text: /* 
   * -- High Performance Computing Linpack Benchmark (HPL)                
   *    HPL - 2.2 - February 24, 2016                          
   *    Antoine P. Petitet                                                
   *    University of Tennessee, Knoxville                                
   *    Innovative Computing Laboratory                                 
   *    (C) Copyright 2000-2008 All Rights Reserved                       
   *                                                                      
   * -- Copyright notice and Licensing terms:                             
   *                                                                      
   * Redistribution  and  use in  source and binary forms, with or without
   * modification, are  permitted provided  that the following  conditions
   * are met:                                                             
   *                                                                      
   * 1. Redistributions  of  source  code  must retain the above copyright
   * notice, this list of conditions and the following disclaimer.        
   *                                                                      
   * 2. Redistributions in binary form must reproduce  the above copyright
   * notice, this list of conditions,  and the following disclaimer in the
   * documentation and/or other materials provided with the distribution. 
   *                                                                      
   * 3. All  advertising  materials  mentioning  features  or  use of this
   * software must display the following acknowledgement:                 
   * This  product  includes  software  developed  at  the  University  of
   * Tennessee, Knoxville, Innovative Computing Laboratory.             
   *                                                                      
   * 4. The name of the  University,  the name of the  Laboratory,  or the
   * names  of  its  contributors  may  not  be used to endorse or promote
   * products  derived   from   this  software  without  specific  written
   * permission.                                                          
   *                                                                      
   * -- Disclaimer:                                                       
   *                                                                      
   * THIS  SOFTWARE  IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,  INCLUDING,  BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY
   * OR  CONTRIBUTORS  BE  LIABLE FOR ANY  DIRECT,  INDIRECT,  INCIDENTAL,
   * SPECIAL,  EXEMPLARY,  OR  CONSEQUENTIAL DAMAGES  (INCLUDING,  BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA OR PROFITS; OR BUSINESS INTERRUPTION)  HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT,  STRICT LIABILITY,  OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
   * ---------------------------------------------------------------------
   */ 
  /*
   * Include files
   */
  #include "hpl.h"
  
  #ifdef STDC_HEADERS
  double HPL_pdlange
  (
     const HPL_T_grid *               GRID,
     const HPL_T_NORM                 NORM,
     const int                        M,
     const int                        N,
     const int                        NB,
     const double *                   A,
     const int                        LDA
  )
  #else
  double HPL_pdlange
  ( GRID, NORM, M, N, NB, A, LDA )
     const HPL_T_grid *               GRID;
     const HPL_T_NORM                 NORM;
     const int                        M;
     const int                        N;
     const int                        NB;
     const double *                   A;
     const int                        LDA;
  #endif
  {
  /* 
   * Purpose
   * =======
   *
   * HPL_pdlange returns  the value of the one norm,  or the infinity norm,
   * or the element of largest absolute value of a distributed matrix A:  
   *  
   *  
   *    max(abs(A(i,j))) when NORM = HPL_NORM_A,                          
   *    norm1(A),        when NORM = HPL_NORM_1,                          
   *    normI(A),        when NORM = HPL_NORM_I,                          
   *  
   * where norm1 denotes the one norm of a matrix (maximum column sum) and
   * normI denotes  the infinity norm of a matrix (maximum row sum).  Note
   * that max(abs(A(i,j))) is not a matrix norm.
   *
   * Arguments
   * =========
   *
   * GRID    (local input)                 const HPL_T_grid *
   *         On entry,  GRID  points  to the data structure containing the
   *         process grid information.
   *
   * NORM    (global input)                const HPL_T_NORM
   *         On entry,  NORM  specifies  the  value to be returned by this
   *         function as described above.
   *
   * M       (global input)                const int
   *         On entry,  M  specifies  the number  of rows of the matrix A.
   *         M must be at least zero.
   *
   * N       (global input)                const int
   *         On entry,  N specifies the number of columns of the matrix A.
   *         N must be at least zero.
   *
   * NB      (global input)                const int
   *         On entry,  NB specifies the blocking factor used to partition
   *         and distribute the matrix. NB must be larger than one.
   *
   * A       (local input)                 const double *
   *         On entry,  A  points to an array of dimension  (LDA,LocQ(N)),
   *         that contains the local pieces of the distributed matrix A.
   *
   * LDA     (local input)                 const int
   *         On entry, LDA specifies the leading dimension of the array A.
   *         LDA must be at least max(1,LocP(M)).
   *
   * ---------------------------------------------------------------------
   */ 
  /*
   * .. Local Variables ..
   */
     double                     s, v0=HPL_rzero, * work = NULL;
     MPI_Comm                   Acomm, Ccomm, Rcomm;
     int                        ii, jj, mp, mycol, myrow, npcol, nprow,
                                nq;
  /* ..
   * .. Executable Statements ..
   */
     (void) HPL_grid_info( GRID, &nprow, &npcol, &myrow, &mycol );
     Rcomm = GRID->row_comm; Ccomm = GRID->col_comm;
     Acomm = GRID->all_comm;
  
