pcamax_.c

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/* ---------------------------------------------------------------------
*
*  -- PBLAS routine (version 2.0) --
*     University of Tennessee, Knoxville, Oak Ridge National Laboratory,
*     and University of California, Berkeley.
*     April 1, 1998
*
*  ---------------------------------------------------------------------
*/
/*
*  Include files
*/
#include "pblas.h"
#include "PBpblas.h"
#include "PBtools.h"
#include "PBblacs.h"
#include "PBblas.h"
 
#ifdef __STDC__
void pcamax_( Int * N, float * AMAX, Int * INDX,
              float * X, Int * IX, Int * JX, Int * DESCX, Int * INCX )
#else
void pcamax_( N, AMAX, INDX, X, IX, JX, DESCX, INCX )
/*
*  .. Scalar Arguments ..
*/
   Int            * INCX, * INDX, * IX, * JX, * N;
   float          * AMAX;
/*
*  .. Array Arguments ..
*/
   Int            * DESCX;
   float          * X;
#endif
{
/*
*  Purpose
*  =======
*
*  PCAMAX  computes the global index of the maximum element in  absolute
*  value of a subvector sub( X ).  The global index is returned in  INDX
*  and the value of that element is returned in AMAX,
*
*  where
*
*     sub( X ) denotes X(IX,JX:JX+N-1) if INCX = M_X,
*                      X(IX:IX+N-1,JX) if INCX = 1 and INCX <> M_X.
*
*  Notes
*  =====
*
*  A description  vector  is associated with each 2D block-cyclicly dis-
*  tributed matrix.  This  vector  stores  the  information  required to
*  establish the  mapping  between a  matrix entry and its corresponding
*  process and memory location.
*
*  In  the  following  comments,   the character _  should  be  read  as
*  "of  the  distributed  matrix".  Let  A  be a generic term for any 2D
*  block cyclicly distributed matrix.  Its description vector is DESC_A:
*
*  NOTATION         STORED IN       EXPLANATION
*  ---------------- --------------- ------------------------------------
*  DTYPE_A (global) DESCA[ DTYPE_ ] The descriptor type.
*  CTXT_A  (global) DESCA[ CTXT_  ] The BLACS context handle, indicating
*                                   the NPROW x NPCOL BLACS process grid
*                                   A  is  distributed over. The context
*                                   itself  is  global,  but  the handle
*                                   (the integer value) may vary.
*  M_A     (global) DESCA[ M_     ] The  number of rows in the distribu-
*                                   ted matrix A, M_A >= 0.
*  N_A     (global) DESCA[ N_     ] The number of columns in the distri-
*                                   buted matrix A, N_A >= 0.
*  IMB_A   (global) DESCA[ IMB_   ] The number of rows of the upper left
*                                   block of the matrix A, IMB_A > 0.
*  INB_A   (global) DESCA[ INB_   ] The  number  of columns of the upper
*                                   left   block   of   the  matrix   A,
*                                   INB_A > 0.
*  MB_A    (global) DESCA[ MB_    ] The blocking factor used to  distri-
*                                   bute the last  M_A-IMB_A  rows of A,
*                                   MB_A > 0.
*  NB_A    (global) DESCA[ NB_    ] The blocking factor used to  distri-
*                                   bute the last  N_A-INB_A  columns of
*                                   A, NB_A > 0.
*  RSRC_A  (global) DESCA[ RSRC_  ] The process row over which the first
*                                   row of the matrix  A is distributed,
*                                   NPROW > RSRC_A >= 0.
*  CSRC_A  (global) DESCA[ CSRC_  ] The  process column  over  which the
*                                   first column of  A  is  distributed.
*                                   NPCOL > CSRC_A >= 0.
*  LLD_A   (local)  DESCA[ LLD_   ] The  leading dimension  of the local
*                                   array  storing  the  local blocks of
*                                   the distributed matrix A,
*                                   IF( Lc( 1, N_A ) > 0 )
*                                      LLD_A >= MAX( 1, Lr( 1, M_A ) )
*                                   ELSE
*                                      LLD_A >= 1.
*
*  Let K be the number of  rows of a matrix A starting at the global in-
*  dex IA,i.e, A( IA:IA+K-1, : ). Lr( IA, K ) denotes the number of rows
*  that the process of row coordinate MYROW ( 0 <= MYROW < NPROW ) would
*  receive if these K rows were distributed over NPROW processes.  If  K
*  is the number of columns of a matrix  A  starting at the global index
*  JA, i.e, A( :, JA:JA+K-1, : ), Lc( JA, K ) denotes the number  of co-
*  lumns that the process MYCOL ( 0 <= MYCOL < NPCOL ) would  receive if
*  these K columns were distributed over NPCOL processes.
*
*  The values of Lr() and Lc() may be determined via a call to the func-
*  tion PB_Cnumroc:
*  Lr( IA, K ) = PB_Cnumroc( K, IA, IMB_A, MB_A, MYROW, RSRC_A, NPROW )
*  Lc( JA, K ) = PB_Cnumroc( K, JA, INB_A, NB_A, MYCOL, CSRC_A, NPCOL )
*
*  Arguments
*  =========
*
*  N       (global input) INTEGER
