dsyconv.f

Go to the documentation of this file.

*> \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' )
.NOT..AND..NOT.      IF( UPPER  LSAME( UPLO, 'l' ) ) THEN
         INFO = -1
.NOT..AND..NOT.      ELSE IF( CONVERT  LSAME( WAY, 'r' ) ) THEN
         INFO = -2
.LT.      ELSE IF( N0 ) THEN
         INFO = -3
.LT.      ELSE IF( LDAMAX( 1, N ) ) THEN
         INFO = -5
 
      END IF
.NE.      IF( INFO0 ) THEN
         CALL XERBLA( 'dsyconv', -INFO )
         RETURN
      END IF
*
*     Quick return if possible
*
.EQ.      IF( N0 )
     $   RETURN
*
      IF( UPPER ) THEN
*
*      A is UPPER
*
*      Convert A (A is upper)
*
*        Convert VALUE
*
         IF ( CONVERT ) THEN
            I=N
            E(1)=ZERO
.GT.            DO WHILE ( I  1 )
.LT.               IF( IPIV(I)  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
.GE.         DO WHILE ( I  1 )
.GT.            IF( IPIV(I)  0) THEN
               IP=IPIV(I)
.LT.               IF( I  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)
.LT.               IF( I  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
.LE.            DO WHILE ( I  N )
.GT.               IF( IPIV(I)  0 ) THEN
                  IP=IPIV(I)
.LT.                  IF( I  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
.LT.                 IF( I  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
.GT.            DO WHILE ( I  1 )
.LT.               IF( IPIV(I)  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
.LE.            DO WHILE ( I  N )
.LT..AND..LT.               IF( IN  IPIV(I)  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
.LE.         DO WHILE ( I  N )
.GT.            IF( IPIV(I)  0 ) THEN
               IP=IPIV(I)
.GT.               IF (I  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)
.GT.              IF (I  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
.GE.            DO WHILE ( I  1 )
.GT.               IF( IPIV(I)  0 ) THEN
                  IP=IPIV(I)
.GT.                  IF (I  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
.GT.                  IF (I  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
.LE.            DO WHILE ( I  N-1 )
.LT.               IF( IPIV(I)  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