PB_CInOutV2.c

Go to the documentation of this file.

/* ---------------------------------------------------------------------
*
*  -- PBLAS auxiliary 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 PB_CInOutV2( PBTYP_T * TYPE, char * CONJUG, char * ROWCOL, Int M,
                  Int N, Int KA, Int * DESCA, Int K, char * Y, Int IY,
                  Int JY, Int * DESCY, char * YROC, char * * YAPTR,
                  Int * DYA, Int * YAFREE, Int * YASUM, Int * YAPBY )
#else
void PB_CInOutV2( TYPE, CONJUG, ROWCOL, M, N, KA, DESCA, K, Y, IY, JY,
                  DESCY, YROC, YAPTR, DYA, YAFREE, YASUM, YAPBY )
/*
*  .. Scalar Arguments ..
*/
   char           * CONJUG, * ROWCOL, * YROC;
   Int            * YAPBY, * YAFREE, IY, JY, K, KA, M, N, * YASUM;
   PBTYP_T        * TYPE;
/*
*  .. Array Arguments ..
*/
   Int            * DESCA, * DESCY, * DYA;
   char           * Y, * * YAPTR;
#endif
{
/*
*  Purpose
*  =======
*
*  PB_CInOutV2  returns a pointer to an array that contains a one-dimen-
*  sional  input/output subvector  which  is replicated over the rows or
*  columns of a submatrix described by DESCA. A  subvector is  specified
*  on input to this routine that is reused whenever possible. On return,
*  the subvector is specified  by  a  pointer to some data, a descriptor
*  array describing its layout, a logical value indicating if this local
*  piece of data has been dynamically allocated by this function, a  lo-
*  gical  value  specifying if sum reduction should occur, and finally a
*  logical  value specifying if it is necessary to copy back the alloca-
*  ted data to the original data. This routine is specifically  designed
*  for  traditional Level 2 like PBLAS  operations using an input/output
*  vector such as PxTRSV.
*
*  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
*  =========
*
*  TYPE    (local input) pointer to a PBTYP_T structure
*          On entry,  TYPE  is a pointer to a structure of type PBTYP_T,
*          that contains type information (See pblas.h).
*
*  CONJUG  (global input) pointer to CHAR
*          On  entry,  CONJUG  specifies  if  this routine should return
*          the conjugate subvector as follows:
*             = 'N' or 'n':           The initial subvector is returned,
*             = 'Z' or 'z':         The conjugate subvector is returned.
*
*  ROWCOL  (global input) pointer to CHAR
*          On entry, ROWCOL  specifies  if  this routine should return a
*          row or column subvector replicated over the underlying subma-
*          trix as follows:
*             = 'R' or 'r':                 A row subvector is returned,
*             = 'C' or 'c':              A column subvector is returned.
*
*  M       (global input) INTEGER
*          On entry,  M  specifies the number of rows of  the underlying
*          submatrix described by DESCA. M must be at least zero.
*
*  N       (global input) INTEGER
*          On entry, N specifies the number of columns of the underlying
*          submatrix described by DESCA. N must be at least zero.
*
*  KA      (global input) INTEGER
*          On entry, KA  specifies a global row index when ROWCOL is 'R'
*          or 'r' and a global column index otherwise. This index deter-
*          mines a process row or column in which the  output  subvector
*          contains a copy of the input subvector.
*
*  DESCA   (global and local input/output) INTEGER array
*          On entry, DESCA is an integer array of dimension DLEN_.  This
*          is the array descriptor for the matrix A. EXCEPTIONALLY, THIS
*          INTERNAL  ROUTINE  MAY  MODIFY DESCA IN ORDER TO MINIMIZE THE
*          AMOUNT OF DATA TO BE MOVED FOR THE VECTOR Y. SEE  PxGEMV  FOR
*          AN EXAMPLE.
*
*  K       (global input) INTEGER
*          On entry,  K  specifies the length of the non-distributed di-
*          mension of the subvector sub( Y ). K must be at least zero.
