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/*
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 * -- High Performance Computing Linpack Benchmark (HPL)
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 *    HPL - 2.0 - September 10, 2008
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 *    Antoine P. Petitet
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 *    University of Tennessee, Knoxville
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 *    Innovative Computing Laboratory
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 *    (C) Copyright 2000-2008 All Rights Reserved
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 *
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 * -- Copyright notice and Licensing terms:
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 *
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 * Redistribution  and  use in  source and binary forms, with or without
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 * modification, are  permitted provided  that the following  conditions
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 * are met:
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 *
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 * 1. Redistributions  of  source  code  must retain the above copyright
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 * notice, this list of conditions and the following disclaimer.
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 *
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 * 2. Redistributions in binary form must reproduce  the above copyright
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 * notice, this list of conditions,  and the following disclaimer in the
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 * documentation and/or other materials provided with the distribution.
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 *
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 * 3. All  advertising  materials  mentioning  features  or  use of this
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 * software must display the following acknowledgement:
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 * This  product  includes  software  developed  at  the  University  of
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 * Tennessee, Knoxville, Innovative Computing Laboratory.
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 *
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 * 4. The name of the  University,  the name of the  Laboratory,  or the
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 * names  of  its  contributors  may  not  be used to endorse or promote
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 * products  derived   from   this  software  without  specific  written
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 * permission.
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 *
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 * -- Disclaimer:
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 *
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 * THIS  SOFTWARE  IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,  INCLUDING,  BUT NOT
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 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY
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 * OR  CONTRIBUTORS  BE  LIABLE FOR ANY  DIRECT,  INDIRECT,  INCIDENTAL,
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 * SPECIAL,  EXEMPLARY,  OR  CONSEQUENTIAL DAMAGES  (INCLUDING,  BUT NOT
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA OR PROFITS; OR BUSINESS INTERRUPTION)  HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT,  STRICT LIABILITY,  OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 * ---------------------------------------------------------------------
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 */
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/*
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 * Include files
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 */
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#include "hpl.h"
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#ifdef STDC_HEADERS
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void HPL_pdpanllN
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(
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   HPL_T_panel *                    PANEL,
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   const int                        M,
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   const int                        N,
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   const int                        ICOFF,
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   double *                         WORK
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)
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#else
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void HPL_pdpanllN
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( PANEL, M, N, ICOFF, WORK )
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   HPL_T_panel *                    PANEL;
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   const int                        M;
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   const int                        N;
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   const int                        ICOFF;
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   double *                         WORK;
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#endif
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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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 * HPL_pdpanllN factorizes  a panel of columns that is a sub-array of a
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 * larger one-dimensional panel A  using the Left-looking variant of the
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 * usual one-dimensional algorithm.  The lower triangular N0-by-N0 upper
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 * block of the panel is stored in no-transpose form (i.e. just like the
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 * input matrix itself).
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 *
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 * Bi-directional  exchange  is  used  to  perform  the  swap::broadcast
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 * operations  at once  for one column in the panel.  This  results in a
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 * lower number of slightly larger  messages than usual.  On P processes
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 * and assuming bi-directional links,  the running time of this function
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 * can be approximated by (when N is equal to N0):
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 *
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 *    N0 * log_2( P ) * ( lat + ( 2*N0 + 4 ) / bdwth ) +
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 *    N0^2 * ( M - N0/3 ) * gam2-3
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 *
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 * where M is the local number of rows of  the panel, lat and bdwth  are
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 * the latency and bandwidth of the network for  double  precision  real
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 * words, and  gam2-3  is  an estimate of the  Level 2 and Level 3  BLAS
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 * rate of execution. The  recursive  algorithm  allows indeed to almost
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 * achieve  Level 3 BLAS  performance  in the panel factorization.  On a
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 * large  number of modern machines,  this  operation is however latency
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 * bound,  meaning  that its cost can  be estimated  by only the latency
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 * portion N0 * log_2(P) * lat.  Mono-directional links will double this
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 * communication cost.
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 *
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 * Note that  one  iteration of the the main loop is unrolled. The local
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 * computation of the absolute value max of the next column is performed
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 * just after its update by the current column. This allows to bring the
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 * current column only  once through  cache at each  step.  The  current
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 * implementation  does not perform  any blocking  for  this sequence of
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 * BLAS operations, however the design allows for plugging in an optimal
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 * (machine-specific) specialized  BLAS-like kernel.  This idea has been
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 * suggested to us by Fred Gustavson, IBM T.J. Watson Research Center.
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 *
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 * Arguments
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 * =========
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 *
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 * PANEL   (local input/output)          HPL_T_panel *
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 *         On entry,  PANEL  points to the data structure containing the
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 *         panel information.
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 *
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 * M       (local input)                 const int
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 *         On entry,  M specifies the local number of rows of sub(A).
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 *
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 * N       (local input)                 const int
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 *         On entry,  N specifies the local number of columns of sub(A).
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 *
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 * ICOFF   (global input)                const int
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 *         On entry, ICOFF specifies the row and column offset of sub(A)
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 *         in A.
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 *
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 * WORK    (local workspace)             double *
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 *         On entry, WORK  is a workarray of size at least 2*(4+2*N0).
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 *
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 * ---------------------------------------------------------------------
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 */
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/*
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 * .. Local Variables ..
