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      SUBROUTINE ZTRSM(SIDE,UPLO,TRANSA,DIAG,M,N,ALPHA,A,LDA,B,LDB)
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*     .. Scalar Arguments ..
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      DOUBLE COMPLEX ALPHA
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      INTEGER LDA,LDB,M,N
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      CHARACTER DIAG,SIDE,TRANSA,UPLO
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*     ..
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*     .. Array Arguments ..
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      DOUBLE COMPLEX A(LDA,*),B(LDB,*)
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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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*  ZTRSM  solves one of the matrix equations
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*
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*     op( A )*X = alpha*B,   or   X*op( A ) = alpha*B,
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*
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*  where alpha is a scalar, X and B are m by n matrices, A is a unit, or
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*  non-unit,  upper or lower triangular matrix  and  op( A )  is one  of
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*
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*     op( A ) = A   or   op( A ) = A'   or   op( A ) = conjg( A' ).
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*
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*  The matrix X is overwritten on B.
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*
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*  Arguments
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*  ==========
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*
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*  SIDE   - CHARACTER*1.
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*           On entry, SIDE specifies whether op( A ) appears on the left
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*           or right of X as follows:
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*
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*              SIDE = 'L' or 'l'   op( A )*X = alpha*B.
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*
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*              SIDE = 'R' or 'r'   X*op( A ) = alpha*B.
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*
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*           Unchanged on exit.
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*
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*  UPLO   - CHARACTER*1.
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*           On entry, UPLO specifies whether the matrix A is an upper or
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*           lower triangular matrix as follows:
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*
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*              UPLO = 'U' or 'u'   A is an upper triangular matrix.
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*
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*              UPLO = 'L' or 'l'   A is a lower triangular matrix.
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*
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*           Unchanged on exit.
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*
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*  TRANSA - CHARACTER*1.
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*           On entry, TRANSA specifies the form of op( A ) to be used in
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*           the matrix multiplication as follows:
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*
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*              TRANSA = 'N' or 'n'   op( A ) = A.
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*
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*              TRANSA = 'T' or 't'   op( A ) = A'.
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*
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*              TRANSA = 'C' or 'c'   op( A ) = conjg( A' ).
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*
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*           Unchanged on exit.
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*
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*  DIAG   - CHARACTER*1.
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*           On entry, DIAG specifies whether or not A is unit triangular
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*           as follows:
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*
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*              DIAG = 'U' or 'u'   A is assumed to be unit triangular.
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*
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*              DIAG = 'N' or 'n'   A is not assumed to be unit
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*                                  triangular.
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*
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*           Unchanged on exit.
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*
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*  M      - INTEGER.
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*           On entry, M specifies the number of rows of B. M must be at
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*           least zero.
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*           Unchanged on exit.
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*
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*  N      - INTEGER.
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*           On entry, N specifies the number of columns of B.  N must be
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*           at least zero.
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*           Unchanged on exit.
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*
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*  ALPHA  - COMPLEX*16      .
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*           On entry,  ALPHA specifies the scalar  alpha. When  alpha is
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*           zero then  A is not referenced and  B need not be set before
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*           entry.
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*           Unchanged on exit.
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*
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*  A      - COMPLEX*16       array of DIMENSION ( LDA, k ), where k is m
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*           when  SIDE = 'L' or 'l'  and is  n  when  SIDE = 'R' or 'r'.
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*           Before entry  with  UPLO = 'U' or 'u',  the  leading  k by k
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*           upper triangular part of the array  A must contain the upper
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*           triangular matrix  and the strictly lower triangular part of
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*           A is not referenced.
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*           Before entry  with  UPLO = 'L' or 'l',  the  leading  k by k
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*           lower triangular part of the array  A must contain the lower
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*           triangular matrix  and the strictly upper triangular part of
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*           A is not referenced.
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*           Note that when  DIAG = 'U' or 'u',  the diagonal elements of
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*           A  are not referenced either,  but are assumed to be  unity.
