diff --git a/src/coll_patterns/recursive_knomial.h b/src/coll_patterns/recursive_knomial.h
index e234b0cafb..5935fbddb6 100644
--- a/src/coll_patterns/recursive_knomial.h
+++ b/src/coll_patterns/recursive_knomial.h
@@ -85,7 +85,7 @@ static inline ucc_rank_t ucc_kn_pattern_radix_pow_init(ucc_knomial_pattern_t *p,
 static inline void
 ucc_knomial_pattern_init_impl(ucc_rank_t size, ucc_rank_t rank,
                               ucc_kn_radix_t radix, ucc_knomial_pattern_t *p,
-                              int backward, int extra)
+                              int backward, int has_extra)
 {
     ucc_rank_t fs = radix;
     ucc_rank_t n_full_subtrees;
@@ -102,7 +102,7 @@ ucc_knomial_pattern_init_impl(ucc_rank_t size, ucc_rank_t rank,
     p->backward      = backward;
     p->iteration     = 0;
     n_full_subtrees  = ucc_kn_pattern_n_full(p);
-    p->n_extra       = extra ? size - n_full_subtrees * p->full_pow_size : 0;
+    p->n_extra       = has_extra ? size - n_full_subtrees * p->full_pow_size : 0;
     p->n_iters       = (p->n_extra && n_full_subtrees == 1) ?
         p->pow_radix_sup - 1 : p->pow_radix_sup;
     p->radix_pow     = ucc_kn_pattern_radix_pow_init(p, backward);
diff --git a/src/components/tl/ucp/gather/gather_knomial.c b/src/components/tl/ucp/gather/gather_knomial.c
index 7871a9209e..7052540306 100644
--- a/src/components/tl/ucp/gather/gather_knomial.c
+++ b/src/components/tl/ucp/gather/gather_knomial.c
@@ -16,19 +16,20 @@
         task->gather_kn.phase = _phase;                                        \
     } while (0)
 
-static inline uint32_t calc_buffer_size(ucc_rank_t trank, uint32_t radix,
+static inline uint32_t calc_buffer_size(ucc_rank_t vrank, uint32_t radix,
                                         ucc_rank_t tsize)
 {
     uint32_t radix_valuation;
 
-    if (trank == 0) {
+    if (vrank == 0) {
         return tsize;
     }
 
-    radix_valuation = calc_valuation(trank, radix);
-    return (uint32_t)ucc_min(pow(radix, radix_valuation), tsize - trank);
+    radix_valuation = calc_valuation(vrank, radix);
+    return (uint32_t)ucc_min(pow(radix, radix_valuation), tsize - vrank);
 }
 
+/* gather knomial is used as regular gather collective and as part of reduce SRG */
 void ucc_tl_ucp_gather_knomial_progress(ucc_coll_task_t *coll_task)
 {
     ucc_tl_ucp_task_t     *task      = ucc_derived_of(coll_task, ucc_tl_ucp_task_t);
@@ -86,8 +87,8 @@ void ucc_tl_ucp_gather_knomial_progress(ucc_coll_task_t *coll_task)
                                                     task->gather_kn.dist);
                     }
                     UCPCHECK_GOTO(ucc_tl_ucp_recv_nb(scratch_offset,
-                                                        msg_size, mtype, peer,
-                                                        team, task),
+                                                     msg_size, mtype, peer,
+                                                     team, task),
                                   task, out);
                 } else {
                     /*
@@ -176,10 +177,11 @@ void ucc_tl_ucp_gather_knomial_progress(ucc_coll_task_t *coll_task)
                                                  root_at_level, team, task),
                                 task, out);
             } else {
+                // need to split in this case due to root and tree topology
                 msg_size = data_size * (tsize - rank);
                 UCPCHECK_GOTO(ucc_tl_ucp_send_nb(task->gather_kn.scratch,
-                                                    msg_size, mtype,
-                                                    root_at_level, team, task),
+                                                 msg_size, mtype,
+                                                 root_at_level, team, task),
                                 task, out);
                 msg_size = data_size * (num_blocks - (tsize - rank));
                 UCPCHECK_GOTO(
@@ -226,6 +228,8 @@ ucc_status_t ucc_tl_ucp_gather_knomial_start(ucc_coll_task_t *coll_task)
                               task->gather_kn.radix, args->src.info.count * size,
                               &task->gather_kn.p);
     } else {
+        /* reduce srg */
+        ucc_assert(args->coll_type == UCC_COLL_TYPE_REDUCE);
         task->gather_kn.scratch = args->dst.info.buffer;
         ucc_kn_gx_pattern_init(size, VRANK(trank, root, size),
                                task->gather_kn.radix, args->dst.info.count,
@@ -265,7 +269,7 @@ ucc_status_t ucc_tl_ucp_gather_knomial_init_common(ucc_tl_ucp_task_t *task,
     ucc_datatype_t     dt;
     size_t             count, data_size;
     uint32_t           buffer_size;
-    int                isleaf;
+    int                is_leaf;
 
     if (UCC_IS_ROOT(*args, trank)) {
         count = args->dst.info.count;
@@ -288,10 +292,11 @@ ucc_status_t ucc_tl_ucp_gather_knomial_init_common(ucc_tl_ucp_task_t *task,
     if (args->coll_type == UCC_COLL_TYPE_REDUCE) {
         task->gather_kn.scratch = args->dst.info.buffer;
     } else {
-        isleaf = ((vrank % radix != 0) || (vrank == tsize - 1));
+        ucc_assert(args->coll_type == UCC_COLL_TYPE_GATHER);
+        is_leaf = ((vrank % radix != 0) || (vrank == tsize - 1));
         if (vrank == 0) {
             task->gather_kn.scratch = args->dst.info.buffer;
-        } else if (isleaf) {
+        } else if (is_leaf) {
             task->gather_kn.scratch = args->src.info.buffer;
         } else {
             buffer_size = calc_buffer_size(vrank, task->gather_kn.radix, tsize);