*
*  Y       (local input) pointer to CHAR
*          On entry, Y is an array of dimension (LLD_Y, Ky), where LLD_Y
*          is   at  least  MAX( 1, Lr( K, IY ) ) when YROC is 'R' or 'r'
*          and  MAX( 1, Lr( 1, IY+Ly-1 ) )   otherwise, and,  Ky  is  at
*          least  Lc( 1, JY+Ly-1 )   when   YROC  is  'R'  or  'r'   and
*          Lc( K, JY ) otherwise. Ly is N when  ROWCOL is 'R' or 'r' and
*          M  otherwise.  Before  entry,  this array  contains the local
*          entries of the  matrix Y.
*
*  IY      (global input) INTEGER
*          On entry, IY  specifies Y's global row index, which points to
*          the beginning of the submatrix sub( Y ).
*
*  JY      (global input) INTEGER
*          On entry, JY  specifies Y's global column index, which points
*          to the beginning of the submatrix sub( Y ).
*
*  DESCY   (global and local input) INTEGER array
*          On entry, DESCY  is an integer array of dimension DLEN_. This
*          is the array descriptor for the matrix Y.
*
*  YROC    (global input) pointer to CHAR
*          On entry,  YROC  specifies  the  orientation of the subvector
*          sub( Y ). When YROC is 'R' or 'r',  sub( Y ) is a row vector,
*          and a column vector otherwise.
*
*  YAPTR   (local output) pointer to pointer to CHAR
*          On exit, * YAPTR  is an array containing the same data as the
*          subvector  sub( Y )  which is replicated over the rows or co-
*          lumns of the  underlying  matrix  as  specified by ROWCOL and
*          DESCA.
*
*  DYA     (global and local output) INTEGER array
*          On exit, DYA is a descriptor array of dimension DLEN_ descri-
*          bing the data layout of the data pointed to by * YAPTR.
*
*  YAFREE  (local output) INTEGER
*          On exit, YAFREE  specifies  if  it  was possible to reuse the
*          subvector sub( Y ),  i.e., if some dynamic memory was alloca-
*          ted for the data pointed to by * YAPTR or not. When YAFREE is
*          zero, no  dynamic memory was allocated. Otherwise, some dyna-
*          mic memory  was  allocated by this function that one MUST re-
*          lease as soon as possible.
*
*  YASUM   (global output) INTEGER
*          On exit, YASUM  specifies if a global sum reduction should be
*          performed to obtain the correct sub( Y ). When YASUM is zero,
*          no reduction  is  to be performed, otherwise reduction should
*          occur.
*
*  YAPBY   (global output) INTEGER
*          On exit, YAPBY  specifies  if  the data pointed to by * YAPTR
*          must be move back onto sub( Y ) to obtain the correct result.
*          When YAPBY is zero, no supplementary data movement is  neces-
*          sary, otherwise a data redistribution should occur.
*
*  -- Written on April 1, 1998 by
*     Antoine Petitet, University of Tennessee, Knoxville 37996, USA.
*
*  ---------------------------------------------------------------------
*/
/*
*  .. Local Scalars ..
*/
   Int            Acol, Acoldst, Aimb, Ainb, AisD, AisR, Amb, Amp, Anb, Anq,
                  Arow, Arowdst, Ycol, Yii, Yimb, Yimb1, Yinb, Yinb1, YisD,
                  YisR, YisRow, Yjj, Yld, Ymb, Ymp, Ynb, Ynq, Yrow, ctxt,
                  izero=0, nprow, myrow, npcol, mycol;
/* ..
*  .. Executable Statements ..
