Add v2 Learners (standalone)

Makefile

@@ -375,6 +375,8 @@ CNTKLIBRARY_SRC =\
 	$(SOURCEDIR)/CNTKv2LibraryDll/Utils.cpp \
 	$(SOURCEDIR)/CNTKv2LibraryDll/Value.cpp \
 	$(SOURCEDIR)/CNTKv2LibraryDll/Variable.cpp \
+    $(SOURCEDIR)/CNTKv2LibraryDll/Learner.cpp \
+
 
 CNTKLIBRARY_SRC+=$(CNTK_COMMON_SRC)
 CNTKLIBRARY_SRC+=$(COMPUTATION_NETWORK_LIB_SRC)

Source/CNTKv2LibraryDll/API/CNTKLibrary.h

@@ -285,6 +285,7 @@ namespace CNTK
     class NDArrayView final : public std::enable_shared_from_this<NDArrayView>
     {
         friend class CompositeFunction;
+        friend class LearnerBase;
 
         template <typename T, typename ...CtorArgTypes>
         friend inline std::shared_ptr<T> MakeSharedObject(CtorArgTypes&& ...ctorArgs);
@@ -1396,4 +1397,342 @@ namespace CNTK
     /// of the computation graph which can be "Combine"d to create a single Function with 2 outputs; viz. CrossEntropy loss and ClassificationError output.
     ///
     CNTK_API FunctionPtr Combine(const std::initializer_list<FunctionPtr>& operands, const std::wstring& name = L"");
+
+    ///
+    /// A serializable value represents one of:
+    /// a) Boolean
+    /// b) Signed long integer
+    /// c) Single and double precision floating point values
+    /// d) NDShape
+    /// e) vector<DictionaryValue>
+    ///
+    /// TODO:  we need to have native support for DictionaryValue<vector> and DictionaryValue<NDArrayView>.
+    class CNTK_API DictionaryValue final
+    {
+    public:
+        enum class Type : unsigned int
+        {
+            None,
+            Bool,
+            SizeT,
+            Float,
+            Double,
+            NDShape,
+            Vector
+        };
+
+        static const char* TypeName(Type type)
+        {
+            switch (type)
+            {
+            case Type::None:
+                return "None";
+            case Type::Bool:
+                return "Bool";
+            case Type::SizeT:
+                return "SizeT";
+            case Type::Float:
+                return "Float";
+            case Type::Double:
+                return "Double";
+            case Type::NDShape:
+                return "NDShape";
+            case Type::Vector:
+                return "Vector";
+            default:
+                LogicError("Unknown DictionaryValue::Type");
+            }
+        }
+
+    public:
+        DictionaryValue() : m_valueType(Type::None)
+        {
+        }
+
+        DictionaryValue(bool value) : m_valueType(GetValueType<bool>())
+        {
+            m_data.m_boolean = value;
+        }
+
+        DictionaryValue(size_t value) : m_valueType(GetValueType<size_t>())
+        {
+            m_data.m_sizeT = value;
+        }
+
+        DictionaryValue(float value) : m_valueType(GetValueType<float>())
+        {
+            m_data.m_float = value;
+        }
+
+        DictionaryValue(double value) : m_valueType(GetValueType<double>())
+        {
+            m_data.m_double = value;
+        }
+
+        template <typename T>
+        DictionaryValue(const T& value) : m_valueType(GetValueType<T>())
+        {
+            static_assert(std::is_same<T, NDShape>::value ||
+                          std::is_same<T, std::vector<DictionaryValue>>::value,
+                          "Unsupported ValueType");
+
+            AllocateDataPtr(value);
+        }
+
+        DictionaryValue(const DictionaryValue& other) : m_valueType(Type::Bool)
+        {
+            // The m_valueType must have been set to a non-ptr type to prevent an attempt to interpret
+            // the underlying underlying uninitialized value as a ptr and free it.
+            *this = other;
+        }
+
+        DictionaryValue& operator=(const DictionaryValue& other)
+        {
+            if (this != &other)
+            {
+                FreeDataPtr();
+
+                m_valueType = other.m_valueType;
+                m_data = other.m_data;
+
+                if (other.m_valueType == Type::NDShape)
+                    AllocateDataPtr(other.GetValue<NDShape>());
+                else if (other.m_valueType == Type::Vector)
+                    AllocateDataPtr(other.GetValue<std::vector<DictionaryValue>>());
+            }
+
+            return *this;
+        }
+
+        ~DictionaryValue()
+        {
+            FreeDataPtr();
+        }
+
+        template <typename T, typename std::enable_if<std::is_same<T, bool>::value>::type* = nullptr>
+        const T& GetValue() const
+        {
+            VerifyType<T>();
+            return m_data.m_boolean;
+        }
+
+        template <typename T, typename std::enable_if<std::is_same<T, size_t>::value>::type* = nullptr>
+        const T& GetValue() const
+        {
+            VerifyType<T>();
+            return m_data.m_sizeT;
+        }
+
+        template <typename T, typename std::enable_if<std::is_same<T, float>::value>::type* = nullptr>
+        const T& GetValue() const
+        {
+            VerifyType<T>();
+            return m_data.m_float;
+        }
+
+        template <typename T, typename std::enable_if<std::is_same<T, double>::value>::type* = nullptr>
+        const T& GetValue() const
+        {
+            VerifyType<T>();
+            return m_data.m_double;
+        }
+
+        template <typename T, typename std::enable_if<std::is_same<T, NDShape>::value || std::is_same<T, std::vector<DictionaryValue>>::value>::type* = nullptr>
+        const T& GetValue() const
+        {
+            VerifyType<T>();
+            return *(reinterpret_cast<T*>(m_data.m_ptr));
+        }
+
+        bool HasValue() const
+        {
+            return m_valueType != Type::None;
+        }
+
+        Type ValueType() const
+        {
+            return m_valueType;
+        }
+
+        friend CNTK_API Microsoft::MSR::CNTK::File& operator>>(Microsoft::MSR::CNTK::File& stream, DictionaryValue& us);
+        friend CNTK_API Microsoft::MSR::CNTK::File& operator<<(Microsoft::MSR::CNTK::File& stream, const DictionaryValue& us);
+
+    private:
+        template <typename T>
+        static Type GetValueType()
+        {
+            static_assert(std::is_same<T, bool>::value ||
+                          std::is_same<T, size_t>::value ||
+                          std::is_same<T, float>::value ||
+                          std::is_same<T, double>::value ||
+                          std::is_same<T, NDShape>::value ||
+                          std::is_same<T, std::vector<DictionaryValue>>::value,
+                          "Unsupported ValueType");
+
+            if (std::is_same<T, bool>::value)                                      return Type::Bool;
