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shmem_int_and_to_all(3), shmem_int4_and_to_all(3), shmem_int8_and_to_all(3),
shmem_long_and_to_all(3), shmem_longlong_and_to_all(3), shmem_short_and_to_all(3)
 Performs a bitwise AND operation on symmetric arrays over the active set
of PEs.
C or C++:
#include <mpp/shmem.h>
void shmem_int_and_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_and_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_and_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_and_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_AND_TO_ALL(target, source, nreduce,
& PE_start, logPE_stride, PE_size, pWrk, pSync)
CALL SHMEM_INT8_AND_TO_ALL(target, source, nreduce,
& PE_start, logPE_stride, PE_size, pWrk, pSync)
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).
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. 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 arguments are as follows:
 target
 A symmetric
array, of length nreduce elements, to receive the result 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_and_to_all: Integer, with an element size of
8 bytes
 shmem_int4_and_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 must be of type long and size _SHMEM_REDUCE_SYNC_SIZE.
In Fortran, pSync must be 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 for the local PE:
The target array is updated. The values in the pSync array are restored
to the original values.
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 the following 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.
Example 1: This Fortran example statically initializes the pSync
array and finds the logical AND 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, FOOAND
COMMON /COM/ FOO, FOOAND, PWRK
INTRINSIC MY_PE
IF ( MOD(MY_PE(),2) .EQ. 0) THEN
CALL SHMEM_INT8_AND_TO_ALL(FOOAND, FOO, NR, 0, 1, N$PES/2,
& PWRK, PSYNC)
PRINT *, ’Result on PE ’, MY_PE(), ’ is ’, FOOAND
ENDIF
Example 2: Consider the following C call:
shmem_int_and_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_and_to_all(&(target[0]), &(source[0]), 1, 0, 0, 8,
pwrk1, psync1);
shmem_int_and_to_all(&(target[1]), &(source[1]), 1, 0, 0, 8,
pwrk2, psync2);
shmem_int_and_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.
f90(1), intro_shmem(3)
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