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* MPI_Sendrecv user+internal levels
[simgrid.git] / src / smpi / smpi_mpi.c
index 79ad9bf..c1f5253 100644 (file)
+
+
 #include "private.h"
+#include "smpi_coll_private.h"
 
-XBT_LOG_NEW_DEFAULT_SUBCATEGORY(smpi_mpi, smpi, "Logging specific to SMPI (mpi)");
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(smpi_mpi, smpi,
+                                "Logging specific to SMPI (mpi)");
 
 int SMPI_MPI_Init(int *argc, char ***argv)
 {
-       smpi_mpi_init();
-       smpi_bench_begin();
-       return MPI_SUCCESS;
+  smpi_process_init(argc, argv);
+  smpi_bench_begin();
+  return MPI_SUCCESS;
 }
 
 int SMPI_MPI_Finalize()
 {
-       smpi_bench_end();
-       smpi_mpi_finalize();
-       return MPI_SUCCESS;
+  smpi_bench_end();
+  smpi_process_finalize();
+  return MPI_SUCCESS;
 }
 
 // right now this just exits the current node, should send abort signal to all
-// hosts in the communicator;
+// hosts in the communicator (TODO)
 int SMPI_MPI_Abort(MPI_Comm comm, int errorcode)
 {
-       smpi_exit(errorcode);
-       return 0;
+  smpi_exit(errorcode);
+  return 0;
 }
 
 int SMPI_MPI_Comm_size(MPI_Comm comm, int *size)
 {
-       int retval = MPI_SUCCESS;
+  int retval = MPI_SUCCESS;
 
-       smpi_bench_end();
+  smpi_bench_end();
 
-       if (NULL == comm) {
-               retval = MPI_ERR_COMM;
-       } else if (NULL == size) {
-               retval = MPI_ERR_ARG;
-       } else {
-               *size = comm->size;
-       }
+  if (NULL == comm) {
+    retval = MPI_ERR_COMM;
+  } else if (NULL == size) {
+    retval = MPI_ERR_ARG;
+  } else {
+    *size = comm->size;
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
 int SMPI_MPI_Comm_rank(MPI_Comm comm, int *rank)
 {
-       int retval = MPI_SUCCESS;
+  int retval = MPI_SUCCESS;
 
-       smpi_bench_end();
+  smpi_bench_end();
 
-       if (NULL == comm) {
-               retval = MPI_ERR_COMM;
-       } else if (NULL == rank) {
-               retval = MPI_ERR_ARG;
-       } else {
-               *rank = smpi_mpi_comm_rank(comm);
-       }
+  if (NULL == comm) {
+    retval = MPI_ERR_COMM;
+  } else if (NULL == rank) {
+    retval = MPI_ERR_ARG;
+  } else {
+    *rank = smpi_mpi_comm_rank(comm);
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
-int SMPI_MPI_Type_size(MPI_Datatype datatype, size_t *size)
+int SMPI_MPI_Type_size(MPI_Datatype datatype, size_t * size)
 {
-       int retval = MPI_SUCCESS;
+  int retval = MPI_SUCCESS;
 
-       smpi_bench_end();
+  smpi_bench_end();
 
-       if (NULL == datatype) {
-               retval = MPI_ERR_TYPE;
-       } else if (NULL == size) {
-               retval = MPI_ERR_ARG;
-       } else {
-               *size = datatype->size;
-       }
+  if (NULL == datatype) {
+    retval = MPI_ERR_TYPE;
+  } else if (NULL == size) {
+    retval = MPI_ERR_ARG;
+  } else {
+    *size = datatype->size;
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
 int SMPI_MPI_Barrier(MPI_Comm comm)
 {
-       int retval = MPI_SUCCESS;
+  int retval = MPI_SUCCESS;
+  int arity=4;
+
+  smpi_bench_end();
 
-       smpi_bench_end();
+  if (NULL == comm) {
+    retval = MPI_ERR_COMM;
+  } else {
 
-       if (NULL == comm) {
-               retval = MPI_ERR_COMM;
-       } else {
-               retval = smpi_mpi_barrier(comm);
-       }
+    /*
+     * original implemantation:
+     * retval = smpi_mpi_barrier(comm);
+     * this one is unrealistic: it just cond_waits, means no time.
+     */
+     retval = nary_tree_barrier( comm, arity );
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
-int SMPI_MPI_Irecv(void *buf, int count, MPI_Datatype datatype, int src, int tag, MPI_Comm comm, MPI_Request *request)
+int SMPI_MPI_Irecv(void *buf, int count, MPI_Datatype datatype, int src,
+                   int tag, MPI_Comm comm, MPI_Request * request)
 {
-       int retval = MPI_SUCCESS;
+  int retval = MPI_SUCCESS;
 