+            if (std::is_same<T, size_t>::value)                                    return Type::SizeT;
+            if (std::is_same<T, float>::value)                                     return Type::Float;
+            if (std::is_same<T, double>::value)                                    return Type::Double;
+            if (std::is_same<T, NDShape>::value)                                   return Type::NDShape;
+            if (std::is_same<T, std::vector<DictionaryValue>>::value)              return Type::Vector;
+        }
+
+        template <typename T>
+        void VerifyType() const
+        {
+            if (GetValueType<T>() != m_valueType)
+                RuntimeError("Reading a DictionaryValue as the wrong type; Reading as type %s when actual type is %s", typeid(T).name(), DictionaryValue::TypeName(m_valueType));
+        }
+
+        template <typename T>
+        void AllocateDataPtr(const T& value);
+
+        template <typename T>
+        void FreePtrAsType();
+
+        void FreeDataPtr();
+
+        Type m_valueType;
+
+        union ValueData
+        {
+            bool m_boolean;
+            size_t m_sizeT;
+            float m_float;
+            double m_double;
+            void* m_ptr;
+        } m_data;
+
+        const size_t version = 1;
+    };
+
+    ///
+    /// A type denoting a dictionary (keyed by Unicode strings) of serializable values (dynamically typed).
+    ///
+    class CNTK_API Dictionary final
+    {
+    public:
+        Dictionary();
+        ~Dictionary();
+
+        // Disallow copy construction and assignment
+        Dictionary(const Dictionary&) = delete; Dictionary& operator=(const Dictionary&) = delete;
+
+        Dictionary(Dictionary&& other);
+        Dictionary& operator=(Dictionary&& other);
+
+        DictionaryValue& operator[](const std::wstring& key)
+        {
+            return operator[](key.c_str());
+        }
+
+        DictionaryValue& operator[](const wchar_t* key);
+
+        DictionaryValue operator[](const std::wstring& key) const
+        {
+            return operator[](key.c_str());
+        }
+
+        DictionaryValue operator[](const wchar_t* key) const;
+
+        bool Contains(const std::wstring& key) const
+        {
+            return Contains(key.c_str());
+        }
+
+        bool Contains(const wchar_t* key) const;
+
+        friend CNTK_API Microsoft::MSR::CNTK::File& operator>>(Microsoft::MSR::CNTK::File& stream, Dictionary& us);
+        friend CNTK_API Microsoft::MSR::CNTK::File& operator<<(Microsoft::MSR::CNTK::File& stream, const Dictionary& us);
+
+    private:
+        std::unordered_map<std::wstring, DictionaryValue>* m_dictionaryData;
+        const size_t version = 1;
+    };
+
+    ///
+    /// Abstraction for learning a subset of parameters of a learnable function using first order gradient values
+    /// For e.g momentum, AdaGrad, RMSProp etc. are different types of learners with their own algorithms for
+    /// learning parameter values using first order gradients.
+    ///
+    class Learner : public std::enable_shared_from_this<Learner>
+    {
+    public:
+        //
+        // Method to update the parameters associated with this learner. By returning false, this method indicates that
+        // learning has stopped for all of the parameters associated with this learner
+        //
+        CNTK_API virtual bool Update(const std::unordered_map<Variable, ValuePtr>& parameterValues,
+                                     const std::unordered_map<Variable, const ValuePtr>& gradientValues,
+                                     size_t trainingSampleCount) = 0;
+
+        ///
+        /// Returns the set of parameters associated with this learner.
+        ///
+        const std::unordered_set<Variable>& Parameters() const { return m_parameters; }
+
+        // TODO: move the following two methods into ISerializable interface, make 
+        // Learner (and all other entities that need checkpointing capability) implement it.
+        ///
+        /// Optionally overridable method to checkpoint the learner's state.
+        ///
+        CNTK_API virtual Dictionary GetCheckpointState() const = 0;
+
+        ///
+        /// Optionally overridable method to restore the learner's state from a previous checkpoint.
+        ///
+        CNTK_API virtual void RestoreFromCheckpoint(const Dictionary& checkpoint) = 0;
+
+        virtual ~Learner()
+        {
+        }
+
+    protected:
+        Learner(const std::unordered_set<Variable>& parameters)
+            : m_parameters(parameters)
+        {
+        }
+
+        std::unordered_set<Variable> m_parameters;
+
+    };
+
+    ///
+    /// Create an instance of the CNTK built-in SGD learner.
+    ///
+    /// TODO: add additional SGD parameters here (a collection of learning rate values)
+    CNTK_API LearnerPtr SGDLearner(const std::unordered_set<Variable>& parameters,
+                                   const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    ///
+    /// Create an instance of the CNTK built-in Momentum SGD learner.
+    ///
+    /// TODO: add additional Momentum parameters here (a collection of momentum rate values)
+    CNTK_API LearnerPtr MomentumSGDLearner(const std::unordered_set<Variable>& parameters,
+                                           const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    ///
+    /// Create an instance of the CNTK built-in Nesterov's accelerated SGD learner.
+    ///
+    CNTK_API LearnerPtr NesterovLearner(const std::unordered_set<Variable>& parameters,
+                                        const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    ///
+    /// Create an instance of the CNTK built-in AdaGrad learner.
+    ///
+    CNTK_API LearnerPtr AdaGradLearner(const std::unordered_set<Variable>& parameters, bool needAveMultiplier = true,
+                                       const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    ///
+    /// Create an instance of the CNTK built-in FSAdaGrad (improved AdaGrad) learner.
+    ///
+    CNTK_API LearnerPtr FSAdaGradLearner(const std::unordered_set<Variable>& parameters,
+                                         const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    ///
+    /// Create an instance of the CNTK built-in RMSProp learner.
+    ///
+    CNTK_API LearnerPtr RMSPropLearner(const std::unordered_set<Variable>& parameters,
+                                       double gamma, double inc, double dec, double max, double min, bool needAveMultiplier = true,
+                                       const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
 }

