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 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.
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 ALSO¶
intro_shmem(3), shmem_put(3)