-       smpi_bench_end();
+  smpi_bench_end();
 
-       retval = smpi_create_request(buf, count, datatype, src, 0, tag, comm, request);
-       if (NULL != *request && MPI_SUCCESS == retval) {
-               retval = smpi_mpi_irecv(*request);
-       }
+  retval = smpi_create_request(buf, count, datatype, src, 0, tag, comm,
+                               request);
+  if (NULL != *request && MPI_SUCCESS == retval) {
+    retval = smpi_mpi_irecv(*request);
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
-int SMPI_MPI_Recv(void *buf, int count, MPI_Datatype datatype, int src, int tag, MPI_Comm comm, MPI_Status *status)
+int SMPI_MPI_Recv(void *buf, int count, MPI_Datatype datatype, int src,
+                  int tag, MPI_Comm comm, MPI_Status * status)
 {
-       int retval = MPI_SUCCESS;
-       smpi_mpi_request_t request;
+  int retval = MPI_SUCCESS;
+  smpi_mpi_request_t request;
 
-       smpi_bench_end();
+  smpi_bench_end();
 
-       retval = smpi_create_request(buf, count, datatype, src, 0, tag, comm, &request);
-       if (NULL != request && MPI_SUCCESS == retval) {
-               retval = smpi_mpi_irecv(request);
-               if (MPI_SUCCESS == retval) {
-                       retval = smpi_mpi_wait(request, status);
-               }
-               xbt_mallocator_release(smpi_global->request_mallocator, request);
-       }
+  retval = smpi_create_request(buf, count, datatype, src, 0, tag, comm,
+                               &request);
+  if (NULL != request && MPI_SUCCESS == retval) {
+    retval = smpi_mpi_irecv(request);
+    if (MPI_SUCCESS == retval) {
+      retval = smpi_mpi_wait(request, status);
+    }
+    xbt_mallocator_release(smpi_global->request_mallocator, request);
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
-int SMPI_MPI_Isend(void *buf, int count, MPI_Datatype datatype, int dst, int tag, MPI_Comm comm, MPI_Request *request)
+int SMPI_MPI_Isend(void *buf, int count, MPI_Datatype datatype, int dst,
+                   int tag, MPI_Comm comm, MPI_Request * request)
 {
-       int retval = MPI_SUCCESS;
+  int retval = MPI_SUCCESS;
 
-       smpi_bench_end();
+  smpi_bench_end();
 
-       retval = smpi_create_request(buf, count, datatype, 0, dst, tag, comm, request);
-       if (NULL != *request && MPI_SUCCESS == retval) {
-               retval = smpi_mpi_isend(*request);
-       }
+  retval = smpi_create_request(buf, count, datatype, 0, dst, tag, comm,
+                               request);
+  if (NULL != *request && MPI_SUCCESS == retval) {
+    retval = smpi_mpi_isend(*request);
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
-int SMPI_MPI_Send(void *buf, int count, MPI_Datatype datatype, int dst, int tag, MPI_Comm comm)
+int SMPI_MPI_Send(void *buf, int count, MPI_Datatype datatype, int dst,
+                  int tag, MPI_Comm comm)
 {
-       int retval = MPI_SUCCESS;
-       smpi_mpi_request_t request;
+  int retval = MPI_SUCCESS;
+  smpi_mpi_request_t request;
 
-       smpi_bench_end();
+  smpi_bench_end();
 
-       retval = smpi_create_request(buf, count, datatype, 0, dst, tag, comm, &request);
-       if (NULL != request && MPI_SUCCESS == retval) {
-               retval = smpi_mpi_isend(request);
-               if (MPI_SUCCESS == retval) {
-                       smpi_mpi_wait(request, MPI_STATUS_IGNORE);
-               }
-               xbt_mallocator_release(smpi_global->request_mallocator, request);
-       }
+  retval = smpi_create_request(buf, count, datatype, 0, dst, tag, comm,
+                               &request);
+  if (NULL != request && MPI_SUCCESS == retval) {
+    retval = smpi_mpi_isend(request);
+    if (MPI_SUCCESS == retval) {
+      smpi_mpi_wait(request, MPI_STATUS_IGNORE);
+    }
+    xbt_mallocator_release(smpi_global->request_mallocator, request);
+  }
 
