* INTEGER INFO, LDA, N
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* ..
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* .. Array Arguments ..
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* INTEGER IPIV( * )
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* REAL A( LDA, * ), E( * )
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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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*> SSYCONV convert A given by TRF into L and D and vice-versa.
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*> Get Non-diag elements of D (returned in workspace) and
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*> apply or reverse permutation done in TRF.
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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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*> Specifies whether the details of the factorization are stored
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*> as an upper or lower triangular matrix.
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*> = 'U': Upper triangular, form is A = U*D*U**T;
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*> = 'L': Lower triangular, form is A = L*D*L**T.
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*> \endverbatim
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*>
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*> \param[in] WAY
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*> \verbatim
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*> WAY is CHARACTER*1
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*> = 'C': Convert
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*> = 'R': Revert
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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 order of the matrix A. N >= 0.
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*> \endverbatim
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*>
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*> \param[in,out] A
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*> \verbatim
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*> A is REAL array, dimension (LDA,N)
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*> The block diagonal matrix D and the multipliers used to
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*> obtain the factor U or L as computed by SSYTRF.
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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[in] IPIV
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*> \verbatim
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*> IPIV is INTEGER array, dimension (N)
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*> Details of the interchanges and the block structure of D
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*> as determined by SSYTRF.
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*> \endverbatim
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*>
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*> \param[out] E
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*> \verbatim
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*> E is REAL array, dimension (N)
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*> E stores the supdiagonal/subdiagonal of the symmetric 1-by-1
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*> or 2-by-2 block diagonal matrix D in LDLT.
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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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*> < 0: if INFO = -i, the i-th argument had an illegal value
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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 realSYcomputational
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*
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* =====================================================================
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SUBROUTINE SSYCONV( UPLO, WAY, N, A, LDA, IPIV, E, INFO )
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*
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* -- LAPACK computational 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, WAY
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INTEGER INFO, LDA, N
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* ..
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* .. Array Arguments ..
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INTEGER IPIV( * )
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REAL A( LDA, * ), E( * )
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* ..
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*
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* =====================================================================
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*
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* .. Parameters ..
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REAL ZERO
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PARAMETER ( ZERO = 0.0E+0 )
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* ..
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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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*
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* .. External Subroutines ..
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EXTERNAL XERBLA
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* .. Local Scalars ..
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LOGICAL UPPER, CONVERT
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INTEGER I, IP, J
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REAL TEMP
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* ..
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* .. Executable Statements ..
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*
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INFO = 0
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UPPER = LSAME( UPLO, 'U' )
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CONVERT = LSAME( WAY, 'C' )
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IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
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INFO = -1
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ELSE IF( .NOT.CONVERT .AND. .NOT.LSAME( WAY, 'R' ) ) THEN
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INFO = -2
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ELSE IF( N.LT.0 ) THEN
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INFO = -3
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ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
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INFO = -5
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END IF
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'SSYCONV', -INFO )
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RETURN
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END IF
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*
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* Quick return if possible
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*
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IF( N.EQ.0 )
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$ RETURN
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*
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IF( UPPER ) THEN
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*
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* A is UPPER
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*
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* Convert A (A is upper)
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*
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* Convert VALUE
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*
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IF ( CONVERT ) THEN
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I=N
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E(1)=ZERO
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DO WHILE ( I .GT. 1 )
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IF( IPIV(I) .LT. 0 ) THEN
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E(I)=A(I-1,I)
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E(I-1)=ZERO
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A(I-1,I)=ZERO
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I=I-1
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ELSE
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E(I)=ZERO
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ENDIF
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I=I-1
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END DO
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*
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* Convert PERMUTATIONS
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*
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I=N
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DO WHILE ( I .GE. 1 )
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IF( IPIV(I) .GT. 0) THEN
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IP=IPIV(I)
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IF( I .LT. N) THEN
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DO 12 J= I+1,N
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TEMP=A(IP,J)
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A(IP,J)=A(I,J)
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A(I,J)=TEMP
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12 CONTINUE
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ENDIF
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ELSE
