ExtPot.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/potentials/ExtPot/ExtPot.h"
#include "eon/potentials/ExtPot/ExtPotCommand.h"
#include "eon/potentials/ExternalCommand.h"
 
#include <atomic>
#include <filesystem>
#include <format>
#include <fstream>
#include <stdexcept>
#include <string>
#include <system_error>
 
#ifdef _WIN32
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#ifndef NOMINMAX
#define NOMINMAX
#endif
#include <process.h>
#include <windows.h>
#else
#include <unistd.h>
#endif
 
namespace {
 
// The names the external program reads and writes. They are part of the
// documented interface and stay fixed; the directory holding them is what
// varies from one client to the next.
constexpr const char *kToExtPot = "from_eon_to_extpot";
constexpr const char *kFromExtPot = "from_extpot_to_eon";
 
// Names the directory eOn was started in for a wrapper that needs to reach
// back to it.
constexpr const char *kRunDirVariable = "EON_EXTPOT_RUN_DIR";
 
long processId() {
#ifdef _WIN32
  return static_cast<long>(_getpid());
#else
  return static_cast<long>(getpid());
#endif
}
 
#ifdef _WIN32
std::string windowsPythonCommand() {
  char buf[MAX_PATH];
  const DWORD n =
      SearchPathA(nullptr, "python.exe", nullptr, MAX_PATH, buf, nullptr);
  if (n > 0 && n < MAX_PATH) {
    return eonc::pot::shellQuote(std::string(buf));
  }
  return "python";
}
#endif

std::string composeCommand(const std::string &workDir,
                           const std::string &runDir,
                           const std::string &command) {
#ifdef _WIN32
  const std::string quotedCommand =
      eonc::pot::wrapResolvedProgram(command, windowsPythonCommand());
  // cmd.exe: quotes around name=value so the value does not include them.
  return std::format("cd /d {} && set \"{}={}\" && {}",
                     eonc::pot::shellQuote(workDir), kRunDirVariable, runDir,
                     quotedCommand);
#else
  const std::string quotedCommand = eonc::pot::wrapResolvedProgram(command, {});
  return std::format("cd {} && export {}={} && {}",
                     eonc::pot::shellQuote(workDir), kRunDirVariable,
                     eonc::pot::shellQuote(runDir), quotedCommand);
#endif
}

std::string resolveCommand(const std::string &command) {
  std::error_code ec;
  const std::filesystem::path named{command};
  if (!std::filesystem::is_regular_file(named, ec) || ec) {
    return command;
  }
  const std::filesystem::path resolved = std::filesystem::absolute(named, ec);
  if (ec) {
    return command;
  }
  return resolved.string();
}
 
} // namespace
 
ExtPot::ExtPot(const Parameters &p)
    : Potential(p),
      eon_extpot_path{resolveCommand(p.potential_options.extPotPath)} {}
 
void ExtPot::cleanMemory(void) {
  if (exchangeDir.empty() || retainExchangeDir) {
    return;
  }
  std::error_code ec;
  std::filesystem::remove(exchangeDir / kToExtPot, ec);
  std::filesystem::remove(exchangeDir / kFromExtPot, ec);
  // Removes the directory only when it is empty, so whatever else the
  // external program wrote there stays.
  std::filesystem::remove(exchangeDir, ec);
}
 
ExtPot::~ExtPot() { cleanMemory(); }
 
void ExtPot::prepareExchangeDir() {
  std::error_code ec;
  if (exchangeDir.empty()) {
    // One directory per potential object. A client started alongside this
    // one carries a different process id, and a second potential in this
    // process a different index, so no two of them name the same file.
    static std::atomic<long> instanceCount{0};
    const std::filesystem::path named{
        std::format("extpot_{}_{}", processId(), instanceCount.fetch_add(1))};
    exchangeDir = std::filesystem::absolute(named, ec);
    if (ec) {
      exchangeDir.clear();
      throw std::runtime_error(std::format("Could not resolve {}: {}",
                                           named.string(), ec.message()));
    }
  }
  std::filesystem::create_directory(exchangeDir, ec);
  if (ec) {
    throw std::runtime_error(std::format("Could not create {} to run {} in: {}",
                                         exchangeDir.string(), eon_extpot_path,
                                         ec.message()));
  }
  // A result left by an earlier call, or by a client that died holding this
  // process id, is read as this call's forces when the external program
  // writes nothing.
  std::filesystem::remove(exchangeDir / kFromExtPot, ec);
}
 
void ExtPot::force(long N, const double *R, const int *atomicNrs, double *F,
                   double *U, double *variance, const double *box) {
  variance = nullptr;
  if (eon_extpot_path.empty()) {
    throw std::runtime_error(
        "ExtPot needs potential_options.extPotPath to name a program to run");
  }
  prepareExchangeDir();
  retainExchangeDir = true;
  passToSystem(N, R, atomicNrs, box);
  std::error_code ec;
  const std::filesystem::path runDir = std::filesystem::current_path(ec);
  eonc::pot::runOrThrow(composeCommand(exchangeDir.string(),
                                       ec ? std::string{} : runDir.string(),
                                       eon_extpot_path));
  recieveFromSystem(N, F, U);
  retainExchangeDir = false;
  return;
}
 
void ExtPot::passToSystem(long N, const double *R, const int *atomicNrs,
                          const double *box)
// 'positions' of all particles and box
{
  const std::filesystem::path toExtPot = exchangeDir / kToExtPot;
  std::ofstream out(toExtPot, std::ios::trunc);
  if (!out) {
    throw std::runtime_error(
        std::format("Could not open {} for writing", toExtPot.string()));
  }
 
  for (int i = 0; i < 3; i++) {
    out << std::format("{:.19f}\t{:.19f}\t{:.19f}\n", box[i * 3 + 0],
                       box[i * 3 + 1], box[i * 3 + 2]);
  }
 
  for (long i = 0; i < N; i++) {
    out << std::format("{}\t{:.19f}\t{:.19f}\t{:.19f}\n", atomicNrs[i],
                       R[i * 3 + 0], R[i * 3 + 1], R[i * 3 + 2]);
  }
 
  out.close();
  if (!out) {
    throw std::runtime_error(
        std::format("Could not write the structure to {}", toExtPot.string()));
  }
  return;
}
 
void ExtPot::recieveFromSystem(long N, double *F, double *U)
// first line must be the total 'energy', the following lines should be the
// 'forces'
{
  const std::filesystem::path fromExtPot = exchangeDir / kFromExtPot;
  std::ifstream in(fromExtPot);
  if (!in) {
    throw std::runtime_error(
        std::format("Could not open {}; the external program left no result",
                    fromExtPot.string()));
  }
 
  if (!(in >> *U)) {
    throw std::runtime_error(
        std::format("Could not read the energy from {}", fromExtPot.string()));
  }
 
  for (long i = 0; i < N; i++) {
    if (!(in >> F[i * 3 + 0] >> F[i * 3 + 1] >> F[i * 3 + 2])) {
      throw std::runtime_error(
          std::format("{} holds forces for {} atoms, expected {}",
                      fromExtPot.string(), i, N));
    }
  }
  return;
}