-       smpi_bench_begin();
+  smpi_bench_begin();
 
-       return retval;
+  return retval;
 }
 
-int SMPI_MPI_Wait(MPI_Request *request, MPI_Status *status) {
-       return smpi_mpi_wait(*request, status);
+
+/**
+ * MPI_Sendrecv internal level 
+ **/
+int smpi_mpi_sendrecv(void *sendbuf, int sendcount, MPI_Datatype sendtype, int dest, int sendtag, 
+                   void *recvbuf, int recvcount, MPI_Datatype recvtype, int source, int recvtag,
+                   MPI_Comm comm, MPI_Status *status)
+{
+int rank;
+int retval = MPI_SUCCESS;
+smpi_mpi_request_t srequest;
+smpi_mpi_request_t rrequest;
+
+         rank = smpi_mpi_comm_rank(comm);
+
+         /* send */
+         retval = smpi_create_request(sendbuf, sendcount, sendtype, 
+                               rank,dest,sendtag, 
+                               comm, &srequest);
+         smpi_mpi_isend(srequest);
+        
+         /* recv */
+         retval = smpi_create_request(recvbuf, recvcount, recvtype, 
+                               source, rank,recvtag, 
+                               comm, &rrequest);
+         smpi_mpi_irecv(rrequest);
+
+         smpi_mpi_wait(srequest, MPI_STATUS_IGNORE);
+         //printf("[%d] isend request src=%d dst=%d tag=%d COMPLETED (retval=%d) \n",rank,rank,dest,sendtag,retval);
+         smpi_mpi_wait(rrequest, MPI_STATUS_IGNORE);
+         //printf("[%d] irecv request src=%d -> dst=%d tag=%d COMPLETED (retval=%d)\n",rank,source,rank,recvtag,retval);
+
+         return(retval);
 }
+/**
+ * MPI_Sendrecv user entry point
+ **/
+int SMPI_MPI_Sendrecv(void *sendbuf, int sendcount, MPI_Datatype sendtype, int dest, int sendtag, 
+                   void *recvbuf, int recvcount, MPI_Datatype recvtype, int source, int recvtag,
+                   MPI_Comm comm, MPI_Status *status)
+{
+int retval = MPI_SUCCESS;
 
-int SMPI_MPI_Bcast(void *buf, int count, MPI_Datatype datatype, int root, MPI_Comm comm) {
+  smpi_bench_end();
+  smpi_mpi_sendrecv( sendbuf, sendcount, sendtype, dest, sendtag, 
+                        recvbuf, recvcount, recvtype, source, recvtag,
+                        comm, status);
+  smpi_bench_begin();
 
-       int retval = MPI_SUCCESS;
-       int rank;
-       smpi_mpi_request_t request;
+  return retval;
 
-       smpi_bench_end();
+       
+}
 
-       rank = smpi_mpi_comm_rank(comm);
+/**
+ * MPI_Wait and friends
+ **/
+int SMPI_MPI_Wait(MPI_Request * request, MPI_Status * status)
+{
+  return smpi_mpi_wait(*request, status);
+}
 
-       if (rank == root) {
-               retval = smpi_create_request(buf, count, datatype, root, (root + 1) % comm->size, 0, comm, &request);
-               request->forward = comm->size - 1;
-               smpi_mpi_isend(request);
-       } else {
-               retval = smpi_create_request(buf, count, datatype, MPI_ANY_SOURCE, rank, 0, comm, &request);
-               smpi_mpi_irecv(request);
-       }
+int SMPI_MPI_Waitall(int count, MPI_Request requests[], MPI_Status status[])
+{
+  return smpi_mpi_waitall(count, requests, status);
+}
+
+int SMPI_MPI_Waitany(int count, MPI_Request requests[], int *index,
+                     MPI_Status status[])
+{
+  return smpi_mpi_waitany(count, requests, index, status);
+}
 
-       smpi_mpi_wait(request, MPI_STATUS_IGNORE);
-       xbt_mallocator_release(smpi_global->request_mallocator, request);
+/**
+ * MPI_Bcast
+ **/
 