*
*/
/*
*  Initialize the output parameters to a default value
*/
   *YAFREE = 0;
   *YASUM  = 0;
   *YAPBY  = 0;
   *YAPTR  = NULL;
/*
*  Quick return if possible
*/
   if( ( M <= 0 ) || ( N <= 0 ) || ( K <= 0 ) )
   {
      if( Mupcase( ROWCOL[0] ) == CROW )
      {
         PB_Cdescset( DYA, K, N, 1, DESCA[INB_], 1, DESCA[NB_], DESCA[RSRC_],
                      DESCA[CSRC_], DESCA[CTXT_], 1 );
      }
      else
      {
         PB_Cdescset( DYA, M, K, DESCA[IMB_], 1, DESCA[MB_], 1, DESCA[RSRC_],
                      DESCA[CSRC_], DESCA[CTXT_], DESCA[LLD_] );
      }
      return;
   }
/*
*  Retrieve process grid information
*/
   Cblacs_gridinfo( ( ctxt = DESCY[CTXT_] ), &nprow, &npcol, &myrow, &mycol );
/*
*  Retrieve sub( Y )'s local information: Yii, Yjj, Yrow, Ycol
*/
   Minfog2l( IY, JY, DESCY, nprow, npcol, myrow, mycol, Yii, Yjj, Yrow, Ycol );
/*
*  Is sub( Y ) distributed or not, replicated or not ?
*/
   if( ( YisRow = ( Mupcase( YROC[0] ) == CROW ) ) != 0 )
   {
      YisD = ( ( Ycol >=  0 ) && ( npcol >  1 ) );
      YisR = ( ( Yrow == -1 ) || ( nprow == 1 ) );
   }
   else
   {
      YisD = ( ( Yrow >=  0 ) && ( nprow >  1 ) );
      YisR = ( ( Ycol == -1 ) || ( npcol == 1 ) );
   }
 
   Aimb = DESCA[ IMB_  ]; Ainb = DESCA[ INB_  ];
   Amb  = DESCA[ MB_   ]; Anb  = DESCA[ NB_   ];
   Arow = DESCA[ RSRC_ ]; Acol = DESCA[ CSRC_ ];
 
   if( Mupcase( ROWCOL[0] ) == CROW )
   {
/*
*  Want a row vector
*/
      AisR = ( ( Arow <  0 ) || ( nprow == 1 ) );
/*
*  Figure out in which process row sub( Y ) or a copy of it should be found
*/
      Arowdst = PB_Cindxg2p( KA, Aimb, Amb, Arow, Arow, nprow );
 
      if( YisRow && ( Mupcase( CONJUG[0] ) == CNOCONJG ) )
      {
/*
*  It is possible to reuse sub( Y ) iff sub( Y ) is already a row vector and
*  the data does not need to be conjugated.
*/
         AisD = ( ( Acol >= 0 ) && ( npcol >  1 ) );
 
         Yinb = DESCY[INB_]; Ynb = DESCY[NB_];
         Yinb1 = PB_Cfirstnb( N, JY, Yinb, Ynb );
/*
*  sub( Y ) is aligned with A (reuse condition) iff both operands are not
*  distributed, or both of them are distributed and start in the same process
*  column and either N is smaller than the first blocksize of sub( Y ) and A,
*  or their column blocking factors match.
*/
         if( ( !AisD && !YisD ) ||
             ( ( AisD && YisD )  &&
               ( ( Acol == Ycol ) &&
                 ( ( ( Ainb >= N     ) && ( Yinb1 >= N ) ) ||
                   ( ( Ainb == Yinb1 ) && ( Anb == Ynb ) ) ) ) ) )
         {
            Ynq = PB_Cnumroc( N, 0, Yinb1, Ynb, mycol, Ycol, npcol );
            Ymp = ( YisR ? K : ( ( myrow == Yrow ) ? K : 0 ) );
            Yld = MAX( 1, K );
 
            if( YisR )
            {
/*
*  If sub( Y ) is replicated, there is no need to move sub( Y ) after the
*  operation (*YAPBY = 0), and it can be reused where needed and zeroed out
*  elsewhere.
