VertexGenerators.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2019-2020 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.


#pragma once

#include "Acts/Definitions/Algebra.hpp"
#include "ActsExamples/Framework/RandomNumbers.hpp"
#include "ActsExamples/Generators/EventGenerator.hpp"

#include <random>

namespace ActsExamples {

struct FixedVertexGenerator : public EventGenerator::VertexGenerator {
  Acts::Vector4 fixed = Acts::Vector4::Zero();

  Acts::Vector4 operator()(RandomEngine& /* unused */) const override {
    return fixed;
  }
};

struct GaussianVertexGenerator : public EventGenerator::VertexGenerator {
  // standard deviation comes first, since it is more likely to be modified
  Acts::Vector4 stddev = {0.0, 0.0, 0.0, 0.0};
  Acts::Vector4 mean = {0.0, 0.0, 0.0, 0.0};

  Acts::Vector4 operator()(RandomEngine& rng) const override {
    auto normal = std::normal_distribution<double>(0.0, 1.0);
    Acts::Vector4 rndNormal = {
        normal(rng),
        normal(rng),
        normal(rng),
        normal(rng),
    };
    return mean + rndNormal.cwiseProduct(stddev);
  }
};

}  // namespace ActsExamples