SpectrumAlgorithm.h

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2016 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#pragma once
 
#include <tuple>
 
#include "MantidAPI/Algorithm.h"
#include "MantidAPI/MatrixWorkspace_fwd.h"
#include "MantidAlgorithms/DllConfig.h"
#include "MantidKernel/IndexSet.h"
 
namespace Mantid {
 
namespace DataObjects {
class EventWorkspace;
}
 
namespace Algorithms {
 
class MANTID_ALGORITHMS_DLL SpectrumAlgorithm : public API::Algorithm {
private:
  template <std::size_t...> struct seq {};
  // Doxygen does not like recursive types.
  template <std::size_t N, std::size_t... S>
  struct gens                                      
      : gens<N - 1, N - 1, S...>  { 
  };
  template <std::size_t... S> struct gens<0, S...> { 
    using type = seq<S...>;
  };
 
  template <typename Tp, typename... List> struct contains : std::true_type {};
  template <typename Tp, typename Head, typename... Rest>
  struct contains<Tp, Head, Rest...>
      : std::conditional<std::is_same<Tp, Head>::value, std::true_type, contains<Tp, Rest...>>::type {};
  template <typename Tp> struct contains<Tp> : std::false_type {};
 
  template <class... Flags, class WS, class T, std::size_t... S, class OP>
  void for_each(WS &workspace, T getters, seq<S...>, const OP &operation) {
    // If we get the flag Indices::FromProperty we use a potential user-defined
    // range property, otherwise default to the full range of all histograms.
    Kernel::IndexSet indexSet(workspace.getNumberHistograms());
    if (contains<Indices::FromProperty, Flags...>())
      indexSet = getWorkspaceIndexSet(workspace);
    auto size = static_cast<int64_t>(indexSet.size());
    API::Progress progress(this, 0.0, 1.0, size);
 
    PARALLEL_FOR_IF(Kernel::threadSafe(workspace))
    for (int64_t i = 0; i < size; ++i) {
      PARALLEL_START_INTERRUPT_REGION
      // Note the small but for now negligible overhead from the IndexSet access
      // in the case where it is not used.
      operation(std::get<S>(getters)(workspace, indexSet[i])...);
      progress.report(name());
      PARALLEL_END_INTERRUPT_REGION
    }
    PARALLEL_CHECK_INTERRUPT_REGION
 
    ifEventWorkspaceClearMRU(workspace);
  }
 
  template <class WS> void ifEventWorkspaceClearMRU(const WS &workspace) { UNUSED_ARG(workspace); }
 
  std::string m_indexMinPropertyName;
  std::string m_indexMaxPropertyName;
  std::string m_indexRangePropertyName;
 
protected:
  ~SpectrumAlgorithm() = default;
 
  // A strongly typed enum used in non-type variadic template arguments would
  // have been the other candidate. However, combining flags from multiple enums
  // would not have been possible, so all flags would have been required to be
  // in the same scoped enum, and we want to avoid noisy flag definitions like
  // Flags::IndicesFromProperty or Flags::SkipMasked.
  struct Indices {
    struct FromProperty {};
  };
 
  template <class... Flags, class WS, class... Args, class OP>
  void for_each(WS &workspace, std::tuple<Args...> getters, const OP &operation) {
    // This comment explains some of the rationale and mechanism for the way
    // templates are used in this and other variants of for_each().
    // For several variants of for_each() we require a variable number of
    // arguments for more than one entity, e.g., getters for the input workspace
    // and getters for the output workspace. For both of them we would thus like
    // to use a variadic template. However, we cannot make all those getters
    // direct arguments to for_each(), because the compiler then cannot tell
    // were the boundary between the two parameter packs is. Therefore getters
    // are packed into tuples.
    // At some point we need to extract the getters from the tuple. To this end,
    // we use the gens template, which recursively constructs a sequence of
    // indices which are gen used with std::get<>.
    // The Flags template parameter is used for passing in flags known at
    // compile time.
    for_each<Flags...>(workspace, getters, typename gens<sizeof...(Args)>::type(), operation);
  }
 
  void declareWorkspaceIndexSetProperties(const std::string &indexMinPropertyName = "IndexMin",
                                          const std::string &indexMaxPropertyName = "IndexMax",
                                          const std::string &indexRangePropertyName = "WorkspaceIndexList");
  Kernel::IndexSet getWorkspaceIndexSet(const API::MatrixWorkspace &workspace) const;
};
 
template <> void SpectrumAlgorithm::ifEventWorkspaceClearMRU(const DataObjects::EventWorkspace &workspace);
 
using SpectrumAlgorithm_sptr = std::shared_ptr<SpectrumAlgorithm>;
 
} // namespace Algorithms
} // namespace Mantid