G4CacheDetails.hh

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// $Id$
//
// ---------------------------------------------------------------
// GEANT 4 class header file
//
// Class Description:
//    The classes contained in this header files are used by
//     G4Cache to store a TLS instance of the cached object.
//    These classes should not be used by client code, but
//    are used by one of the G4Cache classes.
//
//    This class is container of the cached value
//    Not memory efficient, but CPU efficient (constant time access)
//    A different version with a map instead of a vector should be
//    memory efficient
//    and less CPU efficient (log-time access).
//    If really a lot of these objects are used
//    we may want to consider the map version to save some memory
//
//    These are simplified "split-classes" without any
//    copy-from-master logic. Each cached object is associated
//    a unique identified (an integer), that references an instance
//    of the cached value (of template type VALTYPE) in a
//    static TLS data structure
//
//    In case the cache is used for a cached object the object class
//    has to provide a default constructor. Alternatively pointers to
//    objects can be stored in the cache and this limitation is removed
//    but explicit handling of memory (new/delete) of cached object becomes
//    client responsibility.
//
// History:
//    21 Oct 2013: A. Dotti - First implementation
//
// Todos: - Understand if map based class can be more efficent than
//          vector one
//        - Evaluate use of specialized allocator for TLS "new"

#include <vector>
#include "G4Threading.hh"

#ifdef g4cdebug
#include <iostream>
#include <sstream>
using std::cout;
using std::endl;
#endif

// A TLS storage for a cache of type VALTYPE
template<class VALTYPE>
class G4CacheReference {
public:
    inline void Initialize( unsigned int id );
    // Initliaze TLS storage

    inline void Destroy( unsigned int id , G4bool last);
    // Cleanup TLS storage for instance id. If last==true
    // destroy and cleanup object container

    inline VALTYPE& GetCache(unsigned int id) const;
    // Returns cached value for instance id
private:
    typedef std::vector<VALTYPE*> cache_container;
    // Implementation detail: the cached object is stored as a
    // pointer. See Note (1)
    static G4ThreadLocal cache_container *cache;
};

// Note (1) : Object is stored as a pointer to avoid too large
//            std::vector in case of stored objects and allow use
//            of spcialized allocators

// Template specialization for pointers
// Note that objects are not owned by cache, for this
// version of the cache the explicit new/delete of the
// cached object
template<class VALTYPE>
class G4CacheReference<VALTYPE*> {
public:
    inline void Initialize( unsigned int id );
    
    inline void Destroy( unsigned int id , G4bool last);
    
    inline VALTYPE*& GetCache(unsigned int id) const;

private:
    typedef std::vector<VALTYPE*> cache_container;
    static G4ThreadLocal cache_container *cache;
};

// Template specialization for probably the most used case: double
// Be more efficient avoiding unnecessary "new/delete"
template<>
class G4CacheReference<G4double> {
public:
    inline void Initialize( unsigned int id );
    
    inline void Destroy( unsigned int id , G4bool last);
    
    inline G4double& GetCache(unsigned int id) const;

private:
    typedef std::vector<G4double> cache_container;
    static G4ThreadLocal std::vector<G4double> *cache;
};


//================================
// Implementation details follow
//================================

//======= Implementation: G4CacheReference<V>

template<class V>
void G4CacheReference<V>::Initialize(unsigned int id)
{
#ifdef g4cdebug
    if ( cache == 0 )
        cout<<"Generic template"<<endl;
#endif
    //Create cache container
    if ( cache == 0 )
        cache = new cache_container;
    if ( cache->size() <= id )
        cache->resize(id+1,static_cast<V*>(0));
    if ( (*cache)[id] == 0 ) (*cache)[id]=new V;
    
}

template<class V>
void G4CacheReference<V>::Destroy( unsigned int id, G4bool last )
{
    if ( cache ) {
#ifdef g4cdebug
        cout<<"Destroying element"<<id<<" is last?"<<last<<endl;
#endif
        if ( cache->size() <id && (*cache)[id] ) {
            delete (*cache)[id];
            (*cache)[id]=0;
        }
        if (last ) {
            delete cache;
            cache = 0;
        }
    }
}

template<class V>
V& G4CacheReference<V>::GetCache(unsigned int id) const
{
    return *(cache->operator[](id));
}

template<class V>
G4ThreadLocal typename G4CacheReference<V>::cache_container * G4CacheReference<V>::cache = 0;

//======= Implementation: G4CacheReference<V*>
template<class V>
void G4CacheReference<V*>::Initialize( unsigned int id )
{
#ifdef g4cdebug
    if ( cache == 0 )
        cout<<"Pointer template"<<endl;
#endif
    if ( cache == 0 )
        cache = new cache_container;
    if ( cache->size() <= id )
        cache->resize(id+1,static_cast<V*>(0));
    //No need to create pointee
    //if ( (*cache)[id] == 0 ) (*cache)[id]=new VALTYPE;
}

template<class V>
inline void G4CacheReference<V*>::Destroy( unsigned int id , G4bool last)
{
    if ( cache ) {
#ifdef g4cdebug
        cout<<"Destroying element"<<id<<" is last?"<<last<<"-Pointer template specialization-"<<endl;
#endif
        if ( cache->size() <id && (*cache)[id] ) {
            //Ownership is for client
            //delete (*cache)[id];
            (*cache)[id]=0;
        }
        if (last ) {
            delete cache;
            cache = 0;
        }
    }
}

template<class V>
V*& G4CacheReference<V*>::GetCache(unsigned int id) const
{
    return (cache->operator[](id));
}

template<class V>
G4ThreadLocal typename G4CacheReference<V*>::cache_container * G4CacheReference<V*>::cache=0;

//======= Implementation: G4CacheReference<double>
void G4CacheReference<G4double>::Initialize( unsigned int id )
{
#ifdef g4cdebug
    cout<<"Specialized template for G4double"<<endl;
#endif
    if ( cache == 0 )
        cache = new cache_container;
    if ( cache->size() <= id )
        cache->resize(id+1,static_cast<G4double>(0));
}

void G4CacheReference<G4double>::Destroy( unsigned int /*id*/ , G4bool last) {
    if ( cache && last ) {
#ifdef g4cdebug
        cout<<"Destroying element"<<id<<" is last?"<<last<<"-Pointer template specialization-"<<endl;
#endif
        delete cache;
        cache = 0;
    }
}

G4double& G4CacheReference<G4double>::GetCache(unsigned int id) const {
    return cache->operator[](id);
}

//G4ThreadLocal std::vector<G4double>* G4CacheReference<G4double>::cache = 0;