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 */
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   double                     * A, * L1, * L1ptr;
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#ifdef HPL_CALL_VSIPL
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   vsip_mview_d               * Av0, * Av1, * Yv1, * Xv0, * Xv1;
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#endif
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   int                        Mm1, Nm1, curr, ii, iip1, jj, kk, lda,
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                              m=M, n0;
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/* ..
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 * .. Executable Statements ..
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 */
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#ifdef HPL_DETAILED_TIMING
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   HPL_ptimer( HPL_TIMING_PFACT );
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#endif
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   A    = PANEL->A;   lda = PANEL->lda;
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   L1   = PANEL->L1;  n0  = PANEL->jb;
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   curr = (int)( PANEL->grid->myrow == PANEL->prow );
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   Nm1 = N - 1; jj = ICOFF;
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   if( curr != 0 ) { ii = ICOFF; iip1 = ii+1; Mm1 = m-1; }
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   else            { ii = 0;     iip1 = ii;   Mm1 = m;   }
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#ifdef HPL_CALL_VSIPL
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/*
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 * Admit the blocks
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 */
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   (void) vsip_blockadmit_d( PANEL->Ablock,  VSIP_TRUE );
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   (void) vsip_blockadmit_d( PANEL->L1block, VSIP_TRUE );
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/*
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 * Create the matrix views
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 */
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   Av0 = vsip_mbind_d( PANEL->Ablock,  0, 1, lda,       lda, PANEL->pmat->nq );
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   Xv0 = vsip_mbind_d( PANEL->L1block, 0, 1, PANEL->jb, PANEL->jb, PANEL->jb );
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#endif
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/*
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 * Find local absolute value max in first column and initialize WORK[0:3]
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 */
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   HPL_dlocmax( PANEL, m, ii, jj, WORK );
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   while( Nm1 > 0 )
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   {
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/*
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 * Swap and broadcast the current row
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 */
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      HPL_pdmxswp(  PANEL, m, ii, jj, WORK );
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      HPL_dlocswpN( PANEL,    ii, jj, WORK );
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      L1ptr = Mptr( L1, ICOFF, jj+1, n0 ); kk = jj + 1 - ICOFF;
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      HPL_dtrsv( HplColumnMajor, HplLower, HplNoTrans, HplUnit, kk,
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                 Mptr( L1, ICOFF, ICOFF, n0 ), n0, L1ptr,  1 );
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/*
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 * Scale  current column by its absolute value max entry  -  Update  and
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 * find local  absolute value max  in next column (Only one pass through
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 * cache for each next column).  This sequence of operations could bene-
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 * fit from a specialized  blocked implementation.
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 */
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      if( WORK[0] != HPL_rzero )
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         HPL_dscal( Mm1, HPL_rone / WORK[0], Mptr( A, iip1, jj, lda ), 1 );
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#ifdef HPL_CALL_VSIPL
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/*
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 * Create the matrix subviews
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 */
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      Av1 = vsip_msubview_d( Av0, PANEL->ii+iip1, PANEL->jj+ICOFF, Mm1, kk );
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      Xv1 = vsip_msubview_d( Xv0, ICOFF,        jj+1,              kk,   1 );
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      Yv1 = vsip_msubview_d( Av0, PANEL->ii+iip1, PANEL->jj+jj+1,  Mm1,  1 );
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      vsip_gemp_d( -HPL_rone, Av1, VSIP_MAT_NTRANS, Xv1, VSIP_MAT_NTRANS,
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                   HPL_rone, Yv1 );
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/*
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 * Destroy the matrix subviews
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 */
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      (void) vsip_mdestroy_d( Yv1 );
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      (void) vsip_mdestroy_d( Xv1 );
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      (void) vsip_mdestroy_d( Av1 );
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#else
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      HPL_dgemv( HplColumnMajor, HplNoTrans, Mm1, kk,  -HPL_rone,
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                 Mptr( A, iip1, ICOFF, lda ), lda, L1ptr, 1,
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                 HPL_rone, Mptr( A, iip1, jj+1, lda ),  1 );
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#endif
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      HPL_dlocmax( PANEL, Mm1, iip1, jj+1, WORK );
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      if( curr != 0 )
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      {
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         HPL_dcopy( kk, L1ptr,  1, Mptr( A, ICOFF, jj+1, lda ), 1 );
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         ii = iip1; iip1++; m = Mm1; Mm1--;
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      }
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      Nm1--; jj++;
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   }
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/*
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 * Swap and broadcast last row - Scale last column by its absolute value
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 * max entry
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 */
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   HPL_pdmxswp(  PANEL, m, ii, jj, WORK );
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   HPL_dlocswpN( PANEL,    ii, jj, WORK );
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   if( WORK[0] != HPL_rzero )
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      HPL_dscal( Mm1, HPL_rone / WORK[0], Mptr( A, iip1, jj, lda ), 1 );
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#ifdef HPL_CALL_VSIPL
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/*
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 * Release the blocks
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 */
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   (void) vsip_blockrelease_d( vsip_mgetblock_d( Xv0 ), VSIP_TRUE );
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   (void) vsip_blockrelease_d( vsip_mgetblock_d( Av0 ), VSIP_TRUE );
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/*
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 * Destroy the matrix views
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 */
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   (void) vsip_mdestroy_d( Xv0 );
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   (void) vsip_mdestroy_d( Av0 );
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#endif
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#ifdef HPL_DETAILED_TIMING
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   HPL_ptimer( HPL_TIMING_PFACT );
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#endif
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/*
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 * End of HPL_pdpanllN
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 */
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}