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NAME

       shmem_int_or_to_all(3),          shmem_int4_or_to_all(3),         shmem_int8_or_to_all(3),
       shmem_long_or_to_all(3), shmem_longlong_or_to_all(3), shmem_short_or_to_all(3) -  Performs
       a bitwise OR function reduction across a set of processing elements (PEs)

SYNOPSIS

       C or C++:
       #include <mpp/shmem.h>

       void shmem_int_or_to_all(int *target, const int *source,
         int nreduce, int PE_start, int logPE_stride, int PE_size,
         int *pWrk, long *pSync);

       void shmem_long_or_to_all(long *target, const long *source,
         int nreduce, int PE_start, int logPE_stride, int PE_size,
         long *pWrk, long *pSync);

       void shmem_longlong_or_to_all(long long *target,
         const long long *source, int nreduce, int PE_start, int logPE_stride,
         int PE_size, long long *pWrk, long *pSync);

       void shmem_short_or_to_all(short *target, const short *source,
         int nreduce, int PE_start, int logPE_stride, int PE_size,
         short *pWrk, long *pSync);

       Fortran:
       INCLUDE "mpp/shmem.fh"

       INTEGER pSync(SHMEM_REDUCE_SYNC_SIZE)
       INTEGER nreduce, PE_start, logPE_stride, PE_size

       CALL SHMEM_INT4_OR_TO_ALL(target, source, nreduce, PE_start,
       & logPE_stride, PE_size, pWrk, pSync)

       CALL SHMEM_INT8_OR_TO_ALL(target, source, nreduce, PE_start,
       & logPE_stride, PE_size, pWrk, pSync)

DESCRIPTION

       The  shared  memory  (SHMEM)  reduction  routines  compute  one  or more reductions across
       symmetric arrays on multiple virtual PEs.  A  reduction  performs  an  associative  binary
       operation  across  a  set  of  values.  For  a list of other SHMEM reduction routines, see
       intro_shmem(3).

       As with all SHMEM collective routines, each of these routines assumes that only PEs in the
       active  set  call  the  routine.  If  a  PE not in the active set calls a SHMEM collective
       routine, undefined behavior results.

       The nreduce argument determines the number of separate reductions to perform.  The  source
       array on all PEs in the active set provides one element for each reduction. The results of
       the reductions are placed in the target array on all PEs in the active set. The active set
       is defined by the PE_start, logPE_stride, PE_size triplet.

       The  source  and  target  arrays  may  be  the same array, but they may not be overlapping
       arrays.

       The arguments are as follows:

       target A symmetric array of  length  nreduce  elements  to  receive  the  results  of  the
              reduction  operations.  The  data  type  of  target  varies with the version of the
              reduction routine being called. When calling from  C/C++,  refer  to  the  SYNOPSIS
              section for data type information. When calling from Fortran, the target data types
              are as follows:

              shmem_int8_or_to_all Integer, with an element size of 8 bytes.

              shmem_int4_or_to_all Integer, with an element size of 4 bytes.

       source A symmetric array, of length nreduce elements, that contains one element  for  each
              separate  reduction  operation. The source argument must have the same data type as
              target.

       nreduce
              The number of elements in the target and source arrays. nreduce  must  be  of  type
              integer. If you are using Fortran, it must be a default integer value.

       PE_start
              The  lowest  virtual  PE  number of the active set of PEs. PE_start must be of type
              integer. If you are using Fortran, it must be a default integer value.

       logPE_stride
              The log (base 2) of the stride between consecutive virtual PE numbers in the active
              set.  logPE_stride  must be of type integer. If you are using Fortran, it must be a
              default integer value.