*/
               *YASUM = ( AisR ? 0 : ( nprow > 1 ) );
               *YAPBY = 0;
               Yld    = DESCY[ LLD_ ];
               if( Ynq > 0 )
               {
                  *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
                  if( !AisR && ( myrow != Arowdst ) )
                     TYPE->Ftzpad( C2F_CHAR( ALL ), C2F_CHAR( NOCONJG ), &K,
                                   &Ynq, &izero, TYPE->zero, TYPE->zero, *YAPTR,
                                   &Yld );
               }
            }
            else
            {
/*
*  sub( Y ) is not replicated, the descriptor of A may need to be modified ...
*/
               if( AisR )
               {
/*
*  If A is replicated, use only the copy in the process row where sub( Y )
*  resides -> modify DESCA !!!
*/
                  *YASUM         = 0;
                  *YAPBY         = 0;
                  Yld            = DESCY[ LLD_ ];
                  DESCA[ IMB_  ] = M;
                  DESCA[ RSRC_ ] = Yrow;
                  if( ( Ynq > 0 ) && ( Ymp > 0 ) )
                     *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
               }
               else
               {
                  if( PB_Cspan( M, 0, Aimb, Amb, Arow, nprow ) )
                  {
/*
*  Otherwise, A is not replicated, let assume in addition that it spans more
*  than one process row.
*/
                     *YASUM = ( nprow > 1 );
                     *YAPBY = 0;
 
                     if( myrow == Yrow )
                     {
/*
*  If sub( Y ) is not in the desired process row, send it there and zero it.
*  Otherwise, reuse it.
*/
                        Yld = DESCY[ LLD_ ];
                        if( Ynq > 0 )
                        {
                           *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
                           if( Yrow != Arowdst )
                           {
                              TYPE->Cgesd2d( ctxt, K, Ynq, *YAPTR, Yld, Arowdst,
                                             mycol );
                              TYPE->Ftzpad( C2F_CHAR( ALL ),
                                            C2F_CHAR( NOCONJG ), &K, &Ynq,
                                            &izero, TYPE->zero, TYPE->zero,
                                            *YAPTR, &Yld );
                           }
                        }
                     }
                     else
                     {
/*
*  Allocate space in the other process rows and initialize to zero. If sub( Y )
*  was not in the desired process row, receive it.
*/
                        Yld = MAX( 1, K );
                        if( Ynq > 0 )
                        {
                           *YAPTR  = PB_Cmalloc( K * Ynq * TYPE->size );
                           *YAFREE = 1;
                           if( ( Yrow  != Arowdst ) && ( myrow == Arowdst ) )
                              TYPE->Cgerv2d( ctxt, K, Ynq, *YAPTR, Yld, Yrow,
                                             mycol );
                           else
                              TYPE->Ftzpad( C2F_CHAR( ALL ),
                                            C2F_CHAR( NOCONJG ), &K, &Ynq,
                                            &izero, TYPE->zero, TYPE->zero,
                                            *YAPTR, &Yld );
                        }
                     }
                  }
                  else
                  {
/*
*  A spans only one process row
*/
                     if( Yrow == Arow )
                     {
/*
*  If A and sub( Y ) resides in the same process row, things are easy.
*/
                        *YASUM = 0;
                        *YAPBY = 0;
                        Yld    = DESCY[ LLD_ ];
                        if( ( myrow == Yrow ) && ( Ynq > 0 ) )
                           *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
                     }
                     else
                     {
/*
*  Otherwise, sub( Y ) resides in another process row, thus allocate zero-data
*  in process row where a copy of sub( Y ) is desired, and receive it. Set
*  *YAPBY to 1, so that this data will be added (moved) after the local
*  operation has been performed.