Source/CNTKv2LibraryDll/API/CNTKLibraryInternals.h

@@ -47,6 +47,8 @@ namespace Microsoft { namespace MSR { namespace CNTK {
 
     template <typename ElementType>
     class ComputationNode;
+
+    class File;
 }}}
 
 // TODO: The following should be reconciled with the equivalent code in the CNTK implementation
@@ -158,4 +160,7 @@ namespace CNTK
 
     class Function;
     typedef std::shared_ptr<Function> FunctionPtr;
+
+    class Learner;
+    typedef std::shared_ptr<Learner> LearnerPtr;
 }

Source/CNTKv2LibraryDll/CNTKv2LibraryDll.vcxproj

@@ -128,6 +128,7 @@
     <ClInclude Include="API\CNTKLibrary.h" />
     <ClInclude Include="API\CNTKLibraryInternals.h" />
     <ClInclude Include="Function.h" />
+    <ClInclude Include="Learner.h" />
     <ClInclude Include="Utils.h" />
     <ClInclude Include="stdafx.h" />
     <ClInclude Include="targetver.h" />
@@ -140,6 +141,7 @@
       </PrecompiledHeader>
     </ClCompile>
     <ClCompile Include="Function.cpp" />
+    <ClCompile Include="Learner.cpp" />
     <ClCompile Include="NDArrayView.cpp" />
     <ClCompile Include="NDMask.cpp" />
     <ClCompile Include="stdafx.cpp">

Source/CNTKv2LibraryDll/CNTKv2LibraryDll.vcxproj.filters

@@ -10,6 +10,7 @@
     <ClCompile Include="Variable.cpp" />
     <ClCompile Include="Utils.cpp" />
     <ClCompile Include="NDMask.cpp" />
+    <ClCompile Include="Learner.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="stdafx.h" />
@@ -22,6 +23,7 @@
       <Filter>API</Filter>
     </ClInclude>
     <ClInclude Include="Function.h" />
+    <ClInclude Include="Learner.h" />
   </ItemGroup>
   <ItemGroup>
     <Filter Include="API">