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*           Unchanged on exit.
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*
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*  LDA    - INTEGER.
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*           On entry, LDA specifies the first dimension of A as declared
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*           in the calling (sub) program.  When  SIDE = 'L' or 'l'  then
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*           LDA  must be at least  max( 1, m ),  when  SIDE = 'R' or 'r'
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*           then LDA must be at least max( 1, n ).
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*           Unchanged on exit.
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*
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*  B      - COMPLEX*16       array of DIMENSION ( LDB, n ).
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*           Before entry,  the leading  m by n part of the array  B must
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*           contain  the  right-hand  side  matrix  B,  and  on exit  is
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*           overwritten by the solution matrix  X.
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*
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*  LDB    - INTEGER.
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*           On entry, LDB specifies the first dimension of B as declared
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*           in  the  calling  (sub)  program.   LDB  must  be  at  least
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*           max( 1, m ).
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*           Unchanged on exit.
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*
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*
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*  Level 3 Blas routine.
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*
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*  -- Written on 8-February-1989.
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*     Jack Dongarra, Argonne National Laboratory.
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*     Iain Duff, AERE Harwell.
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*     Jeremy Du Croz, Numerical Algorithms Group Ltd.
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*     Sven Hammarling, Numerical Algorithms Group Ltd.
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*
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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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*     ..
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*     .. Intrinsic Functions ..
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      INTRINSIC DCONJG,MAX
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*     ..
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*     .. Local Scalars ..
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      DOUBLE COMPLEX TEMP
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      INTEGER I,INFO,J,K,NROWA
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      LOGICAL LSIDE,NOCONJ,NOUNIT,UPPER
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*     ..
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*     .. Parameters ..
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      DOUBLE COMPLEX ONE
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      PARAMETER (ONE= (1.0D+0,0.0D+0))
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      DOUBLE COMPLEX ZERO
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      PARAMETER (ZERO= (0.0D+0,0.0D+0))
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*     ..
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*
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*     Test the input parameters.
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*
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      LSIDE = LSAME(SIDE,'L')
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      IF (LSIDE) THEN
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          NROWA = M
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      ELSE
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          NROWA = N
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      END IF
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      NOCONJ = LSAME(TRANSA,'T')
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      NOUNIT = LSAME(DIAG,'N')
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      UPPER = LSAME(UPLO,'U')
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*
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      INFO = 0
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      IF ((.NOT.LSIDE) .AND. (.NOT.LSAME(SIDE,'R'))) THEN
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          INFO = 1
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      ELSE IF ((.NOT.UPPER) .AND. (.NOT.LSAME(UPLO,'L'))) THEN
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          INFO = 2
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      ELSE IF ((.NOT.LSAME(TRANSA,'N')) .AND.
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     +         (.NOT.LSAME(TRANSA,'T')) .AND.
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     +         (.NOT.LSAME(TRANSA,'C'))) THEN
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          INFO = 3
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      ELSE IF ((.NOT.LSAME(DIAG,'U')) .AND. (.NOT.LSAME(DIAG,'N'))) THEN
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          INFO = 4
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      ELSE IF (M.LT.0) THEN
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          INFO = 5
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      ELSE IF (N.LT.0) THEN
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          INFO = 6
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      ELSE IF (LDA.LT.MAX(1,NROWA)) THEN
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          INFO = 9
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      ELSE IF (LDB.LT.MAX(1,M)) THEN
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          INFO = 11
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      END IF
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      IF (INFO.NE.0) THEN
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          CALL XERBLA('ZTRSM ',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 (M.EQ.0 .OR. N.EQ.0) RETURN
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*
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*     And when  alpha.eq.zero.
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*
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      IF (ALPHA.EQ.ZERO) THEN
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          DO 20 J = 1,N
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              DO 10 I = 1,M
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                  B(I,J) = ZERO
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   10         CONTINUE
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   20     CONTINUE
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          RETURN
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      END IF
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*
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*     Start the operations.