*          On entry,  N  specifies the length of the subvector sub( X ).
*          N must be at least zero.
*
*  AMAX    (global output) COMPLEX array
*          On exit,  AMAX  specifies the largest entry in absolute value
*          of the  subvector  sub( X )  only in its scope (See below for
*          further details).
*
*  INDX    (global output) INTEGER
*          On exit, INDX  specifies the global index of the maximum ele-
*          ment in absolute  value of the subvector sub( X ) only in its
*          scope (See below for further details).
*
*  X       (local input) COMPLEX array
*          On entry, X is an array of dimension (LLD_X, Kx), where LLD_X
*          is   at  least  MAX( 1, Lr( 1, IX ) )  when  INCX = M_X   and
*          MAX( 1, Lr( 1, IX+N-1 ) )  otherwise,  and,  Kx  is  at least
*          Lc( 1, JX+N-1 )  when  INCX = M_X  and Lc( 1, JX ) otherwise.
*          Before  entry,  this array  contains the local entries of the
*          matrix X.
*
*  IX      (global input) INTEGER
*          On entry, IX  specifies X's global row index, which points to
*          the beginning of the submatrix sub( X ).
*
*  JX      (global input) INTEGER
*          On entry, JX  specifies X's global column index, which points
*          to the beginning of the submatrix sub( X ).
*
*  DESCX   (global and local input) INTEGER array
*          On entry, DESCX  is an integer array of dimension DLEN_. This
*          is the array descriptor for the matrix X.
*
*  INCX    (global input) INTEGER
*          On entry,  INCX   specifies  the  global  increment  for  the
*          elements of  X.  Only two values of  INCX   are  supported in
*          this version, namely 1 and M_X. INCX  must not be zero.
*
*  Further Details
*  ===============
*
*  When  the  result  of  a vector-oriented PBLAS call is a scalar, this
*  scalar  is set only within the process scope which owns the vector(s)
*  being operated on. Let sub( X ) be a generic term for the input  vec-
*  tor(s). Then, the processes owning the correct the answer is determi-
*  ned as follows:  if  an  operation involves more than one vector, the
*  processes receiving the result will be the union of the following set
*  of processes for each vector:
*
*  If N = 1, M_X = 1 and INCX = 1,  then  one cannot determine if a pro-
*  cess  row  or  process column owns the vector operand, therefore only
*  the process owning sub( X ) receives the correct result;
*
*  If  INCX = M_X, then sub( X )  is a vector distributed over a process
*  row. Each process in this row receives the result;
*
*  If  INCX = 1, then  sub( X )  is  a vector distributed over a process
*  column. Each process in this column receives the result;
*
*  -- Written on April 1, 1998 by
*     Antoine Petitet, University of Tennessee, Knoxville 37996, USA.
*
*  ---------------------------------------------------------------------
*/
/*
*  .. Local Scalars ..
*/
   char           cbtop, cctop, rbtop, rctop;
   Int            Xcol, Xgindx, Xi, Xii, Ximb, Xinb, Xj, Xjj, Xlindx, Xld, Xmb,
                  Xnb, Xnp, Xnq, Xrow, Xsrc, ctxt, dist, dst, idumm, info, k,
                  maxpos, mycol, mydist, myrow, npcol, nprow, src, size;
   PBTYP_T        * type;
/*
*  .. Local Arrays ..
*/
   char           * Xptr;
   Int            Xd[DLEN_];
   cmplx          work[4];
/* ..
*  .. Executable Statements ..
*
*/
   PB_CargFtoC( *IX, *JX, DESCX, &Xi, &Xj, Xd );
#ifndef NO_ARGCHK
/*
*  Test the input parameters
*/
   Cblacs_gridinfo( ( ctxt = Xd[CTXT_] ), &nprow, &npcol, &myrow, &mycol );
   if( !( info = ( ( nprow == -1 ) ? -( 701 + CTXT_ ) : 0 ) ) )
      PB_Cchkvec( ctxt, "PCAMAX", "X", *N, 1, Xi, Xj, Xd, *INCX, 7, &info );
   if( info ) { PB_Cabort( ctxt, "PCAMAX", info ); return; }
#endif
/*
*  Initialize INDX and AMAX
*/
   *INDX = 0; AMAX[REAL_PART] = ZERO; AMAX[IMAG_PART] = ZERO;
/*
*  Quick return if possible
*/
   if( *N == 0 ) return;
/*
*  Retrieve process grid information
*/
#ifdef NO_ARGCHK
   Cblacs_gridinfo( ( ctxt = Xd[CTXT_] ), &nprow, &npcol, &myrow, &mycol );
#endif
/*
*  Retrieve sub( X )'s local information: Xii, Xjj, Xrow, Xcol
*/
   PB_Cinfog2l( Xi, Xj, Xd, nprow, npcol, myrow, mycol, &Xii, &Xjj,
                &Xrow, &Xcol );
/*
*  Handle degenerate case separately, sub( X )'s scope is just one process
*/
   if( ( *INCX == 1 ) && ( Xd[M_] == 1 ) && ( *N == 1 ) )
   {
/*
*  Make sure I own some data and compute INDX and AMAX
*/
      if( ( ( myrow == Xrow ) || ( Xrow < 0 ) ) &&
          ( ( mycol == Xcol ) || ( Xcol < 0 ) ) )
      {
         *INDX = *JX;
         type = PB_Cctypeset();
         Xptr = Mptr( ((char *) X), Xii, Xjj, Xd[LLD_], type->size );
         AMAX[REAL_PART] = ((float*)(Xptr))[REAL_PART];
         AMAX[IMAG_PART] = ((float*)(Xptr))[IMAG_PART];
      }
      return;
   }
   else if( *INCX == Xd[M_] )
   {
/*
*  sub( X ) resides in (a) process row(s)
*/
      if( ( myrow == Xrow ) || ( Xrow < 0 ) )
      {
         rctop = *PB_Ctop( &ctxt, COMBINE, ROW, TOP_GET );
 
