qsim_von_neumann.cc

// Copyright 2019 Google LLC. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <unistd.h>

#include <algorithm>
#include <cmath>
#include <complex>
#include <functional>
#include <limits>
#include <string>

#include "../lib/circuit_qsim_parser.h"
#include "../lib/formux.h"
#include "../lib/fuser_mqubit.h"
#include "../lib/gates_qsim.h"
#include "../lib/io_file.h"
#include "../lib/run_qsim.h"
#include "../lib/simmux.h"
#include "../lib/util_cpu.h"

constexpr char usage[] = "usage:\n  ./qsim_von_neumann -c circuit -d maxtime "
                         "-s seed -t threads -f max_fused_size "
                         "-v verbosity -z\n";

struct Options {
  std::string circuit_file;
  unsigned maxtime = std::numeric_limits<unsigned>::max();
  unsigned seed = 1;
  unsigned num_threads = 1;
  unsigned max_fused_size = 2;
  unsigned verbosity = 0;
  bool denormals_are_zeros = false;
};

Options GetOptions(int argc, char* argv[]) {
  Options opt;

  int k;

  while ((k = getopt(argc, argv, "c:d:s:t:f:v:z")) != -1) {
    switch (k) {
      case 'c':
        opt.circuit_file = optarg;
        break;
      case 'd':
        opt.maxtime = std::atoi(optarg);
        break;
      case 's':
        opt.seed = std::atoi(optarg);
        break;
      case 't':
        opt.num_threads = std::atoi(optarg);
        break;
      case 'f':
        opt.max_fused_size = std::atoi(optarg);
        break;
      case 'v':
        opt.verbosity = std::atoi(optarg);
        break;
      case 'z':
        opt.denormals_are_zeros = true;
        break;
      default:
        qsim::IO::errorf(usage);
        exit(1);
    }
  }

  return opt;
}

bool ValidateOptions(const Options& opt) {
  if (opt.circuit_file.empty()) {
    qsim::IO::errorf("circuit file is not provided.\n");
    qsim::IO::errorf(usage);
    return false;
  }

  return true;
}

int main(int argc, char* argv[]) {
  using namespace qsim;

  auto opt = GetOptions(argc, argv);
  if (!ValidateOptions(opt)) {
    return 1;
  }

  Circuit<GateQSim<float>> circuit;
  if (!CircuitQsimParser<IOFile>::FromFile(opt.maxtime, opt.circuit_file,
                                           circuit)) {
    return 1;
  }

  if (opt.denormals_are_zeros) {
    SetFlushToZeroAndDenormalsAreZeros();
  }

  struct Factory {
    Factory(unsigned num_threads) : num_threads(num_threads) {}

    using Simulator = qsim::Simulator<For>;
    using StateSpace = Simulator::StateSpace;

    StateSpace CreateStateSpace() const {
      return StateSpace(num_threads);
    }

    Simulator CreateSimulator() const {
      return Simulator(num_threads);
    }

    unsigned num_threads;
  };

  using Simulator = Factory::Simulator;
  using StateSpace = Simulator::StateSpace;
  using State = StateSpace::State;
  using Fuser = MultiQubitGateFuser<IO, GateQSim<float>>;
  using Runner = QSimRunner<IO, Fuser, Factory>;

  auto measure = [&opt, &circuit](
      unsigned k, const StateSpace& state_space, const State& state) {
    using Op = std::plus<double>;

    auto f = [](unsigned n, unsigned m, uint64_t i,
                const StateSpace& state_space, const State& state) -> double {
      auto p = std::norm(state_space.GetAmpl(state, i));
      return p != 0 ? p * std::log(p) : 0;
    };

    double entropy = -For(opt.num_threads).RunReduce(
        uint64_t{1} << state.num_qubits(), f, Op(), state_space, state);
    IO::messagef("entropy=%g\n", entropy);
  };

  Runner::Parameter param;
  param.max_fused_size = opt.max_fused_size;
  param.seed = opt.seed;
  param.verbosity = opt.verbosity;

  Runner::Run(param, Factory(opt.num_threads), circuit, measure);

  return 0;
}