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Process incoming chunk data immediately upon receipt. #1730

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Aug 19, 2021
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Process incoming chunk data immediately upon receipt. #1730

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5 changes: 4 additions & 1 deletion src/meep.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -777,9 +777,11 @@ struct comms_sequence {
// Upon destruction, the comms_manager waits for completion of all enqueued operations.
class comms_manager {
public:
using receive_callback = std::function<void()>;
virtual ~comms_manager() {}
virtual void send_real_async(const void *buf, size_t count, int dest, int tag) = 0;
virtual void receive_real_async(void *buf, size_t count, int source, int tag) = 0;
virtual void receive_real_async(void *buf, size_t count, int source, int tag,
const receive_callback &cb) = 0;
virtual size_t max_transfer_size() const { return std::numeric_limits<size_t>::max(); };
};

Expand Down Expand Up @@ -2149,6 +2151,7 @@ class fields {
double max_eps() const;
// step.cpp
void step_boundaries(field_type);
void process_incoming_chunk_data(field_type ft, const chunk_pair &comm_pair);

bool nosize_direction(direction d) const;
direction normal_direction(const volume &where) const;
Expand Down
20 changes: 17 additions & 3 deletions src/mympi.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -89,15 +89,26 @@ class mpi_comms_manager : public comms_manager {
mpi_comms_manager() {}
~mpi_comms_manager() override {
#ifdef HAVE_MPI
if (!reqs.empty()) {
MPI_Waitall(reqs.size(), reqs.data(), MPI_STATUSES_IGNORE);
int num_pending_requests = reqs.size();
std::vector<int> completed_indices(num_pending_requests);
while (num_pending_requests) {
int num_completed_requests = 0;
MPI_Waitsome(reqs.size(), reqs.data(), &num_completed_requests, completed_indices.data(),
MPI_STATUSES_IGNORE);
for (int i = 0; i < num_completed_requests; ++i) {
int request_idx = completed_indices[i];
callbacks[request_idx]();
reqs[request_idx] = MPI_REQUEST_NULL;
--num_pending_requests;
}
}
#endif
}

void send_real_async(const void *buf, size_t count, int dest, int tag) override {
#ifdef HAVE_MPI
reqs.emplace_back();
callbacks.push_back(/*no-op*/ []{});
MPI_Isend(buf, static_cast<int>(count), MPI_REALNUM, dest, tag, mycomm, &reqs.back());
#else
(void)buf;
Expand All @@ -107,9 +118,11 @@ class mpi_comms_manager : public comms_manager {
#endif
}

void receive_real_async(void *buf, size_t count, int source, int tag) override {
void receive_real_async(void *buf, size_t count, int source, int tag,
const receive_callback &cb) override {
#ifdef HAVE_MPI
reqs.emplace_back();
callbacks.push_back(cb);
MPI_Irecv(buf, static_cast<int>(count), MPI_REALNUM, source, tag, mycomm, &reqs.back());
#else
(void)buf;
Expand All @@ -127,6 +140,7 @@ class mpi_comms_manager : public comms_manager {
#ifdef HAVE_MPI
std::vector<MPI_Request> reqs;
#endif
std::vector<receive_callback> callbacks;
};

} // namespace
Expand Down
129 changes: 74 additions & 55 deletions src/step.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -168,6 +168,59 @@ void fields_chunk::phase_material(int phasein_time) {
}
}

void fields::process_incoming_chunk_data(field_type ft, const chunk_pair &comm_pair) {
am_now_working_on(Boundaries);
int this_chunk_idx = comm_pair.second;
const int pair_idx = chunk_pair_to_index(comm_pair);
const realnum *pair_comm_block = static_cast<realnum *>(comm_blocks[ft][pair_idx]);

{
const comms_key key = {ft, CONNECT_PHASE, comm_pair};
size_t num_transfers = get_comm_size(key) / 2; // Two realnums per complex
if (num_transfers) {
const std::complex<realnum> *pair_comm_block_complex =
reinterpret_cast<const std::complex<realnum> *>(pair_comm_block);
const std::vector<realnum *> &incoming_connection =
chunks[this_chunk_idx]->connections_in.at(key);
const std::vector<std::complex<realnum> > &connection_phase_for_ft =
chunks[this_chunk_idx]->connection_phases[key];

for (size_t n = 0; n < num_transfers; ++n) {
std::complex<realnum> temp = connection_phase_for_ft[n] * pair_comm_block_complex[n];
*(incoming_connection[2 * n]) = temp.real();
*(incoming_connection[2 * n + 1]) = temp.imag();
}
pair_comm_block += 2 * num_transfers;
}
}

{
const comms_key key = {ft, CONNECT_NEGATE, comm_pair};
const size_t num_transfers = get_comm_size(key);
if (num_transfers) {
const std::vector<realnum *> &incoming_connection =
chunks[this_chunk_idx]->connections_in.at(key);
for (size_t n = 0; n < num_transfers; ++n) {
*(incoming_connection[n]) = -pair_comm_block[n];
}
pair_comm_block += num_transfers;
}
}

