NAME¶

array - container in distributed environment (rheolef-6.1)

SYNOPSYS¶

STL-like vector container for a distributed memory machine model.

EXAMPLE¶

A sample usage of the class is:

     int main(int argc, char**argv) {
        environment distributed(argc, argv);
        array<double> x(distributor(100), 3.14);
        dout << x << endl;
     }
 

The array<T> interface is similar to those of the std::vector<T> with the addition of some communication features in the distributed case: write accesses with entry/assembly and read access with dis_at.

DISTRIBUTED WRITE ACCESS¶

Loop on any dis_i that is not managed by the current processor:

        x.dis_entry (dis_i) = value;
 

and then, after loop, perform all communication:

        x.dis_entry_assembly();
 

After this command, each value is stored in the array, available the processor associated to dis_i.

DISTRIBUTED READ ACCESS¶

First, define the set of indexes:

        std::set<size_t> ext_idx_set;
 

Then, loop on dis_i indexes that are not managed by the current processor:

        ext_idx_set.insert (dis_i);
 

After the loop, performs the communications:

        x.set_dis_indexes (ext_idx_set);
 

After this command, each values associated to the dis_i index, and that belongs to the index set, is now available also on the current processor as:

        value = x.dis_at (dis_i);
 

For convenience, if dis_i is managed by the current processor, this function returns also the value.

NOTE¶

The class takes two template parameters: one for the type T and the second for the memory model M, that could be either M=distributed or M=sequential. The two cases are associated to two diferent implementations, but proposes exactly the same interface. The sequential interface propose also a supplementary constructor:

        array<double,sequential> x(local_size, init_val);
 

This constructor is a STL-like one but could be consufused in the distributed case, since there are two sizes: a local one and a global one. In that case, the use of the distributor, as a generalization of the size concept, clarify the situation (see distributor(2)).

IMPLEMENTATION NOTE¶

"scatter" via "get_dis_entry". "gather" via "dis_entry(dis_i) = value" or "dis_entry(dis_i) += value". Note that += applies when T=idx_set where idx_set is a wrapper class of std::set<size_t> ; the += operator represents the union of a set. The operator= is used when T=double or others simple T types without algebra. If there is a conflict, i.e. several processes set the dis_i index, then the result of operator+= depends upon the order of the process at each run and is not deterministic. Such ambiguous behavior is not detected yet at run time.

IMPLEMENTATION¶

template <class T, class A>
class array<T,sequential,A> : public smart_pointer<array_seq_rep<T,A> > {
public:

// typedefs:

    typedef array_seq_rep<T,A>            rep;
    typedef smart_pointer<rep>            base;

    typedef sequential                    memory_type;
    typedef typename rep::size_type       size_type;
    typedef typename rep::difference_type difference_type;
    typedef typename rep::value_type      value_type;
    typedef typename rep::reference       reference;
    typedef typename rep::dis_reference   dis_reference;
    typedef typename rep::iterator        iterator;
    typedef typename rep::const_reference const_reference;
    typedef typename rep::const_iterator  const_iterator;

// allocators:


    array       (size_type loc_size = 0,       const T& init_val = T(), const A& alloc = A());
    void resize (size_type loc_size = 0,       const T& init_val = T());
    array       (const distributor& ownership, const T& init_val = T(), const A& alloc = A());
    void resize (const distributor& ownership, const T& init_val = T());

// local accessors & modifiers:

    A get_allocator() const              { return base::data().get_allocator(); }
    size_type     size () const          { return base::data().size(); }
    size_type dis_size () const          { return base::data().dis_size(); }
    const distributor& ownership() const { return base::data().ownership(); }
    const communicator& comm() const     { return ownership().comm(); }

    reference       operator[] (size_type i)       { return base::data().operator[] (i); }
    const_reference operator[] (size_type i) const { return base::data().operator[] (i); }
    reference       operator() (size_type i)       { return base::data().operator[] (i); }
    const_reference operator() (size_type i) const { return base::data().operator[] (i); }
    const_reference dis_at (size_type dis_i) const { return operator[] (dis_i); }

          iterator begin()       { return base::data().begin(); }
    const_iterator begin() const { return base::data().begin(); }
          iterator end()         { return base::data().end(); }
    const_iterator end() const   { return base::data().end(); }

