Optimized Data Transfers Based on the OpenCL Event Management Mechanism

Listing 5

A code with the OpenCL extension for host-to-device communication.

()  cl_context ctx;

()  MPI_Request req;

()  cl_event evt[2];

()

()  if( rank == 0 ){

()   /* receiving data from a remote device */

()   MPI_Irecv(recvbuf, bufsz, MPI_CL_MEM, 1, 0, MPI_COMM_WORLD,&req);

()   /* creating an event object of MPI_Irecv */

()   evt[0] = clCreateEventFromMPIRequest(ctx,&req,NULL);

()  /* executing a kernel during the data transfer */

()  clEnqueueNDRangeKernel(…, &evt[1]);

()

()  /* executing this after the computation and communication */

()  clEnqueueWriteBuffer(cmd, buf, …, 2, evt, NULL);

() }

() else if(rank ==  1){

()  /* send data to a remote host */

()  clEnqueueSendBuffer(cmd, buf, CL_TRUE, 0, bufsz, 0,…);

() }