recvbuf = xbt_new(char, size);
retval =
MPI_Sendrecv(buf, count, datatype, dst, sendtag, recvbuf, count,
datatype, src, recvtag, comm, status);
if(retval==MPI_SUCCESS){
recvbuf = xbt_new(char, size);
retval =
MPI_Sendrecv(buf, count, datatype, dst, sendtag, recvbuf, count,
datatype, src, recvtag, comm, status);
if(retval==MPI_SUCCESS){