Add layers.Normalization.

src/TensorFlowNET.Core/Keras/ArgsDefinition/Normalization/NormalizationArgs.cs

@@ -0,0 +1,15 @@
+using Newtonsoft.Json;
+
+namespace Tensorflow.Keras.ArgsDefinition;
+
+public class NormalizationArgs : PreprocessingLayerArgs
+{
+    [JsonProperty("axis")]
+    public Axis? Axis { get; set; }
+    [JsonProperty("mean")]
+    public float? Mean { get; set; }
+    [JsonProperty("variance")]
+    public float? Variance { get; set; }
+    
+    public bool Invert { get; set; } = false;
+}

src/TensorFlowNET.Core/Keras/Layers/ILayer.cs

@@ -23,5 +23,6 @@ namespace Tensorflow.Keras
         TensorShapeConfig BuildInputShape { get; }
         TF_DataType DType { get; }
         int count_params();
+        void adapt(Tensor data, int? batch_size = null, int? steps = null);
     }
 }

src/TensorFlowNET.Core/Keras/Layers/ILayersApi.cs

@@ -156,6 +156,7 @@ namespace Tensorflow.Keras.Layers
            IInitializer beta_initializer = null,
            IInitializer gamma_initializer = null);
 
+        public ILayer Normalization(int? axis = -1, float? mean = null, float? variance = null, bool invert = false);
         public ILayer LeakyReLU(float alpha = 0.3f);
 
         public ILayer LSTM(int units,

src/TensorFlowNET.Core/NumPy/ShapeHelper.cs

@@ -9,6 +9,9 @@ namespace Tensorflow.NumPy
     {
         public static long GetSize(Shape shape)
         {
+            if (shape.IsNull)
+                return 0;
+
             // scalar
             if (shape.ndim == 0)
                 return 1;

src/TensorFlowNET.Core/Operations/NnOps/RNNCell.cs

@@ -159,5 +159,10 @@ namespace Tensorflow
         }
 
         public Trackable GetTrackable() { throw new NotImplementedException(); }
+
+        public void adapt(Tensor data, int? batch_size = null, int? steps = null)
+        {
+            throw new NotImplementedException();
+        }
     }
 }

src/TensorFlowNET.Core/tensorflow.cs

@@ -16,6 +16,7 @@
 
 using Serilog;
 using Serilog.Core;
+using System.Reflection;
 using System.Threading;
 using Tensorflow.Contexts;
 using Tensorflow.Eager;
@@ -52,7 +53,29 @@ namespace Tensorflow
         ThreadLocal<IEagerRunner> _runner = new ThreadLocal<IEagerRunner>(() => new EagerRunner());
         public IEagerRunner Runner => _runner.Value;
 
-        public IKerasApi keras { get; set; }
+        private IKerasApi _keras;
+        public IKerasApi keras 
+        { 
+            get
+            {
+                if (_keras != null)
+                {
+                    return _keras;
+                }
+
+                var k = Assembly.Load("Tensorflow.Keras");
+                var cls = k.GetTypes().FirstOrDefault(x => x.GetInterfaces().Contains(typeof(IKerasApi)));
+                if (cls != null)
+                {
+                    _keras = Activator.CreateInstance(cls) as IKerasApi;
+                    return _keras;
+                }
+                else
+                {
+                    throw new Exception("Can't find keras library.");
+                }
+            }
+        }
 
         public tensorflow()
         {

src/TensorFlowNET.Keras/Engine/Layer.cs

@@ -344,5 +344,10 @@ namespace Tensorflow.Keras.Engine
 
         public virtual IKerasConfig get_config()
             => args;
+
+        public virtual void adapt(Tensor data, int? batch_size = null, int? steps = null)
+        {
+            
+        }
     }
 }

src/TensorFlowNET.Keras/KerasInterface.cs

@@ -20,10 +20,6 @@ namespace Tensorflow.Keras
     {
         private static KerasInterface _instance = null;
         private static readonly object _lock = new object();  
-        private KerasInterface()
-        {
-            Tensorflow.Binding.tf.keras = this;
-        }
 
