[float8] Allow specifying arbitrary dtype for each tensor

ghstack-source-id: aa9f551c8d274f349c4298932fc95c88040abb09
Pull Request resolved: #1326

test/float8/test_base.py

@@ -25,6 +25,8 @@
 
 from torchao.float8.config import (
     CastConfig,
+    e4m3_dtype,
+    e5m2_dtype,
     Float8LinearConfig,
     Float8LinearRecipeName,
     recipe_name_to_linear_config,
@@ -51,8 +53,6 @@
 )
 from torchao.float8.float8_utils import (
     compute_error,
-    e4m3_dtype,
-    e5m2_dtype,
     fp8_tensor_statistics,
     FP8_TYPES,
     tensor_to_scale,

test/float8/test_compile.py

@@ -21,6 +21,7 @@
 import torch.nn as nn
 from torchao.float8.config import (
     CastConfig,
+    e4m3_dtype,
     Float8LinearConfig,
     ScalingType,
     Float8LinearRecipeName,
@@ -41,7 +42,6 @@
     GemmInputRole,
     ScaledMMConfig,
 )
-from torchao.float8.float8_utils import e4m3_dtype
 from torchao.testing.float8.test_utils import get_test_float8_linear_config
 
 from torch._dynamo.test_case import TestCase as DynamoTestCase

test/float8/test_dtensor.py

@@ -27,8 +27,8 @@
 from torchao.float8 import Float8LinearConfig
 from torchao.float8.float8_linear_utils import convert_to_float8_training
 
-from torchao.float8.config import CastConfig, ScalingType
-from torchao.float8.float8_scaling_utils import NoopFwToFloat8E5M2BwDynamic
+from torchao.float8.config import CastConfig, e4m3_dtype, ScalingType
+from torchao.float8.float8_scaling_utils import NoopFwToFloat8BwDynamic
 from torchao.float8.float8_tensor import (
     Float8Tensor,
     GemmInputRole,
@@ -40,7 +40,7 @@
     Float8RowwiseParallel,
     PrepareFloat8ModuleInput,
 )
-from torchao.float8.float8_utils import e4m3_dtype, tensor_to_scale
+from torchao.float8.float8_utils import tensor_to_scale
 from torch.distributed._tensor import distribute_tensor, DTensor, Replicate, Shard
 from torch.distributed.device_mesh import DeviceMesh, init_device_mesh
 from torch.distributed.tensor.parallel import parallelize_module
@@ -197,7 +197,7 @@ def _test_dtensor_fp8_autograd(mesh: DeviceMesh, size=16):
     )
 
     out = torch.nn.functional.linear(dist_x_fp8, dist_weight_fp8)
-    out = NoopFwToFloat8E5M2BwDynamic.apply(out, LinearMMConfig())
+    out = NoopFwToFloat8BwDynamic.apply(out, LinearMMConfig(), fp8_dtype)
     assert isinstance(out, DTensor), f"Expected DTensor, got {type(out)}"
     loss = torch.sum(torch.abs(out - dist_target))
     loss.backward()

torchao/float8/config.py

@@ -62,6 +62,7 @@ class CastConfig:
     scaling_type: ScalingType = ScalingType.DYNAMIC
     scaling_granularity: ScalingGranularity = ScalingGranularity.TENSORWISE
     static_scale: Optional[torch.Tensor] = None
+    dtype: torch.dtype = torch.uint8  # dummy dtype to satisfy typing
 
     def short_str(self):
         return f"{self.scaling_type.short_str()}_{self.scaling_granularity.short_str()}"
@@ -75,6 +76,10 @@ def __post_init__(self):
             assert (
                 self.scaling_type is ScalingType.DYNAMIC
             ), "only dynamic scaling type is supported for axiswise scaling granularity"
+        if self.scaling_type is not ScalingType.DISABLED:
+            assert (
+                self.dtype.is_floating_point and self.dtype.itemsize == 1
+            ), "must specify a 8-bit floating-point dtype"
 
 
 @dataclass(frozen=True)
@@ -124,6 +129,12 @@ def __post_init__(self):
                 self.e5m2_dtype = torch.float8_e5m2fnuz
 