{
const comms_key key = {ft, CONNECT_COPY, comm_pair};
const size_t num_transfers = get_comm_size(key);
if (num_transfers) {
const std::vector<realnum *> &incoming_connection =
chunks[this_chunk_idx]->connections_in.at(key);
for (size_t n = 0; n < num_transfers; ++n) {
*(incoming_connection[n]) = pair_comm_block[n];
}
}
}
finished_working();
}

void fields::step_boundaries(field_type ft) {
connect_chunks(); // re-connect if !chunk_connections_valid

Expand All @@ -178,8 +231,12 @@ void fields::step_boundaries(field_type ft) {
const auto &sequence = comms_sequence_for_field[ft];
for (const comms_operation &op : sequence.receive_ops) {
if (chunks[op.other_chunk_idx]->is_mine()) { continue; }
chunk_pair comm_pair{op.other_chunk_idx, op.my_chunk_idx};
comms_manager::receive_callback cb = [this, ft, comm_pair]() {
process_incoming_chunk_data(ft, comm_pair);
};
manager->receive_real_async(comm_blocks[ft][op.pair_idx], static_cast<int>(op.transfer_size),
op.other_proc_id, op.tag);
op.other_proc_id, op.tag, cb);
}

// Do the metals first!
Expand All @@ -198,70 +255,32 @@ void fields::step_boundaries(field_type ft) {
for (connect_phase ip : all_connect_phases) {
const comms_key key = {ft, ip, comm_pair};
const size_t pair_comm_size = get_comm_size(key);
const std::vector<realnum *> &outgoing_connection =
chunks[op.my_chunk_idx]->connections_out[key];
for (size_t n = 0; n < pair_comm_size; ++n) {
outgoing_comm_block[n] = *(outgoing_connection[n]);
if (pair_comm_size) {
const std::vector<realnum *> &outgoing_connection =
chunks[op.my_chunk_idx]->connections_out.at(key);
for (size_t n = 0; n < pair_comm_size; ++n) {
outgoing_comm_block[n] = *(outgoing_connection[n]);
}
outgoing_comm_block += pair_comm_size;
}
outgoing_comm_block += pair_comm_size;
}
if (chunks[op.other_chunk_idx]->is_mine()) { continue; }
manager->send_real_async(comm_blocks[ft][pair_idx], static_cast<int>(op.transfer_size),
op.other_proc_id, op.tag);
}

// Process local transfers, which do not depend on a communication mechanism across nodes.
for (const comms_operation &op : sequence.receive_ops) {
if (chunks[op.other_chunk_idx]->is_mine()) {
process_incoming_chunk_data(ft, {op.other_chunk_idx, op.my_chunk_idx});
}
}
finished_working();

am_now_working_on(MpiOneTime);
// Let the communication manager drop out of scope to complete all outstanding requests.
}
finished_working();

// Finally, copy incoming data to the fields themselves, multiplying phases:
am_now_working_on(Boundaries);
for (int i = 0; i < num_chunks; i++) {
if (!chunks[i]->is_mine()) continue;

for (int j = 0; j < num_chunks; j++) {
const chunk_pair comm_pair{j, i};
const int pair_idx = chunk_pair_to_index(comm_pair);
const realnum *pair_comm_block = static_cast<realnum *>(comm_blocks[ft][pair_idx]);

{
const std::complex<realnum> *pair_comm_block_complex =
reinterpret_cast<const std::complex<realnum> *>(pair_comm_block);
const comms_key key = {ft, CONNECT_PHASE, comm_pair};
const std::vector<realnum *> &incoming_connection = chunks[i]->connections_in[key];
const std::vector<std::complex<realnum> > &connection_phase_for_ft =
chunks[i]->connection_phases[key];
size_t num_transfers = get_comm_size(key) / 2; // Two realnums per complex

for (size_t n = 0; n < num_transfers; ++n) {
std::complex<realnum> temp = connection_phase_for_ft[n] * pair_comm_block_complex[n];
*(incoming_connection[2 * n]) = temp.real();
*(incoming_connection[2 * n + 1]) = temp.imag();
}
pair_comm_block += 2 * num_transfers;
}

{
const comms_key key = {ft, CONNECT_NEGATE, comm_pair};
const std::vector<realnum *> &incoming_connection = chunks[i]->connections_in[key];
const size_t num_transfers = get_comm_size(key);
for (size_t n = 0; n < num_transfers; ++n) {
*(incoming_connection[n]) = -pair_comm_block[n];
}
pair_comm_block += num_transfers;
}

{
const comms_key key = {ft, CONNECT_COPY, comm_pair};
const std::vector<realnum *> &incoming_connection = chunks[i]->connections_in[key];
const size_t num_transfers = get_comm_size(key);
for (size_t n = 0; n < num_transfers; ++n) {
*(incoming_connection[n]) = pair_comm_block[n];
}
}
}
// As data is received, the installed callback handles copying the data from the comm buffer
// back into the chunk field array.
}
finished_working();
}
Expand Down