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      SUBROUTINE ZPOTF2F( UPLO, N, A, LDA, INFO )
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*
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*  -- LAPACK routine (version 3.0) --
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*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
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*     Courant Institute, Argonne National Lab, and Rice University
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*     September 30, 1994
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*
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*     .. Scalar Arguments ..
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      CHARACTER          UPLO
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      INTEGER            INFO, LDA, N
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*     ..
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*     .. Array Arguments ..
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      COMPLEX*16         A( LDA, * )
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*     ..
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*
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*  Purpose
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*  =======
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*
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*  ZPOTF2 computes the Cholesky factorization of a complex Hermitian
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*  positive definite matrix A.
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*
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*  The factorization has the form
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*     A = U' * U ,  if UPLO = 'U', or
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*     A = L  * L',  if UPLO = 'L',
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*  where U is an upper triangular matrix and L is lower triangular.
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*
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*  This is the unblocked version of the algorithm, calling Level 2 BLAS.
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*
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*  Arguments
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*  =========
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*
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*  UPLO    (input) CHARACTER*1
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*          Specifies whether the upper or lower triangular part of the
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*          Hermitian matrix A is stored.
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*          = 'U':  Upper triangular
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*          = 'L':  Lower triangular
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*
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*  N       (input) INTEGER
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*          The order of the matrix A.  N >= 0.
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*
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*  A       (input/output) COMPLEX*16 array, dimension (LDA,N)
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*          On entry, the Hermitian matrix A.  If UPLO = 'U', the leading
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*          n by n upper triangular part of A contains the upper
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*          triangular part of the matrix A, and the strictly lower
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*          triangular part of A is not referenced.  If UPLO = 'L', the
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*          leading n by n lower triangular part of A contains the lower
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*          triangular part of the matrix A, and the strictly upper
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*          triangular part of A is not referenced.
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*
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*          On exit, if INFO = 0, the factor U or L from the Cholesky
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*          factorization A = U'*U  or A = L*L'.
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*
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*  LDA     (input) INTEGER
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*          The leading dimension of the array A.  LDA >= max(1,N).
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*
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*  INFO    (output) INTEGER
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*          = 0: successful exit
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*          < 0: if INFO = -k, the k-th argument had an illegal value
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*          > 0: if INFO = k, the leading minor of order k is not
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*               positive definite, and the factorization could not be
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*               completed.
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*
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*  =====================================================================
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*
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*     .. Parameters ..
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      DOUBLE PRECISION   ONE, ZERO
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      PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 )
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      COMPLEX*16         CONE
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      PARAMETER          ( CONE = ( 1.0D+0, 0.0D+0 ) )
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*     ..
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*     .. Local Scalars ..
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      LOGICAL            UPPER
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      INTEGER            J
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      DOUBLE PRECISION   AJJ
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*     ..
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*     .. External Functions ..
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      LOGICAL            LSAME
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      COMPLEX*16         ZDOTC
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      EXTERNAL           LSAME, ZDOTC
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*     ..
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*     .. External Subroutines ..
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      EXTERNAL           XERBLA, ZDSCAL, ZGEMV, ZLACGV
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*     ..
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*     .. Intrinsic Functions ..
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      INTRINSIC          DBLE, MAX, SQRT
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*     ..
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*     .. Executable Statements ..
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*
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*     Test the input parameters.
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*
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      INFO = 0
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      UPPER = LSAME( UPLO, 'U' )
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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( N.LT.0 ) THEN
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         INFO = -2
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      ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
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         INFO = -4
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      END IF
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      IF( INFO.NE.0 ) THEN
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         CALL XERBLA( 'ZPOTF2', -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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*        Compute the Cholesky factorization A = U'*U.
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*
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         DO 10 J = 1, N
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*
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*           Compute U(J,J) and test for non-positive-definiteness.
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*
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            AJJ = DBLE( A( J, J ) ) - ZDOTC( J-1, A( 1, J ), 1,
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     $            A( 1, J ), 1 )
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            IF( AJJ.LE.ZERO ) THEN
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               A( J, J ) = AJJ
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               GO TO 30
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            END IF
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            AJJ = SQRT( AJJ )
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            A( J, J ) = AJJ
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*
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*           Compute elements J+1:N of row J.
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*
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            IF( J.LT.N ) THEN
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               CALL ZLACGV( J-1, A( 1, J ), 1 )
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               CALL ZGEMV( 'Transpose', J-1, N-J, -CONE, A( 1, J+1 ),
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     $                     LDA, A( 1, J ), 1, CONE, A( J, J+1 ), LDA )
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               CALL ZLACGV( J-1, A( 1, J ), 1 )
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               CALL ZDSCAL( N-J, ONE / AJJ, A( J, J+1 ), LDA )
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            END IF
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   10    CONTINUE
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      ELSE
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*
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*        Compute the Cholesky factorization A = L*L'.
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*
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         DO 20 J = 1, N
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*
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*           Compute L(J,J) and test for non-positive-definiteness.
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*
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            AJJ = DBLE( A( J, J ) ) - ZDOTC( J-1, A( J, 1 ), LDA,
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     $            A( J, 1 ), LDA )
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            IF( AJJ.LE.ZERO ) THEN
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               A( J, J ) = AJJ
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               GO TO 30
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            END IF
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            AJJ = SQRT( AJJ )
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            A( J, J ) = AJJ
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*
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*           Compute elements J+1:N of column J.
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*
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            IF( J.LT.N ) THEN
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               CALL ZLACGV( J-1, A( J, 1 ), LDA )
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               CALL ZGEMV( 'No transpose', N-J, J-1, -CONE, A( J+1, 1 ),
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     $                     LDA, A( J, 1 ), LDA, CONE, A( J+1, J ), 1 )
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               CALL ZLACGV( J-1, A( J, 1 ), LDA )
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               CALL ZDSCAL( N-J, ONE / AJJ, A( J+1, J ), 1 )
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            END IF
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   20    CONTINUE
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      END IF
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      GO TO 40
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*
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   30 CONTINUE
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      INFO = J
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*
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   40 CONTINUE
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      RETURN
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*
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*     End of ZPOTF2
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*
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      END