         if( ( rctop == CTOP_DEFAULT ) || ( rctop == CTOP_TREE1 ) )
         {
/*
*  Inline the 1-tree combine for communication savings
*/
            Xinb = Xd[INB_ ]; Xnb = Xd[NB_ ]; Xsrc = Xd[CSRC_];
            Xnq = PB_Cnumroc( *N, Xj, Xinb, Xnb, mycol, Xsrc, npcol );
/*
*  Make sure I own some data and compute local INDX and AMAX
*/
            if( Xnq > 0 )
            {
               Xld = Xd[LLD_];
               type = PB_Cctypeset(); size = type->size;
               Xlindx = Xjj - 1 +
                        icamax_( &Xnq, Mptr( ((char *) X), Xii, Xjj, Xld,
                                 size ), &Xld );
               Mindxl2g( Xgindx, Xlindx, Xinb, Xnb, mycol, Xsrc, npcol );
               Xptr = Mptr( ((char *) X), Xii, Xlindx, Xld, size );
               work[0][REAL_PART] = ((float*)(Xptr))[REAL_PART];
               work[0][IMAG_PART] = ((float*)(Xptr))[IMAG_PART];
               work[1][REAL_PART] = ((float )( Xgindx+1 ));
               work[1][IMAG_PART] = ZERO;
            }
            else
            {
               work[0][REAL_PART] = ZERO;
               work[0][IMAG_PART] = ZERO;
               work[1][REAL_PART] = ZERO;
               work[1][IMAG_PART] = ZERO;
            }
/*
*  Combine the local results using a 1-tree topology within process column 0
*  if npcol > 1 or Xcol >= 0, i.e sub( X ) is distributed.
*/
            if( ( npcol >= 2 ) && ( Xcol >= 0 ) )
            {
               mydist = mycol;
               k      = 1;
l_10:
               if( mydist & 1 )
               {
                  dist = k * ( mydist - 1 );
                  dst  = MPosMod( dist, npcol );
                  Ccgesd2d( ctxt, 2, 1, ((char*)work), 2, myrow, dst );
                  goto l_20;
               }
               else
               {
                  dist = mycol + k;
                  src  = MPosMod( dist, npcol );
 
