Constant folding with Quantize (#1833)

* Constant folding with Quantize

* updated with review comments

Author: vdevaram

src/ngraph/pass/constant_folding.cpp

@@ -29,6 +29,7 @@
 #include "ngraph/op/multiply.hpp"
 #include "ngraph/op/negative.hpp"
 #include "ngraph/op/pad.hpp"
+#include "ngraph/op/quantize.hpp"
 #include "ngraph/op/reshape.hpp"
 #include "ngraph/op/subtract.hpp"
 #include "ngraph/pattern/matcher.hpp"
@@ -43,6 +44,7 @@
 #include "ngraph/runtime/reference/multiply.hpp"
 #include "ngraph/runtime/reference/negate.hpp"
 #include "ngraph/runtime/reference/pad.hpp"
+#include "ngraph/runtime/reference/quantize.hpp"
 #include "ngraph/runtime/reference/reshape.hpp"
 #include "ngraph/runtime/reference/subtract.hpp"
 
@@ -529,3 +531,81 @@ void ngraph::pass::ConstantFolding::construct_constant_dequantize()
     auto dequantize_matcher = make_shared<pattern::Matcher>(dequant, constant_dequantize_callback);
     this->add_matcher(dequantize_matcher);
 }
+
+template <class REAL, class QUANT>
+shared_ptr<op::Constant> make_constant_quantize(shared_ptr<op::Constant> constant,
+                                                shared_ptr<op::Quantize> quant,
+                                                shared_ptr<op::Constant> scale,
+                                                shared_ptr<op::Constant> offset)
+{
+    auto out_shape = constant->get_shape();
+    vector<QUANT> out_vec(shape_size(out_shape));
+
+    runtime::reference::quantize<REAL, QUANT>(constant->get_vector<REAL>().data(),
+                                              scale->get_vector<REAL>().data(),
+                                              offset->get_vector<QUANT>().data(),
+                                              out_vec.data(),
+                                              constant->get_shape(),
+                                              scale->get_shape(),
+                                              quant->get_axes());
+
+    return make_shared<op::Constant>(quant->get_element_type(), out_shape, out_vec);
+}
+
+void ngraph::pass::ConstantFolding::construct_constant_quantize()
+{
+    auto constant_label =
+        make_shared<pattern::op::Label>(element::f32, Shape{2}, pattern::has_class<op::Constant>());
+    auto q_scale = op::Constant::create(element::f32, Shape{}, {1});
+    auto q_offset = op::Constant::create(element::i8, Shape{}, {0});
+    auto mode = op::Quantize::RoundMode::HALF_AWAY_FROM_ZERO;
+    auto quant_op =
+        make_shared<op::Quantize>(constant_label, q_scale, q_offset, element::i8, AxisSet{}, mode);
+    auto quant = make_shared<pattern::op::Label>(quant_op, nullptr, NodeVector{quant_op});
+
+    auto constant_quantize_callback = [constant_label, quant](pattern::Matcher& m) {
+        NGRAPH_DEBUG << "In callback for constant_quantize_callback against node = "
+                     << m.get_match_root()->get_name();
+
+        auto pattern_map = m.get_pattern_map();
+
+        auto constant_match = dynamic_pointer_cast<op::Constant>(pattern_map[constant_label]);
+        auto quant_match = pattern_map[quant];
+        auto quantize_op = dynamic_pointer_cast<op::Quantize>(quant_match);
+        auto args = quant_match->get_arguments();
+        auto scale = static_pointer_cast<op::Constant>(args[1]);
+        auto offset = static_pointer_cast<op::Constant>(args[2]);
+
+        auto type = quant_match->get_element_type();
+
+        if (constant_match->get_element_type() != element::f32)
+        {
+            return false;
+        }
+
+        if (quantize_op->get_round_mode() != op::Quantize::RoundMode::HALF_AWAY_FROM_ZERO)
+        {
+            return false;
+        }
+
+        if (type == element::u8)
+        {
+            replace_node(
+                m.get_match_root(),
+                make_constant_quantize<float, uint8_t>(constant_match, quantize_op, scale, offset));
+            return true;
+        }
+        else if (type == element::i8)
+        {
+            replace_node(
+                m.get_match_root(),
+                make_constant_quantize<float, int8_t>(constant_match, quantize_op, scale, offset));
+            return true;
+        }
+
+        return false;
+    };
+
+    auto quantize_matcher = make_shared<pattern::Matcher>(quant, constant_quantize_callback);
+    this->add_matcher(quantize_matcher);
+}

