Align Int4Tensor implementation details with the design of Float8Tensor

Summary:
Int4Tensor is the non-preshuffled version of int4 quantized Tensor, data is [N, K/2], scale/zero_point has shape: [K/group_size, N]

Multiple fixes for Int4Tensor to align with the design of Float8Tensor (only calling fbgemm ops)
* defined `tensor_data_names` and `tensor_attribute_names` so we can remove some of the implementations from TorchAOBaseTensor
* Migrated op implementation and tests from #2387

Note: This is just refactoring Int4Tensor, no BC related changes in this PR

Int4Tensor path is exposed in version 2 of `Int4WeightOnlyConfig` (default version is still 1, which is using the old AQT path

Test Plan:
python test/quantization/quantize_/workflows/int4/test_int4_tensor.py

Reviewers:

Subscribers:

Tasks:

Tags:

stack-info: PR: #2687, branch: jerryzh168/stack/16

Author: jerryzh168

test/quantization/quantize_/workflows/int4/test_int4_tensor.py

@@ -8,25 +8,21 @@
 
 import torch
 from torch.testing._internal.common_utils import (
-    TestCase,
+    instantiate_parametrized_tests,
+    parametrize,
     run_tests,
 )
 
-from torchao.quantization import (
-    Int4WeightOnlyConfig,
-    quantize_,
-)
+from torchao.quantization import Int4WeightOnlyConfig, quantize_
 from torchao.quantization.utils import compute_error
-from torchao.utils import (
-    TORCH_VERSION_AT_LEAST_2_8,
-    is_sm_at_least_90,
-)
+from torchao.testing.utils import TorchAOIntegrationTestCase
+from torchao.utils import TORCH_VERSION_AT_LEAST_2_8, is_sm_at_least_90
 
 
 @unittest.skipIf(not TORCH_VERSION_AT_LEAST_2_8, "Need pytorch 2.8+")
 @unittest.skipIf(not torch.cuda.is_available(), "Need CUDA available")
 @unittest.skipIf(not is_sm_at_least_90(), "Nedd sm90+")
-class TestInt4Tensor(TestCase):
+class TestInt4Tensor(TorchAOIntegrationTestCase):
     def setUp(self):
         self.config = Int4WeightOnlyConfig(
             group_size=128,
@@ -61,50 +57,46 @@ def test_slice(self):
         quantize_(dummy, self.config)
         weight1 = dummy.weight.narrow(0, 0, 64)
         weight2 = dummy.weight.narrow(1, 0, 128)
-        self.assertEqual(weight1._data, dummy.weight._data.narrow(0, 0, 64))
+        self.assertEqual(weight1.qdata, dummy.weight.qdata.narrow(0, 0, 64))
         self.assertEqual(weight1.scale, dummy.weight.scale.narrow(1, 0, 64))
-        self.assertEqual(weight2._data, dummy.weight._data.narrow(1, 0, 64))
+        self.assertEqual(weight1.zero_point, dummy.weight.zero_point.narrow(1, 0, 64))
+        self.assertEqual(weight2.qdata, dummy.weight.qdata.narrow(1, 0, 64))
         self.assertEqual(weight2.scale, dummy.weight.scale.narrow(0, 0, 1))
+        self.assertEqual(weight2.zero_point, dummy.weight.zero_point.narrow(0, 0, 1))
 
         # check for sliced weight, before and after float8 quantization
         # does not differ too much
         input = torch.randn(2, 256, dtype=dtype, device=device)
         res_ref = dummy1(input)
-        dummy.weight = torch.nn.Parameter(weight1, requires_grad=False)
+        dummy.weight = torch.nn.Parameter(weight1.contiguous(), requires_grad=False)
         res = dummy(input)
         assert compute_error(res, res_ref) > 20
 
         input = torch.randn(2, 128, dtype=dtype, device=device)
         res_ref = dummy2(input)
-        dummy.weight = torch.nn.Parameter(weight2, requires_grad=False)
+        dummy.weight = torch.nn.Parameter(weight2.contiguous(), requires_grad=False)
         res = dummy(input)
         assert compute_error(res, res_ref) > 15
 
-    def test_slice_and_copy_(self):
+    def test_slice_preserves_aliasing(self):
+        config = self.config
         l = torch.nn.Linear(1024, 1024).to("cuda").to(torch.bfloat16)
         l.weight = torch.nn.Parameter(
             torch.zeros(1024, 1024, dtype=torch.bfloat16, device="cuda")
         )
-        quantize_(l, self.config)
+        quantize_(l, config)
         param = l.weight
         param_data = param.data
         param_data = param_data.narrow(0, 0, 512)
-        assert param.data._data.data_ptr() == param_data._data.data_ptr()
+        # Making sure the aliasing is preserved in sliced quantized Tensor
+        assert param.data.qdata.data_ptr() == param_data.qdata.data_ptr()
         assert param.data.scale.data_ptr() == param_data.scale.data_ptr()
         assert param.data.zero_point.data_ptr() == param_data.zero_point.data_ptr()
-        orig_value = param.data._data[0][0].item()
-
-        # dummy_l has random input (shouldn't be 0)
-        dummy_l = torch.nn.Linear(1024, 1024).to("cuda").to(torch.bfloat16)
-        quantize_(dummy_l, self.config)
-        quantized = dummy_l.weight
-        quantized = quantized.narrow(0, 0, 512)
 
-        param_data.copy_(quantized)
-
-        # making sure param.data is updated
-        assert param.data._data[0][0] != orig_value
+    def test_slice_and_copy_similar_to_vllm(self):
+        self._test_slice_and_copy_similar_to_vllm(self.config)
 
+    @unittest.skipIf(not is_sm_at_least_90(), "Nedd sm90+")
     def test_bmm(self):
         class M(torch.nn.Module):
             def __init__(self, weight):
@@ -126,20 +118,103 @@ def forward(self, x):
         quantized = m(input)
         self.assertTrue(compute_error(original, quantized) > 18)
 
-    def test_to_device(self):
+    @parametrize(
+        "sizes",
+        [
+            ((128,), 256, 128),
+            ((32, 128), 64, 256),
+            ((2, 32, 128), 64, 256),
+        ],
+    )
+    def test_to_device(self, sizes):
+        config = self.config
+        M, N, K = sizes
+        dtype = torch.bfloat16
         for device in self.GPU_DEVICES:
-            linear = torch.nn.Linear(128, 256, dtype=torch.bfloat16)
-            quantize_(linear, self.config)
+            input_tensor = torch.randn(*M, K, dtype=dtype, device=device)
+            linear = torch.nn.Linear(K, N, dtype=dtype)
+            quantize_(linear, config)
             linear.to(device)
+            linear(input_tensor)
 
-            linear = torch.nn.Linear(128, 256, dtype=torch.bfloat16)
-            quantize_(linear, self.config)
+            linear = torch.nn.Linear(K, N, dtype=dtype)
+            quantize_(linear, config)
             linear.to(device=device)
+            linear(input_tensor)
 
-            linear = torch.nn.Linear(128, 256, dtype=torch.bfloat16)
-            quantize_(linear, self.config)
+            linear = torch.nn.Linear(K, N, dtype=dtype)
+            quantize_(linear, config)
             linear.to(device)
+            linear(input_tensor)
+
+    @parametrize(
+        "sizes",
+        [
+            ((128,), 256, 128),
+            ((32, 128), 64, 256),
+            ((2, 32, 128), 64, 256),
+        ],
+    )
+    def test_cat(self, sizes):
+        config = self.config
+        dtype = torch.bfloat16
+        device = "cuda"
+        M, N, K = sizes
+        linear1 = torch.nn.Linear(K, N, dtype=dtype, device=device)
+        linear2 = torch.nn.Linear(K, N, dtype=dtype, device=device)
+        input_cat1 = torch.randn(*M, K, dtype=dtype, device=device)
+
+        cat_weight1 = torch.cat([linear1.weight, linear2.weight], dim=0)
+        dummy_linear1 = torch.nn.Linear(K, N, bias=False, dtype=dtype, device=device)
+
+        dummy_linear1.weight = torch.nn.Parameter(cat_weight1)
+        quantize_(dummy_linear1, config)
+
+        quantize_(linear1, config)
+        quantize_(linear2, config)
+
+        cat_qweight1 = torch.cat([linear1.weight, linear2.weight], dim=0)
+        self.assertTrue(cat_qweight1.shape, (2 * N, K))
+        self.assertEqual(
+            dummy_linear1.weight.qdata,
+            cat_qweight1.qdata,
+        )
+        self.assertEqual(
+            dummy_linear1.weight.scale,
+            cat_qweight1.scale,
+        )
+        self.assertEqual(
+            dummy_linear1.weight.zero_point,
+            cat_qweight1.zero_point,
+        )
+
+        # making sure cat_qweight1 can be used for inference
+        dummy_linear1.weight = torch.nn.Parameter(cat_qweight1, requires_grad=False)
+        dummy_linear1(input_cat1)
+
+        # align the scale and zero_point before concatenation
+        linear2.weight.scale = linear1.weight.scale
+        linear2.weight.zero_point = linear1.weight.zero_point
+        cat_qweight2 = torch.cat([linear1.weight, linear2.weight], dim=1)
+        self.assertTrue(cat_qweight2.shape, (N, 2 * K))
+        ref_data = torch.cat(
+            [
+                linear1.weight.qdata,
+                linear2.weight.qdata,
+            ],
+            dim=1,
+        )
+        ref_scale = linear1.weight.scale
+        ref_zero_point = linear1.weight.zero_point
+        self.assertEqual(cat_qweight2.qdata, ref_data)
+        self.assertEqual(cat_qweight2.scale, ref_scale)
+        self.assertEqual(cat_qweight2.zero_point, ref_zero_point)
+
+    def test_moe_weight_reshape_ops(self):
+        self._test_moe_weight_reshape_ops(self.config)
+
 
+instantiate_parametrized_tests(TestInt4Tensor)
 
 if __name__ == "__main__":
     run_tests()

test/test_utils.py

@@ -76,7 +76,7 @@ def __init__(self, qdata, attr, device=None):
                 self.qdata = qdata
                 self.attr = attr
 
-        l = torch.nn.Linear(1, 1)
+        l = torch.nn.Linear(2, 3)
         l.weight = torch.nn.Parameter(MyTensor(l.weight, "attr"))
         lp_tensor = l.weight
         # test __tensor_flatten__ and __tensor_unflatten__
@@ -107,18 +107,24 @@ def __init__(self, qdata, attr, device=None):
         # explicitly testing aten.alias
         lp_tensor = torch.ops.aten.alias(lp_tensor)
         lp_tensor = lp_tensor.clone()
+        # making qdata not contiguous
+        lp_tensor.qdata = lp_tensor.qdata.transpose(0, 1).contiguous()
+        lp_tensor.qdata = lp_tensor.qdata.transpose(0, 1)
+        self.assertFalse(lp_tensor.qdata.is_contiguous())
         lp_tensor = lp_tensor.contiguous()
+        # making sure contiguous call works
+        self.assertTrue(lp_tensor.qdata.is_contiguous())
 
         # copy_
-        another_tensor = torch.nn.Linear(1, 1).weight
+        another_tensor = torch.nn.Linear(2, 3).weight
         # attribute has to be the same
         another_lp_tensor = MyTensor(another_tensor, "attr")
         # initially tensor values are not the same
-        self.assertNotEqual(lp_tensor.qdata[0], another_lp_tensor.qdata[0])
+        self.assertNotEqual(lp_tensor.qdata[0][0], another_lp_tensor.qdata[0][0])
         lp_tensor.copy_(another_lp_tensor)
         self.assertEqual(lp_tensor.attr, "attr")
         # after copy_, the tensor values should match
-        self.assertEqual(lp_tensor.qdata[0], another_lp_tensor.qdata[0])
+        self.assertEqual(lp_tensor.qdata[0][0], another_lp_tensor.qdata[0][0])
 
 
 if __name__ == "__main__":

torchao/quantization/quant_api.py

@@ -1160,6 +1160,7 @@ def _int4_weight_only_quantize_tensor(weight, config):
     block_size = tuple([1 for _ in range(weight.ndim - 1)] + [group_size])
 
     if config.VERSION == 2:
+        block_size = list(block_size)
         if packing_format == PackingFormat.PRESHUFFLED:
             new_weight = Int4PreshuffledTensor.from_float(
                 weight,
@@ -1168,7 +1169,7 @@ def _int4_weight_only_quantize_tensor(weight, config):
             )
             return new_weight
         elif packing_format == PackingFormat.PLAIN:
-            new_weight = Int4Tensor.from_float(
+            new_weight = Int4Tensor.from_hp(
                 weight,
                 block_size,
             )
@@ -2212,7 +2213,7 @@ def _(module: torch.nn.Module, config: FbgemmConfig) -> torch.nn.Module:
                 activation_dtype=torch.bfloat16,
             )
         else:
-            weight = Int4Tensor.from_float(
+            weight = Int4Tensor.from_hp(
                 module.weight,
                 config.block_size,
             )