*> \brief \b DGETRS
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at 
*            http://www.netlib.org/lapack/explore-html/ 
*
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*
*  Definition:
*  ===========
*
*       SUBROUTINE DGETRS( TRANS, N, NRHS, A, LDA, IPIV, B, LDB, INFO )
* 
*       .. Scalar Arguments ..
*       CHARACTER          TRANS
*       INTEGER            INFO, LDA, LDB, N, NRHS
*       ..
*       .. Array Arguments ..
*       INTEGER            IPIV( * )
*       DOUBLE PRECISION   A( LDA, * ), B( LDB, * )
*       ..
*  
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> DGETRS solves a system of linear equations
*>    A * X = B  or  A**T * X = B
*> with a general N-by-N matrix A using the LU factorization computed
*> by DGETRF.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] TRANS
*> \verbatim
*>          TRANS is CHARACTER*1
*>          Specifies the form of the system of equations:
*>          = 'N':  A * X = B  (No transpose)
*>          = 'T':  A**T* X = B  (Transpose)
*>          = 'C':  A**T* X = B  (Conjugate transpose = Transpose)
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          The order of the matrix A.  N >= 0.
*> \endverbatim
*>
*> \param[in] NRHS
*> \verbatim
*>          NRHS is INTEGER
*>          The number of right hand sides, i.e., the number of columns
*>          of the matrix B.  NRHS >= 0.
*> \endverbatim
*>
*> \param[in] A
*> \verbatim
*>          A is DOUBLE PRECISION array, dimension (LDA,N)
*>          The factors L and U from the factorization A = P*L*U
*>          as computed by DGETRF.
*> \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)
*>          The pivot indices from DGETRF; for 1<=i<=N, row i of the
*>          matrix was interchanged with row IPIV(i).
*> \endverbatim
*>
*> \param[in,out] B
*> \verbatim
*>          B is DOUBLE PRECISION array, dimension (LDB,NRHS)
*>          On entry, the right hand side matrix B.
*>          On exit, the solution matrix X.
*> \endverbatim
*>
*> \param[in] LDB
*> \verbatim
*>          LDB is INTEGER
*>          The leading dimension of the array B.  LDB >= max(1,N).
*> \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. 
*
*> \date November 2011
*
*> \ingroup doubleGEcomputational
*
*  =====================================================================
      SUBROUTINE GAL_DGETRS(TRANS,N,NRHS,A,LDA,IPIV,B,LDB,INFO)
*
*  -- LAPACK computational routine (version 3.4.0) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2011
*
*     .. Scalar Arguments ..
      CHARACTERTRANS
      INTEGER INFO,LDA,LDB,N,NRHS
*     ..
*     .. Array Arguments ..
      INTEGER IPIV(*)
      DOUBLE PRECISION A(LDA,*),B(LDB,*)
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION ONE
      PARAMETER (ONE=1.0D+0)
*     ..
*     .. Local Scalars ..
      LOGICAL NOTRAN
*     ..
*     .. External Functions ..
      LOGICAL GAL_LSAME
      EXTERNAL GAL_LSAME
*     ..
*     .. External Subroutines ..
      EXTERNAL GAL_DLASWP,GAL_DTRSM,GAL_XERBLA
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC MAX
*     ..
*     .. Executable Statements ..
*
*     Test the input parameters.
*
      INFO=0
      NOTRAN=GAL_LSAME(TRANS,'N')
      IF(.NOT.NOTRAN.AND..NOT.GAL_LSAME(TRANS,'T').AND..NOT.
     $GAL_LSAME(TRANS,'C'))THEN
      INFO=-1
      ELSE IF(N.LT.0)THEN
      INFO=-2
      ELSE IF(NRHS.LT.0)THEN
      INFO=-3
      ELSE IF(LDA.LT.MAX(1,N))THEN
      INFO=-5
      ELSE IF(LDB.LT.MAX(1,N))THEN
      INFO=-8
      END IF
      IF(INFO.NE.0)THEN
      CALL GAL_XERBLA('GAL_DGETRS',-INFO)
      RETURN
      END IF
*
*     Quick return if possible
*
      IF(N.EQ.0.OR.NRHS.EQ.0)
     $RETURN
*
      IF(NOTRAN)THEN
*
*        Solve A * X = B.
*
*        Apply row interchanges to the right hand sides.
*
      CALL GAL_DLASWP(NRHS,B,LDB,1,N,IPIV,1)
*
*        Solve L*X = B, overwriting B with X.
*
      CALL GAL_DTRSM('LEFT','LOWER','NOTRANSPOSE','UNIT',N,NRHS,
     $ONE,A,LDA,B,LDB)
*
*        Solve U*X = B, overwriting B with X.
*
      CALL GAL_DTRSM('LEFT','UPPER','NOTRANSPOSE','NON-UNIT',N,
     $NRHS,ONE,A,LDA,B,LDB)
      ELSE 
*
*        Solve A**T * X = B.
*
*        Solve U**T *X = B, overwriting B with X.
*
      CALL GAL_DTRSM('LEFT','UPPER','TRANSPOSE','NON-UNIT',N,NRHS,
     $ONE,A,LDA,B,LDB)
*
*        Solve L**T *X = B, overwriting B with X.
*
      CALL GAL_DTRSM('LEFT','LOWER','TRANSPOSE','UNIT',N,NRHS,ONE,
     $A,LDA,B,LDB)
*
*        Apply row interchanges to the solution vectors.
*
      CALL GAL_DLASWP(NRHS,B,LDB,1,N,IPIV,-1)
      END IF
*
      RETURN
*
*     End of DGETRS
*
      END 
