Signaling Operations#

This section specifies the Intel® SHMEM support for put-with-signal, nonblocking put-with-signal, and signal-fetch routines. The put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion. The signal-fetch routine provides support for fetching a signal update operation.

Atomicity Guarantees for Signaling Operations#

All signaling operations put-with-signal, nonblocking put-with-signal, and signal-fetch are performed on a signal data object, a remotely accessible symmetric object of type uint64_t. A signal operator in the put-with-signal routine is an Intel® SHMEM library constant that determines the type of update to be performed as a signal on the signal data object.

All signaling operations on the signal data object complete as if performed atomically with respect to the following:

  • other blocking or nonblocking variant of the put-with-signal routine that updates the signal data object using the same signal update operator;

  • signal-fetch routine that fetches the signal data object; and

  • any point-to-point synchronization routine that accesses the signal data object.

Available Signal Operators#

With the atomicity guarantees as described in Section Atomicity Guarantees for Signaling Operations, the following options can be used as a signal operator.

  • ISHMEM_SIGNAL_SET An update to signal data object is an atomic set operation. It writes an unsigned 64-bit value as a signal into the signal data object on a remote PE as an atomic operation.

  • ISHMEM_SIGNAL_ADD An update to signal data object is an atomic add operation. It adds an unsigned 64-bit value as a signal into the signal data object on a remote PE as an atomic operation.

Blocking Put-Signal#

ISHMEM_PUT_SIGNAL#

The put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion.

In the functions below, TYPE is one of the standard RMA types and has a corresponding TYPENAME specified by Table Standard RMA Types.

template<typename TYPE>
void ishmem_put_signal(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe)#
void ishmem_TYPENAME_put_signal(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe)#
void ishmem_TYPENAME_putmem_signal(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe)#
Parameters:

  • dest – Symmetric address of the destination data object. The type of dest should match the TYPE and TYPENAME according to the table of Standard RMA types.

  • source – Local address of the data object containing the data to be copied. The type of source should match the TYPE and TYPENAME according to the table of Standard RMA types.

  • nelems – Number of elements in the dest and source arrays. For ishmem_putmem_signal, elements are bytes.

  • sig_addr – Symmetric address of the signal data object to be updated on the remote PE as a signal.

  • signal – Unsigned 64-bit value that is used for updating the remote sig_addr signal data object.

  • sig_op – Signal operator that represents the type of update to be performed on the remote sig_addr signal data object.

  • pe – PE number of the remote PE.

Callable from the host and device.

Description: The put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion. The routines return after the data has been copied out of the source array on the local PE.

The sig_op signal operator determines the type of update to be performed on the remote sig_addr signal data object. The completion of signal update based on the sig_op signal operator using the signal flag on the remote PE indicates the delivery of its corresponding dest data words into the data object on the remote PE.

An update to the sig_addr signal data object through a put-with-signal routine completes as if performed atomically as described in Section Atomicity Guarantees for Signaling Operations. The various options as described in Section Available Signal Operators can be used as the sig_op signal operator.

The dest and sig_addr data objects must both be remotely accessible and may not be overlapping in memory.

The completion of signal update using the signal flag on the remote PE indicates only the delivery of its corresponding dest data words into the data object on the remote PE. Without a memory-ordering operation, there is no implied ordering between the signal update of a put-with-signal routine and another data transfer. For example, the completion of the signal update in a sequence consisting of a put routine followed by a put-with-signal routine does not imply delivery of the put routine’s data.

ISHMEMX_PUT_SIGNAL_WORK_GROUP#

The put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion.

In the functions below, TYPE is one of the standard RMA types and has a corresponding TYPENAME specified by Table Standard RMA Types.

template<typename TYPE, typename Group>
void ishmemx_put_signal_work_group(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe, const Group &group)#
template<typename Group>
void ishmemx_TYPENAME_put_signal_work_group(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe, const Group &group)#
template<typename Group>
void ishmemx_putmem_signal_work_group(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe, const Group &group)#
Parameters:

  • dest – Symmetric address of the destination data object. The type of dest should match the TYPE and TYPENAME according to the table of Standard RMA types.

  • source – Local address of the data object containing the data to be copied. The type of source should match the TYPE and TYPENAME according to the table of Standard RMA types.

  • nelems – Number of elements in the dest and source arrays. For ishmemx_putmem_signal_work_group, elements are bytes.

  • sig_addr – Symmetric address of the signal data object to be updated on the remote PE as a signal.

  • signal – Unsigned 64-bit value that is used for updating the remote sig_addr signal data object.

  • sig_op – Signal operator that represents the type of update to be performed on the remote sig_addr signal data object.

  • pe – PE number of the remote PE.

  • group – The SYCL group or sub_group on which to collectively perform the Put operation.

Callable from the device.

Description:

The put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion. The routines return after the data has been copied out of the source array on the local PE.

The sig_op signal operator determines the type of update to be performed on the remote sig_addr signal data object. The completion of signal update based on the sig_op signal operator using the signal flag on the remote PE indicates the delivery of its corresponding dest data words into the data object on the remote PE.

An update to the sig_addr signal data object through a put-with-signal routine completes as if performed atomically as described in Section Atomicity Guarantees for Signaling Operations. The various options as described in Section Available Signal Operators can be used as the sig_op signal operator.

The dest and sig_addr data objects must both be remotely accessible and may not be overlapping in memory.