                  if( mycol < src )
                  {
                     Ccgerv2d( ctxt, 2, 1, ((char*) work[2]), 2, myrow,
                               src );
                     if( ( ABS( work[0][REAL_PART] ) +
                           ABS( work[0][IMAG_PART] ) ) <
                         ( ABS( work[2][REAL_PART] ) +
                           ABS( work[2][IMAG_PART] ) ) )
                     {
                        work[0][REAL_PART] = work[2][REAL_PART];
                        work[0][IMAG_PART] = work[2][IMAG_PART];
                        work[1][REAL_PART] = work[3][REAL_PART];
                     }
                  }
                  mydist >>= 1;
               }
               k <<= 1;
 
               if( k < npcol ) goto l_10;
l_20:
/*
*  Process column 0 broadcasts the combined values of INDX and AMAX within
*  their process row.
*/
               rbtop = *PB_Ctop( &ctxt, BCAST, ROW, TOP_GET );
               if( mycol == 0 )
               {
                  Ccgebs2d( ctxt, ROW, &rbtop, 2, 1, ((char*)work), 2 );
               }
               else
               {
                  Ccgebr2d( ctxt, ROW, &rbtop, 2, 1, ((char*)work), 2,
                            myrow, 0 );
               }
            }
/*
*  Set INDX and AMAX to the replicated answers contained in work. If AMAX is
*  zero, then select a coherent INDX.
*/
            AMAX[REAL_PART] = work[0][REAL_PART];
            AMAX[IMAG_PART] = work[0][IMAG_PART];
            *INDX = ( ( ( AMAX[REAL_PART] == ZERO ) &&
                        ( AMAX[IMAG_PART] == ZERO ) ) ?
                    ( *JX ) : ( (Int)(work[1][REAL_PART]) ) );
         }
         else
         {
/*
*  Otherwise use the current topology settings to combine the results
*/
            Xinb = Xd[INB_ ]; Xnb = Xd[NB_ ]; Xsrc = Xd[CSRC_];
            Xnq = PB_Cnumroc( *N, Xj, Xinb, Xnb, mycol, Xsrc, npcol );
/*
*  Make sure I own some data and compute local INDX and AMAX
*/
            if( Xnq > 0 )
            {
/*
*  Compute the local maximum and its corresponding local index
*/
               Xld = Xd[LLD_];
               type = PB_Cctypeset(); size = type->size;
               Xlindx = Xjj - 1 +
                        icamax_( &Xnq, Mptr( ((char *) X), Xii, Xjj, Xld,
                                 size ), &Xld );
               Xptr = Mptr( ((char *) X), Xii, Xlindx, Xld, size );
               AMAX[REAL_PART] = ((float*)(Xptr))[REAL_PART];
               AMAX[IMAG_PART] = ((float*)(Xptr))[IMAG_PART];
            }
            else
            {
               AMAX[REAL_PART] = ZERO;
               AMAX[IMAG_PART] = ZERO;
            }
 
