OpenBLAS/lapack-netlib/SRC/ssb2st_kernels.f

*> \brief \b SSB2ST_KERNELS
*
*  @generated from zhb2st_kernels.f, fortran z -> s, Wed Dec  7 08:22:40 2016
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
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*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ssb2st_kernels.f">
*> [TXT]</a>
*> \endhtmlonly
*
*  Definition:
*  ===========
*
*       SUBROUTINE  SSB2ST_KERNELS( UPLO, WANTZ, TTYPE,
*                                   ST, ED, SWEEP, N, NB, IB,
*                                   A, LDA, V, TAU, LDVT, WORK)
*
*       IMPLICIT NONE
*
*       .. Scalar Arguments ..
*       CHARACTER          UPLO
*       LOGICAL            WANTZ
*       INTEGER            TTYPE, ST, ED, SWEEP, N, NB, IB, LDA, LDVT
*       ..
*       .. Array Arguments ..
*       REAL               A( LDA, * ), V( * ),
*                          TAU( * ), WORK( * )
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> SSB2ST_KERNELS is an internal routine used by the SSYTRD_SB2ST
*> subroutine.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] UPLO
*> \verbatim
*>          UPLO is CHARACTER*1
*> \endverbatim
*>
*> \param[in] WANTZ
*> \verbatim
*>          WANTZ is LOGICAL which indicate if Eigenvalue are requested or both
*>          Eigenvalue/Eigenvectors.
*> \endverbatim
*>
*> \param[in] TTYPE
*> \verbatim
*>          TTYPE is INTEGER
*> \endverbatim
*>
*> \param[in] ST
*> \verbatim
*>          ST is INTEGER
*>          internal parameter for indices.
*> \endverbatim
*>
*> \param[in] ED
*> \verbatim
*>          ED is INTEGER
*>          internal parameter for indices.
*> \endverbatim
*>
*> \param[in] SWEEP
*> \verbatim
*>          SWEEP is INTEGER
*>          internal parameter for indices.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER. The order of the matrix A.
*> \endverbatim
*>
*> \param[in] NB
*> \verbatim
*>          NB is INTEGER. The size of the band.
*> \endverbatim
*>
*> \param[in] IB
*> \verbatim
*>          IB is INTEGER.
*> \endverbatim
*>
*> \param[in, out] A
*> \verbatim
*>          A is REAL array. A pointer to the matrix A.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*>          LDA is INTEGER. The leading dimension of the matrix A.
*> \endverbatim
*>
*> \param[out] V
*> \verbatim
*>          V is REAL array, dimension 2*n if eigenvalues only are
*>          requested or to be queried for vectors.
*> \endverbatim
*>
*> \param[out] TAU
*> \verbatim
*>          TAU is REAL array, dimension (2*n).
*>          The scalar factors of the Householder reflectors are stored
*>          in this array.
*> \endverbatim
*>
*> \param[in] LDVT
*> \verbatim
*>          LDVT is INTEGER.
*> \endverbatim
*>
*> \param[out] WORK
*> \verbatim
*>          WORK is REAL array. Workspace of size nb.
*> \endverbatim
*>
*>
*> \par Further Details:
*  =====================
*>
*> \verbatim
*>
*>  Implemented by Azzam Haidar.
*>
*>  All details are available on technical report, SC11, SC13 papers.
*>
*>  Azzam Haidar, Hatem Ltaief, and Jack Dongarra.
*>  Parallel reduction to condensed forms for symmetric eigenvalue problems
*>  using aggregated fine-grained and memory-aware kernels. In Proceedings
*>  of 2011 International Conference for High Performance Computing,
*>  Networking, Storage and Analysis (SC '11), New York, NY, USA,
*>  Article 8 , 11 pages.
*>  http://doi.acm.org/10.1145/2063384.2063394
*>
*>  A. Haidar, J. Kurzak, P. Luszczek, 2013.
*>  An improved parallel singular value algorithm and its implementation
*>  for multicore hardware, In Proceedings of 2013 International Conference
*>  for High Performance Computing, Networking, Storage and Analysis (SC '13).
*>  Denver, Colorado, USA, 2013.
*>  Article 90, 12 pages.
*>  http://doi.acm.org/10.1145/2503210.2503292
*>
*>  A. Haidar, R. Solca, S. Tomov, T. Schulthess and J. Dongarra.
*>  A novel hybrid CPU-GPU generalized eigensolver for electronic structure
*>  calculations based on fine-grained memory aware tasks.
*>  International Journal of High Performance Computing Applications.
*>  Volume 28 Issue 2, Pages 196-209, May 2014.
*>  http://hpc.sagepub.com/content/28/2/196
*>
*> \endverbatim
*>
*  =====================================================================
      SUBROUTINE  SSB2ST_KERNELS( UPLO, WANTZ, TTYPE,
     $                            ST, ED, SWEEP, N, NB, IB,
     $                            A, LDA, V, TAU, LDVT, WORK)
*
      IMPLICIT NONE
*
*  -- 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
      LOGICAL            WANTZ
      INTEGER            TTYPE, ST, ED, SWEEP, N, NB, IB, LDA, LDVT
*     ..
*     .. Array Arguments ..
      REAL               A( LDA, * ), V( * ),
     $                   TAU( * ), WORK( * )
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ZERO, ONE
      PARAMETER          ( ZERO = 0.0E+0,
     $                   ONE = 1.0E+0 )
*     ..
*     .. Local Scalars ..
      LOGICAL            UPPER
      INTEGER            I, J1, J2, LM, LN, VPOS, TAUPOS,
     $                   DPOS, OFDPOS, AJETER
      REAL               CTMP
*     ..
*     .. External Subroutines ..
      EXTERNAL           SLARFG, SLARFX, SLARFY
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          MOD
*     .. External Functions ..
      LOGICAL            LSAME
      EXTERNAL           LSAME
*     ..
*     ..
*     .. Executable Statements ..
*
      AJETER = IB + LDVT
      UPPER = LSAME( UPLO, 'U' )

