[quant][pt2e] Add reference representation for dynamic quantized line…

…ar (pytorch#108073)

Summary: att

Test Plan:
python test/test_quantization.py TestQuantizePT2E.test_representation_dynamic_linear
buck2 test 'fbcode//mode/opt' fbcode//caffe2/test:quantization_pt2e -- 'test_representation_dynamic_linear'

Reviewed By: kimishpatel

Differential Revision: D48703076

Pull Request resolved: pytorch#108073
Approved by: https://github.com/andrewor14

test/quantization/pt2e/test_quantize_pt2e.py

@@ -513,6 +513,7 @@ def _test_representation(
         quantizer: Quantizer,
         ref_node_occurrence: Dict[ns, int],
         non_ref_node_occurrence: Dict[ns, int],
+        fixed_output_tol: float = None,
         output_scale_idx: int = 3,
     ) -> torch.nn.Module:
         """ TODO: need to implement output checking based on output_scale once
@@ -542,17 +543,22 @@ def _test_representation(
         self.checkGraphModuleNodes(model_copy, expected_node_occurrence=non_ref_node_occurrence)
         pt2e_quant_output_copy = model_copy(*example_inputs)
 
-        idx = 0
-        for n in model_copy.graph.nodes:
-            if n.target == torch.ops.quantized_decomposed.quantize_per_tensor.default:
-                idx += 1
-                if idx == output_scale_idx:
-                    output_scale = n.args[1]
-        assert output_scale is not None
+
+        output_tol = None
+        if fixed_output_tol is not None:
+            output_tol = fixed_output_tol
+        else:
+            idx = 0
+            for n in model_copy.graph.nodes:
+                if n.target == torch.ops.quantized_decomposed.quantize_per_tensor.default:
+                    idx += 1
+                    if idx == output_scale_idx:
+                        output_tol = n.args[1]
+            assert output_tol is not None
 
         # make sure the result is off by one at most in the quantized integer representation
         self.assertTrue(
-            torch.max(torch.abs(pt2e_quant_output_copy - pt2e_quant_output)) <= (2 * output_scale + 1e-5)
+            torch.max(torch.abs(pt2e_quant_output_copy - pt2e_quant_output)) <= (2 * output_tol + 1e-5)
         )
 
 @skipIfNoQNNPACK
@@ -2201,6 +2207,29 @@ def forward(self, x):
             non_ref_node_occurrence={}
         )
 
+    def test_representation_dynamic_linear(self):
+        class M(torch.nn.Module):
+            def __init__(self):
+                super().__init__()
+                self.linear = torch.nn.Linear(5, 5)
+
+            def forward(self, x):
+                return self.linear(x)
+
+        quantizer = XNNPACKQuantizer()
+        operator_config = get_symmetric_quantization_config(is_per_channel=False, is_dynamic=True)
+        quantizer.set_global(operator_config)
+        example_inputs = (torch.randn(2, 5),)
+
+        self._test_representation(
+            M().eval(),
+            example_inputs,
+            quantizer,
+            ref_node_occurrence={},
+            non_ref_node_occurrence={},
+            fixed_output_tol=1e-4,
+        )
+
     def test_representation_conv2d(self):
         class M(torch.nn.Module):
             def __init__(self):

