[hotfix] polish flash attention (#1802)

colossalai/kernel/cuda_native/flash_attention.py

@@ -10,20 +10,6 @@ import subprocess
 
 import torch
 
-try:
-    import triton
-    import triton.language as tl
-    HAS_TRITON = True
-except ImportError:
-    print('please install triton from https://github.com/openai/triton')
-    HAS_TRITON = False
-try:
-    from flash_attn.flash_attn_interface import flash_attn_unpadded_func
-    HAS_FLASH_ATTN = True
-except ImportError:
-    HAS_FLASH_ATTN = False
-    print('please install flash_attn from https://github.com/HazyResearch/flash-attention')
-
 
 def triton_check():
     cuda_home = os.getenv("CUDA_HOME", default="/usr/local/cuda")
@@ -38,9 +24,26 @@ def triton_check():
     return False
 
 
-TRITON_AVALIABLE = triton_check()
+try:
+    import triton
+    import triton.language as tl
+    if triton_check():
+        HAS_TRITON = True
+    else:
+        print("triton requires cuda >= 11.4")
+        HAS_TRITON = False
+except ImportError:
+    print('please install triton from https://github.com/openai/triton')
+    HAS_TRITON = False
+try:
+    from flash_attn.flash_attn_interface import flash_attn_unpadded_func
+    HAS_FLASH_ATTN = True
+except ImportError:
+    HAS_FLASH_ATTN = False
+    print('please install flash_attn from https://github.com/HazyResearch/flash-attention')
+
 
-if TRITON_AVALIABLE:
+if HAS_TRITON:
 
     @triton.jit
     def _fwd_kernel(
@@ -394,7 +397,7 @@ if TRITON_AVALIABLE:
         Return:
             out: (batch, nheads, seq, headdim)
         """
-        if TRITON_AVALIABLE:
+        if HAS_TRITON:
             return _TritonFlashAttention.apply(q, k, v, sm_scale)
         else:
             raise RuntimeError("Triton kernel requires CUDA 11.4+!")

tests/test_utils/test_flash_attention.py

@@ -2,7 +2,7 @@ import pytest
 import torch
 from einops import rearrange
 
-from colossalai.kernel.cuda_native.flash_attention import HAS_FLASH_ATTN, HAS_TRITON, TRITON_AVALIABLE
+from colossalai.kernel.cuda_native.flash_attention import HAS_FLASH_ATTN, HAS_TRITON
 
 if HAS_FLASH_ATTN:
     from colossalai.kernel.cuda_native.flash_attention import flash_attention
@@ -22,7 +22,7 @@ def baseline_attention(Z, N_CTX, H, q, k, v, sm_scale):
     return ref_out
 
 
-@pytest.mark.skipif(HAS_FLASH_ATTN == False, reason="triton is not available")
+@pytest.mark.skipif(HAS_FLASH_ATTN == False, reason="flash is not available")
 @pytest.mark.parametrize('Z, H, N_CTX, D_HEAD', [(3, 2, 16, 8)])
 def test_triton_flash_attention(Z, H, N_CTX, D_HEAD, dtype=torch.float16):
     torch.manual_seed(20)
@@ -39,7 +39,7 @@ def test_triton_flash_attention(Z, H, N_CTX, D_HEAD, dtype=torch.float16):
     ref_dq, q.grad = q.grad.clone(), None
 
     # triton implementation
-    if TRITON_AVALIABLE:
+    if HAS_TRITON:
         tri_out = triton_flash_attention(q, k, v, sm_scale)
         tri_out.backward(dout)
         tri_dv, v.grad = v.grad.clone(), None
@@ -59,7 +59,7 @@ def test_triton_flash_attention(Z, H, N_CTX, D_HEAD, dtype=torch.float16):
             raise TypeError("Error type not match!")
 
 
-@pytest.mark.skipif(HAS_FLASH_ATTN == False, reason="triton is not available")
+@pytest.mark.skipif(HAS_FLASH_ATTN == False, reason="flash is not available")
 @pytest.mark.parametrize('Z, H, N_CTX, D_HEAD', [(3, 2, 16, 8)])
 def test_flash_attention(Z, H, N_CTX, D_HEAD, dtype=torch.float16):
     torch.manual_seed(20)