diff --git a/src/seq_mv/csr_spgemm_device_numer.h b/src/seq_mv/csr_spgemm_device_numer.h
index addf22f00..d58a0292d 100644
--- a/src/seq_mv/csr_spgemm_device_numer.h
+++ b/src/seq_mv/csr_spgemm_device_numer.h
@@ -95,16 +95,19 @@ hypre_spgemm_hash_insert_numer( HYPRE_Int               HashSize,
    return -1;
 }
 
-template <HYPRE_Int SHMEM_HASH_SIZE, char HASHTYPE, HYPRE_Int GROUP_SIZE, bool HAS_GHASH, HYPRE_Int UNROLL_FACTOR>
+template <HYPRE_Int SHMEM_HASH_SIZE, char HASHTYPE, HYPRE_Int GROUP_SIZE, bool HAS_GHASH, bool IA1, HYPRE_Int UNROLL_FACTOR>
 static __device__ __forceinline__
 void
 hypre_spgemm_compute_row_numer( HYPRE_Int               istart_a,
                                 HYPRE_Int               iend_a,
+                                HYPRE_Int               istart_c,
                                 const    HYPRE_Int     *ja,
                                 const    HYPRE_Complex *aa,
                                 const    HYPRE_Int     *ib,
                                 const    HYPRE_Int     *jb,
                                 const    HYPRE_Complex *ab,
+                                HYPRE_Int              *jc,
+                                HYPRE_Complex          *ac,
                                 volatile HYPRE_Int     *s_HashKeys,
                                 volatile HYPRE_Complex *s_HashVals,
                                 HYPRE_Int               g_HashSize,
@@ -150,17 +153,26 @@ hypre_spgemm_compute_row_numer( HYPRE_Int               istart_a,
          {
             const HYPRE_Int     k_idx = read_only_load(jb + k);
             const HYPRE_Complex k_val = (ab ? read_only_load(ab + k) : 1.0) * mult;
-            /* first try to insert into shared memory hash table */
-            HYPRE_Int pos = hypre_spgemm_hash_insert_numer<SHMEM_HASH_SIZE, HASHTYPE, UNROLL_FACTOR>
-                            (s_HashKeys, s_HashVals, k_idx, k_val);
 
-            if (HAS_GHASH && -1 == pos)
+            if (IA1)
             {
-               pos = hypre_spgemm_hash_insert_numer<HASHTYPE>
-                     (g_HashSize, g_HashKeys, g_HashVals, k_idx, k_val);
+               jc[istart_c + k - rowB_start] = k_idx;
+               ac[istart_c + k - rowB_start] = k_val;
             }
+            else
+            {
+               /* first try to insert into shared memory hash table */
+               HYPRE_Int pos = hypre_spgemm_hash_insert_numer<SHMEM_HASH_SIZE, HASHTYPE, UNROLL_FACTOR>
+                  (s_HashKeys, s_HashVals, k_idx, k_val);
 
-            hypre_device_assert(pos != -1);
+               if (HAS_GHASH && -1 == pos)
+               {
+                  pos = hypre_spgemm_hash_insert_numer<HASHTYPE>
+                     (g_HashSize, g_HashKeys, g_HashVals, k_idx, k_val);
+               }
+
+               hypre_device_assert(pos != -1);
+            }
          }
       }
    }
@@ -321,10 +333,32 @@ hypre_spgemm_numeric( const HYPRE_Int                   M,
                              istart_a, iend_a,
                              GROUP_SIZE >= HYPRE_WARP_SIZE ? warp_lane_id : lane_id);
 
+      /* start/end position of row of C */
+      HYPRE_Int istart_c = 0;
+#if defined(HYPRE_DEBUG)
+      HYPRE_Int iend_c = 0;
+      group_read<GROUP_SIZE>(ic + ii, GROUP_SIZE >= HYPRE_WARP_SIZE || i < M,
+                             istart_c, iend_c,
+                             GROUP_SIZE >= HYPRE_WARP_SIZE ? warp_lane_id : lane_id);
+#else
+      group_read<GROUP_SIZE>(ic + ii, GROUP_SIZE >= HYPRE_WARP_SIZE || i < M,
+                             istart_c,
+                             GROUP_SIZE >= HYPRE_WARP_SIZE ? warp_lane_id : lane_id);
+#endif
+
       /* work with two hash tables */
-      hypre_spgemm_compute_row_numer<SHMEM_HASH_SIZE, HASHTYPE, GROUP_SIZE, HAS_GHASH, UNROLL_FACTOR>
-         (istart_a, iend_a, ja, aa, ib, jb, ab, group_s_HashKeys, group_s_HashVals, ghash_size,
-          jg + istart_g, ag + istart_g);
+      if (iend_a == istart_a + 1)
+      {
+         hypre_spgemm_compute_row_numer<SHMEM_HASH_SIZE, HASHTYPE, GROUP_SIZE, HAS_GHASH, true, UNROLL_FACTOR>
+            (istart_a, iend_a, istart_c, ja, aa, ib, jb, ab, jc, ac, group_s_HashKeys, group_s_HashVals, ghash_size,
+             jg + istart_g, ag + istart_g);
+      }
+      else
+      {
+         hypre_spgemm_compute_row_numer<SHMEM_HASH_SIZE, HASHTYPE, GROUP_SIZE, HAS_GHASH, false, UNROLL_FACTOR>
+            (istart_a, iend_a, istart_c, ja, aa, ib, jb, ab, jc, ac, group_s_HashKeys, group_s_HashVals, ghash_size,
+             jg + istart_g, ag + istart_g);
+      }
 
       if (GROUP_SIZE > HYPRE_WARP_SIZE)
       {
@@ -333,21 +367,10 @@ hypre_spgemm_numeric( const HYPRE_Int                   M,
 
       HYPRE_Int jsum = 0;
 
-      /* copy results into the final C */
+      /* the first warp of the group copies results into the final C
+       * if GROUP_SIZE < WARP_SIZE, the whole group copies */
       if (get_warp_in_group_id<GROUP_SIZE>() == 0)
       {
-         HYPRE_Int istart_c = 0;
-#ifdef HYPRE_DEBUG
-         HYPRE_Int iend_c = 0;
-         group_read<GROUP_SIZE>(ic + ii, GROUP_SIZE >= HYPRE_WARP_SIZE || i < M,
-                                istart_c, iend_c,
-                                GROUP_SIZE >= HYPRE_WARP_SIZE ? warp_lane_id : lane_id);
-#else
-         group_read<GROUP_SIZE>(ic + ii, GROUP_SIZE >= HYPRE_WARP_SIZE || i < M,
-                                istart_c,
-                                GROUP_SIZE >= HYPRE_WARP_SIZE ? warp_lane_id : lane_id);
-#endif
-
          jsum = hypre_spgemm_copy_from_hash_into_C_row<GROUP_SIZE, SHMEM_HASH_SIZE, HAS_GHASH, UNROLL_FACTOR>
                 (lane_id,
                  GROUP_SIZE >= HYPRE_WARP_SIZE || i < M ? group_s_HashKeys : NULL,