torch/ao/quantization/pt2e/representation/rewrite.py

@@ -85,6 +85,72 @@ def _reference_quantized_linear(
     return out_i8
 
 
+_DYNAMIC_QUANTIZED_LINEAR_EXAMPLE_INPUTS = (
+    torch.randn((2, 5), dtype=torch.float),
+    -128,
+    127,
+    torch.finfo(torch.float32).eps,
+    torch.randint(-128, 127, (5, 5), dtype=torch.int8),
+    torch.randn(1, dtype=torch.float),
+    torch.zeros(1, dtype=torch.int),
+    torch.tensor([-127], dtype=torch.int),
+    torch.tensor([127], dtype=torch.int),
+    torch.randn(1, dtype=torch.float),
+)
+
+
+def _qdq_dynamic_quantized_linear(
+    x_fp32, x_quant_min, x_quant_max, x_eps,
+    weight_i8, weight_scale, weight_zero_point, weight_quant_min, weight_quant_max,
+    bias_fp32,
+):
+    x_scale, x_zero_point = torch.ops.quantized_decomposed.choose_qparams(x_fp32, x_quant_min, x_quant_max, x_eps, torch.int8)
+    x_i8 = torch.ops.quantized_decomposed.quantize_per_tensor(
+        x_fp32, x_scale, x_zero_point, x_quant_min, x_quant_max, torch.int8)
+    x_fp32 = torch.ops.quantized_decomposed.dequantize_per_tensor(
+        x_i8, x_scale, x_zero_point, x_quant_min, x_quant_max, torch.int8)
+    weight_fp32 = torch.ops.quantized_decomposed.dequantize_per_tensor(
+        weight_i8, weight_scale, weight_zero_point, weight_quant_min, weight_quant_max, torch.int8)
+    out_fp32 = torch.ops.aten.linear.default(x_fp32, weight_fp32, bias_fp32)
+    return out_fp32
+
+def _reference_dynamic_quantized_linear(
+    x_fp32, x_quant_min, x_quant_max, x_eps,
+    weight_i8, weight_scale, weight_zero_point, weight_quant_min, weight_quant_max,
+    bias_fp32,
+):
+    x_scale, x_zero_point = torch.ops.quantized_decomposed.choose_qparams(x_fp32, x_quant_min, x_quant_max, x_eps, torch.int8)
+    # decomposed representation for quantize_per_tensor
+    # TODO: use out_dtype(mul, ...) here when the op is ready
+    x_fp32 = x_fp32 / x_scale  # fp32
+    # round modes might be different here
+    # pytorch is rounding to even, which is also common for most of the backends
+    x_fp32 = torch.round(x_fp32)  # fp32
+    x_i32 = x_fp32.to(dtype=torch.int32)  # int32
+    x_i32 = x_i32 + x_zero_point  # int32
+    # clamp works for fp32, int32 and int8 dtypes
+    x_i32 = torch.clamp(x_i32, x_quant_min, x_quant_max)  # int32
+    x_i8 = x_i32.to(dtype=torch.int8)
+
+    weight_i8 = torch.ops.aten.clamp(weight_i8, weight_quant_min, weight_quant_max)
+
+    x_i16 = x_i8.to(torch.int16)
+    weight_i16 = weight_i8.to(torch.int16)
+    # always set bias to None so that the same representation can work for the case
+    # no matter if bias_scale == x_scale * weight_scale or not
+    acc_i32 = out_dtype(
+        torch.ops.aten.linear.default,
+        torch.int32,
+        x_i16 - x_zero_point,
+        weight_i16 - weight_zero_point,
+        None)
+    bias_scale = x_scale * weight_scale
+    bias_i32 = out_dtype(torch.ops.aten.div.Tensor, torch.int32, bias_fp32, bias_scale)
+    acc_i32 = acc_i32 + bias_i32
+    out_fp32 = acc_i32 * (x_scale * weight_scale)
+    return out_fp32
+
+
 _QUANTIZED_CONV2d_EXAMPLE_INPUTS = (
     torch.randint(-128, 127, (1, 3, 3, 3), dtype=torch.int8),
     torch.randn(1, dtype=torch.float),
@@ -465,6 +531,27 @@ class _RewriteInfo:
     replacement_post_trans: Optional[Callable[[GraphModule], GraphModule]] = None
 
 _REWRITE_INFO_LIST = [
+    _RewriteInfo(
+        _DYNAMIC_QUANTIZED_LINEAR_EXAMPLE_INPUTS,
+        _qdq_dynamic_quantized_linear,
+        _reference_dynamic_quantized_linear,
+        partial(
+            _replace_literals_with_existing_placeholders,
+            literal_to_ph_idx={
+                -128: 1,
+                127: 2,
+                torch.finfo(torch.float32).eps: 3
+            }
+        ),
+        partial(
+            _replace_literals_with_existing_placeholders,
+            literal_to_ph_idx={
+                -128: 1,
+                127: 2,
+                torch.finfo(torch.float32).eps: 3
+            }
+        ),
+    ),
     _RewriteInfo(
         _QUANTIZED_LINEAR_EXAMPLE_INPUTS,
         _qdq_quantized_linear,