coll/libnbc: add knomial tree algorithm for MPI_Ibcast

mkurnosov · mkurnosov · commit b0429d25dfb1 · 2018-10-09T20:43:04.000+07:00
Signed-off-by: Mikhail Kurnosov &lt;mkurnosov@gmail.com&gt;
diff --git a/ompi/mca/coll/libnbc/coll_libnbc.h b/ompi/mca/coll/libnbc/coll_libnbc.h
@@ -70,6 +70,8 @@ BEGIN_C_DECLS
 #define NBC_NUM_COLL 17
 
 extern bool libnbc_ibcast_skip_dt_decision;
+extern int libnbc_ibcast_algorithm;
+extern int libnbc_ibcast_knomial_radix;
 extern int libnbc_iexscan_algorithm;
 extern int libnbc_iscan_algorithm;
 
diff --git a/ompi/mca/coll/libnbc/coll_libnbc_component.c b/ompi/mca/coll/libnbc/coll_libnbc_component.c
@@ -46,6 +46,17 @@ static int libnbc_priority = 10;
 static bool libnbc_in_progress = false;     /* protect from recursive calls */
 bool libnbc_ibcast_skip_dt_decision = true;
 
+int libnbc_ibcast_algorithm = 0;             /* ibcast user forced algorithm */
+int libnbc_ibcast_knomial_radix = 4;
+static mca_base_var_enum_value_t ibcast_algorithms[] = {
+    {0, "ignore"},
+    {1, "linear"},
+    {2, "binomial"},
+    {3, "chain"},
+    {4, "knomial"},
+    {0, NULL}
+};
+
 int libnbc_iexscan_algorithm = 0;             /* iexscan user forced algorithm */
 static mca_base_var_enum_value_t iexscan_algorithms[] = {
     {0, "ignore"},
@@ -175,6 +186,24 @@ libnbc_register(void)
                                            MCA_BASE_VAR_SCOPE_READONLY,
                                            &libnbc_ibcast_skip_dt_decision);
 
+    libnbc_ibcast_algorithm = 0;
+    (void) mca_base_var_enum_create("coll_libnbc_ibcast_algorithms", ibcast_algorithms, &new_enum);
+    mca_base_component_var_register(&mca_coll_libnbc_component.super.collm_version,
+                                    "ibcast_algorithm",
+                                    "Which ibcast algorithm is used: 0 ignore, 1 linear, 2 binomial, 3 chain, 4 knomial",
+                                    MCA_BASE_VAR_TYPE_INT, new_enum, 0, MCA_BASE_VAR_FLAG_SETTABLE,
+                                    OPAL_INFO_LVL_5, MCA_BASE_VAR_SCOPE_ALL,
+                                    &libnbc_ibcast_algorithm);
+    OBJ_RELEASE(new_enum);
+
+    libnbc_ibcast_knomial_radix = 4;
+    (void) mca_base_component_var_register(&mca_coll_libnbc_component.super.collm_version,
+                                           "ibcast_knomial_radix", "k-nomial tree radix for the ibcast algorithm (radix > 1)",
+                                           MCA_BASE_VAR_TYPE_INT, NULL, 0, 0,
+                                           OPAL_INFO_LVL_9,
+                                           MCA_BASE_VAR_SCOPE_READONLY,
+                                           &libnbc_ibcast_knomial_radix);
+
     libnbc_iexscan_algorithm = 0;
     (void) mca_base_var_enum_create("coll_libnbc_iexscan_algorithms", iexscan_algorithms, &new_enum);
     mca_base_component_var_register(&mca_coll_libnbc_component.super.collm_version,
diff --git a/ompi/mca/coll/libnbc/nbc_ibcast.c b/ompi/mca/coll/libnbc/nbc_ibcast.c
@@ -26,6 +26,8 @@ static inline int bcast_sched_linear(int rank, int p, int root, NBC_Schedule *sc
                                      MPI_Datatype datatype);
 static inline int bcast_sched_chain(int rank, int p, int root, NBC_Schedule *schedule, void *buffer, int count,
                                     MPI_Datatype datatype, int fragsize, size_t size);
+static inline int bcast_sched_knomial(int rank, int comm_size, int root, NBC_Schedule *schedule, void *buf,
+                                      int count, MPI_Datatype datatype, int knomial_radix);
 