         public static KerasInterface Instance
         {

src/TensorFlowNET.Keras/Layers/LayersApi.cs

@@ -872,5 +872,14 @@ namespace Tensorflow.Keras.Layers
                 Sparse = sparse,
                 CountWeights = count_weights
             });
+
+        public ILayer Normalization(int? axis = -1, float? mean = null, float? variance = null, bool invert = false)
+            => new Normalization(new NormalizationArgs
+            {
+                Axis = axis,
+                Mean = mean,
+                Variance = variance,
+                Invert = invert
+            });
     }
 }

src/TensorFlowNET.Keras/Layers/Normalization/Normalization.cs

@@ -0,0 +1,173 @@
+/*****************************************************************************
+   Copyright 2023 Haiping Chen. All Rights Reserved.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+******************************************************************************/
+
+using Tensorflow.Keras.ArgsDefinition;
+
+namespace Tensorflow.Keras.Layers
+{
+    public class Normalization : PreprocessingLayer
+    {
+        NormalizationArgs _args;
+
+        int[] axis;
+        int[] _reduce_axis;
+        IVariableV1 adapt_mean, adapt_variance, count;
+        Tensor mean, variance;
+        Shape _broadcast_shape;
+        float? input_mean, input_variance;
+        TF_DataType compute_dtype = tf.float32;
+
+        public Normalization(NormalizationArgs args) : base(args)
+        {
+            _args = args;
+            if (args.Axis == null)
+            {
+                axis = new int[0];
+            }
+            else
+            {
+                axis = args.Axis.axis;
+            }
+            input_mean = args.Mean;
+            input_variance = args.Variance;
+        }
+
+        public override void build(Shape input_shape)
+        {
+            base.build(input_shape);
+            var ndim = input_shape.ndim;
+            foreach (var (idx, x) in enumerate(axis))
+                if (x < 0)
+                    axis[idx] = ndim + x;
+
+            var _keep_axis = axis.Select(d => d >= 0 ? d : d + ndim).ToArray();
+            _reduce_axis = range(ndim).Where(d => !_keep_axis.Contains(d)).ToArray();
+            var _reduce_axis_mask = range(ndim).Select(d => _keep_axis.Contains(d) ? 0 : 1).ToArray();
+            // Broadcast any reduced axes.
+            _broadcast_shape = new Shape(range(ndim).Select(d => _keep_axis.Contains(d) ? input_shape.dims[d] : 1).ToArray());
+            var mean_and_var_shape = _keep_axis.Select(d => input_shape.dims[d]).ToArray();
+
+            var param_dtype = DType == TF_DataType.DtInvalid ? TF_DataType.TF_FLOAT : DType;
+            var param_shape = input_shape;
+
+            if(input_mean == null)
+            {
+                adapt_mean = add_weight("mean",
+                    mean_and_var_shape,
+                    dtype: tf.float32,
+                    initializer: tf.zeros_initializer,
+                    trainable: false);
+
+                adapt_variance = add_weight("variance",
+                    mean_and_var_shape,
+                    dtype: tf.float32,
+                    initializer: tf.ones_initializer,
+                    trainable: false);
+
+                count = add_weight("count",
+                    Shape.Scalar,
+                    dtype: tf.int64,
+                    initializer: tf.zeros_initializer,
+                    trainable: false);
+
+                finalize_state();
+            }
+            else
+            {
+                mean = input_mean * np.ones(mean_and_var_shape);
+                variance = input_variance * np.ones(mean_and_var_shape);
+                mean = tf.reshape(mean, _broadcast_shape);
+                variance = tf.reshape(variance, _broadcast_shape);
+                mean = tf.cast(mean, compute_dtype);
+                variance = tf.cast(variance, compute_dtype);
+            }
+        }
+
+        public override void reset_state()
+        {
+            if (input_mean != null && !built)
+            {
+                return;
+            }
+            adapt_mean.assign(tf.zeros_like(adapt_mean.AsTensor()));
+            adapt_variance.assign(tf.ones_like(adapt_variance.AsTensor()));
+            count.assign(tf.zeros_like(count.AsTensor()));
+        }
+
+        public override void finalize_state()
+        {
+            if (input_mean != null && !built)
+            {
+                return;
+            }
+            mean = tf.reshape(adapt_mean.AsTensor(), _broadcast_shape);
+            variance = tf.reshape(adapt_variance.AsTensor(), _broadcast_shape);
+        }
+
+        public override void update_state(Tensor data)
+        {
+            data = tf.cast(data, adapt_mean.dtype);
+            var (batch_mean, batch_variance) = tf.nn.moments(data, axes: _reduce_axis);
+            var batch_shape = tf.shape(data, out_type: count.dtype);
+
+            var batch_count = constant_op.constant(1L);
+            if (_reduce_axis != null)
+            {
+                var batch_reduce_shape = tf.gather(batch_shape,  constant_op.constant(_reduce_axis));
+                batch_count = tf.reduce_prod(batch_reduce_shape);
+            }
+            var total_count = batch_count + count.AsTensor();
+            var batch_weight = tf.cast(batch_count, dtype: compute_dtype) / tf.cast(
+                total_count, dtype: compute_dtype);
+            var existing_weight = 1.0 - batch_weight;
+            var total_mean = adapt_mean.AsTensor() * existing_weight + batch_mean * batch_weight;
+
+            var total_variance = (
+                    adapt_variance.AsTensor() + tf.square(adapt_mean.AsTensor() - total_mean)
+                ) * existing_weight + (
+                    batch_variance + tf.square(batch_mean - total_mean)
+                ) * batch_weight;
+            adapt_mean.assign(total_mean);
+            adapt_variance.assign(total_variance);
+            count.assign(total_count);
+        }
+
+        public override Shape ComputeOutputShape(Shape input_shape)
+        {
+            return input_shape;
+        }
+
+        public override void adapt(Tensor data, int? batch_size = null, int? steps = null)
+        {
+            base.adapt(data, batch_size: batch_size, steps: steps);
+        }
+
+        protected override Tensors Call(Tensors inputs, Tensor state = null, bool? training = null)
+        {
+            if (_args.Invert)
+            {
+                return mean + (
+                    inputs * tf.maximum(tf.sqrt(variance), keras.backend.epsilon())
+            );
+            }
+            else
+            {
+                return (inputs - mean) / tf.maximum(
+                    tf.sqrt(variance), keras.backend.epsilon());
+            }
+        }
+    }
+}

