SHMEM_WAIT(3)SHMEM_WAIT(3)NAME
shmem_int_wait, shmem_int_wait_until, shmem_int4_wait,
shmem_int4_wait_until, shmem_int8_wait, shmem_int8_wait_until,
shmem_long_wait, shmem_long_wait_until, shmem_longlong_wait,
shmem_longlong_wait_until, shmem_short_wait, shmem_short_wait_until,
shmem_wait, shmem_wait_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(int *var, int value);
void shmem_int_wait_until(int *var, int cond, int value);
void shmem_long_wait(long *var, long value);
void shmem_long_wait_until(long *var, int cond, long value);
void shmem_longlong_wait(long long *var, long long value);
void shmem_longlong_wait_until(long long *var, int cond, long long
value);
void shmem_short_wait(short *var, short value);
void shmem_short_wait_until(short *var, int cond, short value);
void shmem_wait(long *ivar, long cmp_value);
void shmem_wait_until(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 mechanism is useful when a processor needs to tell another
processor that it has completed some action.
The arguments are as follows:
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:
Function Type of ivar
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 default 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:
cmp Value Comparison
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 that implied in the
SYNOPSIS section. 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
subroutine:
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 ALSOintro_shmem(3), shmem_put(3)
Message Passing Toolkit: MPI Programmer's Manual
