KING

difference between SIMD and MIMD

• difference kinds of computer architecture is using the Flynn to classify
  • SISD
  • SIMD
  • MISD
  • MIMD
• we only talk about the SIMD and MIMD here
  • SIMD means that one command deal with many data streams
    • most of the single core machine is SIMD machine
    • and these kinds of machine is most used in the image processing and multimedia processing.

- MIMD means that many commands deal with many data streams
    - the lastest multicore platform is a MIMD machine
    - the MIMD are asynchronous
    - 

the multi core hardware architecture

• the multicore CPU is combine many CPU into one chip. and each CPU core has a single processor.
  • each core has it’s own cache. (some other may share one cache between multi CPU)

message passing

• There are two methods in the message passing
  • MPI_Send
    • void * buffer, int count, MPI_Datatype datatype, int destination, int tag, MPI_Comm communicator
    • e.g
      • MPI_Send(&x, 1, MPI_FLOAT, 1, 0, MPI_COMM_WORLD);
  • MPI_Recv
    • void * buffer, int count, MPI_Datatype datatype, int source, int tag, MPI_Comm communicator, MPI_Status status
    • MPI_Recv(&x, 1, MPI_FLOAT, 0, 0, MPI_COMM_WORLD, &status);

sample program

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#include "mpi.h"
int main(int argc, char *argv[]){
  int rank; //rank of the process
  int source; //rank of the sender
  int dest;   //rank of the receiver
  int num;    //number of the processers
  int tags;
  char messages[1000];
  MPI_Status status;

  //setting up the MPI
  MPI_init(&argc, &argv);

  //find out the rank of the curret program
  MPI_Comm_rank(MPI_COMM_WORLD, rank);

  //find out the number of the processers
  MPI_Common_Size(MPI_COMM_WORLD, &p);

  if(rank != 0){ //if the current program is not the root program
      sprintf(message, "hello from %d", rank);
      dest = 0;
      MPI_Send(message, strlen(message) + 1, MPI_CHAR, dest, tag, MPI_COMM_WORLD);
  }else{
      sprintf(message, "hello from ");
      MPI_Recv(message, 100, MPI_CHAR, source, tag, MPI_COMM_WORLD, &status);
      printf("%s\n", message);
  }
  MPI_Finalize();
}

how to run the program

• for c++
  • mpic++ -o test test.cpp
• for c
  • mpicc -o test test.c
• run
  • for m core computer
    • mpirun -np m test