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IP=-IPIV(I)
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IF( I .LT. N) THEN
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DO 13 J= I+1,N
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TEMP=A(IP,J)
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A(IP,J)=A(I-1,J)
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A(I-1,J)=TEMP
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13 CONTINUE
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ENDIF
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I=I-1
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ENDIF
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I=I-1
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END DO
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ELSE
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*
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* Revert A (A is upper)
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*
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*
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* Revert PERMUTATIONS
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*
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I=1
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DO WHILE ( I .LE. N )
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IF( IPIV(I) .GT. 0 ) THEN
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IP=IPIV(I)
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IF( I .LT. N) THEN
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DO J= I+1,N
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TEMP=A(IP,J)
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A(IP,J)=A(I,J)
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A(I,J)=TEMP
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END DO
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ENDIF
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ELSE
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IP=-IPIV(I)
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I=I+1
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IF( I .LT. N) THEN
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DO J= I+1,N
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TEMP=A(IP,J)
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A(IP,J)=A(I-1,J)
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A(I-1,J)=TEMP
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END DO
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ENDIF
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ENDIF
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I=I+1
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END DO
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*
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* Revert VALUE
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*
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I=N
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DO WHILE ( I .GT. 1 )
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IF( IPIV(I) .LT. 0 ) THEN
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A(I-1,I)=E(I)
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I=I-1
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ENDIF
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I=I-1
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END DO
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END IF
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ELSE
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*
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* A is LOWER
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*
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IF ( CONVERT ) THEN
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*
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* Convert A (A is lower)
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*
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*
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* Convert VALUE
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*
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I=1
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E(N)=ZERO
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DO WHILE ( I .LE. N )
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IF( I.LT.N .AND. IPIV(I) .LT. 0 ) THEN
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E(I)=A(I+1,I)
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E(I+1)=ZERO
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A(I+1,I)=ZERO
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I=I+1
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ELSE
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E(I)=ZERO
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ENDIF
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I=I+1
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END DO
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*
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* Convert PERMUTATIONS
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*
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I=1
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DO WHILE ( I .LE. N )
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IF( IPIV(I) .GT. 0 ) THEN
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IP=IPIV(I)
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IF (I .GT. 1) THEN
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DO 22 J= 1,I-1
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TEMP=A(IP,J)
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A(IP,J)=A(I,J)
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A(I,J)=TEMP
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22 CONTINUE
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ENDIF
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ELSE
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IP=-IPIV(I)
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IF (I .GT. 1) THEN
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DO 23 J= 1,I-1
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TEMP=A(IP,J)
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A(IP,J)=A(I+1,J)
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A(I+1,J)=TEMP
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23 CONTINUE
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ENDIF
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I=I+1
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ENDIF
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I=I+1
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END DO
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ELSE
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*
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* Revert A (A is lower)
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*
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*
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* Revert PERMUTATIONS
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*
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I=N
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DO WHILE ( I .GE. 1 )
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IF( IPIV(I) .GT. 0 ) THEN
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IP=IPIV(I)
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IF (I .GT. 1) THEN
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DO J= 1,I-1
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TEMP=A(I,J)
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A(I,J)=A(IP,J)
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A(IP,J)=TEMP
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END DO
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ENDIF
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ELSE
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IP=-IPIV(I)
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I=I-1
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IF (I .GT. 1) THEN
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DO J= 1,I-1
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TEMP=A(I+1,J)
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A(I+1,J)=A(IP,J)
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A(IP,J)=TEMP
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END DO
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ENDIF
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ENDIF
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I=I-1
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END DO
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*
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* Revert VALUE
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*
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I=1
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DO WHILE ( I .LE. N-1 )
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IF( IPIV(I) .LT. 0 ) THEN
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A(I+1,I)=E(I)
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I=I+1
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ENDIF
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I=I+1
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END DO
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END IF
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END IF
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RETURN
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*
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* End of SSYCONV
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*
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END
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