[Torch, QNN] Support dynamic quantization flow to enable importing quantized transformer models

python/tvm/relay/frontend/pytorch.py

@@ -2741,7 +2741,7 @@ def _run_jit_passes(graph):
     # pylint: disable=c-extension-no-member
     import torch
 
-    if is_version_greater_than("1.5.0"):
+    if is_version_greater_than("1.5.1"):
         # This is required for torchvision detection models from 1.6 above
         # It is the same as _jit_pass_inline, except that it has some special
         # case behaviors for some ops such as aten::__interpolate()
@@ -3383,7 +3383,8 @@ def from_pytorch(script_module, input_infos, custom_convert_map=None, default_dt
     ret_name = _get_input_names(graph.return_node())
 
     # For quantized models
-    if "aten::quantize_per_tensor" in op_names:
+    quantized_ops = set(["aten::quantize_per_tensor", "quantized::linear_dynamic"])
+    if len(quantized_ops.intersection(set(op_names))) > 0:
         weight_quant_params = qnn_torch.get_weight_quant_params(script_module)
         qnn_torch.add_input_quant_params_to_op_inputs(graph)
         qnn_torch.add_quant_params_to_outputs(outputs, packed_param_map, weight_quant_params)

python/tvm/relay/frontend/qnn_torch.py

@@ -173,7 +173,7 @@ def _get_quant_param_for_input(input_value):
     # 6th and 7th arg are output scale and zp respectively.
 
     # PyTorch 1.6 changed qconv API
-    if is_version_greater_than("1.5.0"):
+    if is_version_greater_than("1.5.1"):
         qconv_indices = (2, 3)
     else:
         qconv_indices = (6, 7)
@@ -575,13 +575,7 @@ def _impl(inputs, _):
         )
 
         return _do_bias_and_requantize(
-            conv_out,
-            bias,
-            input_scale,
-            weight_scale,
-            output_scale,
-            output_zero_point,
-            with_relu,
+            conv_out, bias, input_scale, weight_scale, output_scale, output_zero_point, with_relu
         )
 
     return _impl
@@ -826,6 +820,76 @@ def _impl(inputs, _):
     return _impl
 
 
+def _linear_dynamic():
+    def _calculate_qparam(inp):
+        # reference ATen/native/quantized/cpu/qlinear_dynamic.cpp
+        # ChooseQuantizationParams function
+        mn = _op.min(inp)
+        mx = _op.max(inp)
+
+        # Ensure that the interval contains 0
+        mn = _op.minimum(mn, _op.const(0.0, dtype="float32"))
+        mx = _op.maximum(mx, _op.const(0.0, dtype="float32"))
+
+        qmax = 255
+
+        # reduce_range became True in v1.6
+        if is_version_greater_than("1.5.1"):
+            qmax = 127
+
+        scale = (mx - mn) / _expr.const(qmax, dtype="float32")
+
+        zero_point_from_min = -(mn / scale)
+        zero_point = _op.cast(_op.round(_op.clip(zero_point_from_min, 0.0, qmax)), "int32")
+
+        return scale, zero_point
+
+    def _impl(inputs, _):
+        weight = inputs[1][0]
+        weight_scale = inputs[1][1]
+        weight_zero_point = inputs[1][2]
+
+        inp = inputs[0]
+
+        input_scale, input_zero_point = _calculate_qparam(inp)
+        qinp = relay.qnn.op.quantize(inp, input_scale, input_zero_point, out_dtype="uint8")
+
+        data_shape = infer_shape(inp)
+
+        if len(data_shape) > 2:
+            qinp = _op.reverse_reshape(qinp, [-1, 0])
+
+        weight_shape = infer_shape(weight)
+        units = weight_shape[0]
+        dense = relay.qnn.op.dense(
+            qinp,
+            weight,
+            input_zero_point,
+            weight_zero_point,
+            input_scale,
+            weight_scale,
+            units=units,
+        )
+        bias_var = inputs[1][3]
+
+        dequant_scale = input_scale * weight_scale
+        dense_out = relay.qnn.op.dequantize(
+            dense, dequant_scale, input_zero_point=relay.const(0, "int32"), axis=1
+        )
+
+        if len(data_shape) > 2:
+            new_shape = list(data_shape[:-1])
+            new_shape.append(units)
+            dense_out = _op.reshape(dense_out, new_shape)
+
+        if bias_var is not None:
+            return dense_out + bias_var
+
+        return dense_out
+
+    return _impl
+
+
 convert_map = {
     "aten::quantize_per_tensor": _quantize_per_tensor(),
     "quantized::conv2d_relu": _quantized_conv2d(with_relu=True),
@@ -841,4 +905,5 @@ def _impl(inputs, _):
     "quantized::add_scalar": _add_scalar(),
     "quantized::mul_scalar": _mul_scalar(),
     "quantized::relu6": _relu6(),
+    "quantized::linear_dynamic": _linear_dynamic(),
 }

src/relay/qnn/op/dense.cc

@@ -99,6 +99,18 @@ Expr DenseFourthTerm(int input_zero_point_int, int kernel_zero_point_int, int re
   return MakeConstantScalar(DataType::Int(32), scalar_term);
 }
 
