api/include/gmxapi/session.h

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  35 /*! \file
  36  * \brief Launch and manage a GROMACS session.
  37  *
  38  * \author M. Eric Irrgang <ericirrgang@gmail.com>
  39  *
  40  * \ingroup gmxapi
  41  */
  42
  43 #ifndef GROMACS_SESSION_H
  44 #define GROMACS_SESSION_H
  45
  46 /*! \file
  47  * \brief Declarations for a workflow execution session and helper functions.
  48  *
  49  * \ingroup gmxapi
  50  */
  51
  52 #include <memory>
  53 #include <string>
  54
  55 namespace gmxapi
  56 {
  57
  58 // forward declarations
  59 class Context; // defined in gmxapi/context.h
  60 class MDModule;
  61 class Status;   // defined in gmxapi/status.h
  62 class Workflow; // implementation detail
  63
  64 /*!
  65  * \brief Private implementation class for a session.
  66  *
  67  * Actual implementation class may depend on the execution context, but this should be irrelevant to
  68  * a client. The implementation details are not exposed in the high-level API, but may be in the
  69  * extension API. See developer documentation for details.
  70  *
  71  * \ingroup gmxapi
  72  */
  73 class SessionImpl;
  74
  75 /*!
  76  * \brief Workflow execution session.
  77  *
  78  * When a workflow is launched in an execution context, the result is a Session object
  79  * that serves as a handle to interact with the running workflow. The handle allows dynamic changes
  80  * to the workflow, or control or data crossing the API boundary.
  81  *
  82  * Separating run() from construction allows the client to examine the running execution
  83  * environment or to retrieve the communicator before beginning long-running computation.
  84  *
  85  * The session should be explicitly `close()`ed before destruction to allow exception
  86  * handling during shutdown. The destructor will close() the session if it is not
  87  * closed already, but errors may be hidden.
  88  *
  89  * The session owns a Status object that can be shared and retained by client code
  90  * for further inspection.
  91  *
  92  * \ingroup gmxapi
  93  */
  94 class Session
  95 {
  96 public:
  97     /// A session must be created by launching a workflow in an execution context.
  98     Session() = delete;
  99
 100     /*! \brief A session cannot be copied, only moved.
 101      *
 102      * For shared ownership of a session, use a shared pointer.
 103      * \{
 104      */
 105     Session(const Session&) = delete;
 106     Session& operator=(const Session&) = delete;
 107     //! \}
 108
 109     /*!
 110      * \brief Pass ownership of a Session.
 111      *
 112      * \{
 113      */
 114     Session(Session&&) noexcept = default;
 115     Session& operator=(Session&&) noexcept = default;
 116     //! \}
 117
 118     /*!
 119      * \brief Construct by taking ownership of an implementation object.
 120      *
 121      * \param impl Concrete object to take ownership of.
 122      */
 123     explicit Session(std::unique_ptr<SessionImpl> impl) noexcept;
 124
 125     /*!
 126      * \brief Destroy Session.
 127      *
 128      * If the session is still active (has not been closed) then it will be closed
 129      * with exceptions suppressed. If possible, problems encountered will be
 130      * noted in the Status object, which the client may have retained shared
 131      * ownership of.
 132      */
 133     ~Session();
 134
 135     /*!
 136      * \brief Close a running session.
 137      *
 138      * close() should be called before destroying the Session object so that the
 139      * client can catch any exceptions thrown during shut down that may be
 140      * unavoidable in the parallel computing environment.
 141      *
 142      * \return status of close() operation.
 143      */
 144     Status close();
 145
 146     /*!
 147      * \brief Run the current workflow to completion.
 148      *
 149      * The client should examine the Status object for errors and resulting workflow state.
 150      * \return the Session's Status after the run.
 151      */
 152     Status run() noexcept;
 153
 154     /*!
 155      * \brief Check if session is running.
 156      *
 157      * A Session will be "open" from the point of launch until "close" is
 158      * called. If this is not true, either an error has occurred or there is
 159      * a bug in the implementation.
 160      *
 161      * \return `true` if the session is running, else `false`
 162      */
 163     bool isOpen() const noexcept;
 164
 165     /*! \cond internal
 166      * \brief Get a non-owning handle to the implementation object.
 167      *
 168      * Get a raw pointer to the implementation object. The pointer is valid only during the lifetime of the Session,
 169      * so retain a shared pointer to this Session object or only hold the pointer for the duration of a code block
 170      * guaranteed to exist entirely within the lifetime of a Session object.
 171      *
 172      * \return opaque pointer used by gmxapi implementation and extension code.
 173      */
 174     SessionImpl* getRaw() const noexcept;
 175     //! \endcond
 176
 177 private:
 178     //! \brief opaque pointer to implementation
 179     std::unique_ptr<SessionImpl> impl_;
 180 };
 181
 182 /*!
 183  * \brief Add a uniquely identifiable restraint instance to the MD simulator.
 184  *
 185  * \param session Session with an MD runner to attach a restraint to.
 186  * \param restraint wrapped restraint force calculation object.
 187  * \return success if restraint was attached successfully, else failure.
 188  *
 189  * \todo Clarify whether we are adding modules generally, adding restraint modules, or adding restraints.
 190  * \todo Update for new scheme in which all restraints are managed by a single Restraint module.
 191  * \todo Figure out what this object should return to provide more utility and rigorous error checking.
 192  */
 193 Status addSessionRestraint(Session* session, std::shared_ptr<gmxapi::MDModule> restraint);
 194
 195 /*!
 196  * \brief Launch a workflow in the provided execution context.
 197  *
 198  * \param context Execution environment
 199  * \param work Directed acyclic graph defining workflow and data flow.
 200  * \return non-unique ownership of the session or nullptr in failure.
 201  *
 202  * The provided context maintains a weak reference to the executing session, while
 203  * the session extends the life of the context.
 204  *
 205  * If session fails to launch (nullptr returned) examine the Status of the context
 206  * for details.
 207  * \ingroup gmxapi
 208  */
 209 std::shared_ptr<Session> launchSession(Context* context, const Workflow& work) noexcept;
 210
 211
 212 } // end namespace gmxapi
 213
 214 #endif // GROMACS_SESSION_H