TNOTIFY¶

Introduction¶

Send flag notification to remote NPU. Used for lightweight synchronization between NPUs without transferring bulk data.

Math Interpretation¶

For NotifyOp::Set:

For NotifyOp::AtomicAdd:

Assembly Syntax¶

PTO-AS form: see PTO-AS Specification.

tnotify %signal_remote, %value {op = #pto.notify_op<Set>} : (!pto.memref<i32>, i32)
tnotify %signal_remote, %value {op = #pto.notify_op<AtomicAdd>} : (!pto.memref<i32>, i32)

C++ Intrinsic¶

Declared in include/pto/comm/pto_comm_inst.hpp:

template <typename GlobalSignalData, typename... WaitEvents>
PTO_INST void TNOTIFY(GlobalSignalData &dstSignalData, int32_t value, NotifyOp op, WaitEvents&... events);

Constraints¶

• Type constraints:
  • GlobalSignalData::DType must be int32_t (32-bit signal).
• Memory constraints:
  • dstSignalData must point to remote address (on target NPU).
  • dstSignalData should be 4-byte aligned.
• Operation semantics:
  • NotifyOp::Set: Direct store to remote memory.
  • NotifyOp::AtomicAdd: Hardware atomic add using st_atomic instruction.

Examples¶

Basic Set Notification¶

#include <pto/comm/pto_comm_inst.hpp>

using namespace pto;

void notify_set(__gm__ int32_t* remote_signal) {
    comm::Signal sig(remote_signal);

    // Set remote signal to 1
    comm::TNOTIFY(sig, 1, comm::NotifyOp::Set);
}

Atomic Counter Increment¶

#include <pto/comm/pto_comm_inst.hpp>

using namespace pto;

void atomic_increment(__gm__ int32_t* remote_counter) {
    comm::Signal counter(remote_counter);

    // Atomically add 1 to remote counter
    comm::TNOTIFY(counter, 1, comm::NotifyOp::AtomicAdd);
}

Producer-Consumer Pattern¶

#include <pto/comm/pto_comm_inst.hpp>

using namespace pto;

// Producer: notify when data is ready
void producer(__gm__ int32_t* remote_flag) {
    // ... produce data ...

    comm::Signal flag(remote_flag);
    comm::TNOTIFY(flag, 1, comm::NotifyOp::Set);
}

// Consumer: wait for data
void consumer(__gm__ int32_t* local_flag) {
    comm::Signal flag(local_flag);
    comm::TWAIT(flag, 1, comm::WaitCmp::EQ);

    // ... consume data ...
}