Source/CNTKv2LibraryDll/Learner.cpp

@@ -0,0 +1,464 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
+//
+
+#include "Learner.h"
+#include "TensorView.h"
+#include "Utils.h"
+
+#define UPDATE_FUNCTION                                                                                       \
+    switch (smoothedGradientValue->Data()->GetDataType())                                                     \
+    {                                                                                                         \
+    case DataType::Float:                                                                                     \
+        Update<float>(parameter, smoothedGradientValue, gradientValue, parameterValue, trainingSampleCount);  \
+        break;                                                                                                \
+    case DataType::Double:                                                                                    \
+        Update<double>(parameter, smoothedGradientValue, gradientValue, parameterValue, trainingSampleCount); \
+        break;                                                                                                \
+    default:                                                                                                  \
+        NOT_IMPLEMENTED;                                                                                      \
+    }
+
+
+using namespace Microsoft::MSR::CNTK;
+using namespace std;
+
+namespace CNTK
+{
+    template <typename ElementType>
+    /*static*/ shared_ptr<const Matrix<ElementType>> LearnerBase::GetMatrix(const NDArrayViewPtr arrayView)
+    {
+        return arrayView->GetMatrix<ElementType>();
+    }
+
+    template <typename ElementType>
+    /*static*/ shared_ptr<Matrix<ElementType>> LearnerBase::GetWritableMatrix(NDArrayViewPtr arrayView)
+    {
+        return arrayView->GetWritableMatrix<ElementType>();
+    }
+
+    template <typename ElementType>
+    /*static*/ const TensorView<ElementType>* LearnerBase::GetTensorView(const NDArrayViewPtr arrayView)
+    {
+        return arrayView->GetTensorView<ElementType>();
+    }
+
+    /*static*/ bool LearnerBase::HasNan(const ValuePtr& value, const char* name)
+    {
+        const auto& data = value->Data();
+        switch (data->GetDataType())
+        {
+        case DataType::Float:
+            return data->GetMatrix<float>()->HasNan(name);
+        case DataType::Double:
+            return data->GetMatrix<double>()->HasNan(name);
+        default:
+            LogicError("Unsupported DataType %s", DataTypeName(data->GetDataType()));
+        }
+    }
+
+    /*static*/ void LearnerBase::Print(const ValuePtr& value, const char* msg)
+    {
+        const auto& data = value->Data();
+        switch (data->GetDataType())
+        {
+        case DataType::Float:
+            data->GetMatrix<float>()->Print(msg);
+            break;
+        case DataType::Double:
+            data->GetMatrix<double>()->Print(msg);
+            break;
+        default:
+            LogicError("Unsupported DataType %s", DataTypeName(data->GetDataType()));
+        }
+    }
+
+    // Clipping gradients to prevent outliers,
+    template <typename ElementType>
+    void LearnerBase::ClipGradient(Matrix<ElementType>& gradient, size_t actualMBSize) const
+    {
+        if (m_additionalOptions.gradientClippingThresholdPerSample != numeric_limits<double>::infinity())
+        {
+            double maxGradientPerMB = m_additionalOptions.gradientClippingThresholdPerSample * actualMBSize;
+            if (m_additionalOptions.gradientClippingWithTruncation)
+                gradient.InplaceTruncate(ElementType(maxGradientPerMB));
+            else
+            {
+                // norm2 normalized
+                double gradientNorm = gradient.FrobeniusNorm();
+                if (gradientNorm > maxGradientPerMB)
+                {
+                    double normFactor = maxGradientPerMB / gradientNorm;
+                    gradient *= ElementType(normFactor);
+                }
+            }
+        }
+    }
+
+    // Performs additional preprocessing before calling the update method 
+    // (gradient clipping and L2 regularization depending on the additional learning parameters).
+    template <typename ElementType>
+    void LearnerBase::PreProcess(const ValuePtr& gradientValue,const ValuePtr& parameterValue, size_t actualMBSize) const
+    {
+        const auto& gradientMatrix = gradientValue->Data()->GetWritableMatrix<ElementType>();
+
+        // clipping gradients to prevent outliers
+        ClipGradient<ElementType>(*gradientMatrix, actualMBSize);
+
+        // L2 regularizer
+        if (m_additionalOptions.l2RegularizationWeight > 0)
+        {
+            // multiply by actualMBSize so that it's invariant to minibatch size since learning rate is per sample
+            auto weight = ElementType(m_additionalOptions.l2RegularizationWeight * actualMBSize);
+            const auto& parameterMatrix = parameterValue->Data()->GetWritableMatrix<ElementType>();
+            Matrix<ElementType>::ScaleAndAdd(weight, *parameterMatrix, *gradientMatrix);
+        }
+    }
+
+    // Performs additional postprocessing after the update method has been executed
+    // (noise injection and L1 regularization specified by the additional learning parameters).
+    template <typename ElementType>
+    void LearnerBase::PostProcess(const Variable& parameter, const ValuePtr& gradientValue,
+                                    const ValuePtr& parameterValue, size_t actualMBSize) const
+    {
+        const auto& parameterMatrix = parameterValue->Data()->GetWritableMatrix<ElementType>();
+        if (m_additionalOptions.gaussianNoiseInjectionStdDev > 0)
+        {
+            const auto& gradientMatrix = gradientValue->Data()->GetWritableMatrix<ElementType>();
+
+            Matrix<ElementType> sgdUpdateNoise((DEVICEID_TYPE)parameterMatrix->GetDeviceId());
+
+            // get the gradient structure since gradient is sparse
+            sgdUpdateNoise.SetValue(*gradientMatrix);
+
+            auto noiseStdDev = ElementType(m_additionalOptions.gaussianNoiseInjectionStdDev);
+
+            // reset its value to random
+            sgdUpdateNoise.SetGaussianRandomValue(ElementType(0.0), noiseStdDev);
+
+            Matrix<ElementType>::ScaleAndAdd(ElementType(1.0), sgdUpdateNoise, *parameterMatrix);
+        }
+
+        // L1 regularizer with proximal gradient descent method
+        if (m_additionalOptions.l1RegularizationWeight > 0)
+        {
+            auto learningRate = ElementType(ParameterDependentLearningRate(parameter));
+            // multiply by actualMBSize so that it's invariant to minibatch size since learning rate is per sample
+            auto weight = ElementType(learningRate * m_additionalOptions.l1RegularizationWeight * actualMBSize);
+            parameterValue->Data()->GetWritableMatrix<ElementType>()->InplaceSoftThreshold(weight);
+        }
+    }
+
+    template <typename ElementType>
+    /*static*/ TensorView<ElementType>* LearnerBase::GetWritableTensorView(NDArrayViewPtr arrayView)
+    {
+        return arrayView->GetWritableTensorView<ElementType>();
+    }
+
+    LearnerBase::LearnerBase(const unordered_set<Variable>& parameters, const DeviceDescriptor& device)
+        : Learner(parameters),
+        m_learningRatePerSample(0.0),
+        m_sampleCount(0)
+    {
+        const unordered_set<Variable>& parameterSet = parameters;
+        for (const auto& parameter : parameterSet)
+        {
+            // TODO: using the same device to allocate data for all smoothed gradients. Is this correct?
+            // Should the device be specified on the per-parameter basis?
+            NDArrayViewPtr view;
+            if (parameter.GetDataType() == DataType::Float)
+            {
+                view = MakeSharedObject<NDArrayView>(0.0f, parameter.Shape(), device);
+            }
+            else
+            {
+                view = MakeSharedObject<NDArrayView>(0.0, parameter.Shape(), device);
+            }
+
+            m_smoothedGradientValues.insert(make_pair(parameter, MakeSharedObject<Value>(view)));
+            m_additionalOptions.learningRateMultipliers.insert(make_pair(parameter, 1.0));
+        }
+    }
+
+    void LearnerBase::ResetSmoothedGradients()
+    {
+        for (const auto& parameter : Parameters())
+        {
+            const auto& smoothedGradientValue = m_smoothedGradientValues.at(parameter);
+            const auto& data = smoothedGradientValue->Data();
+            switch (data->GetDataType())
+            {
+            case DataType::Float:
+                data->SetValue(0.0f);
+                break;
+            case DataType::Double:
+                data->SetValue(0.0);
+                break;
+            default:
+                LogicError("Unsupported DataType %s", ::CNTK::DataTypeName(data->GetDataType()));
+            }
+        }
+    }
+
+    /*virtual*/ bool LearnerBase::Update(const unordered_map<Variable, ValuePtr>& parameterValues,
+                                            const unordered_map<Variable, const ValuePtr>& gradientValues,
+                                            size_t trainingSampleCount) /*override*/
+    {
+        // make sure trainingSampleCount is a valid value
+        assert(trainingSampleCount > 0);
+
+        for (const auto& parameter : Parameters())
+        {
+            const auto& smoothedGradientValue = m_smoothedGradientValues.at(parameter);
+            const auto& gradientValue = gradientValues.at(parameter);
+            const auto& parameterValue = parameterValues.at(parameter);
+
+// TODO: make this a runtime parameter.
+#if DUMPOUTPUT
+            LOGPRINTF(stderr, "Update_%ls\n", parameter.Name().c_str());
+#endif
+
+#ifdef _DEBUG
+            if (HasNan(smoothedGradientValue, "TrainOneEpoch/UpdateWeights/Learner::Update(): "))
+                LogicError("%ls has NaNs in smoothedGradient.", parameter.Name().c_str());
+#endif
+
+#if DUMPOUTPUT
+            LOGPRINTF(stderr, "learnRatePerSample=%0.8f, momentum=%0.8f, actualMBSize=%ld\n",
+                        m_learningRatePerSample, m_momentumPerSample, trainingSampleCount);
+            LOGPRINTF(stderr, "GradUpdateType()=%s, GradientUpdateNoiseStd()=%0.8f\n",
+                        LearnerType().c_str(), m_GaussianNoiseInjectStd);
+            Print(gradientValue, "Gradient Update");
+            Print(smoothedGradientValue, "Smoothed Gradient Input");
+#endif
+            UPDATE_FUNCTION;