*/
                        *YASUM = 0;
                        *YAPBY = 1;
                        if( Ynq > 0 )
                        {
                           if( myrow == Yrow )
                           {
                              Yld    = DESCY[ LLD_ ];
                              TYPE->Cgesd2d( ctxt, K, Ynq, Mptr( Y, Yii, Yjj,
                                             Yld, TYPE->size ), Yld, Arowdst,
                                             mycol );
                           }
                           else if( myrow == Arowdst )
                           {
                              Yld     = MAX( 1, K );
                              *YAPTR  = PB_Cmalloc( K*Ynq*TYPE->size );
                              *YAFREE = 1;
                              TYPE->Cgerv2d( ctxt, K, Ynq, *YAPTR, Yld, Yrow,
                                             mycol );
                           }
                        }
                        Yrow = Arowdst;
                     }
                  }
               }
            }
/*
*  Describe the resulting operand. Note that when reduction should occur, Yrow
*  contains the destination row. Assuming every process row needs the result,
*  Yrow is then -1.
*/
            PB_Cdescset( DYA, K, N, K, Yinb1, 1, Ynb, Yrow, Ycol, ctxt, Yld );
            return;
         }
      }
/*
*  sub( Y ) cannot be reused, force YAPBY to 1 for the later update of sub( Y ).
*/
      *YAPBY = 1;
      Anq    = PB_Cnumroc( N, 0, Ainb, Anb, mycol, Acol, npcol );
      Yld    = MAX( 1, K );
 
      if( YisR )
      {
/*
*  If sub( Y ) is replicated, allocate space in every process row owning some
*  columns of A and initialize it to zero only where needed. There may be some
*  wasted space (suppose A was residing in just one row), however, it is hoped
*  that moving back this data to sub( Y ) will then be cheaper ...
*/
         *YASUM = ( AisR ? 0 : ( nprow > 1 ) );
         if( Anq > 0 )
         {
            *YAPTR  = PB_Cmalloc( K * Anq * TYPE->size );
            *YAFREE = 1;
            if( ( Arowdst >= 0 ) && ( myrow != Arowdst ) )
               TYPE->Ftzpad( C2F_CHAR( ALL ), C2F_CHAR( NOCONJG ), &K, &Anq,
                             &izero, TYPE->zero, TYPE->zero, *YAPTR, &Yld );
         }
      }
      else
      {
/*
*  sub( Y ) resides in only one process row
*/
         if( AisR )
         {
/*
*  If A is replicated, then modify sub( A ) so that only one process row will
*  compute the result before moving it back to sub( Y ).
*/
            *YASUM         = 0;
            DESCA[ IMB_  ] = M;
            if( YisRow )
            {
/*
*  Choose a different process row than Yrow for better performance (more links)
*  in the later move-back phase.
*/
               DESCA[RSRC_] = MModSub1( Yrow, nprow );
            }
            else
            {
               DESCA[RSRC_] = 0;
            }
            if( ( myrow == ( Arowdst = DESCA[RSRC_] ) ) && ( Anq > 0 ) )
            {
               *YAPTR  = PB_Cmalloc( K * Anq * TYPE->size );
               *YAFREE = 1;
            }
         }
         else
         {
            if( PB_Cspan( M, 0, Aimb, Amb, Arow, nprow ) )
            {
/*
*  If A is not replicated, and spans more than just one process row, then
*  allocate space in every process row and zero it where needed.
*/
               *YASUM = ( nprow > 1 );
               if( Anq > 0 )
               {
                  *YAPTR  = PB_Cmalloc( K * Anq * TYPE->size );
                  *YAFREE = 1;
                  if( myrow != Arowdst )
                     TYPE->Ftzpad( C2F_CHAR( ALL ), C2F_CHAR( NOCONJG ), &K,
                                   &Anq, &izero, TYPE->zero, TYPE->zero, *YAPTR,
                                   &Yld );
               }
            }
            else
            {
/*
*  If A is not replicated, and spans only one process row, then allocate space
*  within that process row.
*/
               *YASUM = 0;
               if( ( myrow == Arowdst ) && ( Anq > 0 ) )
               {
                  *YAPTR  = PB_Cmalloc( K * Anq * TYPE->size );
                  *YAFREE = 1;
               }
            }
         }
      }
/*
*  Describe the resulting operand. Note that when reduction should occur,
*  Arowdst contains the destination row. Assuming every process row needs the
*  result, Arowdst is then -1.