src/ngraph/pass/constant_folding.hpp

@@ -35,7 +35,8 @@ class ngraph::pass::ConstantFolding : public ngraph::pass::GraphRewrite
         PAD,
         DEQUANTIZE,
         UNARY,
-        BINARY
+        BINARY,
+        QUANTIZE
     };
 
 public:
@@ -47,6 +48,7 @@ class ngraph::pass::ConstantFolding : public ngraph::pass::GraphRewrite
         construct_constant_pad();
         construct_constant_unary();
         construct_constant_binary();
+        construct_constant_quantize();
         construct_constant_dequantize();
     }
 
@@ -65,6 +67,7 @@ class ngraph::pass::ConstantFolding : public ngraph::pass::GraphRewrite
             case CFTransformations::UNARY: construct_constant_unary(); break;
             case CFTransformations::BINARY: construct_constant_binary(); break;
             case CFTransformations::DEQUANTIZE: construct_constant_dequantize(); break;
+            case CFTransformations::QUANTIZE: construct_constant_quantize(); break;
             }
         }
     }
@@ -75,5 +78,6 @@ class ngraph::pass::ConstantFolding : public ngraph::pass::GraphRewrite
     void construct_constant_pad();
     void construct_constant_unary();
     void construct_constant_binary();
+    void construct_constant_quantize();
     void construct_constant_dequantize();
 };

test/constant_folding.cpp

@@ -250,3 +250,38 @@ TEST(constant_folding, const_dequantize)
     vector<output_c_type> values_dequantize{0, 2, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12};
     ASSERT_EQ(values_dequantize, values_out);
 }
+
+TEST(constant_folding, const_quantize)
+{
+    Shape input_shape{12};
+    Shape scale_offset_shape;
+    AxisSet quantization_axes;
+
+    auto quant_type = element::u8;
+    auto output_type = element::u8;
+    typedef uint8_t output_c_type;
+
+    vector<float> values_in{1.0, 2.0, 2.0, 3.0, 3.0, 4.0, 4.0, 5.0, 5.0, 6.0, 6.0, 7.0};
+    auto constant = op::Constant::create(element::f32, input_shape, values_in);
+    auto scale = op::Constant::create(element::f32, scale_offset_shape, {2});
+    auto offset = op::Constant::create(quant_type, scale_offset_shape, {1});
+    auto mode = op::Quantize::RoundMode::HALF_AWAY_FROM_ZERO;
+    auto quantize =
+        make_shared<op::Quantize>(constant, scale, offset, output_type, quantization_axes, mode);
+    auto f = make_shared<Function>(quantize, op::ParameterVector{});
+
+    pass::Manager pass_manager;
+    pass_manager.register_pass<pass::ConstantFolding>();
+    pass_manager.run_passes(f);
+
+    ASSERT_EQ(count_ops_of_type<op::Quantize>(f), 0);
+    ASSERT_EQ(count_ops_of_type<op::Constant>(f), 1);
+
+    auto new_const =
+        std::dynamic_pointer_cast<op::Constant>(f->get_results().at(0)->get_argument(0));
+    ASSERT_TRUE(new_const);
+    auto values_out = new_const->get_vector<output_c_type>();
+
+    vector<output_c_type> values_quantize{2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5};
+    ASSERT_EQ(values_quantize, values_out);
+}