+
+#if DUMPOUTPUT
+            Print(parameterValue, "Parameter Update");
+#endif
+
+#ifdef _DEBUG
+            if (HasNan(parameterValue, "TrainOneEpoch/UpdateWeights/Learner::Update(): "))
+                LogicError("%ls has NaNs in parameter values after parameter update.", parameter.Name().c_str());
+#endif
+        }
+        m_sampleCount += trainingSampleCount;
+        return false;
+    }
+
+    template <typename ElementType>
+    void LearnerBase::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                             const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const
+    {
+        PreProcess<ElementType>(gradientValue, parameterValue, trainingSampleCount);
+        Update(parameter, smoothedGradientValue, gradientValue, parameterValue, trainingSampleCount);
+        PostProcess<ElementType>(parameter, gradientValue, parameterValue, trainingSampleCount);
+    }
+
+    string LearnerBase::LearnerType() const
+    {
+        auto name = typeid(*this).name(); 
+        if (strncmp(name, "class ", 6) == 0)
+        {
+            // On Windows, the type name contains "class" prefix. 
+            // Return the actual name, omitting the prefix.
+            return &name[6];
+        } 
+        return name;
+    }
+
+    /*virtual*/ Dictionary LearnerBase::GetCheckpointState() const /*override*/
+    {
+        NOT_IMPLEMENTED; // Until the new checkpointing is fully fleshed out, nobody should be calling this.
+        Dictionary checkpoint;
+
+        for (const auto& parameter : Parameters())
+        {
+            // TODO: parameter name is not guaranteed to be unique. Instead, all serializable objects
+            // need to expose "UId" property -- a persistent unique internal name.
+            // Switch to UId as soon as it's available.
+            if (checkpoint.Contains(parameter.Name()))
+            {
+                LogicError("Parameter names must be unique");
+            }
+            const auto& smoothedGradientValue = m_smoothedGradientValues.at(parameter);
+
+            // Potentially, could store things like dimensions, element size, format, etc., but
+            // that seems to be redundant, since all of that is passed in the constructor.
+            checkpoint[parameter.Name()] = SerializeToVector(smoothedGradientValue->Data());
+        }
+        return checkpoint;
+    }
+
+    /*virtual*/ void LearnerBase::RestoreFromCheckpoint(const Dictionary& checkpoint) /*override*/
+    {
+        NOT_IMPLEMENTED; // Until the new checkpointing is fully fleshed out, nobody should be calling this.
+        for (const auto& parameter : Parameters())
+        {
+            if (!checkpoint.Contains(parameter.Name()))
+            {
+                LogicError("Checkpoint does not contain state for parameter %ls", parameter.Name().c_str());
+            }
+            const auto& smoothedGradientValue = m_smoothedGradientValues.at(parameter);
+
+            const DictionaryValue& state = checkpoint[parameter.Name()];
+
+            const auto& data = smoothedGradientValue->Data();
+
+            DeserializeFromVector(data, state.GetValue<vector<DictionaryValue>>());
+        }
+    }
+
+    /*virtual*/ void LearnerSGD::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                                        const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const /*override*/
+    {
+        UPDATE_FUNCTION;
+    }
+
+    template <typename ElementType>
+    void LearnerSGD::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const
+    {
+        UNUSED(trainingSampleCount);
+
+        const auto& smoothedGradientMatrix = GetWritableMatrix<ElementType>(smoothedGradientValue->Data());
+        const auto& gradientMatrix = GetWritableMatrix<ElementType>(gradientValue->Data());
+        const auto& parameterMatrix = GetWritableMatrix<ElementType>(parameterValue->Data());
+
+        const auto& learningRate = ElementType(ParameterDependentLearningRate(parameter));
+
+        // TODO: break up the NormalGrad into 3 different functions, each with its own set of parameters
+        // (one for vanilla SGD, the other for momentum SGD, and the third one for NAG).
+        smoothedGradientMatrix->NormalGrad(*gradientMatrix, *parameterMatrix,
+                                            learningRate, ElementType(m_momentumPerSample), m_useNesterovAcceleration);
+    }
+
+    LearnerAdaGrad::LearnerAdaGrad(const unordered_set<Variable>& parameters, bool needAveMultiplier, const DeviceDescriptor& device)
+        : LearnerBase(parameters, device),
+        m_needAveMultiplier(needAveMultiplier)
+    {
+    }
+
+    /*virtual*/ void LearnerAdaGrad::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const /*override*/
+    {
+        UPDATE_FUNCTION;
+    }
+
+    template <typename ElementType>
+    void LearnerAdaGrad::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                                const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const
+    {
+        UNUSED(trainingSampleCount);
+
+        const auto& smoothedGradientMatrix = GetWritableMatrix<ElementType>(smoothedGradientValue->Data());
+        const auto& gradientMatrix = GetWritableMatrix<ElementType>(gradientValue->Data());
+        const auto& parameterMatrix = GetWritableMatrix<ElementType>(parameterValue->Data());
+
+        auto learningRate = ElementType(ParameterDependentLearningRate(parameter));
+
+        auto aveMultiplier = smoothedGradientMatrix->Adagrad(*gradientMatrix, m_needAveMultiplier);
+        Matrix<ElementType>::ScaleAndAdd(ElementType(-learningRate / aveMultiplier), *gradientMatrix, *parameterMatrix);
+    }
+
+    LearnerFSAdaGrad::LearnerFSAdaGrad(const unordered_set<Variable>& parameters, const DeviceDescriptor& device)
+        : LearnerMomentumSGD(parameters, device)
+    {
+    }
+
+    /*virtual*/ void LearnerFSAdaGrad::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                                                const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const /*override*/
+    {
+        UPDATE_FUNCTION;
+    }
+
+    template <typename ElementType>
+    void LearnerFSAdaGrad::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                                  const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const
+    {
+        UNUSED(trainingSampleCount);
+
+        const auto& smoothedGradientMatrix = GetWritableMatrix<ElementType>(smoothedGradientValue->Data());
+        const auto& gradientMatrix = GetWritableMatrix<ElementType>(gradientValue->Data());
+        const auto& parameterMatrix = GetWritableMatrix<ElementType>(parameterValue->Data());
+
+        //const double momentum = MomentumPerMB(m_momentumPerSample, trainingSampleCount);
+
+        auto learningRate = ElementType(ParameterDependentLearningRate(parameter));
+
+        smoothedGradientMatrix->FSAdagrad(trainingSampleCount, *gradientMatrix, *parameterMatrix,
+                                            learningRate, ElementType(m_momentumPerSample));
+    }
+
+    LearnerRMSProp::LearnerRMSProp(const unordered_set<Variable>& parameters,
+                                    double gamma, double inc, double dec, double max, double min,
+                                    bool needAveMultiplier, const DeviceDescriptor& device)
+                                    : LearnerBase(parameters, device),
+                                    m_gamma(gamma), m_inc(inc), m_dec(dec), m_max(max), m_min(min),
+                                    m_needAveMultiplier(needAveMultiplier)
+    {
+    }
+
+    /*virtual*/ void LearnerRMSProp::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const /*override*/
+    {
+        UPDATE_FUNCTION;
+    }
+
+    template <typename ElementType>
+    void LearnerRMSProp::Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                                const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const
+    {
+        UNUSED(trainingSampleCount);
+
+        const auto& smoothedGradientMatrix = GetWritableMatrix<ElementType>(smoothedGradientValue->Data());
+        const auto& gradientMatrix = GetWritableMatrix<ElementType>(gradientValue->Data());
+        const auto& parameterMatrix = GetWritableMatrix<ElementType>(parameterValue->Data());
+
+        auto learningRate = ElementType(ParameterDependentLearningRate(parameter));
+
+        auto aveMultiplier = smoothedGradientMatrix->RmsProp(*gradientMatrix,
+                                                                ElementType(m_gamma), ElementType(m_inc),
+                                                                ElementType(m_max), ElementType(m_dec),
+                                                                ElementType(m_min), m_needAveMultiplier);
+        Matrix<ElementType>::ScaleAndAdd(ElementType(-learningRate / aveMultiplier), *gradientMatrix, *parameterMatrix);
+    }
+
+    // Explicit template instantiations
+    template shared_ptr<Matrix<float>> LearnerBase::GetWritableMatrix<float>(const NDArrayViewPtr arrayView);
+    template shared_ptr<Matrix<double>> LearnerBase::GetWritableMatrix<double>(const NDArrayViewPtr arrayView);
+    
+    LearnerPtr SGDLearner(const unordered_set<Variable>& parameters, const DeviceDescriptor& device)
+    {
+        return MakeSharedObject<LearnerSGD>(parameters, device);
+    }
+
+    LearnerPtr MomentumSGDLearner(const unordered_set<Variable>& parameters, const DeviceDescriptor& device)
+    {
+        return MakeSharedObject<LearnerMomentumSGD>(parameters, device);
+    }
+
+    LearnerPtr NesterovLearner(const unordered_set<Variable>& parameters, const DeviceDescriptor& device)
+    {
+        return MakeSharedObject<LearnerNesterov>(parameters, device);
+    }
+
+    LearnerPtr AdaGradLearner(const unordered_set<Variable>& parameters, bool needAveMultiplier, const DeviceDescriptor& device)
+    {
+        return MakeSharedObject<LearnerAdaGrad>(parameters, needAveMultiplier, device);
+    }
+
+    LearnerPtr FSAdaGradLearner(const unordered_set<Variable>& parameters, const DeviceDescriptor& device)
+    {
+        return MakeSharedObject<LearnerFSAdaGrad>(parameters, device);
+    }
+
+    LearnerPtr RMSPropLearner(const unordered_set<Variable>& parameters,
+                                double gamma, double inc, double dec, double max, double min, bool needAveMultiplier,
+                                const DeviceDescriptor& device)
+    {
+        return MakeSharedObject<LearnerRMSProp>(parameters, gamma, inc, dec, max, min, needAveMultiplier, device);
+    }
+
+}

