diff --git a/examples/spmm/spmm.cc b/examples/spmm/spmm.cc
index bd0982c06..7cf656e4e 100644
--- a/examples/spmm/spmm.cc
+++ b/examples/spmm/spmm.cc
@@ -289,10 +289,10 @@ class SpMM25D {
       , b_rows_of_col_(b_rows_of_col)
       , a_rows_of_col_(a_rows_of_col)
       , b_cols_of_row_(b_cols_of_row)
-      , k_cnt_(a_cols_of_row_.size()+1)
+      , k_cnt_(a_rows_of_col_.size()+1)
       , ij_keymap_(std::move(ij_keymap))
       , ijk_keymap_(std::move(ijk_keymap))
-      , parallel_bcasts_(parallel_bcasts) {
+      , parallel_bcasts_(std::max(parallel_bcasts, 1L)) {
     Edge<Key<2>, void> a_ctl, b_ctl;
     Edge<Key<2>, int> a_rowctl, b_colctl; // TODO: can we have multiple control inputs per TT?
     auto constraint = ttg::make_shared_constraint<ttg::SequencedKeysConstraint<Key<2>>>(USE_AUTO_CONSTRAINT);
@@ -306,7 +306,7 @@ class SpMM25D {
     local_bcast_b_ = std::make_unique<LocalBcastB>(local_b_ijk_, b_ijk_, a_rows_of_col_, ijk_keymap_);
     multiplyadd_ = std::make_unique<MultiplyAdd>(a_ijk_, b_ijk_, c_ijk_, c_ij_p_, a_cols_of_row_,
                                                  b_rows_of_col_, mTiles, nTiles, ijk_keymap_, constraint,
-                                                 k_cnt_, parallel_bcasts);
+                                                 k_cnt_, parallel_bcasts_);
 
     reduce_c_ = std::make_unique<ReduceC>(c_ij_p_, c, ij_keymap_);
     reduce_c_->template set_input_reducer<0>(
@@ -325,7 +325,8 @@ class SpMM25D {
     std::vector<unsigned long> first_k_map(world.size(), std::numeric_limits<unsigned long>::max());
     std::size_t max_k = a_rows_of_col_.size();
     std::vector<std::size_t> k_cnt;
-    k_cnt.resize(a_cols_of_row_.size(), 0);
+    k_cnt.resize(a_rows_of_col_.size(), 0);
+    int release_k = 0;
     for (auto i = 0ul; i != a_cols_of_row_.size(); ++i) {
       if (a_cols_of_row_[i].empty()) continue;
       for (auto j = 0ul; j != b_rows_of_col_.size(); ++j) {
@@ -362,19 +363,12 @@ class SpMM25D {
       k_cnt_[i++].store(c, std::memory_order_relaxed);
     }
 
-    // release the first bcast(s)
-    auto pbcasts = parallel_bcasts_;
-    auto release_k = k_cnt.begin();
-    auto release_k_ = release_k; // this will be released
+    /* release the first parallel_bcasts_ k that are non-zero */
+    auto k_cnt_iter = k_cnt.begin();
     do {
-      release_k = std::find_if(release_k, k_cnt.end(), [](std::size_t c){ return c > 0; });
-      if (k_cnt.end() == release_k) {
-        break;
-      }
-      release_k_ = release_k;
-      ++release_k;
-    } while (--pbcasts > 0);
-    constraint->release(*release_k_);
+      k_cnt_iter = std::find_if(k_cnt_iter, k_cnt.end(), [](auto c){ return c > 0; });
+    } while (++k_cnt_iter != k_cnt.end() && std::distance(k_cnt_iter, k_cnt.end()) < parallel_bcasts_);
+    constraint->release(std::distance(k_cnt.begin(), k_cnt_iter));
 
     TTGUNUSED(bcast_a_);
     TTGUNUSED(bcast_b_);
@@ -612,12 +606,16 @@ class SpMM25D {
                  (have_next_k ? std::to_string(next_k) : "does not exist"));
       // release the constraint on the next round of broadcasts
       {
-        std::size_t release_k = k;
-        std::size_t bcasts_ahead = parallel_bcasts_;
-        assert(k_cnt_.size() > release_k);
-        if (0 == k_cnt_[release_k].fetch_sub(1, std::memory_order_relaxed)-1) {
-          // this was the last gemm in this k, find the one to release
-          while (++release_k < k_cnt_.size() && (0 == k_cnt_[release_k].load(std::memory_order_relaxed) || --bcasts_ahead > 0))
+        assert(k_cnt_.size() > k);
+        long cnt = k_cnt_[k].fetch_sub(1, std::memory_order_relaxed)-1;
+        assert(cnt >= 0);
+        if (0 == cnt) {
+          auto release_k = k;
+          auto bcasts_ahead = parallel_bcasts_;
+          // this was the last gemm in this k, find the next one to release
+          while (++release_k < k_cnt_.size() &&
+                 (0 == k_cnt_[release_k].load(std::memory_order_relaxed)
+                  || --bcasts_ahead > 0))
           { }
           constraint->release(release_k);
         }