     Mnumroc( mp, M, NB, NB, myrow, 0, nprow );
     Mnumroc( nq, N, NB, NB, mycol, 0, npcol );
  
     if( Mmin( M, N ) == 0 ) { return( v0 ); }
     else if( NORM == HPL_NORM_A )
     {
  /*
   * max( abs( A ) )
   */
        if( ( nq > 0 ) && ( mp > 0 ) )
        {
           for( jj = 0; jj < nq; jj++ )
           {
              for( ii = 0; ii < mp; ii++ )
              { v0 = Mmax( v0, Mabs( *A ) ); A++; }
              A += LDA - mp;
           }
        }
        (void) HPL_reduce( (void *)(&v0), 1, HPL_DOUBLE, HPL_max, 0,
                           Acomm );
     }
     else if( NORM == HPL_NORM_1 )
     {
  /*
   * Find norm_1( A ).
   */
        if( nq > 0 )
        {
           work = (double*)malloc( (size_t)(nq) * sizeof( double ) );
           if( work == NULL )
           { HPL_pabort( __LINE__, "HPL_pdlange", "Memory allocation failed" ); }
  
           for( jj = 0; jj < nq; jj++ )
           {
              s = HPL_rzero;
              for( ii = 0; ii < mp; ii++ ) { s += Mabs( *A ); A++; }
              work[jj] = s; A += LDA - mp;
           }
  /*
   * Find sum of global matrix columns, store on row 0 of process grid
   */
           (void) HPL_reduce( (void *)(work), nq, HPL_DOUBLE, HPL_sum,
                              0, Ccomm );
  /*
   * Find maximum sum of columns for 1-norm
   */
           if( myrow == 0 )
           { v0 = work[HPL_idamax( nq, work, 1 )]; v0 = Mabs( v0 ); }
           if( work ) free( work );
        }
  /*
   * Find max in row 0, store result in process (0,0)
   */
        if( myrow == 0 )
           (void) HPL_reduce( (void *)(&v0), 1, HPL_DOUBLE, HPL_max, 0,
                              Rcomm );
     }
     else if( NORM == HPL_NORM_I )
     {
  /*
   * Find norm_inf( A )
   */
        if( mp > 0 )
        {
           work = (double*)malloc( (size_t)(mp) * sizeof( double ) );
           if( work == NULL )
           { HPL_pabort( __LINE__, "HPL_pdlange", "Memory allocation failed" ); }
  
           for( ii = 0; ii < mp; ii++ ) { work[ii] = HPL_rzero; }
  
           for( jj = 0; jj < nq; jj++ )
           {
              for( ii = 0; ii < mp; ii++ )
              { work[ii] += Mabs( *A ); A++; }
              A += LDA - mp;
           }
  /*       
   * Find sum of global matrix rows, store on column 0 of process grid
   */      
           (void) HPL_reduce( (void *)(work), mp, HPL_DOUBLE, HPL_sum,
                              0, Rcomm );
  /*       
   * Find maximum sum of rows for inf-norm
   */      
           if( mycol == 0 )
           { v0 = work[HPL_idamax( mp, work, 1 )]; v0 = Mabs( v0 ); }
           if( work ) free( work );
        }
  /*
   * Find max in column 0, store result in process (0,0)
   */
        if( mycol == 0 )
           (void) HPL_reduce( (void *)(&v0), 1, HPL_DOUBLE, HPL_max,
                              0, Ccomm );
     }
  /*
   * Broadcast answer to every process in the grid
   */
     (void) HPL_broadcast( (void *)(&v0), 1, HPL_DOUBLE, 0, Acomm );
  
     return( v0 );
  /*
   * End of HPL_pdlange
   */
  }
  