+Expr DenseFourthTerm(const Expr& input_zero_point, const Expr& kernel_zero_point,
+                     int reduction_dim_size) {
+  auto reduction_dim = MakeConstantScalar(DataType::Int(32), reduction_dim_size);
+  return Multiply(Multiply(input_zero_point, kernel_zero_point), reduction_dim);
+}
+
+Expr DenseCombineTerms(const Expr& term1, const Expr& term2, const Expr& term3, const Expr& term4) {
+  auto data_term = Subtract(term1, term2);
+  // Putting constant terms together, so that constant folding can fold it.
+  auto const_term = Subtract(term4, term3);
+  return Add(data_term, const_term);
+}
 /*
  * \brief Forward rewrite the qnn dense op.
  * \param attrs The QNN dense attrs.
@@ -144,14 +156,24 @@ Expr QnnDenseCanonicalize(const Attrs& attrs, const Array<Expr>& new_args,
 
   const auto* qnn_dense_attrs = attrs.as<DenseAttrs>();
 
+  auto term1 = DenseFirstTerm(quantized_data, quantized_kernel, qnn_dense_attrs);
+  auto term2 = DenseSecondTerm(quantized_data, kernel_zero_point);
+  auto term3 = DenseThirdTerm(quantized_kernel, input_zero_point);
+
   // Extract the integer zero points.
-  auto input_zero_point_int = GetScalarFromConstant<int>(input_zero_point);
   auto kernel_zero_point_int = GetScalarFromConstant<int>(kernel_zero_point);
 
+  if (!IsConstScalar(input_zero_point)) {
+    if (kernel_zero_point_int == 0) {
+      return Subtract(term1, term3);
+    }
+    auto term4 = DenseFourthTerm(input_zero_point, kernel_zero_point, reduction_dim_size);
+    return DenseCombineTerms(term1, term2, term3, term4);
+  }
+
+  auto input_zero_point_int = GetScalarFromConstant<int>(input_zero_point);
+
   // Get all the terms as described in the comments.
-  auto term1 = DenseFirstTerm(quantized_data, quantized_kernel, qnn_dense_attrs);
-  auto term2 = DenseSecondTerm(quantized_data, kernel_zero_point);
-  auto term3 = DenseThirdTerm(quantized_kernel, input_zero_point);
   auto term4 = DenseFourthTerm(input_zero_point_int, kernel_zero_point_int, reduction_dim_size);
 
   // Combine those 4 terms depending on the zero points to get the best lowering.
@@ -165,10 +187,7 @@ Expr QnnDenseCanonicalize(const Attrs& attrs, const Array<Expr>& new_args,
     // term 2 and term 4 become zero.
     return Subtract(term1, term3);
   } else {
-    auto data_term = Subtract(term1, term2);
-    // Putting constant terms together, so that constant folding can fold it.
-    auto const_term = Subtract(term4, term3);
-    return Add(data_term, const_term);
+    return DenseCombineTerms(term1, term2, term3, term4);
   }
 }
 

src/relay/qnn/op/quantize.cc

@@ -83,20 +83,27 @@ Expr MakeQuantize(Expr data, Expr output_scale, Expr output_zero_point, int axis
 }
 
 Expr QuantizeLower(const Expr& input_tensor, const Expr& output_scale,
-                   const Expr& output_zero_point, const Array<IndexExpr>& input_shape,
+                   const Expr& output_zero_point, const Array<tvm::relay::Type>& types,
                    const QuantizeAttrs* attrs) {
+  ICHECK_EQ(types.size(), 4);
+  auto in_type = types[0];
+  auto in_tensor_type = in_type.as<TensorTypeNode>();
+  ICHECK(in_tensor_type != nullptr) << "Type information missing."
+                                    << " Please run infer_type pass.";
+  Array<IndexExpr> input_shape = in_tensor_type->shape;
+
   const auto out_dtype = attrs->out_dtype;
   const auto axis = attrs->axis;
 
   size_t n_dim = input_shape.size();
 
   auto expanded_output_scale = output_scale;
-  if (!IsConstScalar(output_scale)) {
+  if (!IsConstScalar(output_scale) && !IsScalarType(types[1])) {
     expanded_output_scale = ExpandBiasToMatchAxis(output_scale, n_dim, {axis});
   }
 
   auto expanded_output_zero_point = output_zero_point;
-  if (!IsConstScalar(output_zero_point)) {
+  if (!IsConstScalar(output_zero_point) && !IsScalarType(types[2])) {
     expanded_output_zero_point = ExpandBiasToMatchAxis(output_zero_point, n_dim, {axis});
   }
 
