[Float8Quant] Add rowwise scaling option to float8 dyanmic quant (#819)

Author: drisspg

ruff.toml

@@ -10,4 +10,5 @@ include = [
     "torchao/float8/float8_tensor.py",
     "torchao/quantization/linear_activation_weight_observer.py",
     "test/quantization/test_observer.py",
+    "test/dtypes/test_affine_quantized_float.py",
 ]

test/dtypes/test_affine_quantized_float.py

@@ -1,34 +1,30 @@
 from torchao.utils import (
     TORCH_VERSION_AT_LEAST_2_5,
-    unwrap_tensor_subclass,
 )
 import pytest
 
 if not TORCH_VERSION_AT_LEAST_2_5:
     pytest.skip("Unsupported PyTorch version", allow_module_level=True)
 
-from numpy import full
-from torch.testing._internal.common_utils import (
-    run_tests,
-)
 from torch._inductor.test_case import TestCase as InductorTestCase
 from torch.testing._internal import common_utils
-from torch._dynamo.testing import CompileCounterWithBackend
 
 from torchao.quantization import (
     quantize_,
     float8_weight_only,
     float8_dynamic_activation_float8_weight,
 )
+from torchao.quantization.observer import PerTensor, PerRow
 from torchao.float8.float8_utils import compute_error
 import torch
 import unittest
 import pytest
-import tempfile
 import copy
 import random
-
-from unittest.mock import patch
+from functools import partial
+from typing import Tuple
+from contextlib import nullcontext
+import io
 
 
 random.seed(0)
@@ -56,6 +52,9 @@ class TestAffineQuantizedFloat8Compile(InductorTestCase):
     @common_utils.parametrize("dtype", [torch.bfloat16, torch.float32])
     @common_utils.parametrize("mode", ["dynamic", "weight-only"])
     @common_utils.parametrize("compile", [True, False])
+    @common_utils.parametrize(
+        "granularity", [PerTensor(), PerRow()] if is_H100 else [PerTensor()]
+    )
     # Inputs are (M,..), K, N
     @common_utils.parametrize(
         "sizes",
@@ -68,33 +67,142 @@ class TestAffineQuantizedFloat8Compile(InductorTestCase):
         ],
     )
     def test_fp8_linear_variants(
-        self, dtype: torch.dtype, mode: str, compile: bool, sizes: tuple
+        self, dtype: torch.dtype, mode: str, compile: bool, sizes: Tuple, granularity
     ):
-        M, N, K = sizes
-        input_tensor = torch.randn(*M, K, dtype=dtype, device="cuda")
-
-        mode_map = {
-            "dynamic": float8_dynamic_activation_float8_weight,
-            "weight-only": float8_weight_only,
-        }
+        raises = (
+            isinstance(granularity, PerRow)
+            and mode == "dynamic"
+            and dtype != torch.bfloat16
+        )
+        context = (
+            nullcontext()
+            if not raises
+            else pytest.raises(
+                AssertionError,
+                match="PerRow quantization only works for bfloat16 precision",
+            )
+        )
+        with context:
+            M, N, K = sizes
+            input_tensor = torch.randn(*M, K, dtype=dtype, device="cuda")
+
+            mode_map = {
+                "dynamic": partial(
+                    float8_dynamic_activation_float8_weight, granularity=granularity
+                ),
+                "weight-only": float8_weight_only,
+            }
+
+            # Create a linear layer with bfloat16 dtype
+            model = ToyLinearModel(K, N).eval().to(dtype).to("cuda")
+
+            quantized_model = copy.deepcopy(model)
+            factory = mode_map[mode]()
+            quantize_(model, factory)
+
+            if compile:
+                quantized_model = torch.compile(quantized_model, fullgraph=True)
+
+            output_original = model(input_tensor)
+            output_quantized = quantized_model(input_tensor)
+
+            error = compute_error(output_original, output_quantized)
+            assert (
+                compute_error(output_original, output_quantized) > 20
+            ), f"Quantization error is too high got a SQNR of {error}"
+
+    def test_invalid_granularity(self):
+        with pytest.raises(ValueError, match="Invalid granularity specification"):
+            float8_dynamic_activation_float8_weight(granularity="invalid")
+
+    def test_mismatched_granularity(self):
+        with pytest.raises(
+            ValueError,
+            match="Different granularities for activation and weight are not supported",
+        ):
+            float8_dynamic_activation_float8_weight(granularity=(PerTensor(), PerRow()))
+
+    def test_unsupported_granularity(self):
+        class UnsupportedGranularity:
+            pass
+
+        with pytest.raises(ValueError, match="Invalid granularity types"):
+            float8_dynamic_activation_float8_weight(
+                granularity=(UnsupportedGranularity(), UnsupportedGranularity())
+            )
 