-       smpi_bench_begin();
+/**
+ * flat bcast 
+ **/
+int flat_tree_bcast(void *buf, int count, MPI_Datatype datatype, int root, MPI_Comm comm);
+int flat_tree_bcast(void *buf, int count, MPI_Datatype datatype, int root,
+                MPI_Comm comm)
+{
+        int rank;
+        int retval = MPI_SUCCESS;
+        smpi_mpi_request_t request;
+
+        rank = smpi_mpi_comm_rank(comm);
+        if (rank == root) {
+                retval = smpi_create_request(buf, count, datatype, root,
+                                (root + 1) % comm->size, 0, comm, &request);
+                request->forward = comm->size - 1;
+                smpi_mpi_isend(request);
+        } else {
+                retval = smpi_create_request(buf, count, datatype, MPI_ANY_SOURCE, rank,
+                                0, comm, &request);
+                smpi_mpi_irecv(request);
+        }
+
+        smpi_mpi_wait(request, MPI_STATUS_IGNORE);
+        xbt_mallocator_release(smpi_global->request_mallocator, request);
+
+        return(retval);
 
-       return retval;
+}
+/**
+ * Bcast internal level 
+ **/
+int smpi_mpi_bcast(void *buf, int count, MPI_Datatype datatype, int root,
+                   MPI_Comm comm)
+{
+  int retval = MPI_SUCCESS;
+  //retval = flat_tree_bcast(buf, count, datatype, root, comm);
+  retval = nary_tree_bcast(buf, count, datatype, root, comm, 2 );
+  return retval;
 }
 
-// FIXME: should be in utilities
-int smpi_compare_rankkeys(const void *a, const void *b);
-int smpi_compare_rankkeys(const void *a, const void *b) {
-    int *x = (int *)a;
-    int *y = (int *)b;
+/**
+ * Bcast user entry point
+ **/
+int SMPI_MPI_Bcast(void *buf, int count, MPI_Datatype datatype, int root,
+                   MPI_Comm comm)
+{
+  int retval = MPI_SUCCESS;
 
-    if (x[1] < y[1]) return -1;
+  smpi_bench_end();
+  smpi_mpi_bcast(buf,count,datatype,root,comm);
+  smpi_bench_begin();
 
-    if (x[1] == y[1]) {
-        if (x[0] < y[0]) return -1;
-        if (x[0] == y[0]) return 0;
-        return 1;
-    }
+  return retval;
+}
 
-    return 1;
+
+
+#ifdef DEBUG_REDUCE
+/**
+ * debugging helper function
+ **/
+static void print_buffer_int(void *buf, int len, char *msg, int rank)
+{
+  int tmp, *v;
+  printf("**[%d] %s: ", rank, msg);
+  for (tmp = 0; tmp < len; tmp++) {
+    v = buf;
+    printf("[%d]", v[tmp]);
+  }
+  printf("\n");
+  free(msg);
+}
+static void print_buffer_double(void *buf, int len, char *msg, int rank)
+{
+  int tmp;
+  double *v;
+  printf("**[%d] %s: ", rank, msg);
+  for (tmp = 0; tmp < len; tmp++) {
+    v = buf;
+    printf("[%lf]", v[tmp]);
+  }
+  printf("\n");
+  free(msg);
 }
 