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*
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      IF (LSIDE) THEN
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          IF (LSAME(TRANSA,'N')) THEN
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*
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*           Form  B := alpha*inv( A )*B.
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*
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              IF (UPPER) THEN
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                  DO 60 J = 1,N
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                      IF (ALPHA.NE.ONE) THEN
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                          DO 30 I = 1,M
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                              B(I,J) = ALPHA*B(I,J)
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   30                     CONTINUE
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                      END IF
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                      DO 50 K = M,1,-1
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                          IF (B(K,J).NE.ZERO) THEN
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                              IF (NOUNIT) B(K,J) = B(K,J)/A(K,K)
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                              DO 40 I = 1,K - 1
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                                  B(I,J) = B(I,J) - B(K,J)*A(I,K)
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   40                         CONTINUE
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                          END IF
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   50                 CONTINUE
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   60             CONTINUE
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              ELSE
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                  DO 100 J = 1,N
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                      IF (ALPHA.NE.ONE) THEN
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                          DO 70 I = 1,M
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                              B(I,J) = ALPHA*B(I,J)
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   70                     CONTINUE
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                      END IF
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                      DO 90 K = 1,M
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                          IF (B(K,J).NE.ZERO) THEN
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                              IF (NOUNIT) B(K,J) = B(K,J)/A(K,K)
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                              DO 80 I = K + 1,M
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                                  B(I,J) = B(I,J) - B(K,J)*A(I,K)
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   80                         CONTINUE
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                          END IF
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   90                 CONTINUE
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  100             CONTINUE
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              END IF
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          ELSE
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*
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*           Form  B := alpha*inv( A' )*B
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*           or    B := alpha*inv( conjg( A' ) )*B.
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*
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              IF (UPPER) THEN
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                  DO 140 J = 1,N
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                      DO 130 I = 1,M
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                          TEMP = ALPHA*B(I,J)
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                          IF (NOCONJ) THEN
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                              DO 110 K = 1,I - 1
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                                  TEMP = TEMP - A(K,I)*B(K,J)
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  110                         CONTINUE
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                              IF (NOUNIT) TEMP = TEMP/A(I,I)
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                          ELSE
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                              DO 120 K = 1,I - 1
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                                  TEMP = TEMP - DCONJG(A(K,I))*B(K,J)
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  120                         CONTINUE
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                              IF (NOUNIT) TEMP = TEMP/DCONJG(A(I,I))
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                          END IF
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                          B(I,J) = TEMP
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  130                 CONTINUE
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  140             CONTINUE
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              ELSE
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                  DO 180 J = 1,N
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                      DO 170 I = M,1,-1
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                          TEMP = ALPHA*B(I,J)
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                          IF (NOCONJ) THEN
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                              DO 150 K = I + 1,M
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                                  TEMP = TEMP - A(K,I)*B(K,J)
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  150                         CONTINUE
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                              IF (NOUNIT) TEMP = TEMP/A(I,I)
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                          ELSE
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                              DO 160 K = I + 1,M
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                                  TEMP = TEMP - DCONJG(A(K,I))*B(K,J)
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  160                         CONTINUE
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                              IF (NOUNIT) TEMP = TEMP/DCONJG(A(I,I))
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                          END IF
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                          B(I,J) = TEMP
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  170                 CONTINUE
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  180             CONTINUE
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              END IF
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          END IF
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      ELSE
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          IF (LSAME(TRANSA,'N')) THEN
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*
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*           Form  B := alpha*B*inv( A ).