 #ifdef NBC_CACHE_SCHEDULE
 /* tree comparison function for schedule cache */
@@ -55,7 +57,7 @@ static int nbc_bcast_init(void *buffer, int count, MPI_Datatype datatype, int ro
 #ifdef NBC_CACHE_SCHEDULE
   NBC_Bcast_args *args, *found, search;
 #endif
-  enum { NBC_BCAST_LINEAR, NBC_BCAST_BINOMIAL, NBC_BCAST_CHAIN } alg;
+  enum { NBC_BCAST_LINEAR, NBC_BCAST_BINOMIAL, NBC_BCAST_CHAIN, NBC_BCAST_KNOMIAL } alg;
   ompi_coll_libnbc_module_t *libnbc_module = (ompi_coll_libnbc_module_t*) module;
 
   rank = ompi_comm_rank (comm);
@@ -73,25 +75,40 @@ static int nbc_bcast_init(void *buffer, int count, MPI_Datatype datatype, int ro
 
   segsize = 16384;
   /* algorithm selection */
-  if( libnbc_ibcast_skip_dt_decision ) {
-    if (p <= 4) {
-      alg = NBC_BCAST_LINEAR;
+  if (libnbc_ibcast_algorithm == 0) {
+    if( libnbc_ibcast_skip_dt_decision ) {
+      if (p <= 4) {
+        alg = NBC_BCAST_LINEAR;
+      }
+      else {
+        alg = NBC_BCAST_BINOMIAL;
+      }
     }
     else {
-      alg = NBC_BCAST_BINOMIAL;
+      if (p <= 4) {
+        alg = NBC_BCAST_LINEAR;
+      } else if (size * count < 65536) {
+        alg = NBC_BCAST_BINOMIAL;
+      } else if (size * count < 524288) {
+        alg = NBC_BCAST_CHAIN;
+        segsize = 8192;
+      } else {
+        alg = NBC_BCAST_CHAIN;
+        segsize = 32768;
+      }
     }
-  }
-  else {
-    if (p <= 4) {
+  } else {
+    /* user forced dynamic decision */
+    if (libnbc_ibcast_algorithm == 1) {
       alg = NBC_BCAST_LINEAR;
-    } else if (size * count < 65536) {
+    } else if (libnbc_ibcast_algorithm == 2) {
       alg = NBC_BCAST_BINOMIAL;
-    } else if (size * count < 524288) {
+    } else if (libnbc_ibcast_algorithm == 3) {
       alg = NBC_BCAST_CHAIN;
-      segsize = 8192;
+    } else if (libnbc_ibcast_algorithm == 4 && libnbc_ibcast_knomial_radix > 1) {
+      alg = NBC_BCAST_KNOMIAL;
     } else {
-      alg = NBC_BCAST_CHAIN;
-      segsize = 32768;
+      alg = NBC_BCAST_LINEAR;
     }
   }
 
@@ -119,6 +136,9 @@ static int nbc_bcast_init(void *buffer, int count, MPI_Datatype datatype, int ro
       case NBC_BCAST_CHAIN:
         res = bcast_sched_chain(rank, p, root, schedule, buffer, count, datatype, segsize, size);
         break;
+      case NBC_BCAST_KNOMIAL:
+        res = bcast_sched_knomial(rank, p, root, schedule, buffer, count, datatype, libnbc_ibcast_knomial_radix);
+        break;
     }
 
     if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
@@ -342,6 +362,53 @@ static inline int bcast_sched_chain(int rank, int p, int root, NBC_Schedule *sch
   return OMPI_SUCCESS;
 }
 
+/*
+ * bcast_sched_knomial:
+ *
+ * Description: an implementation of Ibcast using k-nomial tree algorithm
+ *
+ * Time: (radix - 1)O(log_{radix}(comm_size))
+ * Memory: O(reqs_max)
+ * Schedule length (rounds): O(log(comm_size))
+ */
+static inline int bcast_sched_knomial(
+    int rank, int comm_size, int root, NBC_Schedule *schedule, void *buf,
+    int count, MPI_Datatype datatype, int knomial_radix)
+{
+    int res = OMPI_SUCCESS;
+
+    /* Receive from parent */
+    int vrank = (rank - root + comm_size) % comm_size;
+    int mask = 0x1;
+    while (mask < comm_size) {
+        if (vrank % (knomial_radix * mask)) {
+            int parent = vrank / (knomial_radix * mask) * (knomial_radix * mask);
+            parent = (parent + root) % comm_size;
+            res = NBC_Sched_recv(buf, false, count, datatype, parent, schedule, true);
+            if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
+            break;
+        }
+        mask *= knomial_radix;
+    }
+    mask /= knomial_radix;
+
+    /* Send data to all children */
+    while (mask > 0) {
+        for (int r = 1; r < knomial_radix; r++) {
+            int child = vrank + mask * r;
+            if (child < comm_size) {
+                child = (child + root) % comm_size;
+                res = NBC_Sched_send(buf, false, count, datatype, child, schedule, false);
+                if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
+            }
+        }
+        mask /= knomial_radix;
+    }
+
+cleanup_and_return:
+    return res;
+}
+
 static int nbc_bcast_inter_init(void *buffer, int count, MPI_Datatype datatype, int root,
                                 struct ompi_communicator_t *comm, ompi_request_t ** request,
                                 struct mca_coll_base_module_2_3_0_t *module, bool persistent) {