src/TensorFlowNET.Keras/Layers/Preprocessing/PreprocessingLayer.cs

@@ -3,14 +3,95 @@ using System.Collections.Generic;
 using System.Text;
 using Tensorflow.Keras.ArgsDefinition;
 using Tensorflow.Keras.Engine;
+using Tensorflow.Keras.Engine.DataAdapters;
 
 namespace Tensorflow.Keras.Layers
 {
     public class PreprocessingLayer : Layer
     {
+        bool _is_compiled;
+        bool _is_adapted;
+        IVariableV1 _steps_per_execution;
+        PreprocessingLayerArgs _args;
         public PreprocessingLayer(PreprocessingLayerArgs args) : base(args)
         {
+            _args = args;
+        }
+
+        public override void adapt(Tensor data, int? batch_size = null, int? steps = null)
+        {
+            if (!_is_compiled)
+            {
+                compile();
+            }
+
+            if (built)
+            {
+                reset_state();
+            }
+
+            var data_handler = new DataHandler(new DataHandlerArgs
+            {
+                X = new Tensors(data),
+                BatchSize = _args.BatchSize,
+                Epochs = 1,
+                StepsPerExecution = _steps_per_execution
+            });
+
+            foreach (var (epoch, iterator) in data_handler.enumerate_epochs())
+            {
+                foreach (var _ in data_handler.steps())
+                {
+                    run_step(iterator);
+                }
+            }
+            finalize_state();
+            _is_adapted = true;
+        }
+
+        private void run_step(OwnedIterator iterator)
+        {
+            var data = iterator.next();
+            _adapt_maybe_build(data[0]);
+            update_state(data[0]);
+        }
+
+        public virtual void reset_state()
+        {
+
+        }
+
+        public virtual void finalize_state()
+        {
+
+        }
+
+        public virtual void update_state(Tensor data)
+        {
+
+        }
+
+        private void _adapt_maybe_build(Tensor data)
+        {
+            if (!built)
+            {
+                var data_shape = data.shape;
+                var data_shape_nones = Enumerable.Range(0, data.ndim).Select(x => -1).ToArray();
+                _args.BatchInputShape = BatchInputShape ?? new Shape(data_shape_nones);
+                build(data_shape);
+                built = true;
+            }
+        }
+
+        public void compile(bool run_eagerly = false, int steps_per_execution = 1)
+        {
+            _steps_per_execution = tf.Variable(
+                steps_per_execution,
+                dtype: tf.int64,
+                aggregation: VariableAggregation.OnlyFirstReplica
+            );
 