Source/CNTKv2LibraryDll/Learner.h

@@ -0,0 +1,224 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
+//
+
+#include "stdafx.h"
+#include "CNTKLibrary.h"
+
+namespace CNTK 
+{
+    // A collection of additional options that are applicable for all standard learners 
+    // (after these options are set, they retain their value for the entire lifespan of a learner).
+    struct AdditionalLearningOptions
+    {
+        double l1RegularizationWeight = 0.0;
+        double l2RegularizationWeight = 0.0;
+        double gaussianNoiseInjectionStdDev = 0.0;
+        bool gradientClippingWithTruncation = false;
+        double gradientClippingThresholdPerSample = 0.0;
+        std::unordered_map<Variable, double> learningRateMultipliers;
+    };
+
+    // An abstract base class at the root of the standard learners hierarchy
+    // It implements most of the learner functionality, except for the actual update function,
+    // and adds a few pre-/postprocessing methods (which are invoked before and after the update).
+    class LearnerBase : public Learner
+    {
+    public:
+
+        CNTK_API virtual bool Update(const std::unordered_map<Variable, ValuePtr>& parameterValues,
+                                     const std::unordered_map<Variable, const ValuePtr>& gradientValues,
+                                     size_t trainingSampleCount) override final;
+
+        CNTK_API virtual Dictionary GetCheckpointState() const override;
+
+        CNTK_API virtual void RestoreFromCheckpoint(const Dictionary& checkpoint) override;
+
+        CNTK_API void SetAdditionalOptions(const AdditionalLearningOptions& additionalOptions)
+        {
+            m_additionalOptions = additionalOptions;
+        }
+
+        // TODO: should this be called ResetMomentum?
+        // needed for BlockMomemtumSGD to reset SGD momentum after aggregation.
+        CNTK_API void ResetSmoothedGradients();
+
+        // TODO: move learning rate and momentum scheduling and adjustment functionality 
+        // inside the learner and drop these setters.
+        void SetLearningRate(double value) { m_learningRatePerSample = value; }
+
+    protected:
+        LearnerBase(const std::unordered_set<Variable>& parameters,
+                    const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+        virtual void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const = 0;
+
+        double ParameterDependentLearningRate(const Variable& parameter) const
+        {
+            return m_learningRatePerSample * m_additionalOptions.learningRateMultipliers.at(parameter);
+        }
+
+        std::string LearnerType() const;
+
+        double m_learningRatePerSample;
+
+        AdditionalLearningOptions m_additionalOptions;
+
+        std::unordered_map<Variable, ValuePtr> m_smoothedGradientValues;
+
+        // The following four static protected methods expose private methods of NDArrayView class
+        // (which declares LearnerBase as friend class), so that they are available to subclasses.
+        template <typename ElementType>
+        static std::shared_ptr<const Microsoft::MSR::CNTK::Matrix<ElementType>> GetMatrix(const NDArrayViewPtr arrayView);
+
+        template <typename ElementType>
+        static std::shared_ptr<Microsoft::MSR::CNTK::Matrix<ElementType>> GetWritableMatrix(NDArrayViewPtr arrayView);
+
+        template <typename ElementType>
+        static const Microsoft::MSR::CNTK::TensorView<ElementType>* GetTensorView(const NDArrayViewPtr arrayView);
+
+        template <typename ElementType>
+        static Microsoft::MSR::CNTK::TensorView<ElementType>* GetWritableTensorView(NDArrayViewPtr arrayView);
+
+        template <typename ElementType>
+        void ClipGradient(Microsoft::MSR::CNTK::Matrix<ElementType>& gradient, size_t actualMBSize) const;
+
+        // Performs additional preprocessing before calling the update method 
+        // (gradient clipping and L2 regularization depending on the additional learning parameters).
+        template <typename ElementType>
+        void PreProcess(const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t actualMBSize) const;
+
+        // Performs additional postprocessing after the update method has been executed
+        // (noise injection and L1 regularization specified by the additional learning parameters).
+        template <typename ElementType>
+        void PostProcess(const Variable& parameter, const ValuePtr& gradientValue,
+                         const ValuePtr& parameterValue, size_t actualMBSize) const;
+    private:
+        // Templatized update function, it invokes preprocess and postprocess using the provided
+        // template parameter and also invokes virtual Update method implemented in one of the subclasses.
+        template <typename ElementType>
+        void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                    const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const;
+
+        // TODO: make these functions friends of NDViewArray and move to Utils?
+        static bool HasNan(const ValuePtr& value, const char* name);
+        static void Print(const ValuePtr& value, const char* msg);
+
+        size_t m_sampleCount;
+    };
+
+    // Vanilla gradient descent optimization algorithm.
+    class LearnerSGD : public LearnerBase
+    {
+    public:
+
+        LearnerSGD(const std::unordered_set<Variable>& parameters,
+                   const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice())
+                   : LearnerBase(parameters, device),
+                   m_momentumPerSample(0.0),
+                   m_useNesterovAcceleration(false)
+        {
+        }
+
+    protected:
+
+        virtual void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const override;
+
+        template <typename ElementType>
+        void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                    const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const;
+
+        double m_momentumPerSample;
+        bool m_useNesterovAcceleration;
+    };
+
+    // SGD optimization with momentum. 
+    class LearnerMomentumSGD : public LearnerSGD
+    {
+    public:
+
+        LearnerMomentumSGD(const std::unordered_set<Variable>& parameters,
+                           const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice())
+                           : LearnerSGD(parameters, device)
+        {
+        }
+
+        void SetMomentum(double value) { m_momentumPerSample = value; }
+    };
+
+    // Nesterov's accelerated SGDLearnerBase descent. 
+    class LearnerNesterov : public LearnerSGD
+    {
+    public:
+
+        LearnerNesterov(const std::unordered_set<Variable>& parameters,
+                        const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice())
+                        : LearnerSGD(parameters, device)
+        {
+            m_useNesterovAcceleration = true;
+        }
+    };
+
+    class LearnerAdaGrad : public LearnerBase
+    {
+    public:
+
+        LearnerAdaGrad(const std::unordered_set<Variable>& parameters, bool needAveMultiplier,
+                       const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    protected:
+        bool m_needAveMultiplier;
+
+        virtual void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const override;
+
+        template <typename ElementType>
+        void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                    const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const;
+    };
+
+    class LearnerFSAdaGrad : public LearnerMomentumSGD
+    {
+    public:
+
+        LearnerFSAdaGrad(const std::unordered_set<Variable>& parameters,
+                         const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    protected:
+
+        virtual void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const override;
+
+        template <typename ElementType>
+        void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                    const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const;
+    };
+
+    class LearnerRMSProp : public LearnerBase
+    {
+    public:
+
+        LearnerRMSProp(const std::unordered_set<Variable>& parameters,
+                       double gamma, double inc, double dec, double max, double min, bool needAveMultiplier,
+                       const DeviceDescriptor& device = DeviceDescriptor::DefaultDevice());
+
+    protected:
+
+        double m_gamma;
+        double m_inc;
+        double m_dec;
+        double m_max;
+        double m_min;
+        bool m_needAveMultiplier;
+
+        virtual void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                            const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const override;
+
+        template <typename ElementType>
+        void Update(const Variable& parameter, const ValuePtr& smoothedGradientValue,
+                    const ValuePtr& gradientValue, const ValuePtr& parameterValue, size_t trainingSampleCount) const;
+    };
+}

Source/CNTKv2LibraryDll/NDArrayView.cpp

@@ -338,8 +338,10 @@ namespace CNTK
     template std::shared_ptr<const Matrix<float>> NDArrayView::GetMatrix(size_t rowColSplitPoint/* = AutoSelectRowColSplitPoint*/) const;
     template std::shared_ptr<const Matrix<double>> NDArrayView::GetMatrix(size_t rowColSplitPoint/* = AutoSelectRowColSplitPoint*/) const;
 
-    template std::shared_ptr<Matrix<float>> NDArrayView::GetWritableMatrix(size_t rowColSplitPoint/* = AutoSelectRowColSplitPoint*/);
-    template std::shared_ptr<Matrix<double>> NDArrayView::GetWritableMatrix(size_t rowColSplitPoint/* = AutoSelectRowColSplitPoint*/);
+    template std::shared_ptr<Matrix<float>> NDArrayView::GetWritableMatrix<float>(size_t rowColSplitPoint/* = AutoSelectRowColSplitPoint*/);
+    template std::shared_ptr<Matrix<double>> NDArrayView::GetWritableMatrix<double>(size_t rowColSplitPoint/* = AutoSelectRowColSplitPoint*/);
+    template TensorView<float>* NDArrayView::GetWritableTensorView<float>();
+    template TensorView<double>* NDArrayView::GetWritableTensorView<double>();
 
     template CNTK_API NDArrayView::NDArrayView(const NDShape& viewShape, const SparseIndexType* colStarts, const SparseIndexType* rowIndices, const float* nonZeroValues, size_t numNonZeroValues, const DeviceDescriptor& device, bool readOnly/* = false*/);
     template CNTK_API NDArrayView::NDArrayView(const NDShape& viewShape, const SparseIndexType* colStarts, const SparseIndexType* rowIndices, const double* nonZeroValues, size_t numNonZeroValues, const DeviceDescriptor& device, bool readOnly/* = false*/);

Source/CNTKv2LibraryDll/Utils.cpp

@@ -6,11 +6,138 @@
 #include "stdafx.h"
 #include "CNTKLibrary.h"
 #include "Utils.h"
+#include "File.h"
+
+using namespace std;
 
