Merge pull request #162 from ani300/fp8_sequence_fixes

feat: Per-sequence scaling in FP8 attention, FP8 fixes

Author: andrea-fasoli

fms_mo/aiu_addons/fp8/fp8_attn.py

@@ -70,12 +70,24 @@ def _math_fp8_store_op(
             k_scale = key_cache._scale
             v_scale = value_cache._scale
         else:
-            k_scale = (torch.abs(keys).max() / K_RANGE).to(dtype=torch.float32)
-            v_scale = (torch.abs(values).max() / V_RANGE).to(dtype=torch.float32)
+            k_scale = (
+                (torch.abs(keys).amax(dim=(1, 2, 3)) / K_RANGE)
+                .clamp(min=1e-5)
+                .to(dtype=torch.float32)
+            )
+            v_scale = (
+                (torch.abs(values).amax(dim=(1, 2, 3)) / V_RANGE)
+                .clamp(min=1e-5)
+                .to(dtype=torch.float32)
+            )
 
         # Scale kv tensors for storage
-        keys = (keys / k_scale).to(torch.float8_e4m3fn).transpose(2, 1)
-        values = (values / v_scale).to(torch.float8_e4m3fn).transpose(2, 1)
+        keys = (
+            (keys / k_scale.view(-1, 1, 1, 1)).to(torch.float8_e4m3fn).transpose(2, 1)
+        )
+        values = (
+            (values / v_scale.view(-1, 1, 1, 1)).to(torch.float8_e4m3fn).transpose(2, 1)
+        )
 
         if (
             isinstance(key_cache, ScaledTensor)
@@ -134,10 +146,20 @@ def _math_fp8_compute_op(
             value_cache = value_cache._data
         else:
             # Store op wasn't run (e.g. encoders, use_cache=False)
-            k_scale = (torch.abs(key_cache).max() / K_RANGE).to(dtype=torch.float32)
-            v_scale = (torch.abs(value_cache).max() / V_RANGE).to(dtype=torch.float32)
-            key_cache = (key_cache / k_scale).to(torch.float8_e4m3fn)
-            value_cache = (value_cache / v_scale).to(torch.float8_e4m3fn)
+            k_scale = (
+                (torch.abs(key_cache).amax(dim=(1, 2, 3)) / K_RANGE)
+                .clamp(min=1e-5)
+                .to(dtype=torch.float32)
+            )
+            v_scale = (
+                (torch.abs(value_cache).amax(dim=(1, 2, 3)) / V_RANGE)
+                .clamp(min=1e-5)
+                .to(dtype=torch.float32)
+            )
+            key_cache = (key_cache / k_scale.view(-1, 1, 1, 1)).to(torch.float8_e4m3fn)
+            value_cache = (value_cache / v_scale.view(-1, 1, 1, 1)).to(
+                torch.float8_e4m3fn
+            )
 
         # If store wasn't run, we need to transpose the tensors here
         # TODO: Refactor FMS to avoid edge cases where this fails; add use_cache param here
@@ -192,14 +214,20 @@ def _math_fp8_compute_op(
                 * scale_factor
             )
         else:
-            key_t = (key_cache.to(dtype=orig_dtype) * k_scale).transpose(-2, -1)
+            key_t = (
+                (key_cache.to(dtype=orig_dtype) * k_scale.view(-1, 1, 1, 1))
+                .to(dtype=orig_dtype)
+                .transpose(-2, -1)
+            )
             attn_weight = query @ key_t
             attn_weight *= scale_factor
         attn_weight += attn_bias
         attn_weight = torch.softmax(attn_weight, dim=-1)
         attn_weight = torch.dropout(attn_weight, p_dropout, train=True)
         # Do matmul in orig_dtype
-        attn = attn_weight @ (value_cache.to(dtype=orig_dtype) * v_scale)
+        attn = attn_weight @ (
+            value_cache.to(dtype=orig_dtype) * v_scale.view(-1, 1, 1, 1)
+        ).to(dtype=orig_dtype)
 
         attn = attn.to(orig_dtype).transpose(2, 1).contiguous()
         return attn
@@ -226,9 +254,15 @@ def _spyre_scaled_paged_store_op(
             value_cache, ScaledTensor
         ), "kv cache must be preallocated"
         if not key_cache._scaled:
-            key_cache._scale = (torch.abs(keys).max() / 200.0).to(dtype=torch.float32)
-            value_cache._scale = (torch.abs(values).max() / 100.0).to(
-                dtype=torch.float32
+            key_cache._scale = (
+                (torch.abs(keys).amax(dim=(1, 2, 3)) / K_RANGE)
+                .clamp(min=1e-5)
+                .to(dtype=torch.float32)
+            )
+            value_cache._scale = (
+                (torch.abs(values).amax(dim=(1, 2, 3)) / V_RANGE)
+                .clamp(min=1e-5)
+                .to(dtype=torch.float32)
             )
 
         result_key_cache_data, result_value_cache_data = (

fms_mo/aiu_addons/fp8/fp8_linear.py

@@ -20,6 +20,7 @@
 import torch
 
 # Local
+from fms_mo.aiu_addons.fp8 import fp8_spyre_op  # pylint: disable=unused-import
 from fms_mo.prep import available_packages
 
