copy paste in a working impl of flash attention from ring-attention-p…

…ytorch repo for modification. get basic scaffolding ready

native_sparse_attention_pytorch/native_sparse_attention.py

@@ -191,6 +191,7 @@ def __init__(
         num_compressed_mem_kv = 1,
         norm = True,
         use_diff_topk = False,
+        use_triton_kernel = False,
         interpolated_importance_score = False,
         query_heads_share_selected_kv = True, # if set to True, importance score is averaged across query heads to select top-n buckets of kv per kv head - but can be set to False for each query head within a group to look at different sets of kv buckets. will be more memory and compute of course
         compress_mlp: Module | None = None,
@@ -287,6 +288,8 @@ def __init__(
 
         self.num_selected_blocks = num_selected_blocks
 
+        self.use_triton_kernel = use_triton_kernel
+
         # they combine the three sparse branches through a learned combine with sigmoid activation
 
         if not exists(strategy_combine_mlp):
@@ -438,7 +441,17 @@ def forward(
                 gates = gates.cumprod(dim = -1)[..., -1]
                 gates = repeat(gates, 'b h ... -> b (h qh) ...', qh = fine_num_grouped_queries)
 
-            if exists(fine_selection_flex_mask):
+            if self.use_triton_kernel:
+                from native_sparse_attention_pytorch.triton_native_sparse_attention import native_sparse_attend
+
+                fine_attn_out = native_sparse_attend(
+                    fq, fk, fv,
+                    self.selection_block_size,
+                    selected_block_indices,
+                    fine_num_grouped_queries
+                )
+
+            elif exists(fine_selection_flex_mask):
                 # flex attention for the selection for fine attention
 
                 fine_block_mask = fine_selection_flex_mask(selected_block_indices, num_grouped_queries = fine_num_grouped_queries)

native_sparse_attention_pytorch/transformer.py

@@ -35,6 +35,9 @@ def exists(v):
 def default(v, d):
     return v if exists(v) else d
 
+def at_most_one_of(*bools):
+    return sum([*map(int, bools)]) <= 1
+
 # attention
 
 class Attention(Module):
@@ -123,6 +126,7 @@ def __init__(
         use_sparse_attn = False,
         use_flex_sliding_window = False,
         use_flex_fine_selection = False,
+        use_triton_fine_selection = False,
         sparse_attn_kwargs: dict = dict(
             sliding_window_size = 32,
             compress_block_size = 4,
@@ -131,6 +135,8 @@ def __init__(
         )
     ):
         super().__init__()
+        assert at_most_one_of(use_flex_fine_selection, use_triton_fine_selection), 'either using flex or custom triton kernel for fine attn, but not both'
+
         self.token_emb = nn.Embedding(num_tokens, dim)
 
         if use_flex_sliding_window or use_flex_fine_selection:
@@ -149,6 +155,7 @@ def __init__(
                     dim_head = dim_head,
                     heads = heads,
                     kv_heads = kv_heads,
+                    use_triton_kernel = use_triton_fine_selection,
                     **sparse_attn_kwargs
                 )
             else: