[BUG Report]: System.NullReferenceException during fit()

[avipreshel]

Description

I have a pretty plain code with a custom loss function. The code throws a null exception right at the beginning

`using Tensorflow;
using Tensorflow.Keras.Losses;
using Tensorflow.Keras.Metrics;
using Tensorflow.Keras.Optimizers;
using Tensorflow.NumPy;
using Tensorflow.Operations.Initializers;
using static Tensorflow.Binding;
using static Tensorflow.KerasApi;

namespace KerasDotNet
{
internal class WeightedF1Loss : ILossFunc
{
public string Reduction => throw new NotImplementedException();

    public string Name => nameof(WeightedF1Loss);

    Tensor _beta;
    Tensor _epsilon;
    public WeightedF1Loss(float beta)
    {
        _beta = tf.constant(beta, dtype: TF_DataType.TF_FLOAT);
        _epsilon = tf.constant(float.Epsilon, dtype: TF_DataType.TF_FLOAT);
    }

    public Tensor Call(Tensor y_true, Tensor y_pred, Tensor sample_weight)
    {
        y_pred = tf.cast(y_pred >= 0.7f, TF_DataType.TF_FLOAT);

        var tp = tf.reduce_sum(y_true * y_pred);
        var fp = tf.reduce_sum((1 - y_true) * y_pred);
        var fn = tf.reduce_sum(y_true * (1 - y_pred));
        var precision = tp / (tp + fp + _epsilon);
        var recall = tp / (tp + fn + _epsilon);
        var f1_score = (tf.square(_beta) + 1) * (precision * recall) / (tf.square(_beta) * precision + recall + _epsilon);
        var res = 1 - f1_score;
        return res;
    }
}

internal class Program
{
    static void Main(string[] args)
    {
        //tf.enable_eager_execution(); ==> Runs the same with or without this line
        var x = np.array(new float[,] { { 1, 1, 1 }, { 2, 2, 2 }, { 1, 0, 3 }, { 1, 1, 3 } });
        var y = np.array(new float[,] { { 0 }, { 1 }, { 1 }, { 0 } });

        var loss = new WeightedF1Loss(0.2f);
        var inputs = keras.Input(shape: 3);
        var l1 = keras.layers.Dense(2, activation: "relu").Apply(inputs);
        var outputs = keras.layers.Dense(1, activation: "sigmoid").Apply(l1);

        var model = keras.Model(inputs, outputs);
        model.compile(optimizer: new Adam(), loss: loss, new[] { "precision", "recall" });

        model.summary();

        model.fit(x, y, batch_size: 1, epochs: 10);


    }
}

}`

The exception is thrown from GetDataType() since "data" is null.

Stack trace dump:

Tensorflow.Binding.dll!Tensorflow.Binding.GetDataType(object data) Line 615 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.ops.convert_to_tensor(object value, Tensorflow.TF_DataType dtype, string name, bool as_ref, Tensorflow.TF_DataType preferred_dtype, Tensorflow.Contexts.Context ctx) Line 353 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.tensorflow.convert_to_tensor(object value, Tensorflow.TF_DataType dtype, string name, Tensorflow.TF_DataType preferred_dtype) Line 2038 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.Eager.EagerRunner.AddInputToOp(object inputs, bool add_type_attr, Tensorflow.OpDef.Types.ArgDef input_arg, System.Collections.Generic.List flattened_attrs, System.Collections.Generic.List<Tensorflow.Tensor> flattened_inputs, Tensorflow.Eager.SafeEagerOpHandle op, Tensorflow.Status status) Line 450 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.Eager.EagerRunner.TFE_FastPathExecute(Tensorflow.FastPathOpExecInfo op_exec_info) Line 319 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.Contexts.Context.ExecEagerAction(string OpType, string Name, Tensorflow.ExecuteOpArgs args) Line 494 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.Contexts.Context.ExecuteOp(string opType, string name, Tensorflow.ExecuteOpArgs args) Line 534 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.gen_training_ops.resource_apply_adam(Tensorflow.Tensor var, Tensorflow.Tensor m, Tensorflow.Tensor v, Tensorflow.Tensor beta1_power, Tensorflow.Tensor beta2_power, Tensorflow.Tensor lr, Tensorflow.Tensor beta1, Tensorflow.Tensor beta2, Tensorflow.Tensor epsilon, Tensorflow.Tensor grad, bool use_locking, bool use_nesterov, string name) Line 7 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Optimizers.Adam._resource_apply_dense(Tensorflow.IVariableV1 var, Tensorflow.Tensor grad, System.Collections.Generic.Dictionary<Tensorflow.Keras.Optimizers.DeviceDType, System.Collections.Generic.Dictionary<string, Tensorflow.Tensor>> apply_state) Line 79 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Optimizers.OptimizerV2.apply_grad_to_update_var(Tensorflow.IVariableV1 var, Tensorflow.Tensor grad, System.Collections.Generic.Dictionary<Tensorflow.Keras.Optimizers.DeviceDType, System.Collections.Generic.Dictionary<string, Tensorflow.Tensor>> apply_state) Line 108 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Optimizers.OptimizerV2._distributed_apply.AnonymousMethod__1(Tensorflow.ops.NameScope ) Line 130 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.Binding.tf_with<Tensorflow.ops.NameScope>(Tensorflow.ops.NameScope py, System.Action<Tensorflow.ops.NameScope> action) Line 256 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Optimizers.OptimizerV2._distributed_apply.AnonymousMethod__0(Tensorflow.ops.NameScope ) Line 133 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.Binding.tf_with<Tensorflow.ops.NameScope>(Tensorflow.ops.NameScope py, System.Action<Tensorflow.ops.NameScope> action) Line 256 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Optimizers.OptimizerV2._distributed_apply(System.Collections.Generic.IEnumerable<(Tensorflow.Tensor, Tensorflow.IVariableV1)> grads_and_vars, string name, System.Collections.Generic.Dictionary<Tensorflow.Keras.Optimizers.DeviceDType, System.Collections.Generic.Dictionary<string, Tensorflow.Tensor>> _apply_state) Line 134 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Optimizers.OptimizerV2.apply_gradients.AnonymousMethod__1(Tensorflow.ops.NameScope ) Line 73 C# Symbols loaded.
Tensorflow.Binding.dll!Tensorflow.Binding.tf_with<Tensorflow.ops.NameScope, Tensorflow.Operation>(Tensorflow.ops.NameScope py, System.Func<Tensorflow.ops.NameScope, Tensorflow.Operation> action) Line 263 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Optimizers.OptimizerV2.apply_gradients(System.Collections.Generic.IEnumerable<(Tensorflow.Tensor, Tensorflow.IVariableV1)> grads_and_vars, string name, bool experimental_aggregate_gradients) Line 75 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Engine.Model._minimize(Tensorflow.Gradients.GradientTape tape, Tensorflow.Keras.Engine.IOptimizer optimizer, Tensorflow.Tensor loss, System.Collections.Generic.List<Tensorflow.IVariableV1> trainable_variables) Line 897 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Engine.Model.train_step(Tensorflow.Keras.Engine.DataAdapters.DataHandler data_handler, Tensorflow.Tensors x, Tensorflow.Tensors y) Line 877 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Engine.Model.train_step_function(Tensorflow.Keras.Engine.DataAdapters.DataHandler data_handler, Tensorflow.OwnedIterator iterator) Line 856 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Engine.Model.FitInternal(Tensorflow.Keras.Engine.DataAdapters.DataHandler data_handler, int epochs, int verbose, System.Collections.Generic.List<Tensorflow.Keras.Engine.ICallback> callbackList, (Tensorflow.NumPy.NDArray, Tensorflow.NumPy.NDArray)? validation_data, System.Func<Tensorflow.Keras.Engine.DataAdapters.DataHandler, Tensorflow.OwnedIterator, System.Collections.Generic.Dictionary<string, float>> train_step_func) Line 660 C# Symbols loaded.
Tensorflow.Keras.dll!Tensorflow.Keras.Engine.Model.fit(Tensorflow.NumPy.NDArray x, Tensorflow.NumPy.NDArray y, int batch_size, int epochs, int verbose, System.Collections.Generic.List<Tensorflow.Keras.Engine.ICallback> callbacks, float validation_split, (Tensorflow.NumPy.NDArray val_x, Tensorflow.NumPy.NDArray val_y)? validation_data, bool shuffle, int initial_epoch, int max_queue_size, int workers, bool use_multiprocessing) Line 474 C# Symbols loaded.
KerasDotNet.dll!KerasDotNet.Program.Main(string[] args) Line 62 C# Symbols loaded.

Reproduction Steps

Run the code in the snipped as it's A self contained code (does not ready any files or configuration).

• TensorFlow.NET v0.110.4
• TensorFlow.Keras v0.11.4
• SciSharp.TensorFlow.Redist-Windows-GPU v2.10.3
• Dotnet 7
• Visual Studio 2022

System specs:
Windows 10 x64
RTX 2080 Super

Known Workarounds

None

Configuration and Other Information

No response

[PavelBakurov]

Same here

[ThirdStreetDev]

I'm having the same problem.

[PederHP]

I have the same problem but in a slightly different situation where I get it for batch sizes greater than 1, but epoch counts greater than 1 do not trigger it.