*/
      PB_Cdescset( DYA, K, N, K, Ainb, 1, Anb, Arowdst, Acol, ctxt, Yld );
/*
*  Move sub( Y ) in the desired processes and with the correct layout
*/
      if( YisRow )
      {
         PB_Cpaxpby( TYPE, CONJUG, K, N, TYPE->one, Y, IY, JY, DESCY, ROW,
                     TYPE->zero, *YAPTR, 0, 0, DYA, ROW );
      }
      else
      {
         PB_Cpaxpby( TYPE, CONJUG, N, K, TYPE->one, Y, IY, JY, DESCY, COLUMN,
                     TYPE->zero, *YAPTR, 0, 0, DYA, ROW );
      }
   }
   else
   {
/*
*  Want a column vector with original data in col KA
*/
      AisR = ( ( Acol <  0 ) || ( npcol == 1 ) );
/*
*  Figure out in which process column sub( Y ) or a copy of it should be found.
*/
      Acoldst = PB_Cindxg2p( KA, Ainb, Anb, Acol, Acol, npcol );
 
      if( !( YisRow ) && ( Mupcase( CONJUG[0] ) == CNOCONJG ) )
      {
/*
*  It is possible to reuse sub( Y ) iff sub( Y ) is already a column vector and
*  the data does not need to be conjugated.
*/
         AisD = ( ( Arow >= 0 ) && ( nprow >  1 ) );
 
         Yimb = DESCY[IMB_]; Ymb = DESCY[MB_];
         Yimb1 = PB_Cfirstnb( M, IY, Yimb, Ymb );
/*
*  sub( Y ) is aligned with A (reuse condition) iff both operands are not
*  distributed, or both of them are distributed and start in the same process
*  row and either M is smaller than the first blocksize of sub( Y ) and A, or
*  their row blocking factors match.
*/
         if( ( !AisD && !YisD ) ||
             ( ( AisD && YisD )  &&
               ( ( Arow == Yrow ) &&
                 ( ( ( Aimb >= M     ) && ( Yimb1 >= M ) ) ||
                   ( ( Aimb == Yimb1 ) && ( Amb == Ymb ) ) ) ) ) )
         {
            Ymp = PB_Cnumroc( M, 0, Yimb1, Ymb, myrow, Yrow, nprow );
            Ynq = ( YisR ? K : ( ( mycol == Ycol ) ? K : 0 ) );
            Yld = MAX( 1, Ymp );
 
            if( YisR )
            {
/*
*  If sub( Y ) is replicated, there is no need to move sub( Y ) after the
*  operation (*YAPBY = 0), and it can be reused where needed and zeroed out
*  elsewhere.
*/
               *YASUM = ( AisR ? 0 : ( npcol > 1 ) );
               *YAPBY = 0;
               Yld    = DESCY[ LLD_ ];
               if( Ymp > 0 )
               {
                  *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
                  if( !AisR && ( mycol != Acoldst ) )
                     TYPE->Ftzpad( C2F_CHAR( ALL ), C2F_CHAR( NOCONJG ), &Ymp,
                                   &K, &izero, TYPE->zero, TYPE->zero, *YAPTR,
                                   &Yld );
               }
            }
            else
            {
/*
*  sub( Y ) is not replicated, the descriptor of A may need to be modified ...
*/
               if( AisR )
               {
/*
*  If A is replicated, use only the copy in the process column where sub( Y )
*  resides -> modify DESCA !!!
*/
                  *YASUM         = 0;
                  *YAPBY         = 0;
                  Yld            = DESCY[ LLD_ ];
                  DESCA[ INB_  ] = N;
                  DESCA[ CSRC_ ] = Ycol;
                  if( ( Ymp > 0 ) && ( Ynq > 0 ) )
                     *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
               }
               else
               {
                  if( PB_Cspan( N, 0, Ainb, Anb, Acol, npcol ) )
                  {
/*
*  Otherwise, A is not replicated, let assume in addition that it spans more
*  than one process column.