-// FIXME: needs to return null in event of MPI_UNDEFINED color...
-// FIXME: seriously, this isn't pretty
-int SMPI_MPI_Comm_split(MPI_Comm comm, int color, int key, MPI_Comm *comm_out)
+
+#endif
+/**
+ * MPI_Reduce internal level 
+ **/
+int smpi_mpi_reduce(void *sendbuf, void *recvbuf, int count,
+                MPI_Datatype datatype, MPI_Op op, int root, MPI_Comm comm)
 {
-       int retval = MPI_SUCCESS;
-
-       int index, rank;
-       smpi_mpi_request_t request;
-       int colorkey[2];
-       smpi_mpi_status_t status;
-
-       smpi_bench_end();
-
-       // FIXME: need to test parameters
-
-       index = smpi_host_index();
-       rank  = comm->index_to_rank_map[index];
-
-       if (0 == rank) {
-               int colormap[comm->size];
-        int keymap[comm->size];
-        int rankkeymap[comm->size * 2];
-               int i, j;
-               smpi_mpi_communicator_t tempcomm = NULL;
-               int colortmp;
-               int keycount;
-               int indextmp;
-
-               colormap[0] = color;
-        keymap[0]   = key;
-
-               // FIXME: use scatter/gather or similar instead of individual comms
-               for (i = 1; i < comm->size; i++) {
-                       retval = smpi_create_request(colorkey, 2, MPI_INT, MPI_ANY_SOURCE,
-                    rank, MPI_ANY_TAG, comm, &request);
-                       smpi_mpi_irecv(request);
-                       smpi_mpi_wait(request, &status);
-                       colormap[status.MPI_SOURCE] = colorkey[0];
-                       keymap[status.MPI_SOURCE]   = colorkey[1];
-                       xbt_mallocator_release(smpi_global->request_mallocator, request);
-               }
-
-               for (i = 0; i < comm->size; i++) {
-                       if (-1 == colormap[i]) {
-                               continue;
-                       }
-                       colortmp = colormap[i];
-                       keycount = 0;
-                       for (j = i; j < comm->size; j++) {
-                               if(colortmp == colormap[j]) {
-                                       colormap[j] = -1;
-                                       rankkeymap[keycount * 2]     = j;
-                                       rankkeymap[keycount * 2 + 1] = keymap[j];
-                                       keycount++;
-                               }
-                       }
-            qsort(rankkeymap, keycount, sizeof(int) * 2, &smpi_compare_rankkeys);
-                       tempcomm                    = xbt_new(s_smpi_mpi_communicator_t, 1);
-                       tempcomm->barrier_count     = 0;
-                       tempcomm->size              = keycount;
-                       tempcomm->barrier_mutex     = SIMIX_mutex_init();
-                       tempcomm->barrier_cond      = SIMIX_cond_init();
-                       tempcomm->rank_to_index_map = xbt_new(int, keycount);
-                       tempcomm->index_to_rank_map = xbt_new(int, smpi_global->host_count);
-                       for (j = 0; j < smpi_global->host_count; j++) {
-                               tempcomm->index_to_rank_map[j] = -1;
-                       }
-                       for (j = 0; j < keycount; j++) {
-                               indextmp = comm->rank_to_index_map[rankkeymap[j*2]];
-                               tempcomm->rank_to_index_map[j]        = indextmp;
-                               tempcomm->index_to_rank_map[indextmp] = j;
+        int retval = MPI_SUCCESS;
+        int rank;
+        int size;
+        int i;
+        int tag = 0;
+        smpi_mpi_request_t *requests;
+        smpi_mpi_request_t request;
+
+        smpi_bench_end();
+
+        rank = smpi_mpi_comm_rank(comm);
+        size = comm->size;
+
+        if (rank != root) {           // if i am not ROOT, simply send my buffer to root
+
+#ifdef DEBUG_REDUCE
+                print_buffer_int(sendbuf, count, xbt_strdup("sndbuf"), rank);
+#endif
+                retval = smpi_create_request(sendbuf, count, datatype, rank, root, tag, comm,
+                                        &request);
+                smpi_mpi_isend(request);
+                smpi_mpi_wait(request, MPI_STATUS_IGNORE);
+                xbt_mallocator_release(smpi_global->request_mallocator, request);
+
+        } else {
+                // i am the ROOT: wait for all buffers by creating one request by sender