The completion of signal update using the signal flag on the remote PE indicates only the delivery of its corresponding dest data words into the data object on the remote PE. Without a memory-ordering operation, there is no implied ordering between the signal update of a put-with-signal routine and another data transfer. For example, the completion of the signal update in a sequence consisting of a put routine followed by a put-with-signal routine does not imply delivery of the put routine’s data.

Nonblocking Put-Signal#

ISHMEM_PUT_NBI_SIGNAL#

The nonblocking put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion.

In the functions below, TYPE is one of the standard RMA types and has a corresponding TYPENAME specified by Table Standard RMA Types.

template<typename TYPE>
void ishmem_put_signal_nbi(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe)#
void ishmem_TYPENAME_put_signal_nbi(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe)#
Parameters:

  • dest – Symmetric address of the destination data object. The type of dest should match the TYPE of TYPENAME according to the table of Standard RMA types.

  • source – Local address of the data object containing the data to be copied. The type of source should match the TYPE and TYPENAME according to the table of Standard RMA types.

  • nelems – Number of elements in the dest and source arrays. For ishmem_putmem, elements are bytes.

  • sig_addr – Symmetric address of the signal data object to be updated on the remote PE as a signal.

  • signal – Unsigned 64-bit value that is used for updating the remote sig_addr signal data object.

  • sig_op – Signal operator that represents the type of update to be performed on the remote sig_addr signal data object.

  • pe – PE number of the remote PE.

Callable from the host and device.

Description: The nonblocking put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion.

The routines return after initiating the operation. The operation is considered complete after a subsequent call to ishmem_quiet or ishmemx_quiet_work_group. At the completion of the quiet operation, the data has been copied out of the source array on the local PE and delivered into the dest array on the destination PE.

The delivery of the signal flag on the remote PE indicates only the delivery of its corresponding dest data words into the data object on the remote PE. Furthermore, two successive nonblocking put-with-signal routines, or a nonblocking put-with-signal routine with another data transfer may deliver data out of order unless a call to ishmem_fence or ishmemx_fence_work_group is introduced between the two calls.

The sig_op signal operator determines the type of update to be performed on the remote sig_addr signal data object.

An update to the sig_addr signal data object through a nonblocking put-with-signal routine completes as if performed atomically as described in Section Atomicity Guarantees for Signaling Operations. The various options as described in Section Available Signal Operators can be used as the sig_op signal operator.

The dest and sig_addr data objects must both be remotely accessible and may not be overlapping in memory.

ISHMEMX_PUT_NBI_SIGNAL_WORK_GROUP#

The nonblocking put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion.

In the functions below, TYPE is one of the standard RMA types and has a corresponding TYPENAME specified by Table Standard RMA Types.

template<typename TYPE, typename Group>
void ishmemx_put_signal_nbi_work_group(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe, const Group &group)#
template<typename Group>
void ishmemx_TYPENAME_put_signal_nbi_work_group(TYPE *dest, const TYPE *source, size_t nelems, uint64_t *sig_addr, uint64_t signal, int sig_op, int pe, const Group &group)#
Parameters:

  • dest – Symmetric address of the destination data object. The type of dest should match the TYPE of TYPENAME according to the table of Standard RMA types.

  • source – Local address of the data object containing the data to be copied. The type of source should match the TYPE and TYPENAME according to the table of Standard RMA types.

  • nelems – Number of elements in the dest and source arrays. For ishmem_putmem, elements are bytes.

  • sig_addr – Symmetric address of the signal data object to be updated on the remote PE as a signal.

  • signal – Unsigned 64-bit value that is used for updating the remote sig_addr signal data object.

  • sig_op – Signal operator that represents the type of update to be performed on the remote sig_addr signal data object.

  • pe – PE number of the remote PE.

  • group – The SYCL group or sub_group on which to collectively perform the Put operation.

Callable from the device.

Description:

The nonblocking put-with-signal routines provide a method for copying data from a contiguous local data object to a data object on a specified PE and subsequently updating a remote flag to signal completion.

The routines return after initiating the operation. The operation is considered complete after a subsequent call to ishmem_quiet or ishmemx_quiet_work_group. At the completion of the quiet operation, the data has been copied out of the source array on the local PE and delivered into the dest array on the destination PE.

The delivery of the signal flag on the remote PE indicates only the delivery of its corresponding dest data words into the data object on the remote PE. Furthermore, two successive nonblocking put-with-signal routines, or a nonblocking put-with-signal routine with another data transfer may deliver data out of order unless a call to ishmem_fence or ishmemx_fence_work_group is introduced between the two calls.

The sig_op signal operator determines the type of update to be performed on the remote sig_addr signal data object.

An update to the sig_addr signal data object through a nonblocking put-with-signal routine completes as if performed atomically as described in Section Atomicity Guarantees for Signaling Operations. The various options as described in Section Available Signal Operators can be used as the sig_op signal operator.

The dest and sig_addr data objects must both be remotely accessible and may not be overlapping in memory.

ISHMEM_SIGNAL_FETCH#

Fetches the signal update on a local data object.

uint64_t ishmem_signal_fetch(const uint64_t *sig_addr)#
Parameters:

sig_addr – Local address of the remotely accessible signal variable.

Returns:

The contents of the signal data object, sig_addr, at the calling PE.

Callable from the host and device.

Description: ishmem_signal_fetch performs a fetch operation and returns the contents of the sig_addr signal data object. Access to sig_addr signal object at the calling PE is expected to satisfy the atomicity guarantees as described in Section Atomicity Guarantees for Signaling Operations.