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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
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)
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:
- 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 SYNOPSIS section. If you
are using Fortran, it must be of type integer 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 integer 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 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:
- 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 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.
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
intro_shmem(3), shmem_put(3)
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