 # pylint: disable=not-callable

fms_mo/aiu_addons/fp8/fp8_spyre_op.py

@@ -29,12 +29,7 @@
 # open issue in PyLint: https://github.com/pytorch/pytorch/issues/119482
 
 
-aten = torch.ops.aten
-DispatchKey = torch._C.DispatchKey  # type: ignore[attr-defined]
-
-
-@torch.library.register_kernel("aten::_scaled_mm", "cpu")
-def _scaled_mm_cpu(
+def _scaled_mm_cpu_out(
     mat1: Tensor,
     mat2: Tensor,
     scale1: Tensor,
@@ -43,15 +38,50 @@ def _scaled_mm_cpu(
     scale_result: Optional[Tensor] = None,
     out_dtype: Optional[torch.dtype] = None,
     use_fast_accum: bool = False,
+    *,
+    out: Optional[Tensor] = None,
 ) -> Tensor:
     if out_dtype is None:
         out_dtype = torch.float32
     mat1 = (mat1.to(dtype=out_dtype) * scale1).to(dtype=out_dtype)
     mat2 = (mat2.to(dtype=out_dtype) * scale2).to(dtype=out_dtype)
 
     if bias is not None:
-        return torch.addmm(bias, mat1, mat2).to(dtype=out_dtype)
-    return torch.mm(mat1, mat2).to(dtype=out_dtype)
+        ret = torch.addmm(bias, mat1, mat2).to(dtype=out_dtype)
+    else:
+        ret = torch.mm(mat1, mat2).to(dtype=out_dtype)
+
+    if out is not None:
+        out.copy_(ret)
+        return out
+    return ret
+
+
+torch.library.register_kernel(torch.ops.aten._scaled_mm.out, "cpu", _scaled_mm_cpu_out)
+
+
+@torch.library.register_kernel("aten::_scaled_mm", "cpu")
+def _scaled_mm_cpu(
+    mat1: Tensor,
+    mat2: Tensor,
+    scale1: Tensor,
+    scale2: Tensor,
+    bias: Optional[Tensor] = None,
+    scale_result: Optional[Tensor] = None,
+    out_dtype: Optional[torch.dtype] = None,
+    use_fast_accum: bool = False,
+) -> Tensor:
+    return _scaled_mm_cpu_out(
+        mat1,
+        mat2,
+        scale1,
+        scale2,
+        bias,
+        scale_result,
+        out_dtype,
+        use_fast_accum,
+        out=None,
+    )
 
 
 @torch.library.custom_op("spyre::scaled_bmm", mutates_args=())
@@ -127,7 +157,6 @@ def scaled_paged_attn_store(
     Scales key and value tensors, and stores them to the paged KV cache
     using the same schema as vLLM.
     """
-    print("Should never hit")
     result_key_cache = key_cache.clone()
     result_value_cache = value_cache.clone()
     for seq_i, slot_mapping_seq in enumerate(slot_mapping):
@@ -136,10 +165,10 @@ def scaled_paged_attn_store(
             position = slot.item() % 64
 
             result_key_cache[block_number, position, :, :] = (
-                key[seq_i, tok_i, :, :] / key_scale
+                key[seq_i, tok_i, :, :] / key_scale[seq_i]
             ).to(dtype=torch.float8_e4m3fn)
             result_value_cache[block_number, position, :, :] = (
-                value[seq_i, tok_i, :, :] / value_scale
+                value[seq_i, tok_i, :, :] / value_scale[seq_i]
             ).to(dtype=torch.float8_e4m3fn)
     return result_key_cache, result_value_cache
 
@@ -179,7 +208,6 @@ def scaled_paged_attn_compute(
     Implements a CPU fallback to run the kernel that has been confirmed
     to match the vLLM fused kernel.
     """
-    print("Should never hit")
     # torch.zeros(NUM_BLOCKS, BLOCK_SIZE, kvheads, head_size, dtype=model_dtype),
     output = torch.zeros_like(query)
     num_query_heads = query.shape[2]
@@ -220,10 +248,10 @@ def scaled_paged_attn_compute(
 
         out = F.scaled_dot_product_attention(  # noqa: E1102
             q.transpose(0, 1).unsqueeze(0),  # format for sdpa
-            (keys.transpose(0, 1).unsqueeze(0).to(dtype=q.dtype) * key_scale).to(
+            (keys.transpose(0, 1).unsqueeze(0).to(dtype=q.dtype) * key_scale[i]).to(
                 dtype=q.dtype
             ),  # format for sdpa
-            (values.transpose(0, 1).unsqueeze(0).to(dtype=q.dtype) * value_scale).to(
+            (values.transpose(0, 1).unsqueeze(0).to(dtype=q.dtype) * value_scale[i]).to(
                 dtype=q.dtype
             ),  # format for sdpa
             is_causal=False,  # decode assumes no causal mask