      IF( UPPER ) THEN
          DPOS    = 2 * NB + 1
          OFDPOS  = 2 * NB
      ELSE
          DPOS    = 1
          OFDPOS  = 2
      ENDIF

*
*     Upper case
*
      IF( UPPER ) THEN
*
          IF( WANTZ ) THEN
              VPOS   = MOD( SWEEP-1, 2 ) * N + ST
              TAUPOS = MOD( SWEEP-1, 2 ) * N + ST
          ELSE
              VPOS   = MOD( SWEEP-1, 2 ) * N + ST
              TAUPOS = MOD( SWEEP-1, 2 ) * N + ST
          ENDIF
*
          IF( TTYPE.EQ.1 ) THEN
              LM = ED - ST + 1
*
              V( VPOS ) = ONE
              DO 10 I = 1, LM-1
                  V( VPOS+I )         = ( A( OFDPOS-I, ST+I ) )
                  A( OFDPOS-I, ST+I ) = ZERO
   10         CONTINUE
              CTMP = ( A( OFDPOS, ST ) )
              CALL SLARFG( LM, CTMP, V( VPOS+1 ), 1,
     $                                       TAU( TAUPOS ) )
              A( OFDPOS, ST ) = CTMP
*
              LM = ED - ST + 1
              CALL SLARFY( UPLO, LM, V( VPOS ), 1,
     $                     ( TAU( TAUPOS ) ),
     $                     A( DPOS, ST ), LDA-1, WORK)
          ENDIF
*
          IF( TTYPE.EQ.3 ) THEN
*
              LM = ED - ST + 1
              CALL SLARFY( UPLO, LM, V( VPOS ), 1,
     $                     ( TAU( TAUPOS ) ),
     $                     A( DPOS, ST ), LDA-1, WORK)
          ENDIF
*
          IF( TTYPE.EQ.2 ) THEN
              J1 = ED+1
              J2 = MIN( ED+NB, N )
              LN = ED-ST+1
              LM = J2-J1+1
              IF( LM.GT.0) THEN
                  CALL SLARFX( 'Left', LN, LM, V( VPOS ),
     $                         ( TAU( TAUPOS ) ),
     $                         A( DPOS-NB, J1 ), LDA-1, WORK)
*
                  IF( WANTZ ) THEN
                      VPOS   = MOD( SWEEP-1, 2 ) * N + J1
                      TAUPOS = MOD( SWEEP-1, 2 ) * N + J1
                  ELSE
                      VPOS   = MOD( SWEEP-1, 2 ) * N + J1
                      TAUPOS = MOD( SWEEP-1, 2 ) * N + J1
                  ENDIF
*
                  V( VPOS ) = ONE
                  DO 30 I = 1, LM-1
                      V( VPOS+I )          =
     $                                    ( A( DPOS-NB-I, J1+I ) )
                      A( DPOS-NB-I, J1+I ) = ZERO
   30             CONTINUE
                  CTMP = ( A( DPOS-NB, J1 ) )
                  CALL SLARFG( LM, CTMP, V( VPOS+1 ), 1, TAU( TAUPOS ) )
                  A( DPOS-NB, J1 ) = CTMP
*
                  CALL SLARFX( 'Right', LN-1, LM, V( VPOS ),
     $                         TAU( TAUPOS ),