-        # Create a linear layer with bfloat16 dtype
-        model = ToyLinearModel(K, N).eval().to(dtype).to("cuda")
+    @unittest.skipIf(not torch.cuda.is_available(), "Need CUDA available")
+    @unittest.skipIf(not is_cuda_8_9, "Requires GPU with compute capability >= 8.9")
+    def test_per_row_with_float32(self):
+        with pytest.raises(
+            AssertionError,
+            match="PerRow quantization only works for bfloat16 precision",
+        ):
+            model = ToyLinearModel(64, 64).eval().to(torch.float32).to("cuda")
+            quantize_(
+                model, float8_dynamic_activation_float8_weight(granularity=PerRow())
+            )
 
-        quantized_model = copy.deepcopy(model)
-        factory = mode_map[mode]()
+    @unittest.skipIf(not torch.cuda.is_available(), "Need CUDA available")
+    @unittest.skipIf(not is_cuda_8_9, "Requires GPU with compute capability >= 8.9")
+    @common_utils.parametrize("mode", ["dynamic", "weight-only"])
+    def test_serialization(self, mode: str):
+        # Create and quantize the model
+        model = ToyLinearModel(16, 32).to(device="cuda")
+        if mode == "dynamic":
+            factory = float8_dynamic_activation_float8_weight()
+        else:
+            factory = float8_weight_only()
         quantize_(model, factory)
 
-        if compile:
-            quantized_model = torch.compile(quantized_model, fullgraph=True)
-
-        output_original = model(input_tensor)
-        output_quantized = quantized_model(input_tensor)
-
-        error = compute_error(output_original, output_quantized)
-        assert (
-            compute_error(output_original, output_quantized) > 20
-        ), f"Quantization error is too high got a SQNR of {error}"
+        # Save the state dict to an in-memory buffer
+        buffer = io.BytesIO()
+        torch.save(model.state_dict(), buffer)
+
+        # Reset the buffer position
+        buffer.seek(0)
+
+        # Load the state dict from the buffer
+        loaded_state_dict = torch.load(buffer)
+
+        # Create a new model and load the state dict
+        with torch.device("meta"):
+            new_model = ToyLinearModel(16, 32)
+            new_model.load_state_dict(loaded_state_dict, assign=True)
+
+        # Compare the original and loaded models
+        if mode == "weight-only":
+            model_weight_1 = model.linear1.weight.layout_tensor.float8_data.to(
+                torch.float32
+            )
+            new_model_weight_1 = new_model.linear1.weight.layout_tensor.float8_data.to(
+                torch.float32
+            )
+
+            model_weight_2 = model.linear2.weight.layout_tensor.float8_data.to(
+                torch.float32
+            )
+            new_model_weight_2 = new_model.linear2.weight.layout_tensor.float8_data.to(
+                torch.float32
+            )
+
+        else:
+            model_weight_1 = model.linear1.weight.original_weight_tensor.layout_tensor.float8_data.to(
+                torch.float32
+            )
+            new_model_weight_1 = new_model.linear1.weight.original_weight_tensor.layout_tensor.float8_data.to(
+                torch.float32
+            )
+
+            model_weight_2 = model.linear2.weight.original_weight_tensor.layout_tensor.float8_data.to(
+                torch.float32
+            )
+            new_model_weight_2 = new_model.linear2.weight.original_weight_tensor.layout_tensor.float8_data.to(
+                torch.float32
+            )
+
+        assert torch.allclose(model_weight_1, new_model_weight_1)
+        assert torch.allclose(model_weight_2, new_model_weight_2)
 
 
 common_utils.instantiate_parametrized_tests(TestAffineQuantizedFloat8Compile)

torchao/dtypes/affine_quantized_tensor.py

@@ -26,6 +26,12 @@
     is_device,
     get_out_shape,
 )
+from torchao.float8.inference import (
+    preprocess_data,
+    Float8MMConfig,
+    addmm_float8_unwrapped_inference,
+    _is_rowwise_scaled
+)
 from torch.utils._python_dispatch import is_traceable_wrapper_subclass
 from dataclasses import dataclass
 from torchao.utils import (
@@ -1354,53 +1360,61 @@ def _linear_f16_act_fpx_weight_impl(input_tensor, weight_tensor, bias):
 
     return out.view(*act.shape[:-1], out_dim).to(act.dtype)
 
-def _linear_fp_act_fp8_tensor_wise_weight_check(
+def _linear_fp_act_fp8_weight_check(
     input_tensor: Union[torch.Tensor, AffineQuantizedTensor],
     weight_tensor: Union[torch.Tensor, AffineQuantizedTensor],
     bias: Optional[torch.Tensor],
 ) -> bool:
-    def check_aqt_tensorwise(aqt: Union[torch.Tensor, AffineQuantizedTensor]) -> bool:
+    def check_aqt(aqt: Union[torch.Tensor, AffineQuantizedTensor]) -> bool:
         return (
             isinstance(aqt, AffineQuantizedTensor) and
             isinstance(aqt.layout_type, Float8LayoutType)
             and aqt.layout_tensor.dtype in [torch.float8_e4m3fn, torch.float8_e5m2]
-            and aqt.shape == aqt.block_size
+            and (aqt.shape == aqt.block_size or _is_rowwise_scaled(aqt))
         )
-    return check_aqt_tensorwise(input_tensor) and check_aqt_tensorwise(weight_tensor)
+    return check_aqt(input_tensor) and check_aqt(weight_tensor)
+
 
