SHMEM_WAIT(3) Open MPI SHMEM_WAIT(3)
NAME
shmem_int_wait(3), shmem_int_wait(3)_until, shmem_int4_wait(3),
shmem_int4_wait(3)_until, shmem_int8_wait(3), shmem_int8_wait(3)_until,
shmem_long_wait(3), shmem_long_wait(3)_until, shmem_longlong_wait(3),
shmem_longlong_wait(3)_until, shmem_short_wait(3),
shmem_short_wait(3)_until, shmem_wait(3), shmem_wait(3)_until - Waits
for a variable on the local processing element (PE) to change
SYNOPSIS
C or C++:
#include <mpp/shmem.h>
void shmem_int_wait(volatile int *var, int value);
void shmem_int_wait_until(volatile int *var, int cond, int value);
void shmem_long_wait(volatile long *var, long value);
void shmem_long_wait_until(volatile long *var, int cond, long value);
void shmem_longlong_wait(volatile long long *var, long long value);
void shmem_longlong_wait_until(volatile long long *var, int cond,
long long value);
void shmem_short_wait(volatile short *var, short value);
void shmem_short_wait_until(volatile short *var, int cond,
short value);
void shmem_wait(volatile long *ivar, long cmp_value);
void shmem_wait_until(volatile long *ivar, int cmp, long value);
Fortran:
INCLUDE "mpp/shmem.fh"
CALL SHMEM_INT4_WAIT(ivar, cmp_value)
CALL SHMEM_INT4_WAIT_UNTIL(ivar, cmp, cmp_value)
CALL SHMEM_INT8_WAIT(ivar, cmp_value)
CALL SHMEM_INT8_WAIT_UNTIL(ivar, cmp, cmp_value)
CALL SHMEM_WAIT(ivar, cmp_value)
CALL SHMEM_WAIT_UNTIL(ivar, cmp, cmp_value)
DESCRIPTION
shmem_wait and shmem_wait_until wait for ivar to be changed by a remote
write or atomic swap issued by a different processor. These routines
can be used for point-to- point directed synchronization. A call to
shmem_wait does not return until some other processor writes a value,
not equal to cmp_value, into ivar on the waiting processor. A call to
shmem_wait_until does not return until some other processor changes
ivar to satisfy the condition implied by cmp and cmp_value. This mecha-
nism is useful when a processor needs to tell another processor that it
has completed some action.
The arguments are as follows:
target The remotely accessible integer data object to be updated on the
remote PE. If you are using C/C++, the type of target should
match that implied in the SYNOPSIS section. If you are using
the Fortran compiler, it must be of type integer with an element
size of 4 bytes for SHMEM_INT4_ADD and 8 bytes for
SHMEM_INT8_ADD.
value The value to be atomically added to target. If you are using
C/C++, the type of value should match that implied in the SYNOP-
SIS section. If you are using Fortran, it must be of type inte-
ger with an element size of target.
pe An integer that indicates the PE number upon which target is to
be updated. If you are using Fortran, it must be a default inte-
ger value.
ivar A remotely accessible integer variable that is being updated by
another PE. If you are using C/C++, the type of ivar should
match that implied in the SYNOPSIS section. If you are using
Fortran, ivar must be a specific sized integer type according to
the function being called, as follows:
shmem_wait, shmem_wait_until: default INTEGER
shmem_int4_wait, shmem_int4_wait_until: INTEGER*4
shmem_int8_wait, shmem_int8_wait_until: INTEGER*8
cmp The compare operator that compares ivar with cmp_value. cmp must
be of type integer. If you are using Fortran, it must be of de-
fault kind. If you are using C/C++, the type of cmp should match
that implied in the SYNOPSIS section. The following cmp values
are supported:
SHMEM_CMP_EQ
Equal
SHMEM_CMP_NE
Not equal
SHMEM_CMP_GT
Greater than
SHMEM_CMP_LE
Less than or equal to
SHMEM_CMP_LT
Less than
SHMEM_CMP_GE
Greater than or equal to
cmp_value
cmp_value must be of type integer. If you are using C/C++, the
type of cmp_value should match thatimplied in the SYNOPSIS sec-
tion. If you are using Fortran, cmp_value must be an integer of
the same size and kind as ivar. The shmem_wait routines return
when ivar is no longer equal to cmp_value. The shmem_wait_until
routines return when the compare condition is true. The compare
condition is defined by the ivar argument compared with the
cmp_value using the comparison operator, cmp.
EXAMPLES
Example 1: The following call returns when variable ivar is not equal
to 100:
INTEGER*8 IVAR
CALL SHMEM_INT8_WAIT(IVAR, INT8(100))
Example 2: The following call to SHMEM_INT8_WAIT_UNTIL is equivalent to
the call to SHMEM_INT8_WAIT in example 1:
INTEGER*8 IVAR
CALL SHMEM_INT8_WAIT_UNTIL(IVAR, SHMEM_CMP_NE, INT8(100))
Example 3: The following C/C++ call waits until the sign bit in ivar is
set by a transfer from a remote PE:
int ivar;
shmem_int_wait_until(&ivar, SHMEM_CMP_LT, 0);
Example 4: The following Fortran example is in the context of a subrou-
tine:
SUBROUTINE EXAMPLE()
INTEGER FLAG_VAR
COMMON/FLAG/FLAG_VAR
. . .
FLAG_VAR = FLAG_VALUE ! initialize the event variable
. . .
IF (FLAG_VAR .EQ. FLAG_VALUE) THEN
CALL SHMEM_WAIT(FLAG_VAR, FLAG_VALUE)
ENDIF
FLAG_VAR = FLAG_VALUE ! reset the event variable for next time
. . .
END
SEE ALSO
intro_shmem(3), shmem_put(3)
4.1.2 Nov 24, 2021 SHMEM_WAIT(3)
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