+                int src;
+                requests = xbt_malloc((size-1) * sizeof(smpi_mpi_request_t));
+
+                void **tmpbufs = xbt_malloc((size-1) * sizeof(void *));
+                for (i = 0; i < size-1; i++) {
+                        // we need 1 buffer per request to store intermediate receptions
+                        tmpbufs[i] = xbt_malloc(count * datatype->size);
+                }  
+                // root: initiliaze recv buf with my own snd buf
+                memcpy(recvbuf, sendbuf, count * datatype->size * sizeof(char));  
+
+                // i can not use: 'request->forward = size-1;' (which would progagate size-1 receive reqs)
+                // since we should op values as soon as one receiving request matches.
+                for (i = 0; i < size-1; i++) {
+                        // reminder: for smpi_create_request() the src is always the process sending.
+                        src = i < root ? i : i + 1;
+                        retval = smpi_create_request(tmpbufs[i], count, datatype,
+                                        src, root, tag, comm, &(requests[i]));
+                        if (NULL != requests[i] && MPI_SUCCESS == retval) {
+                                if (MPI_SUCCESS == retval) {
+                                        smpi_mpi_irecv(requests[i]);
+                                }
+                        }
+                }
+                // now, wait for completion of all irecv's.
+                for (i = 0; i < size-1; i++) {
+                        int index = MPI_UNDEFINED;
+                        smpi_mpi_waitany( size-1, requests, &index, MPI_STATUS_IGNORE);
+#ifdef DEBUG_REDUCE
+                        printf ("MPI_Waitany() unblocked: root received (completes req[index=%d])\n",index);
+                        print_buffer_int(tmpbufs[index], count, bprintf("tmpbufs[index=%d] (value received)", index),
+                                        rank);
+#endif
+
+                        // arg 2 is modified
+                        op->func(tmpbufs[index], recvbuf, &count, &datatype);
+#ifdef DEBUG_REDUCE
+                        print_buffer_int(recvbuf, count, xbt_strdup("rcvbuf"), rank);
+#endif
+                        xbt_free(tmpbufs[index]);
+                        /* FIXME: with the following line, it  generates an
+                         * [xbt_ex/CRITICAL] Conditional list not empty 162518800.
+                         */
+                        // xbt_mallocator_release(smpi_global->request_mallocator, requests[index]);
+                }
+                xbt_free(requests);
+                xbt_free(tmpbufs);
+        }
+        return retval;
+}
+
+/**
+ * MPI_Reduce user entry point
+ **/
+int SMPI_MPI_Reduce(void *sendbuf, void *recvbuf, int count,
+                   MPI_Datatype datatype, MPI_Op op, int root, MPI_Comm comm)
+{
+int retval = MPI_SUCCESS;
+
+         smpi_bench_end();
+
+         retval = smpi_mpi_reduce(sendbuf, recvbuf, count, datatype, op, root, comm);
+
+         smpi_bench_begin();
+         return retval;
+}
+
+
+
+/**
+ * MPI_Allreduce
+ *
+ * Same as MPI_REDUCE except that the result appears in the receive buffer of all the group members.
+ **/
+int SMPI_MPI_Allreduce( void *sendbuf, void *recvbuf, int count, MPI_Datatype datatype,
+                   MPI_Op op, MPI_Comm comm )
+{
+int retval = MPI_SUCCESS;
+int root=0;  // arbitrary choice
+
+         smpi_bench_end();
+
+         retval = smpi_mpi_reduce( sendbuf, recvbuf, count, datatype, op, root, comm);
+         if (MPI_SUCCESS != retval)
+                   return(retval);
+
+         retval = smpi_mpi_bcast( sendbuf, count, datatype, root, comm);
+
+         smpi_bench_end();
+         return( retval );
+}
+
+
+/**
+ * MPI_Scatter user entry point
+ **/
+int SMPI_MPI_Scatter(void *sendbuf, int sendcount, MPI_Datatype datatype, 
+                        void *recvbuf, int recvcount, MPI_Datatype recvtype,
+                          int root, MPI_Comm comm)
+{
+  int retval = MPI_SUCCESS;
+  int i;
+  int cnt=0;  
+  int rank;
+  int tag=0;
+  char *cptr;  // to manipulate the void * buffers
+  smpi_mpi_request_t *requests;
+  smpi_mpi_request_t request;
+  smpi_mpi_status_t status;
+
+
+  smpi_bench_end();
+
+  rank = smpi_mpi_comm_rank(comm);
+
+  requests = xbt_malloc((comm->size-1) * sizeof(smpi_mpi_request_t));
+  if (rank == root) {