+def preprocess_scale(input_scale: torch.Tensor, input_shape: Tuple[int]):
+    """ Ensures input tensor is correctly formated for _scaled_mm """
+    input_scale = input_scale.unsqueeze(-1)
+    
+    if input_scale.dim() > 2:
+        input_scale = input_scale.reshape(-1, input_scale.shape[-1])
+    
+    return input_scale
 
 def _linear_fp_act_fp8_weight_impl(
     input_tensor: AffineQuantizedTensor,
     weight_tensor: AffineQuantizedTensor,
     bias: Optional[torch.Tensor],
 ):
     """Implements matmul between FP8 input and FP8 weight with compute using _scaled_mm"""
-    from torchao.float8.inference import (
-        preprocess_data,
-        Float8MMConfig,
-        addmm_float8_unwrapped_inference,
-    )
-
     scaled_mm_config = weight_tensor.layout_type.mm_config
-    scaled_mm_config = scaled_mm_config if scaled_mm_config is not None else Float8MMConfig()
+    out_shape = get_out_shape(input_tensor.shape, weight_tensor.shape)
 
+    # Weight tensor preprocessing
     w_layout = weight_tensor.layout_tensor
-    w_data = weight_tensor.layout_tensor.float8_data
-    w_data = w_data.T if w_layout.transposed else w_data
+    assert not w_layout.transposed, "Weight tensor must be contiguous"
+    w_data = w_layout.float8_data
     w_scale = w_layout.scale
-    w_scale = w_scale if w_layout.transposed else w_scale
-
-    out_shape = get_out_shape(input_tensor.shape, weight_tensor.shape)
 
+    # Input tensor preprocessing
     inpt_data = input_tensor.layout_tensor.float8_data
-    # Handle case where input tensor is more than 2D
-    inpt_data = inpt_data.reshape(-1, input_tensor.shape[-1])
     input_scale = input_tensor.layout_tensor.scale
-    if input_scale.dim() > 2:
-        input_scale = input_scale.reshape(-1, input_scale.shape[-1])
+    # Handle case where input tensor is more than 2D
+    inpt_data = inpt_data.reshape(-1, inpt_data.shape[-1])
+
+    # Handle rowwise case
+    if _is_rowwise_scaled(weight_tensor):
+        assert _is_rowwise_scaled(input_tensor), "Input tensor must be rowwise block size"
+        w_scale = w_scale.unsqueeze(-1).T
+        input_scale = preprocess_scale(input_scale, input_tensor.shape)
 
+    # Preprocess data
     inpt_data, w_data = preprocess_data(inpt_data, w_data.T, scaled_mm_config)
 
+    # Perform the computation
     return addmm_float8_unwrapped_inference(
         inpt_data,
         input_scale,
@@ -1459,7 +1473,7 @@ def _register_aqt_quantized_linear_dispatches():
     for dispatch_condition, impl in [
         (_linear_int8_act_int8_weight_check, _linear_int8_act_int8_weight_impl),
         (_linear_int8_act_int8_weight_semi_structured_sparse_check, _linear_int8_act_int8_weight_semi_structured_sparse_impl),
-        (_linear_fp_act_fp8_tensor_wise_weight_check, _linear_fp_act_fp8_weight_impl),
+        (_linear_fp_act_fp8_weight_check, _linear_fp_act_fp8_weight_impl),
         (_linear_bf16_act_uint4_weight_check, _linear_bf16_act_uint4_weight_impl),
         (_linear_fp_act_int8_weight_check, _linear_fp_act_int8_weight_impl),
         (_linear_f16_act_fpx_weight_check, _linear_f16_act_fpx_weight_impl),

torchao/float8/inference.py

@@ -97,3 +97,11 @@ def addmm_float8_unwrapped_inference(
         use_fast_accum=use_fast_accum,
     )
     return output
+
+
+def _is_rowwise_scaled(x) -> bool:
+    """Checks if an AQT tensor is rowwise scaled
+    Args:
+        x: AffineQuantizedTensor tensor
+    """
+    return x.block_size == (1,) * (x.dim() - 1) + (x.shape[-1],)

torchao/quantization/observer.py

@@ -53,6 +53,16 @@ class PerAxis(GranularityType):
     """
     axis: int
 
+@dataclass(frozen=True)
+class PerRow(GranularityType):
+    """
+    Represents row-wise granularity in quantization.
+
+    This is a special case of per-axis quantization and is unique to Float8 matmuls
+    where the input is quantized with a block_size of (1, ..., input.shape[-1]). And the weight
+    is quantized with a block_size of (1, weight.shape[1]).
+    """
+    pass
 
 # borrowed from torch.ao.quantization.observer
 class _PartialWrapper:
@@ -104,6 +114,8 @@ def get_block_size(
         block_size = list(input_shape)
         block_size[granularity_type.axis] = 1
         return tuple(block_size)
+    elif isinstance(granularity_type, PerRow):
+        return (1,) * (len(input_shape) - 1) + (input_shape[-1],)
     raise ValueError(f"Unsupported GranularityType: {granularity_type}")