     $                         A( DPOS-NB+1, J1 ), LDA-1, WORK)
              ENDIF
          ENDIF
*
*     Lower case
*
      ELSE
*
          IF( WANTZ ) THEN
              VPOS   = MOD( SWEEP-1, 2 ) * N + ST
              TAUPOS = MOD( SWEEP-1, 2 ) * N + ST
          ELSE
              VPOS   = MOD( SWEEP-1, 2 ) * N + ST
              TAUPOS = MOD( SWEEP-1, 2 ) * N + ST
          ENDIF
*
          IF( TTYPE.EQ.1 ) THEN
              LM = ED - ST + 1
*
              V( VPOS ) = ONE
              DO 20 I = 1, LM-1
                  V( VPOS+I )         = A( OFDPOS+I, ST-1 )
                  A( OFDPOS+I, ST-1 ) = ZERO
   20         CONTINUE
              CALL SLARFG( LM, A( OFDPOS, ST-1 ), V( VPOS+1 ), 1,
     $                                       TAU( TAUPOS ) )
*
              LM = ED - ST + 1
*
              CALL SLARFY( UPLO, LM, V( VPOS ), 1,
     $                     ( TAU( TAUPOS ) ),
     $                     A( DPOS, ST ), LDA-1, WORK)

          ENDIF
*
          IF( TTYPE.EQ.3 ) THEN
              LM = ED - ST + 1
*
              CALL SLARFY( UPLO, LM, V( VPOS ), 1,
     $                     ( TAU( TAUPOS ) ),
     $                     A( DPOS, ST ), LDA-1, WORK)

          ENDIF
*
          IF( TTYPE.EQ.2 ) THEN
              J1 = ED+1
              J2 = MIN( ED+NB, N )
              LN = ED-ST+1
              LM = J2-J1+1
*
              IF( LM.GT.0) THEN
                  CALL SLARFX( 'Right', LM, LN, V( VPOS ),
     $                         TAU( TAUPOS ), A( DPOS+NB, ST ),
     $                         LDA-1, WORK)
*
                  IF( WANTZ ) THEN
                      VPOS   = MOD( SWEEP-1, 2 ) * N + J1
                      TAUPOS = MOD( SWEEP-1, 2 ) * N + J1
                  ELSE
                      VPOS   = MOD( SWEEP-1, 2 ) * N + J1
                      TAUPOS = MOD( SWEEP-1, 2 ) * N + J1
                  ENDIF
*
                  V( VPOS ) = ONE
                  DO 40 I = 1, LM-1
                      V( VPOS+I )        = A( DPOS+NB+I, ST )
                      A( DPOS+NB+I, ST ) = ZERO
   40             CONTINUE
                  CALL SLARFG( LM, A( DPOS+NB, ST ), V( VPOS+1 ), 1,
     $                                        TAU( TAUPOS ) )
*
                  CALL SLARFX( 'Left', LM, LN-1, V( VPOS ),
     $                         ( TAU( TAUPOS ) ),
     $                         A( DPOS+NB-1, ST+1 ), LDA-1, WORK)

              ENDIF
          ENDIF
      ENDIF
*
      RETURN
*
*     End of SSB2ST_KERNELS
*
      END