ServeRpcServer.cpp

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/*
** This file is part of eOn.
**
** SPDX-License-Identifier: BSD-3-Clause
**
** Copyright (c) 2010--present, eOn Development Team
** All rights reserved.
**
** Repo:
** https://github.com/TheochemUI/eOn
*/

 
#include "eon/ServeRpcServer.h"
#include "eon/BaseStructures.h"
#include "eon/EonLogger.h"
 
#include <atomic>
#include <capnp/ez-rpc.h>
#include <kj/debug.h>
#include <mutex>
 
// Cap'n Proto generated header (from Potentials.capnp).
// This defines `class Potential` -- which collides with eOn's Potential class,
// hence the separate translation unit.
#include "Potentials.capnp.h"
 
namespace {

class CallbackPotImpl final : public Potential::Server {
public:
  explicit CallbackPotImpl(ForceCallback cb)
      : m_callback(std::move(cb)) {}
 
  kj::Promise<void> calculate(CalculateContext context) override {
    auto fip = context.getParams().getFip();
    const size_t numAtoms = fip.getPos().size() / 3;
 
    KJ_REQUIRE(fip.getAtmnrs().size() == numAtoms, "AtomNumbers size mismatch");
 
    // Extract flat arrays from capnp
    std::vector<double> positions(numAtoms * 3);
    auto capnpPos = fip.getPos();
    for (size_t i = 0; i < numAtoms * 3; ++i) {
      positions[i] = capnpPos[i];
    }
 
    std::vector<int> atomicNrs(numAtoms);
    auto capnpAtmnrs = fip.getAtmnrs();
    for (size_t i = 0; i < numAtoms; ++i) {
      atomicNrs[i] = capnpAtmnrs[i];
    }
 
    double box[9] = {};
    auto capnpBox = fip.getBox();
    for (size_t i = 0; i < 9 && i < capnpBox.size(); ++i) {
      box[i] = capnpBox[i];
    }
 
    // Call the force callback
    std::vector<double> forces(numAtoms * 3, 0.0);
    double energy = 0.0;
    m_callback(static_cast<long>(numAtoms), positions.data(), atomicNrs.data(),
               forces.data(), &energy, box);
 
    // Serialize result back to capnp
    auto result = context.getResults();
    auto pres = result.initResult();
    pres.setEnergy(energy);
 
    auto forcesList = pres.initForces(numAtoms * 3);
    for (size_t i = 0; i < numAtoms * 3; ++i) {
      forcesList.set(i, forces[i]);
    }
 
    return kj::READY_NOW;
  }
 
private:
  ForceCallback m_callback;
};
 
} // anonymous namespace
 
void eonc::startRpcServer(ForceCallback callback, const std::string &host,
                          uint16_t port) {
  EONC_LOG_INFO("Starting Cap'n Proto RPC server on {}:{}", host, port);
 
  capnp::EzRpcServer server(kj::heap<CallbackPotImpl>(std::move(callback)),
                            host, port);
 
  auto &waitScope = server.getWaitScope();
  EONC_LOG_INFO("Server ready on port {}. Ctrl+C to stop.", port);
  kj::NEVER_DONE.wait(waitScope);
}
 
// ---------------------------------------------------------------------------
// Pooled (round-robin gateway) server
// ---------------------------------------------------------------------------
 
namespace {

class PooledCallbackPotImpl final : public Potential::Server {
public:
  explicit PooledCallbackPotImpl(std::vector<ForceCallback> pool)
      : m_pool(std::move(pool)),
        m_mutexes(m_pool.size()),
        m_next(0) {}
 
  kj::Promise<void> calculate(CalculateContext context) override {
    size_t idx = m_next.fetch_add(1, std::memory_order_relaxed) % m_pool.size();
 
    auto fip = context.getParams().getFip();
    const size_t numAtoms = fip.getPos().size() / 3;
 
    KJ_REQUIRE(fip.getAtmnrs().size() == numAtoms, "AtomNumbers size mismatch");
 
    std::vector<double> positions(numAtoms * 3);
    auto capnpPos = fip.getPos();
    for (size_t i = 0; i < numAtoms * 3; ++i) {
      positions[i] = capnpPos[i];
    }
 
    std::vector<int> atomicNrs(numAtoms);
    auto capnpAtmnrs = fip.getAtmnrs();
    for (size_t i = 0; i < numAtoms; ++i) {
      atomicNrs[i] = capnpAtmnrs[i];
    }
 
    double box[9] = {};
    auto capnpBox = fip.getBox();
    for (size_t i = 0; i < 9 && i < capnpBox.size(); ++i) {
      box[i] = capnpBox[i];
    }
 
    std::vector<double> forces(numAtoms * 3, 0.0);
    double energy = 0.0;
 
    std::lock_guard<std::mutex> lock(m_mutexes[idx]);
    m_pool[idx](static_cast<long>(numAtoms), positions.data(), atomicNrs.data(),
                forces.data(), &energy, box);
 
    auto result = context.getResults();
    auto pres = result.initResult();
    pres.setEnergy(energy);
 
    auto forcesList = pres.initForces(numAtoms * 3);
    for (size_t i = 0; i < numAtoms * 3; ++i) {
      forcesList.set(i, forces[i]);
    }
 
    return kj::READY_NOW;
  }
 
private:
  std::vector<ForceCallback> m_pool;
  std::vector<std::mutex> m_mutexes;
  std::atomic<size_t> m_next;
};
 
} // anonymous namespace
 
void eonc::startPooledRpcServer(std::vector<ForceCallback> pool,
                                const std::string &host, uint16_t port) {
  EONC_LOG_INFO("Starting pooled RPC gateway on {}:{} with {} instances", host,
                port, pool.size());
 
  capnp::EzRpcServer server(kj::heap<PooledCallbackPotImpl>(std::move(pool)),
                            host, port);
 
  auto &waitScope = server.getWaitScope();
  EONC_LOG_INFO("Gateway ready on port {}. Ctrl+C to stop.", port);
  kj::NEVER_DONE.wait(waitScope);
}