Added Support for Rotary Positional Embeddings (#99)

* feat: added rotary support in kvcache

* confirmed non-fused rotary passes all tests

flash_attn/flash_attn_triton_amd/interface_fa.py

@@ -6,6 +6,8 @@
 from .fwd_ref import attention_forward_pytorch_ref_impl
 from .bwd_ref import attention_backward_pytorch_ref_impl
 from .utils import MetaData, get_shape_from_layout, DEBUG
+from einops import rearrange, repeat
+from flash_attn.layers.rotary import apply_rotary_emb
 
 USE_REF = os.environ.get('FLASH_ATTENTION_TRITON_AMD_REF', '0').lower() in ('1', 'true', 'yes')
 
@@ -516,6 +518,43 @@ def fwd_kvcache(
         batch, _ , nheads_q, _= q.shape
         metadata.need_alibi(alibi_slopes, batch, nheads_q)
 
+    # rotary boolean
+    apply_rotary = torch.is_tensor(rotary_cos) and torch.is_tensor(rotary_sin)
+    if apply_rotary:
+        metadata.need_rotary(rotary_sin, rotary_cos, rotary_interleaved)
+
+    # Rotary Embedding Implementation
+    if apply_rotary:
+        if metadata.causal:     # NOTE: when support is added. Add `or metadata.local`
+            q_ro = apply_rotary_emb(
+                q,
+                metadata.rotary_cos,
+                metadata.rotary_sin,
+                seqlen_offsets=metadata.cache_seqlens,
+                interleaved=metadata.rotary_interleaved,
+            )
+        else:
+            q_ro = rearrange(
+                apply_rotary_emb(
+                    rearrange(q, "b s h d -> b 1 (s h) d"),
+                    metadata.rotary_cos,
+                    metadata.rotary_sin,
+                    seqlen_offsets=metadata.cache_seqlens,
+                    interleaved=metadata.rotary_interleaved,
+                ),
+                "b 1 (s h) d -> b s h d",
+                s=metadata.max_seqlens_q,
+            )
+        k_ro = apply_rotary_emb(
+            metadata.k_new,
+            metadata.rotary_cos,
+            metadata.rotary_sin,
+            seqlen_offsets=metadata.cache_seqlens,
+            interleaved=metadata.rotary_interleaved,
+        )
+
+        q, metadata.k_new = q_ro.to(q.dtype), k_ro.to(q.dtype)
+
     # launch kernel
     # TODO: pass output as an arg. Maybe we are copying output which is causing slow down
     output, softmax_lse = attention_decode_forward_triton_impl(

flash_attn/flash_attn_triton_amd/utils.py

@@ -27,6 +27,10 @@ class MetaData():
     dropout_p, return_scores= 0.0, False
     # NOTE: scale sm_scale by log_2(e) and use 2^x in the loop as we do not have native e^x support in HW.
     use_exp2 = False
+    rotary_sin = None
+    rotary_cos = None
+    rotary_interleaved = False
+    rotary_conjunction = False
 
 
     def __repr__(self) -> str:
@@ -85,6 +89,12 @@ def need_alibi(self, alibi_slopes, batch, nheads):
     def need_causal(self):
         self.causal = True
 
+    def need_rotary(self, sin, cos, rotary_interleaved, rotary_conjunction=False):
+        self.rotary_sin = sin
+        self.rotary_cos = cos
+        self.rotary_interleaved = rotary_interleaved
+        self.rotary_conjunction = rotary_conjunction
+
     def need_dropout(self, dropout_p, return_scores):
         self.dropout_p = dropout_p
         self.return_scores = return_scores

tests/test_flash_attn_triton_amd.py

@@ -1850,10 +1850,10 @@ def test_flash_attn_varlen_causal(
 # @pytest.mark.parametrize("causal", [False])
 @pytest.mark.parametrize("seqlen_new_eq_seqlen_q", [True, False])
 # @pytest.mark.parametrize("seqlen_new_eq_seqlen_q", [True])
-# @pytest.mark.parametrize("rotary_interleaved", [False, True])
-@pytest.mark.parametrize("rotary_interleaved", [False])
-# @pytest.mark.parametrize("rotary_fraction", [0.0, 0.5, 1.0])
-@pytest.mark.parametrize("rotary_fraction", [0.0])
+@pytest.mark.parametrize("rotary_interleaved", [False, True])
+# @pytest.mark.parametrize("rotary_interleaved", [False])
+@pytest.mark.parametrize("rotary_fraction", [0.0, 0.5, 1.0])
+# @pytest.mark.parametrize("rotary_fraction", [0.0])
 # @pytest.mark.parametrize("paged_kv_block_size", [None, 256])
 # @pytest.mark.parametrize("paged_kv_block_size", [256, 512])
 @pytest.mark.parametrize("paged_kv_block_size", [None])
@@ -1907,9 +1907,6 @@ def test_flash_attn_kvcache(
 
         if local == True:
             pytest.skip("local sliding window attention not supported on AMD's Triton Backend yet")
-
-        if rotary_interleaved == True or rotary_fraction > 0.0:
-            pytest.skip("rotary embedding not supported on AMD's Triton Backend yet")
 
         if has_leftpad == True:
             pytest.skip("cache_leftpad not supported on AMD's Triton Backend yet")