+          // i am the root: distribute my sendbuf
+          //print_buffer_int(sendbuf, comm->size, xbt_strdup("rcvbuf"), rank);
+          cptr = sendbuf;
+          for (i=0; i < comm->size; i++) {
+                  if ( i!=root ) { // send to processes ...
+
+                          retval = smpi_create_request((void *)cptr, sendcount, 
+                                          datatype, root, i, tag, comm, &(requests[cnt]));
+                          if (NULL != requests[cnt] && MPI_SUCCESS == retval) {
+                                  if (MPI_SUCCESS == retval) {
+                                          smpi_mpi_isend(requests[cnt]);
+                                  }
+                                 }
+                                 cnt++;
+                       } 
+                       else { // ... except if it's me.
+                                 memcpy(recvbuf, (void *)cptr, recvcount*recvtype->size*sizeof(char));
                        }
-                       for (j = 0; j < keycount; j++) {
-                               if (rankkeymap[j*2]) {
-                                       retval = smpi_create_request(&j, 1, MPI_INT, 0,
-                        rankkeymap[j*2], 0, comm, &request);
-                                       request->data = tempcomm;
-                                       smpi_mpi_isend(request);
-                                       smpi_mpi_wait(request, &status);
-                                       xbt_mallocator_release(smpi_global->request_mallocator, request);
-                               } else {
-                                       *comm_out = tempcomm;
-                               }
+                  cptr += sendcount*datatype->size;
+           }
+           for(i=0; i<cnt; i++) { // wait for send to complete
+                           /* FIXME: waitall() should be slightly better */
+                           smpi_mpi_wait(requests[i], &status);
+                           xbt_mallocator_release(smpi_global->request_mallocator, requests[i]);
+
+           }
+  } 
+  else {  // i am a non-root process: wait data from the root
+           retval = smpi_create_request(recvbuf,recvcount, 
+                                 recvtype, root, rank, tag, comm, &request);
+           if (NULL != request && MPI_SUCCESS == retval) {
+                       if (MPI_SUCCESS == retval) {
+                                 smpi_mpi_irecv(request);
                        }
-               }
-       } else {
-               colorkey[0] = color;
-               colorkey[1] = key;
-               retval = smpi_create_request(colorkey, 2, MPI_INT, rank, 0, 0, comm, &request);
-               smpi_mpi_isend(request);
-               smpi_mpi_wait(request, &status);
-               xbt_mallocator_release(smpi_global->request_mallocator, request);
-               retval = smpi_create_request(colorkey, 1, MPI_INT, 0, rank, 0, comm, &request);
-               smpi_mpi_irecv(request);
-               smpi_mpi_wait(request, &status);
-               *comm_out = request->data;
-       }
-
-       smpi_bench_begin();
-
-       return retval;
+           }
+           smpi_mpi_wait(request, &status);
+           xbt_mallocator_release(smpi_global->request_mallocator, request);
+  }
+  xbt_free(requests);
+
+  smpi_bench_begin();
+
+  return retval;
 }
+
+
+/**
+ * MPI_Alltoall user entry point
+ * 
+ * Uses the logic of OpenMPI (upto 1.2.7 or greater) for the optimizations
+ * ompi/mca/coll/tuned/coll_tuned_module.c
+ **/
+int SMPI_MPI_Alltoall(void *sendbuf, int sendcount, MPI_Datatype datatype, 
+                        void *recvbuf, int recvcount, MPI_Datatype recvtype,
+                          MPI_Comm comm)
+{
+  int retval = MPI_SUCCESS;
+  int block_dsize;
+  int rank;
+
+  smpi_bench_end();
+
+  rank = smpi_mpi_comm_rank(comm);
+  block_dsize = datatype->size * sendcount;
+
+  if ((block_dsize < 200) && (comm->size > 12)) {
+           retval = smpi_coll_tuned_alltoall_bruck(sendbuf, sendcount, datatype,
+                                 recvbuf, recvcount, recvtype, comm);
+
+  } else if (block_dsize < 3000) {
+/* use this one !!         retval = smpi_coll_tuned_alltoall_basic_linear(sendbuf, sendcount, datatype,
+                                 recvbuf, recvcount, recvtype, comm);
+                                 */
+  retval = smpi_coll_tuned_alltoall_pairwise(sendbuf, sendcount, datatype,
+                                 recvbuf, recvcount, recvtype, comm);
+  } else {
+
+  retval = smpi_coll_tuned_alltoall_pairwise(sendbuf, sendcount, datatype,
+                                 recvbuf, recvcount, recvtype, comm);
+  }
+
+  smpi_bench_begin();
+
+  return retval;
+}
+
+
+
+
+// used by comm_split to sort ranks based on key values
+int smpi_compare_rankkeys(const void *a, const void *b);
+int smpi_compare_rankkeys(const void *a, const void *b)
+{
+  int *x = (int *) a;
+  int *y = (int *) b;
+
+  if (x[1] < y[1])
+    return -1;
+
+  if (x[1] == y[1]) {
+    if (x[0] < y[0])
+      return -1;
+    if (x[0] == y[0])
+      return 0;
+    return 1;
+  }
+
+  return 1;
+}
+
+int SMPI_MPI_Comm_split(MPI_Comm comm, int color, int key,
+                        MPI_Comm * comm_out)
+{
+  int retval = MPI_SUCCESS;
+
+  int index, rank;
+  smpi_mpi_request_t request;
+  int colorkey[2];
+  smpi_mpi_status_t status;
+
+  smpi_bench_end();
+
+  // FIXME: need to test parameters
+
+  index = smpi_process_index();
+  rank = comm->index_to_rank_map[index];
+
+  // default output
+  comm_out = NULL;
+
+  // root node does most of the real work
+  if (0 == rank) {
+    int colormap[comm->size];
+    int keymap[comm->size];
+    int rankkeymap[comm->size * 2];
+    int i, j;
+    smpi_mpi_communicator_t tempcomm = NULL;
+    int count;
+    int indextmp;
+
+    colormap[0] = color;
+    keymap[0] = key;
+
+    // FIXME: use scatter/gather or similar instead of individual comms
+    for (i = 1; i < comm->size; i++) {
+      retval = smpi_create_request(colorkey, 2, MPI_INT, MPI_ANY_SOURCE,
+                                   rank, MPI_ANY_TAG, comm, &request);
+      smpi_mpi_irecv(request);
+      smpi_mpi_wait(request, &status);
+      colormap[status.MPI_SOURCE] = colorkey[0];
+      keymap[status.MPI_SOURCE] = colorkey[1];
+      xbt_mallocator_release(smpi_global->request_mallocator, request);
+    }
+
+    for (i = 0; i < comm->size; i++) {
+      if (MPI_UNDEFINED == colormap[i]) {
+        continue;
+      }
+      // make a list of nodes with current color and sort by keys
+      count = 0;
+      for (j = i; j < comm->size; j++) {
+        if (colormap[i] == colormap[j]) {
+          colormap[j] = MPI_UNDEFINED;
+          rankkeymap[count * 2] = j;
+          rankkeymap[count * 2 + 1] = keymap[j];
+          count++;
+        }
+      }
+      qsort(rankkeymap, count, sizeof(int) * 2, &smpi_compare_rankkeys);
+
+      // new communicator
+      tempcomm = xbt_new(s_smpi_mpi_communicator_t, 1);
+      tempcomm->barrier_count = 0;
+      tempcomm->size = count;
+      tempcomm->barrier_mutex = SIMIX_mutex_init();
+      tempcomm->barrier_cond = SIMIX_cond_init();
+      tempcomm->rank_to_index_map = xbt_new(int, count);
+      tempcomm->index_to_rank_map = xbt_new(int, smpi_global->process_count);
+      for (j = 0; j < smpi_global->process_count; j++) {
+        tempcomm->index_to_rank_map[j] = -1;
+      }
+      for (j = 0; j < count; j++) {
+        indextmp = comm->rank_to_index_map[rankkeymap[j * 2]];
+        tempcomm->rank_to_index_map[j] = indextmp;
+        tempcomm->index_to_rank_map[indextmp] = j;
+      }
+      for (j = 0; j < count; j++) {
+        if (rankkeymap[j * 2]) {
+          retval = smpi_create_request(&j, 1, MPI_INT, 0,
+                                       rankkeymap[j * 2], 0, comm, &request);
+          request->data = tempcomm;
+          smpi_mpi_isend(request);
+          smpi_mpi_wait(request, &status);
+          xbt_mallocator_release(smpi_global->request_mallocator, request);
+        } else {
+          *comm_out = tempcomm;
+        }
+      }
+    }
+  } else {
+    colorkey[0] = color;
+    colorkey[1] = key;
+    retval = smpi_create_request(colorkey, 2, MPI_INT, rank, 0, 0, comm,
+                                 &request);
+    smpi_mpi_isend(request);
+    smpi_mpi_wait(request, &status);
+    xbt_mallocator_release(smpi_global->request_mallocator, request);
+    if (MPI_UNDEFINED != color) {
+      retval = smpi_create_request(colorkey, 1, MPI_INT, 0, rank, 0, comm,
+                                   &request);
+      smpi_mpi_irecv(request);
+      smpi_mpi_wait(request, &status);
+      *comm_out = request->data;
+    }
+  }
+
+  smpi_bench_begin();
+
+  return retval;
+}
+
+double SMPI_MPI_Wtime(void)
+{
+  return (SIMIX_get_clock());
+}
+
+