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*
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              IF (UPPER) THEN
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                  DO 230 J = 1,N
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                      IF (ALPHA.NE.ONE) THEN
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                          DO 190 I = 1,M
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                              B(I,J) = ALPHA*B(I,J)
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  190                     CONTINUE
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                      END IF
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                      DO 210 K = 1,J - 1
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                          IF (A(K,J).NE.ZERO) THEN
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                              DO 200 I = 1,M
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                                  B(I,J) = B(I,J) - A(K,J)*B(I,K)
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  200                         CONTINUE
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                          END IF
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  210                 CONTINUE
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                      IF (NOUNIT) THEN
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                          TEMP = ONE/A(J,J)
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                          DO 220 I = 1,M
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                              B(I,J) = TEMP*B(I,J)
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  220                     CONTINUE
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                      END IF
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  230             CONTINUE
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              ELSE
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                  DO 280 J = N,1,-1
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                      IF (ALPHA.NE.ONE) THEN
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                          DO 240 I = 1,M
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                              B(I,J) = ALPHA*B(I,J)
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  240                     CONTINUE
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                      END IF
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                      DO 260 K = J + 1,N
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                          IF (A(K,J).NE.ZERO) THEN
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                              DO 250 I = 1,M
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                                  B(I,J) = B(I,J) - A(K,J)*B(I,K)
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  250                         CONTINUE
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                          END IF
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  260                 CONTINUE
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                      IF (NOUNIT) THEN
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                          TEMP = ONE/A(J,J)
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                          DO 270 I = 1,M
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                              B(I,J) = TEMP*B(I,J)
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  270                     CONTINUE
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                      END IF
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  280             CONTINUE
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              END IF
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          ELSE
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*
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*           Form  B := alpha*B*inv( A' )
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*           or    B := alpha*B*inv( conjg( A' ) ).
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*
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              IF (UPPER) THEN
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                  DO 330 K = N,1,-1
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                      IF (NOUNIT) THEN
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                          IF (NOCONJ) THEN
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                              TEMP = ONE/A(K,K)
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                          ELSE
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                              TEMP = ONE/DCONJG(A(K,K))
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                          END IF
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                          DO 290 I = 1,M
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                              B(I,K) = TEMP*B(I,K)
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  290                     CONTINUE
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                      END IF
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                      DO 310 J = 1,K - 1
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                          IF (A(J,K).NE.ZERO) THEN
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                              IF (NOCONJ) THEN
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                                  TEMP = A(J,K)
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                              ELSE
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                                  TEMP = DCONJG(A(J,K))
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                              END IF
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                              DO 300 I = 1,M
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                                  B(I,J) = B(I,J) - TEMP*B(I,K)
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  300                         CONTINUE
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                          END IF
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  310                 CONTINUE
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                      IF (ALPHA.NE.ONE) THEN
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                          DO 320 I = 1,M
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                              B(I,K) = ALPHA*B(I,K)
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  320                     CONTINUE
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                      END IF
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  330             CONTINUE
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              ELSE
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                  DO 380 K = 1,N
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                      IF (NOUNIT) THEN
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                          IF (NOCONJ) THEN
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                              TEMP = ONE/A(K,K)
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                          ELSE
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                              TEMP = ONE/DCONJG(A(K,K))
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                          END IF
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                          DO 340 I = 1,M
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                              B(I,K) = TEMP*B(I,K)
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  340                     CONTINUE
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                      END IF
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                      DO 360 J = K + 1,N
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                          IF (A(J,K).NE.ZERO) THEN
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                              IF (NOCONJ) THEN
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                                  TEMP = A(J,K)
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                              ELSE
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                                  TEMP = DCONJG(A(J,K))
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                              END IF
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                              DO 350 I = 1,M
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                                  B(I,J) = B(I,J) - TEMP*B(I,K)
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  350                         CONTINUE
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                          END IF
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  360                 CONTINUE
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                      IF (ALPHA.NE.ONE) THEN
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                          DO 370 I = 1,M
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                              B(I,K) = ALPHA*B(I,K)
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  370                     CONTINUE
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                      END IF
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  380             CONTINUE
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              END IF
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          END IF
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      END IF
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*
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      RETURN
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*
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*     End of ZTRSM .
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*
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      END