            if( Xcol >= 0 )
            {
/*
*  Combine leave on all the local maximum if Xcol >= 0, i.e sub( X ) is
*  distributed
*/
               Ccgamx2d( ctxt, ROW, &rctop, 1, 1, ((char*)AMAX), 1,
                         &idumm, &maxpos, 1, -1, mycol );
/*
*  Broadcast the corresponding global index
*/
               if( ( AMAX[REAL_PART] != ZERO ) || ( AMAX[IMAG_PART] != ZERO ) )
               {
                  rbtop = *PB_Ctop( &ctxt, BCAST, ROW, TOP_GET );
                  if( mycol == maxpos )
                  {
                     Mindxl2g( Xgindx, Xlindx, Xinb, Xnb, mycol, Xsrc, npcol );
                     *INDX = Xgindx + 1;
                     Cigebs2d( ctxt, ROW, &rbtop, 1, 1, ((char*)INDX), 1 );
                  }
                  else
                  {
                     Cigebr2d( ctxt, ROW, &rbtop, 1, 1, ((char*)INDX), 1,
                               myrow, maxpos );
                  }
               }
               else
               {
/*
*  If AMAX is zero, then select a coherent INDX.
*/
                  *INDX = *JX;
               }
            }
            else
            {
/*
*  sub( X ) is not distributed. If AMAX is zero, then select a coherent INDX.
*/
               *INDX = ( ( ( AMAX[REAL_PART] == ZERO ) &&
                           ( AMAX[IMAG_PART] == ZERO ) ) ?
                         ( *JX ) : Xlindx + 1 );
            }
         }
      }
      return;
   }
   else
   {
/*
*  sub( X ) resides in (a) process column(s)
*/
      if( ( mycol == Xcol ) || ( Xcol < 0 ) )
      {
         cctop = *PB_Ctop( &ctxt, COMBINE, COLUMN, TOP_GET );
 
         if( ( cctop == CTOP_DEFAULT ) || ( cctop == CTOP_TREE1 ) )
         {
/*
*  Inline the 1-tree combine for communication savings
*/
            Ximb = Xd[IMB_ ]; Xmb = Xd[MB_ ]; Xsrc = Xd[RSRC_];
            Xnp = PB_Cnumroc( *N, Xi, Ximb, Xmb, myrow, Xsrc, nprow );
/*
*  Make sure I own some data and compute local INDX and AMAX
*/
            if( Xnp > 0 )
            {
               Xld     = Xd[LLD_];
               type = PB_Cctypeset(); size = type->size;
               Xlindx = Xii - 1 +
                        icamax_( &Xnp, Mptr( ((char *)X), Xii, Xjj, Xld,
                                 size ), INCX );
               Mindxl2g( Xgindx, Xlindx, Ximb, Xmb, myrow, Xsrc, nprow );
               Xptr = Mptr( ((char *) X), Xlindx, Xjj, Xld, size );
               work[0][REAL_PART] = ((float*)(Xptr))[REAL_PART];
               work[0][IMAG_PART] = ((float*)(Xptr))[IMAG_PART];
               work[1][REAL_PART] = ((float )( Xgindx+1 ));
               work[1][IMAG_PART] = ZERO;
            }
            else
            {
               work[0][REAL_PART] = ZERO;
               work[0][IMAG_PART] = ZERO;
               work[1][REAL_PART] = ZERO;
               work[1][IMAG_PART] = ZERO;
            }
/*
*  Combine the local results using a 1-tree topology within process row 0
*  if nprow > 1 or Xrow >= 0, i.e sub( X ) is distributed.
*/
            if( ( nprow >= 2 ) && ( Xrow >= 0 ) )
            {
               mydist = myrow;
               k      = 1;
l_30:
               if( mydist & 1 )
               {
                  dist = k * ( mydist - 1 );
                  dst  = MPosMod( dist, nprow );
                  Ccgesd2d( ctxt, 2, 1, ((char*)work), 2, dst, mycol );
                  goto l_40;
               }
               else
               {
                  dist = myrow + k;
                  src  = MPosMod( dist, nprow );
 
                  if( myrow < src )
                  {
                     Ccgerv2d( ctxt, 2, 1, ((char*) work[2]), 2,
                               src, mycol );
                     if( ( ABS( work[0][REAL_PART] ) +
                           ABS( work[0][IMAG_PART] ) ) <
                         ( ABS( work[2][REAL_PART] ) +
                           ABS( work[2][IMAG_PART] ) ) )
                     {
                        work[0][REAL_PART] = work[2][REAL_PART];
                        work[0][IMAG_PART] = work[2][IMAG_PART];
                        work[1][REAL_PART] = work[3][REAL_PART];
                     }
                  }
                  mydist >>= 1;
               }
               k <<= 1;
 