 
+# User defined type for using the individual F8 type based on config
+type_config = Float8TypeConfig()
+e4m3_dtype = type_config.e4m3_dtype
+e5m2_dtype = type_config.e5m2_dtype
+
+
 @dataclass(frozen=True)
 class Float8GemmConfig:
     """
@@ -158,13 +169,13 @@ class Float8LinearConfig:
     # 3. the same behavior holds for `cast_config_weight` and `cast_config_grad_output`.
     #
     # `input`
-    cast_config_input: CastConfig = CastConfig()
+    cast_config_input: CastConfig = CastConfig(dtype=e4m3_dtype)
     cast_config_input_for_grad_weight: Optional[CastConfig] = None
     # `weight`
-    cast_config_weight: CastConfig = CastConfig()
+    cast_config_weight: CastConfig = CastConfig(dtype=e4m3_dtype)
     cast_config_weight_for_grad_input: Optional[CastConfig] = None
     # `grad_output`
-    cast_config_grad_output: CastConfig = CastConfig()
+    cast_config_grad_output: CastConfig = CastConfig(dtype=e5m2_dtype)
     cast_config_grad_output_for_grad_weight: Optional[CastConfig] = None
 
     #
@@ -279,6 +290,15 @@ def __post_init__(self):
                 is_disabled_1 == is_disabled_2
             ), f"incompatible operand precision for {gemm_name}"
 
+        for cc1, cc2, operand_name in [
+            (cc_i, cc_i_gw, "input"),
+            (cc_w, cc_w_gi, "weight"),
+            (cc_go, cc_go_gw, "grad_output"),
+        ]:
+            assert (
+                cc1.dtype == cc2.dtype
+            ), f"{operand_name} must be cast to the same dtype in both matmuls it's used in"
+
         if self.use_fp8_all_gather_only:
             assert self.enable_fsdp_float8_all_gather, "use_fp8_all_gather_only requires enable_fsdp_float8_all_gather to be True"
 
@@ -315,9 +335,15 @@ def recipe_name_to_linear_config(
 
     elif recipe_name is Float8LinearRecipeName.ALL_AXISWISE:
         # dynamic axiswise scaling with the CUTLASS rowwise kernel
-        cc_i = CastConfig(scaling_granularity=ScalingGranularity.AXISWISE)
-        cc_w = CastConfig(scaling_granularity=ScalingGranularity.AXISWISE)
-        cc_go = CastConfig(scaling_granularity=ScalingGranularity.AXISWISE)
+        cc_i = CastConfig(
+            scaling_granularity=ScalingGranularity.AXISWISE, dtype=e4m3_dtype
+        )
+        cc_w = CastConfig(
+            scaling_granularity=ScalingGranularity.AXISWISE, dtype=e4m3_dtype
+        )
+        cc_go = CastConfig(
+            scaling_granularity=ScalingGranularity.AXISWISE, dtype=e5m2_dtype
+        )
 
         return Float8LinearConfig(
             cast_config_input=cc_i,
@@ -339,12 +365,20 @@ def recipe_name_to_linear_config(
         #     which is more amenable to fast kernels
 
         # output_hp = input_fp8_axiswise_dim0 @ weight_t_axiswise_dim1
-        cc_i = CastConfig(scaling_granularity=ScalingGranularity.AXISWISE)
-        cc_w = CastConfig(scaling_granularity=ScalingGranularity.AXISWISE)
+        cc_i = CastConfig(
+            scaling_granularity=ScalingGranularity.AXISWISE, dtype=e4m3_dtype
+        )
+        cc_w = CastConfig(
+            scaling_granularity=ScalingGranularity.AXISWISE, dtype=e4m3_dtype
+        )
 
         # grad_input_hp = grad_output_fp8_axiswise_dim0 @ weight_fp8_tensorwise
-        cc_go = CastConfig(scaling_granularity=ScalingGranularity.AXISWISE)
-        cc_w_gi = CastConfig(scaling_granularity=ScalingGranularity.TENSORWISE)
+        cc_go = CastConfig(
+            scaling_granularity=ScalingGranularity.AXISWISE, dtype=e4m3_dtype
+        )
+        cc_w_gi = CastConfig(
+            scaling_granularity=ScalingGranularity.TENSORWISE, dtype=e4m3_dtype
+        )
 
         # grad_weight_hp = input_t_hp @ grad_output_hp
         cc_i_gw = CastConfig(scaling_type=ScalingType.DISABLED)