+            _is_compiled = true;
         }
     }
 }

test/TensorFlowNET.Keras.UnitTest/EagerModeTestBase.cs

@@ -1,5 +1,6 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using System;
+using Tensorflow;
 using Tensorflow.Keras;
 using static Tensorflow.Binding;
 

test/TensorFlowNET.Keras.UnitTest/Layers/LayersTest.cs

@@ -177,6 +177,55 @@ namespace TensorFlowNET.Keras.UnitTest
             Assert.IsTrue(output[0].numpy().Equals(new[] { -0.99998f, 0.99998f }));
         }
 
+        /// <summary>
+        /// https://www.tensorflow.org/api_docs/python/tf/keras/layers/Normalization
+        /// </summary>
+        [TestMethod]
+        public void Normalization()
+        {
+            // Calculate a global mean and variance by analyzing the dataset in adapt().
+            var adapt_data = np.array(new[] { 1f, 2f, 3f, 4f, 5f });
+            var input_data = np.array(new[] { 1f, 2f, 3f });
+            var layer = tf.keras.layers.Normalization(axis: null);
+            layer.adapt(adapt_data);
+            var x = layer.Apply(input_data);
+            Assert.AreEqual(x.numpy(), new[] { -1.4142135f, -0.70710677f, 0f });
+
+            // Calculate a mean and variance for each index on the last axis.
+            adapt_data = np.array(new[,]
+            {
+                { 0, 7, 4 },
+                { 2, 9, 6 },
+                { 0, 7, 4 },
+                { 2, 9, 6 }
+            }, dtype: tf.float32);
+            input_data = np.array(new[,] { { 0, 7, 4 } }, dtype: tf.float32);
+            layer = tf.keras.layers.Normalization(axis: -1);
+            layer.adapt(adapt_data);
+            x = layer.Apply(input_data);
+            Equal(x.numpy().ToArray<float>(), new[] { -1f, -1f, -1f });
+
+            // Pass the mean and variance directly.
+            input_data = np.array(new[,] { { 1f }, { 2f }, { 3f } }, dtype: tf.float32);
+            layer = tf.keras.layers.Normalization(mean: 3f, variance: 2f);
+            x = layer.Apply(input_data);
+            Equal(x.numpy().ToArray<float>(), new[] { -1.4142135f, -0.70710677f, 0f });
+
+            // Use the layer to de-normalize inputs (after adapting the layer).
+            adapt_data = np.array(new[,]
+            {
+                { 0, 7, 4 },
+                { 2, 9, 6 },
+                { 0, 7, 4 },
+                { 2, 9, 6 }
+            }, dtype: tf.float32);
+            input_data = np.array(new[,] { { 1, 2, 3 } }, dtype: tf.float32);
+            layer = tf.keras.layers.Normalization(axis: -1, invert: true);
+            layer.adapt(adapt_data);
+            x = layer.Apply(input_data);
+            Equal(x.numpy().ToArray<float>(), new[] { -2f, -10f, -8f });
+        }
+
         /// <summary>
         /// https://www.tensorflow.org/api_docs/python/tf/keras/layers/CategoryEncoding
         /// </summary>