 namespace CNTK
 {
+    template <typename T>
+    void DictionaryValue::AllocateDataPtr(const T& value)
+    {
+        static_assert(is_same<T, NDShape>::value || is_same<T, vector<DictionaryValue>>::value, "AllocateDataPtr called with invalid type");
+        m_data.m_ptr = new T(value);
+    }
+
+    template <typename T>
+    void DictionaryValue::FreePtrAsType()
+    {
+        T* typedPtr = reinterpret_cast<T*>(m_data.m_ptr);
+        delete typedPtr;
+
+        m_data.m_ptr = nullptr;
+    }
+
+    void DictionaryValue::FreeDataPtr()
+    {
+        if (m_valueType == Type::NDShape)
+            FreePtrAsType<NDShape>();
+        else if (m_valueType == Type::Vector)
+            FreePtrAsType<vector<DictionaryValue>>();
+    }
+
+    Microsoft::MSR::CNTK::File& operator>>(Microsoft::MSR::CNTK::File& stream, DictionaryValue& us)
+    {
+        size_t version;
+        stream >> version;
+
+        stream >> us.m_valueType;
+
+        switch (us.ValueType())
+        {
+        case DictionaryValue::Type::Bool:
+            stream >> us.m_data.m_boolean;
+            break;
+        case DictionaryValue::Type::SizeT:
+            stream >> us.m_data.m_sizeT;
+            break;
+        case DictionaryValue::Type::Float:
+            stream >> us.m_data.m_float;
+            break;
+        case DictionaryValue::Type::Double:
+            stream >> us.m_data.m_double;
+            break;
+        case DictionaryValue::Type::NDShape:
+        {
+            size_t size;
+            stream >> size;
+            vector<size_t> dims(size);
+            for (auto i = 0; i < size; i++)
+            {
+                stream >> dims[i];
+            }
+            us.AllocateDataPtr(NDShape(dims));
+            break;
+        }
+        case DictionaryValue::Type::Vector:
+        {
+            size_t size;
+            stream >> size;
+            vector<DictionaryValue> values(size);
+            for (auto i = 0; i < size; i++)
+            {
+                stream >> values[i];
+            }
+            us.AllocateDataPtr(values);
+            break;
+        }
+        default:
+            NOT_IMPLEMENTED;
+        }
+        return stream;
+    }
+
+    Microsoft::MSR::CNTK::File& operator<<(Microsoft::MSR::CNTK::File& stream, const DictionaryValue& us)
+    {
+        stream << us.version;
+
+        stream << us.ValueType();
+
+        switch (us.ValueType())
+        {
+        case DictionaryValue::Type::Bool:
+            stream << us.m_data.m_boolean;
+            break;
+        case DictionaryValue::Type::SizeT:
+            stream << us.m_data.m_sizeT;
+            break;
+        case DictionaryValue::Type::Float:
+            stream << us.m_data.m_float;
+            break;
+        case DictionaryValue::Type::Double:
+            stream << us.m_data.m_double;
+            break;
+        case DictionaryValue::Type::NDShape:
+        {
+            NDShape* shapePtr = reinterpret_cast<NDShape*>(us.m_data.m_ptr);
+            auto size = shapePtr->NumAxes();
+            stream << size;
+            for (auto i = 0; i < size; i++)
+            {
+                stream << shapePtr->operator[](i);
+            }
+            break;
+        }
+        case DictionaryValue::Type::Vector:
+        {
+            vector<DictionaryValue>* vectorPtr =
+                reinterpret_cast<vector<DictionaryValue>*>(us.m_data.m_ptr);
+            auto size = vectorPtr->size();
+            stream << size;
+            for (auto i = 0; i < size; i++)
+            {
+                stream << vectorPtr->operator[](i);
+            }
+            break;
+        }
+        default:
+            NOT_IMPLEMENTED;
+        }
+        return stream;
+    }
+
     Dictionary::Dictionary()
-        : m_dictionaryData(new std::unordered_map < std::wstring, DictionaryValue>)
+        : m_dictionaryData(new unordered_map <wstring, DictionaryValue>)
     {
     }
 
@@ -22,7 +149,7 @@ namespace CNTK
     Dictionary::Dictionary(Dictionary&& other)
         : m_dictionaryData(nullptr)
     {
-        *this = std::move(other);
+        *this = move(other);
     }
 
     Dictionary& Dictionary::operator=(Dictionary&& other)
@@ -51,4 +178,130 @@ namespace CNTK
     {
         return (m_dictionaryData->find(key) != m_dictionaryData->end());
     }
+
+    Microsoft::MSR::CNTK::File& operator<<(Microsoft::MSR::CNTK::File& stream, const Dictionary& us)
+    {
+        stream << us.version;
+        stream << us.m_dictionaryData->size();
+        for (auto it = us.m_dictionaryData->begin(); it != us.m_dictionaryData->end(); ++it)
+        {
+            stream << it->first;
+            stream << it->second;
+        }
+        return stream;
+    }
+
+    Microsoft::MSR::CNTK::File& operator>>(Microsoft::MSR::CNTK::File& stream, Dictionary& us)
+    {
+        size_t version;
+        stream >> version;
+        size_t size;
+        stream >> size;
+        us.m_dictionaryData->reserve(size);
+        for (auto i = 0; i < size; i++)
+        {
+            wstring key;
+            stream >> key;
+            DictionaryValue value;
+            stream >> value;
+            us.m_dictionaryData->insert(make_pair(key, value));
+        }
+        return stream;
+    }
+
+    template <typename T>
+    vector<DictionaryValue> SerializeToVector(const NDArrayViewPtr& viewPtr)
+    {
+        if (viewPtr->IsSparse())
+        {
+            LogicError("Sparse NDArrayView cannot be serialized into a vector.");
+        }
+
+        auto numElements = viewPtr->Shape().TotalSize();
+
+        vector<DictionaryValue> values(numElements);
+
+        NDArrayViewPtr cpuDataViewPtr = viewPtr;
+        if ((viewPtr->Device().Type() != DeviceKind::CPU))
+        {
+            cpuDataViewPtr = MakeSharedObject<NDArrayView>(viewPtr->GetDataType(), viewPtr->Shape(), DeviceDescriptor::CPUDevice());
+            cpuDataViewPtr->CopyFrom(*viewPtr);
+        }
+
+        const T* buffer = cpuDataViewPtr->DataBuffer<T>();
+        for (auto i = 0; i < numElements; ++i)
+        {
+            T v = buffer[i];
+            values[i] = DictionaryValue(v);
+        }
+
+        return values;
+    }
+
+    template <typename T>
+    void DeserializeFromVector(const NDArrayViewPtr& viewPtr, const vector<DictionaryValue>& values)
+    {
+        if (viewPtr->IsSparse())
+        {
+            LogicError("Sparse NDArrayView cannot be deserialized from a vector.");
+        }
+
+        auto numElements = viewPtr->Shape().TotalSize();
+
+        if (values.size() != numElements)
+        {
+            LogicError("Number of elements (%lu) in the deserialized representation does not match the expected value (%lu)",
+                        values.size(), numElements);
+        }
+
+        NDArrayViewPtr cpuDataViewPtr = viewPtr;
+        if ((viewPtr->Device().Type() != DeviceKind::CPU))
+        {
+            cpuDataViewPtr = MakeSharedObject<NDArrayView>(viewPtr->GetDataType(), viewPtr->Shape(), DeviceDescriptor::CPUDevice());
+        }
+
+        T* buffer = cpuDataViewPtr->WritableDataBuffer<T>();
+        for (auto i = 0; i < numElements; ++i)
+        {
+            buffer[i] = values[i].GetValue<T>();
+        }
+
+        if ((viewPtr->Device().Type() != DeviceKind::CPU))
+        {
+            viewPtr->CopyFrom(*cpuDataViewPtr);
+        }
+    }
+
+    // TODO: we store the type info for every element in the vector, which is extremely redundant.
+    // Instead, it'd be nice to introduce some sort of DictionaryValueVector.
+    vector<DictionaryValue> SerializeToVector(const NDArrayViewPtr& viewPtr)
+    {
+        switch (viewPtr->GetDataType())
+        {
+        case DataType::Float:
+            return SerializeToVector<float>(viewPtr);
+        case DataType::Double:
+            return SerializeToVector<double>(viewPtr);
+        default:
+            LogicError("Unsupported DataType %s", DataTypeName(viewPtr->GetDataType()));
+        }
+    }
+
+    void DeserializeFromVector(const NDArrayViewPtr& viewPtr, const vector<DictionaryValue>& values) 
+    {
+        switch (viewPtr->GetDataType())
+        {
+        case DataType::Float:
+            DeserializeFromVector<float>(viewPtr, values);
+            break;
+        case DataType::Double:
+            DeserializeFromVector<double>(viewPtr, values);
+            break;
+        default:
+            LogicError("Unsupported DataType %s", DataTypeName(viewPtr->GetDataType()));
+        }
+    }
+     
+    template void DictionaryValue::AllocateDataPtr<NDShape>(const NDShape& value);
+    template void DictionaryValue::AllocateDataPtr<vector<DictionaryValue>>(const vector<DictionaryValue>& value);
 }