       PE_size
              The number of PEs in the active set. PE_size must be of type integer.  If  you  are
              using Fortran, it must be a default integer value.

       pWrk   A  symmetric  work array. The pWrk argument must have the same data type as target.
              In  C/C++,  this  contains  max(nreduce/2  +   1,   _SHMEM_REDUCE_MIN_WRKDATA_SIZE)
              elements.      In     Fortran,     this     contains     max(nreduce/2     +     1,
              SHMEM_REDUCE_MIN_WRKDATA_SIZE) elements.

       pSync  A  symmetric  work  array.  In  C/C++,   pSync   is   of   type   long   and   size
              _SHMEM_REDUCE_SYNC_SIZE.   In   Fortran,   pSync   is  of  type  integer  and  size
              SHMEM_REDUCE_SYNC_SIZE. If you are using Fortran, it  must  be  a  default  integer
              value.    Every   element  of  this  array  must  be  initialized  with  the  value
              _SHMEM_SYNC_VALUE (in C/C++) or SHMEM_SYNC_VALUE (in Fortran) before any of the PEs
              in the active set enter the reduction routine.

       The  values of arguments nreduce, PE_start, logPE_stride, and PE_size must be equal on all
       PEs in the active set. The same target and source arrays, and the same pWrk and pSync work
       arrays, must be passed to all PEs in the active set.

       Before  any  PE  calls  a reduction routine, you must ensure that the following conditions
       exist (synchronization via a barrier or some other method is often needed to ensure this):
       The  pWrk  and pSync arrays on all PEs in the active set are not still in use from a prior
       call to a collective SHMEM routine. The target array on all PEs in the active set is ready
       to accept the results of the reduction.

       Upon return from a reduction routine, the following are true: The target array is updated.
       The values in the pSync array are restored to the original values.

NOTES

       The terms collective, symmetric, and cache aligned are  defined  in  intro_shmem(3).   All
       SHMEM  reduction  routines  reset  the values in pSync before they return, so a particular
       pSync buffer need only be initialized the first time it is used.

       You must ensure that the pSync array is not being updated on any  PE  in  the  active  set
       while any of the PEs participate in processing of a SHMEM reduction routine. Be careful to
       avoid these situations: If the pSync array is  initialized  at  run  time,  some  type  of
       synchronization is needed to ensure that all PEs in the working set have initialized pSync
       before any of them enter a SHMEM routine called with the pSync  synchronization  array.  A
       pSync  or  pWrk array can be reused in a subsequent reduction routine call only if none of
       the PEs in the active set are still processing a prior reduction routine  call  that  used
       the  same pSync or pWrk arrays. In general, this can be assured only by doing some type of
       synchronization. However, in the special case of reduction routines being called with  the
       same  active set, you can allocate two pSync and pWrk arrays and alternate between them on
       successive calls.

EXAMPLES

       Example 1: This Fortran example statically initializes  the  pSync  array  and  finds  the
       logical OR of the integer variable FOO across all even PEs.
       INCLUDE "mpp/shmem.fh"

       INTEGER PSYNC(SHMEM_REDUCE_SYNC_SIZE)
       DATA PSYNC /SHMEM_REDUCE_SYNC_SIZE*SHMEM_SYNC_VALUE/
       PARAMETER (NR=1)
       REAL PWRK(MAX(NR/2+1,SHMEM_REDUCE_MIN_WRKDATA_SIZE))
       INTEGER FOO, FOOOR
       COMMON /COM/ FOO, FOOOR, PWRK
       INTRINSIC MY_PE

       IF ( MOD(MY_PE(),2) .EQ. 0) THEN
         CALL SHMEM_INT8_OR_TO_ALL(FOOOR, FOO, NR, 0, 1, N$PES/2,
         & PWRK, PSYNC)
         PRINT *,'Result on PE ',MY_PE(),' is ',FOOOR
       ENDIF

       Example 2: Consider the following C/C++ call:
       shmem_int_or_to_all( target, source, 3, 0, 0, 8, pwrk, psync );

       The  preceding  call is more efficient, but semantically equivalent to, the combination of
       the following calls:
       shmem_int_or_to_all(&(target[0]), &(source[0]), 1, 0, 0, 8,
         pwrk1, psync1);
       shmem_int_or_to_all(&(target[1]), &(source[1]), 1, 0, 0, 8,
         pwrk2, psync2);
       shmem_int_or_to_all(&(target[2]), &(source[2]), 1, 0, 0, 8,
         pwrk1, psync1);

       Note  that  two  sets  of  pWrk  and  pSync  arrays  are  used  alternately   because   no
       synchronization is done between calls.

SEE ALSO

       intro_shmem(3)