               if( k < nprow ) goto l_30;
l_40:
/*
*  Process row 0 broadcasts the combined values of INDX and AMAX within their
*  process column.
*/
               cbtop = *PB_Ctop( &ctxt, BCAST, COLUMN, TOP_GET );
               if( myrow == 0 )
               {
                  Ccgebs2d( ctxt, COLUMN, &cbtop, 2, 1, ((char*)work), 2 );
               }
               else
               {
                  Ccgebr2d( ctxt, COLUMN, &cbtop, 2, 1, ((char*)work), 2,
                            0, mycol );
               }
            }
/*
*  Set INDX and AMAX to the replicated answers contained in work. If AMAX is
*  zero, then select a coherent INDX.
*/
            AMAX[REAL_PART] = work[0][REAL_PART];
            AMAX[IMAG_PART] = work[0][IMAG_PART];
            *INDX = ( ( ( AMAX[REAL_PART] == ZERO ) &&
                        ( AMAX[IMAG_PART] == ZERO ) ) ?
                    ( *IX ) : ( (Int)(work[1][REAL_PART]) ) );
         }
         else
         {
/*
*  Otherwise use the current topology settings to combine the results
*/
            Ximb = Xd[IMB_ ]; Xmb = Xd[MB_ ]; Xsrc = Xd[RSRC_];
            Xnp = PB_Cnumroc( *N, Xi, Ximb, Xmb, myrow, Xsrc, nprow );
/*
*  Make sure I own some data and compute local INDX and AMAX
*/
 
            if( Xnp > 0 )
            {
/*
*  Compute the local maximum and its corresponding local index
*/
               Xld = Xd[LLD_];
               type = PB_Cctypeset(); size = type->size;
               Xlindx = Xii - 1 +
                        icamax_( &Xnp, Mptr( ((char *) X), Xii, Xjj, Xld,
                                 size ), INCX );
               Xptr = Mptr( ((char *) X), Xlindx, Xjj, Xld, size );
               AMAX[REAL_PART] = ((float*)(Xptr))[REAL_PART];
               AMAX[IMAG_PART] = ((float*)(Xptr))[IMAG_PART];
            }
            else
            {
               AMAX[REAL_PART] = ZERO;
               AMAX[IMAG_PART] = ZERO;
            }
 
            if( Xrow >= 0 )
            {
/*
*  Combine leave on all the local maximum if Xrow >= 0, i.e sub( X ) is
*  distributed.
*/
               Ccgamx2d( ctxt, COLUMN, &cctop, 1, 1, ((char*)AMAX), 1,
                         &maxpos, &idumm, 1, -1, mycol );
/*
*  Broadcast the corresponding global index
*/
               if( ( AMAX[REAL_PART] != ZERO ) || ( AMAX[IMAG_PART] != ZERO ) )
               {
                  cbtop = *PB_Ctop( &ctxt, BCAST, COLUMN, TOP_GET );
                  if( myrow == maxpos )
                  {
                     Mindxl2g( Xgindx, Xlindx, Ximb, Xmb, myrow, Xsrc, nprow );
                     *INDX = Xgindx + 1;
                     Cigebs2d( ctxt, COLUMN, &cbtop, 1, 1, ((char*)INDX), 1 );
                  }
                  else
                  {
                     Cigebr2d( ctxt, COLUMN, &cbtop, 1, 1, ((char*)INDX), 1,
                               maxpos, mycol );
                  }
               }
               else
               {
/*
*  If AMAX is zero, then select a coherent INDX.
*/
                  *INDX = *IX;
               }
            }
            else
            {
/*
*  sub( X ) is not distributed. If AMAX is zero, then select a coherent INDX.
*/
               *INDX = ( ( ( AMAX[REAL_PART] == ZERO ) &&
                           ( AMAX[IMAG_PART] == ZERO ) ) ?
                         ( *IX ) : Xlindx + 1 );
            }
         }
      }
      return;
   }
/*
*  End of PCAMAX
*/
}
void pcamax_( N, AMAX, INDX, X, IX, JX, DESCX, INCX ) {…}