Source/CNTKv2LibraryDll/Utils.h

@@ -15,245 +15,6 @@ namespace CNTK
     // Forward declarations
     class Dictionary;
 
-    class DictionaryValue
-    {
-    public:
-        enum class Type : unsigned int
-        {
-            None,
-            Bool,
-            SizeT,
-            Double,
-            NDShape,
-            Vector
-        };
-
-        static const char* TypeName(Type type)
-        {
-            if (type == Type::None)
-                return "None";
-            else if (type == Type::Bool)
-                return "Bool";
-            else if (type == Type::SizeT)
-                return "SizeT";
-            else if (type == Type::Double)
-                return "Double";
-            else if (type == Type::NDShape)
-                return "NDShape";
-            else if (type == Type::Vector)
-                return "Vector";
-            else
-                LogicError("Unknown DictionaryValue::Type");
-        }
-
-    public:
-        DictionaryValue()
-            : m_valueType(Type::None)
-        {
-        }
-
-        DictionaryValue(bool value)
-            : m_valueType(GetValueType<bool>())
-        {
-            m_data.m_boolean = value;
-        }
-
-        DictionaryValue(size_t value)
-            : m_valueType(GetValueType<size_t>())
-        {
-            m_data.m_sizeT = value;
-        }
-
-        DictionaryValue(double value)
-            : m_valueType(GetValueType<double>())
-        {
-            m_data.m_double = value;
-        }
-
-        template <typename T>
-        DictionaryValue(const T& value)
-            : m_valueType(GetValueType<T>())
-        {
-            static_assert(std::is_same<T, NDShape>::value ||
-                std::is_same<T, std::vector<DictionaryValue>>::value,
-                "Unsupported ValueType");
-
-            AllocateDataPtr(value);
-        }
-
-        DictionaryValue(const DictionaryValue& other)
-            : m_valueType(Type::Bool)
-        {
-            // The m_valueType must hvae been set to a non-ptr type to prevent an attempt to interpret
-            // the underlying underlying uninitialized value as a ptr and free it.
-            *this = other;
-        }
-
-        DictionaryValue& operator=(const DictionaryValue& other)
-        {
-            if (this != &other)
-            {
-                FreeDataPtr();
-
-                m_valueType = other.m_valueType;
-                m_data = other.m_data;
-
-                if (other.m_valueType == Type::NDShape)
-                    AllocateDataPtr(other.GetValue<NDShape>());
-                else if (other.m_valueType == Type::Vector)
-                    AllocateDataPtr(other.GetValue<std::vector<DictionaryValue>>());
-            }
-
-            return *this;
-        }
-
-        ~DictionaryValue()
-        {
-            FreeDataPtr();
-        }
-
-        template <typename T, typename std::enable_if<std::is_same<T, bool>::value>::type* = nullptr>
-        const T& GetValue() const
-        {
-            VerifyType<T>();
-            return m_data.m_boolean;
-        }
-
-        template <typename T, typename std::enable_if<std::is_same<T, size_t>::value>::type* = nullptr>
-        const T& GetValue() const
-        {
-            VerifyType<T>();
-            return m_data.m_sizeT;
-        }
-
-        template <typename T, typename std::enable_if<std::is_same<T, double>::value>::type* = nullptr>
-        const T& GetValue() const
-        {
-            VerifyType<T>();
-            return m_data.m_double;
-        }
-
-        template <typename T, typename std::enable_if<std::is_same<T, NDShape>::value || std::is_same<T, std::vector<DictionaryValue>>::value>::type* = nullptr>
-        const T& GetValue() const
-        {
-            VerifyType<T>();
-            return *(reinterpret_cast<T*>(m_data.m_ptr));
-        }
-
-        bool HasValue() const
-        {
-            return m_valueType != Type::None;
-        }
-
-        Type ValueType() const
-        {
-            return m_valueType;
-        }
-
-    private:
-        template <typename T>
-        static Type GetValueType()
-        {
-            static_assert(std::is_same<T, bool>::value ||
-                std::is_same<T, size_t>::value ||
-                std::is_same<T, double>::value ||
-                std::is_same<T, NDShape>::value ||
-                std::is_same<T, std::vector<DictionaryValue>>::value ||
-                std::is_same<T, CNTK::Dictionary>::value,
-                "Unsupported ValueType");
-
-            if (std::is_same<T, bool>::value)
-                return Type::Bool;
-            else if (std::is_same<T, size_t>::value)
-                return Type::SizeT;
-            else if (std::is_same<T, double>::value)
-                return Type::Double;
-            else if (std::is_same<T, NDShape>::value)
-                return Type::NDShape;
-            else if (std::is_same<T, std::vector<DictionaryValue>>::value)
-                return Type::Vector;
-        }
-
-        template <typename T>
-        void VerifyType() const
-        {
-            if (GetValueType<T>() != m_valueType)
-                RuntimeError("Reading a DictionaryValue as the wrong type; Reading as type %s when actual type is %s", typeid(T).name(), DictionaryValue::TypeName(m_valueType));
-        }
-
-        template <typename T>
-        void AllocateDataPtr(const T& value)
-        {
-            static_assert(std::is_same<T, NDShape>::value || std::is_same<T, std::vector<DictionaryValue>>::value, "AllocateDataPtr called with invalid type");
-            m_data.m_ptr = new T(value);
-        }
-
-        template <typename T>
-        void FreePtrAsType()
-        {
-            T* typedPtr = reinterpret_cast<T*>(m_data.m_ptr);
-            delete typedPtr;
-
-            m_data.m_ptr = nullptr;
-        }
-
-        void FreeDataPtr()
-        {
-            if (m_valueType == Type::NDShape)
-                FreePtrAsType<NDShape>();
-            else if (m_valueType == Type::Vector)
-                FreePtrAsType<std::vector<DictionaryValue>>();
-        }
-
-    private:
-        Type m_valueType;
-
-        union ValueData
-        {
-            bool m_boolean;
-            size_t m_sizeT;
-            double m_double;
-            void* m_ptr;
-        } m_data;
-    };
-
-    class Dictionary
-    {
-    public:
-        Dictionary();
-        ~Dictionary();
-
-        // Disallow copy contruction and assignment
-        Dictionary(const Dictionary&) = delete; Dictionary& operator=(const Dictionary&) = delete;
-
-        Dictionary(Dictionary&& other);
-        Dictionary& operator=(Dictionary&& other);
-
-        DictionaryValue& operator[](const std::wstring& key)
-        {
-            return operator[](key.c_str());
-        }
-
-        DictionaryValue& operator[](const wchar_t* key);
-
-        DictionaryValue operator[](const std::wstring& key) const
-        {
-            return operator[](key.c_str());
-        }
-
-        DictionaryValue operator[](const wchar_t* key) const;
-
-        bool Contains(const std::wstring& key) const
-        {
-            return Contains(key.c_str());
-        }
-
-        bool Contains(const wchar_t* key) const;
-
-    private:
-        std::unordered_map<std::wstring, DictionaryValue>* m_dictionaryData;
-    };
-
     // Helper to get the size of an element of the specified DataType
     inline size_t ElementSize(DataType dataType)
     {
@@ -363,4 +124,8 @@ namespace CNTK
     {
         return var.IsInput() && var.IsSparse();
     }
+
+    std::vector<DictionaryValue> SerializeToVector(const NDArrayViewPtr& viewPtr);
+
+    void DeserializeFromVector(const NDArrayViewPtr& viewPtr, const std::vector<DictionaryValue>& values);
 }