Oompi String Example

The Object Oriented Message Passing Interface (OOMPI) does not have a means of directly transmitting strings between processes. This problem can be solved by building a class which can encapsulate the two steps needed for transmitting a string. Those steps are

Send the size of the string.
Send an array of chars which contains the content of the string.

The wrapping class then handles at each end the conversion from and to a string object which is inside the class. It is easy to extend this so that the user can directly send and receive string objects. -- JohnFletcher

Example program which shows use of the class OOMPI_string


        #include 

        #include 

        #include 

        #include 

        #include "oompi.h"

        using namespace std;

        // ===============================================================================

        // OOMPI_string definition

        // ===============================================================================

        class OOMPI_string {

        public:

        OOMPI_string() : num(0) { }

        OOMPI_string(const string &ss) : s(ss) { num = s.length() + 1; }

        void Send(OOMPI_Port &to);

        void Recv(OOMPI_Port &from);

        // Set send true for the process which is sending.

        void Bcast(OOMPI_Port &from,bool send=false);

        void Gather(OOMPI_Port &to);

        vector Gather(OOMPI_Port &to,int size,

        int *string_sizes,int *string_displ);

        void Scatter(OOMPI_Port &from);

        void Scatter(OOMPI_Port &from,const vector &v,

        int size,int *string_sizes,int *string_displ);

        void Set(const string &ss) { s = ss; num = s.length() + 1; }

        string Get() const { return s; }

        int Size() const { return num; }

        friend OOMPI_Port& operator << (OOMPI_Port& p,const OOMPI_string &s);

        friend OOMPI_Port& operator >> (OOMPI_Port& p,const OOMPI_string &s);

        private:

        string s;

        int num;

        };

        // ===============================================================================

        // OOMPI_string implementation 

        // ===============================================================================

        // Implementation not included for reasons of space,

        // except for these overloads which hide the OOMPI_string in the user code  

        // and allow strings to be used directly.

        OOMPI_Port& operator << (OOMPI_Port& p,const string &s)

        {

        OOMPI_string os(s);

        os.Send(p);

        return p;

        }


        OOMPI_Port& operator >> (OOMPI_Port& p,string &s)

        {

        OOMPI_string os;

        os.Recv(p);

        s = os.Get();

        return p;

        }


        int main(int argc, char *argv[])

        {

        OOMPI_COMM_WORLD.Init(argc, argv);

        int rank = OOMPI_COMM_WORLD.Rank();

        int size = OOMPI_COMM_WORLD.Size();

        OOMPI_Port to   = OOMPI_COMM_WORLD[0];

        string hello("Hello");

        if (rank == 0) {

        int where;

        for (where = 1; where < size; where++) {

        string how;

        OOMPI_Port source = OOMPI_COMM_WORLD[where];

        source >> how;

        cout << rank << " has " << how << " from " << where << endl;

        }

        } else {

        ostringstream out;

        out << rank << " says " << hello << endl; 

        to << out.str();

        }  

        OOMPI_COMM_WORLD.Finalize();

        return 0;

        }

CategoryCpp