@@ -120,15 +127,7 @@ Expr QuantizeQnnCanonicalize(const Attrs& attrs, const Array<Expr>& new_args,
   const auto* quantize_attrs = attrs.as<QuantizeAttrs>();
   ICHECK(quantize_attrs != nullptr);
 
-  // Find input shape.
-  ICHECK_EQ(types.size(), 4);
-  auto in_type = types[0];
-  auto in_tensor_type = in_type.as<TensorTypeNode>();
-  ICHECK(in_tensor_type != nullptr) << "Type information missing."
-                                    << " Please run infer_type pass.";
-  Array<IndexExpr> input_shape = in_tensor_type->shape;
-
-  return QuantizeLower(data, output_scale, output_zero_point, input_shape, quantize_attrs);
+  return QuantizeLower(data, output_scale, output_zero_point, types, quantize_attrs);
 }
 
 RELAY_REGISTER_OP("qnn.quantize")

src/relay/qnn/utils.h

@@ -179,6 +179,18 @@ static inline bool IsScalarType(const Type& expr_type, const DataType& dtype) {
   return true;
 }
 
+/*
+ * \brief Checks whether an expr type is scalar.
+ * \param expr_type The type of expr to be checked.
+ * \return True if the type is a scalar
+ */
+static inline bool IsScalarType(const Type& expr_type) {
+  const auto* tensor_type = expr_type.as<TensorTypeNode>();
+  CHECK(tensor_type) << "Only tensor type can be checked for scalar values. But got"
+                     << AsText(expr_type, false);
+  return tensor_type->shape.size() == 0;
+}
+
 /*
  * \brief Checks and assigns types to scale and zero points.
  * \param expr_type The type of expr to be checked.

tests/python/frontend/pytorch/qnn_test.py

@@ -27,7 +27,9 @@
 from torch.quantization import fuse_modules, QuantWrapper
 
 import tvm
+import tvm.testing
 from tvm import relay
+from tvm.relay.frontend.pytorch_utils import is_version_greater_than
 from tvm.contrib.download import download_testdata
 
 
@@ -197,9 +199,7 @@ def fuse_model(self):
 
 # test on quantized::mul_scalar with negative scale
 class MulScalarNegative(nn.Module):
-    def __init__(
-        self,
-    ):
+    def __init__(self):
         super().__init__()
         self.float_op = nn.quantized.FloatFunctional()
         self.quant = QuantStub()
@@ -337,12 +337,7 @@ def get_transform():
 
         normalize = transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225])
         return transforms.Compose(
-            [
-                transforms.Resize(256),
-                transforms.CenterCrop(224),
-                transforms.ToTensor(),
-                normalize,
-            ]
+            [transforms.Resize(256), transforms.CenterCrop(224), transforms.ToTensor(), normalize]
         )
 
     def get_real_image(im_height, im_width):
@@ -508,3 +503,45 @@ def test_serialized_modules():
     num_identical = np.sum(np.abs(tvm_result - pt_result) < 1e-2)
     match_ratio = num_identical / float(np.prod(tvm_result.shape))
     assert match_ratio > 0.90
+
+
+def test_quantize_dynamic():
+    # A wrapper is required for quantize_dynamic to work correctly
+    class LinearWrapper(nn.Module):
+        def __init__(self, in_dim, hidden_dim):
+            super().__init__()
+            self.linear = nn.Linear(in_dim, hidden_dim)
+
+        def forward(self, inp):
+            return self.linear(inp)
+
+    torch.manual_seed(0)
+    mod = LinearWrapper(16, 32)
+
+    for qconfig in [
+        torch.quantization.per_channel_dynamic_qconfig,
+        torch.quantization.default_dynamic_qconfig,
+    ]:
+        for ishape in [(16, 16), (10, 16, 16)]:
+            qspec = {nn.Linear: qconfig}
+            qmod = torch.quantization.quantize_dynamic(mod, qconfig_spec=qspec, dtype=torch.qint8)
+
+            inp = torch.randn(*ishape)
+            script_module = torch.jit.trace(qmod, inp).eval()
+
+            with torch.no_grad():
+                pt_result = script_module(inp.clone()).numpy()
+
+            input_name = "input"
+            runtime = get_tvm_runtime(script_module, "input", inp.shape)
+            runtime.set_input(input_name, inp.numpy().copy())
+            runtime.run()
+            tvm_result = runtime.get_output(0).asnumpy()
+
+            # Only compare with the PyTorch result for version v1.6 or newer
+            # Have seen a strange accuracy problem from PyTorch 1.4 and 1.5
+            # Even with the manual random seed set, the same PyTorch
+            # version can outputs slightly different results depending on an environment.
+            # Outputs from v1.6 seem reliable. TVM's outputs are always the same
+            if is_version_greater_than("1.5.1"):
+                tvm.testing.assert_allclose(tvm_result, pt_result, rtol=1e-4, atol=1e-4)