--- /dev/null
+#include "colls.h"
+//#include <star-reduction.c>
+
+int smpi_coll_tuned_allreduce_rdb(void *sbuff, void *rbuff, int count,
+ MPI_Datatype dtype, MPI_Op op, MPI_Comm comm)
+{
+ int nprocs, rank, type_size, tag = 543;
+ int mask, dst, pof2, newrank, rem, newdst;
+ MPI_Aint extent;
+ MPI_Status status;
+ void *tmp_buf = NULL;
+ /*
+ #ifdef MPICH2_REDUCTION
+ MPI_User_function * uop = MPIR_Op_table[op % 16 - 1];
+ #else
+ MPI_User_function *uop;
+ struct MPIR_OP *op_ptr;
+ op_ptr = MPIR_ToPointer(op);
+ uop = op_ptr->op;
+ #endif
+ */
+ MPI_Comm_size(comm, &nprocs);
+ MPI_Comm_rank(comm, &rank);
+
+ MPI_Type_extent(dtype, &extent);
+ tmp_buf = (void *) malloc(count * extent);
+ if (!tmp_buf) {
+ printf("Could not allocate memory for tmp_buf\n");
+ return 1;
+ }
+
+ MPI_Sendrecv(sbuff, count, dtype, rank, 500,
+ rbuff, count, dtype, rank, 500, comm, &status);
+
+ MPI_Type_size(dtype, &type_size);
+
+ // find nearest power-of-two less than or equal to comm_size
+ pof2 = 1;
+ while (pof2 <= nprocs)
+ pof2 <<= 1;
+ pof2 >>= 1;
+
+ rem = nprocs - pof2;
+
+ // In the non-power-of-two case, all even-numbered
+ // processes of rank < 2*rem send their data to
+ // (rank+1). These even-numbered processes no longer
+ // participate in the algorithm until the very end. The
+ // remaining processes form a nice power-of-two.
+
+ if (rank < 2 * rem) {
+ // even
+ if (rank % 2 == 0) {
+
+ MPI_Send(rbuff, count, dtype, rank + 1, tag, comm);
+
+ // temporarily set the rank to -1 so that this
+ // process does not pariticipate in recursive
+ // doubling
+ newrank = -1;
+ } else // odd
+ {
+ MPI_Recv(tmp_buf, count, dtype, rank - 1, tag, comm, &status);
+ // do the reduction on received data. since the
+ // ordering is right, it doesn't matter whether
+ // the operation is commutative or not.
+ star_reduction(op, tmp_buf, rbuff, &count, &dtype);
+
+ // change the rank
+ newrank = rank / 2;
+ }
+ }
+
+ else // rank >= 2 * rem
+ newrank = rank - rem;
+
+ // If op is user-defined or count is less than pof2, use
+ // recursive doubling algorithm. Otherwise do a reduce-scatter
+ // followed by allgather. (If op is user-defined,
+ // derived datatypes are allowed and the user could pass basic
+ // datatypes on one process and derived on another as long as
+ // the type maps are the same. Breaking up derived
+ // datatypes to do the reduce-scatter is tricky, therefore
+ // using recursive doubling in that case.)
+
+ if (newrank != -1) {
+ mask = 0x1;
+ while (mask < pof2) {
+ newdst = newrank ^ mask;
+ // find real rank of dest
+ dst = (newdst < rem) ? newdst * 2 + 1 : newdst + rem;
+
+ // Send the most current data, which is in recvbuf. Recv
+ // into tmp_buf
+ MPI_Sendrecv(rbuff, count, dtype, dst, tag, tmp_buf, count, dtype,
+ dst, tag, comm, &status);
+
+ // tmp_buf contains data received in this step.
+ // recvbuf contains data accumulated so far
+
+ // op is commutative OR the order is already right
+ // we assume it is commuttive op
+ // if (op -> op_commute || (dst < rank))
+ if ((dst < rank)) {
+ star_reduction(op, tmp_buf, rbuff, &count, &dtype);
+ } else // op is noncommutative and the order is not right
+ {
+ star_reduction(op, rbuff, tmp_buf, &count, &dtype);
+
+ // copy result back into recvbuf
+ MPI_Sendrecv(tmp_buf, count, dtype, rank, tag, rbuff, count,
+ dtype, rank, tag, comm, &status);
+ }
+ mask <<= 1;
+ }
+ }
+ // In the non-power-of-two case, all odd-numbered processes of
+ // rank < 2 * rem send the result to (rank-1), the ranks who didn't
+ // participate above.
+
+ if (rank < 2 * rem) {
+ if (rank % 2) // odd
+ MPI_Send(rbuff, count, dtype, rank - 1, tag, comm);
+ else // even
+ MPI_Recv(rbuff, count, dtype, rank + 1, tag, comm, &status);
+ }
+
+ free(tmp_buf);
+ return 0;
+}