*/
                     *YASUM = ( npcol > 1 );
                     *YAPBY = 0;
 
                     if( mycol == Ycol )
                     {
/*
*  If sub( Y ) is not in the desired process column, send it there and zero it.
*  Otherwise, reuse it.
*/
                        Yld = DESCY[ LLD_ ];
                        if( Ymp > 0 )
                        {
                           *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
                           if( Ycol != Acoldst )
                           {
                              TYPE->Cgesd2d( ctxt, Ymp, K, *YAPTR, Yld, myrow,
                                             Acoldst );
                              TYPE->Ftzpad( C2F_CHAR( ALL ),
                                            C2F_CHAR( NOCONJG ), &Ymp, &K,
                                            &izero, TYPE->zero, TYPE->zero,
                                            *YAPTR, &Yld );
                           }
                        }
                     }
                     else
                     {
/*
*  Allocate space in the other process columns and initialize to zero. If
*  sub( Y ) was not in the desired process column, receive it.
*/
                        Yld = MAX( 1, Ymp );
                        if( Ymp > 0 )
                        {
                           *YAPTR  = PB_Cmalloc( Ymp * K * TYPE->size );
                           *YAFREE = 1;
                           if( ( Ycol  != Acoldst ) && ( mycol == Acoldst ) )
                              TYPE->Cgerv2d( ctxt, Ymp, K, *YAPTR, Yld, myrow,
                                             Ycol );
                           else
                              TYPE->Ftzpad( C2F_CHAR( ALL ),
                                            C2F_CHAR( NOCONJG ), &Ymp, &K,
                                            &izero, TYPE->zero, TYPE->zero,
                                            *YAPTR, &Yld );
                        }
                     }
                  }
                  else
                  {
/*
*  A spans only one process column
*/
                     if( Ycol == Acol )
                     {
/*
*  If A and sub( Y ) resides in the same process column, things are easy.
*/
                        *YASUM = 0;
                        *YAPBY = 0;
                        Yld    = DESCY[ LLD_ ];
                        if( ( mycol == Ycol ) && ( Ymp > 0 ) )
                           *YAPTR = Mptr( Y, Yii, Yjj, Yld, TYPE->size );
                     }
                     else
                     {
/*
*  Otherwise, sub( Y ) resides in another process column, thus allocate
*  zero-data in process column where a copy of sub( Y ) is desired, and receive
*  it. Set *YAPBY to 1, so that this data will be added (moved) after the local
*  operation has been performed.
*/
                        *YASUM = 0;
                        *YAPBY = 1;
                        if( Ymp > 0 )
                        {
                           if( mycol == Ycol )
                           {
                              Yld    = DESCY[ LLD_ ];
                              TYPE->Cgesd2d( ctxt, Ymp, K, Mptr( Y, Yii, Yjj,
                                             Yld, TYPE->size ), Yld, myrow,
                                             Acoldst );
                           }
                           else if( mycol == Acoldst )
                           {
                              Yld     = MAX( 1, Ymp ) ;
                              *YAPTR  = PB_Cmalloc( Ymp * K * TYPE->size );
                              *YAFREE = 1;
                              TYPE->Cgerv2d( ctxt, Ymp, K, *YAPTR, Yld, myrow,
                                             Ycol );
                           }
                        }
                        Ycol = Acoldst;
                     }
                  }
               }
            }
/*
*  Describe the resulting operand. Note that when reduction should occur, Ycol
*  contains the destination column. Assuming every process column needs the
*  result, Ycol is then -1.
*/
            PB_Cdescset( DYA, M, K, Yimb1, K, Ymb, 1, Yrow, Ycol, ctxt, Yld );
            return;
         }
      }
/*
*  sub( Y ) cannot be reused, force YAPBY to 1 for the later update of sub( Y ).