// global modifiers (for compatibility with distributed interface):

    dis_reference dis_entry (size_type dis_i) { return base::data().dis_entry(dis_i); }
    void dis_entry_assembly()                 {}
    template<class SetOp> void dis_entry_assembly(SetOp my_set_op)        {}
    template<class SetOp> void dis_entry_assembly_begin (SetOp my_set_op) {}
    template<class SetOp> void dis_entry_assembly_end (SetOp my_set_op)   {}

    void reset_dis_indexes() const {}
    template<class Set> void set_dis_indexes    (const Set& ext_idx_set) const {}
    template<class Set> void append_dis_indexes (const Set& ext_idx_set) const {}
    template<class Set, class Map> void append_dis_entry (const Set& ext_idx_set, Map& ext_idx_map) const {}
    template<class Set, class Map> void get_dis_entry    (const Set& ext_idx_set, Map& ext_idx_map) const {}

// apply a partition:

    template<class RepSize>
    void repartition (                               // old_numbering for *this
        const RepSize&         partition,            // old_ownership
        array<T,sequential,A>& new_array,            // new_ownership (created)
        RepSize&               old_numbering,        // new_ownership
        RepSize&               new_numbering) const  // old_ownership
        { return base::data().repartition (partition, new_array, old_numbering, new_numbering); }

    template<class RepSize>
    void permutation_apply (                       // old_numbering for *this
        const RepSize&          new_numbering,     // old_ownership
        array<T,sequential,A>&  new_array) const   // new_ownership (already allocated)
        { return base::data().permutation_apply (new_numbering, new_array); }

    void reverse_permutation (                                 // old_ownership for *this=iold2dis_inew
        array<size_type,sequential,A>& inew2dis_iold) const   // new_ownership
        { base::data().reverse_permutation (inew2dis_iold.data()); }

// i/o:

    odiststream& put_values (odiststream& ops) const { return base::data().put_values(ops); }
    idiststream& get_values (idiststream& ips)       { return base::data().get_values(ips); }
    template <class GetFunction>
    idiststream& get_values (idiststream& ips, GetFunction get_element)       { return base::data().get_values(ips, get_element); }
    template <class PutFunction>
    odiststream& put_values (odiststream& ops, PutFunction put_element) const { return base::data().put_values(ops, put_element); }
    void dump (std::string name) const { return base::data().dump(name); }
};
 

IMPLEMENTATION¶

template <class T, class A>
class array<T,distributed,A> : public smart_pointer<array_mpi_rep<T,A> > {
public:

// typedefs:

    typedef array_mpi_rep<T,A>            rep;
    typedef smart_pointer<rep>            base;

    typedef distributed                   memory_type;
    typedef typename rep::size_type       size_type;
    typedef typename rep::difference_type difference_type;
    typedef typename rep::value_type      value_type;
    typedef typename rep::reference       reference;
    typedef typename rep::dis_reference   dis_reference;
    typedef typename rep::iterator        iterator;
    typedef typename rep::const_reference const_reference;
    typedef typename rep::const_iterator  const_iterator;
    typedef typename rep::scatter_map_type scatter_map_type;

// allocators:

    array       (const distributor& ownership = distributor(), const T& init_val = T(), const A& alloc = A());
    void resize (const distributor& ownership = distributor(), const T& init_val = T());

// local accessors & modifiers:

    A get_allocator() const              { return base::data().get_allocator(); }
    size_type     size () const          { return base::data().size(); }
    size_type dis_size () const          { return base::data().dis_size(); }
    const distributor& ownership() const { return base::data().ownership(); }
    const communicator& comm() const     { return base::data().comm(); }

    reference       operator[] (size_type i)       { return base::data().operator[] (i); }
    const_reference operator[] (size_type i) const { return base::data().operator[] (i); }
    reference       operator() (size_type i)       { return base::data().operator[] (i); }
    const_reference operator() (size_type i) const { return base::data().operator[] (i); }

          iterator begin()       { return base::data().begin(); }
    const_iterator begin() const { return base::data().begin(); }
          iterator end()         { return base::data().end(); }
    const_iterator end() const   { return base::data().end(); }

// global accessor:

    template<class Set, class Map>
    void append_dis_entry (const Set& ext_idx_set, Map& ext_idx_map) const { base::data().append_dis_entry (ext_idx_set, ext_idx_map); }

    template<class Set, class Map>
    void get_dis_entry    (const Set& ext_idx_set, Map& ext_idx_map) const { base::data().get_dis_entry (ext_idx_set, ext_idx_map); }

    template<class Set>
    void append_dis_indexes (const Set& ext_idx_set) const { base::data().append_dis_indexes (ext_idx_set); }
    void reset_dis_indexes() const { base::data().reset_dis_indexes(); }

    template<class Set>
    void set_dis_indexes    (const Set& ext_idx_set) const { base::data().set_dis_indexes (ext_idx_set); }

    const T& dis_at (size_type dis_i) const { return base::data().dis_at (dis_i); }

    // get all external pairs (dis_i, values):
    const scatter_map_type& get_dis_map_entries() const { return base::data().get_dis_map_entries(); }

// global modifiers (for compatibility with distributed interface):

    dis_reference dis_entry (size_type dis_i)       { return base::data().dis_entry(dis_i); }

    void dis_entry_assembly()                       { return base::data().dis_entry_assembly(); }

    template<class SetOp>
    void dis_entry_assembly       (SetOp my_set_op) { return base::data().dis_entry_assembly       (my_set_op); }
    template<class SetOp>
    void dis_entry_assembly_begin (SetOp my_set_op) { return base::data().dis_entry_assembly_begin (my_set_op); }
    template<class SetOp>
    void dis_entry_assembly_end   (SetOp my_set_op) { return base::data().dis_entry_assembly_end   (my_set_op); }

// apply a partition:

    template<class RepSize>
    void repartition (                              // old_numbering for *this
        const RepSize&        partition,            // old_ownership
        array<T,distributed>& new_array,            // new_ownership (created)
        RepSize&              old_numbering,        // new_ownership
        RepSize&              new_numbering) const  // old_ownership
        { return base::data().repartition (partition.data(), new_array.data(), old_numbering.data(), new_numbering.data()); }

    template<class RepSize>
    void permutation_apply (                       // old_numbering for *this
        const RepSize&          new_numbering,     // old_ownership
        array<T,distributed,A>& new_array) const   // new_ownership (already allocated)
        { base::data().permutation_apply (new_numbering.data(), new_array.data()); }

    void reverse_permutation (                                 // old_ownership for *this=iold2dis_inew
        array<size_type,distributed,A>& inew2dis_iold) const   // new_ownership
        { base::data().reverse_permutation (inew2dis_iold.data()); }

// i/o:

    odiststream& put_values (odiststream& ops) const { return base::data().put_values(ops); }
    idiststream& get_values (idiststream& ips)       { return base::data().get_values(ips); }
    void dump (std::string name) const      { return base::data().dump(name); }

    template <class GetFunction>
    idiststream& get_values (idiststream& ips, GetFunction get_element)       { return base::data().get_values(ips, get_element); }
    template <class PutFunction>
    odiststream& put_values (odiststream& ops, PutFunction put_element) const { return base::data().put_values(ops, put_element); }
    template <class PutFunction, class A2> odiststream& permuted_put_values (
                odiststream& ops, const array<size_type,distributed,A2>& perm, PutFunction put_element) const
                                                                     { return base::data().permuted_put_values (ops, perm.data(), put_element); }
};
 

SEE ALSO¶

distributor(2)