*/
      *YAPBY = 1;
      Amp = PB_Cnumroc( M, 0, Aimb, Amb, myrow, Arow, nprow );
      Yld    = MAX( 1, Amp );
 
      if( YisR )
      {
/*
*  If sub( Y ) is replicated, allocate space in every process column owning some
*  columns of A and initialize it to zero only where needed. There may be some
*  wasted space (suppose A was residing in just one column), however, it is
*  hoped that moving back this data to sub( Y ) will then be cheaper ...
*/
         *YASUM = ( AisR ? 0 : ( npcol > 1 ) );
         if( Amp > 0 )
         {
            *YAPTR  = PB_Cmalloc( Amp * K * TYPE->size );
            *YAFREE = 1;
            if( ( Acoldst >= 0 ) && ( mycol != Acoldst ) )
               TYPE->Ftzpad( C2F_CHAR( ALL ), C2F_CHAR( NOCONJG ), &Amp, &K,
                             &izero, TYPE->zero, TYPE->zero, *YAPTR, &Yld );
         }
      }
      else
      {
/*
*  sub( Y ) resides in only one process column
*/
         if( AisR )
         {
/*
*  If A is replicated, then modify sub( A ) so that only one process column will
*  compute the result before moving it back to sub( Y ).
*/
            *YASUM         = 0;
            DESCA[ INB_  ] = N;
            if( YisRow )
            {
               DESCA[ CSRC_ ] = 0;
            }
            else
            {
/*
*  Choose a different process column than Ycol for better performance (more
*  links) in the later move-back phase.
*/
               DESCA[ CSRC_ ] = MModSub1( Ycol, npcol );
            }
            if( ( mycol == ( Acoldst = DESCA[CSRC_] ) ) && ( Amp > 0 ) )
            {
               *YAPTR  = PB_Cmalloc( Amp * K * TYPE->size );
               *YAFREE = 1;
            }
         }
         else
         {
            if( PB_Cspan( N, 0, Ainb, Anb, Acol, npcol ) )
            {
/*
*  If A is not replicated, and spans more than just one process column, then
*  allocate space in every process column and zero it where needed.
*/
               *YASUM = ( npcol > 1 );
               if( Amp > 0 )
               {
                  *YAPTR  = PB_Cmalloc( Amp * K * TYPE->size );
                  *YAFREE = 1;
                  if( mycol != Acoldst )
                     TYPE->Ftzpad( C2F_CHAR( ALL ), C2F_CHAR( NOCONJG ), &Amp,
                                   &K, &izero, TYPE->zero, TYPE->zero, *YAPTR,
                                   &Yld );
               }
            }
            else
            {
/*
*  If A is not replicated, and spans only one process column, then allocate
*  space within that process column.
*/
               *YASUM = 0;
               if( ( mycol == Acoldst ) && ( Amp > 0 ) )
               {
                  *YAPTR  = PB_Cmalloc( Amp * K * TYPE->size );
                  *YAFREE = 1;
               }
            }
         }
      }
/*
*  Describe the resulting operand. Note that when reduction should occur,
*  Acoldst contains the destination column. Assuming every process column needs
*  the result, Acoldst is then -1.
*/
      PB_Cdescset( DYA, M, K, Aimb, K, Amb, 1, Arow, Acoldst, ctxt, Yld );
/*
*  Move sub( Y ) in the desired processes and with the correct layout
*/
      if( YisRow )
      {
         PB_Cpaxpby( TYPE, CONJUG, K, M, TYPE->one, Y, IY, JY, DESCY, ROW,
                     TYPE->zero, *YAPTR, 0, 0, DYA, COLUMN );
      }
      else
      {
         PB_Cpaxpby( TYPE, CONJUG, M, K, TYPE->one, Y, IY, JY, DESCY, COLUMN,
                     TYPE->zero, *YAPTR, 0, 0, DYA, COLUMN );
      }
   }
/*
*  End of PB_CInOutV2
*/
}