[Image Classification API] No evaluation when batchSize parameter > # of instances in dataset

System information

OS version/distro: Windows 10
.NET Version (eg., dotnet --info): .NET Core 2.2
ML.NET Version: 1.4.0-preview

Issue

What did you do?

Tried to train an image classification model using the Image Classification API. The value set for batchSize parameter is 300. Meanwhile then number of data instances in the test set is 182.

What happened?

No evaluation takes place. 0 batches are processed.

What did you expect?

The model to train and for it to evaluate the number of instances provided. In this case since the number of data instances is less than the amount set for the batchSize parameter, it would process 1 batch instead of 0.

The model to evaluate

Source code / logs

Pipeline:

var trainingPipeline =
                mapLabelTransform
               .Append(mlContext.Model.ImageClassification(
                   featuresColumnName: "ImagePath",
                   labelColumnName: "LabelAsKey",
                   arch: ImageClassificationEstimator.Architecture.ResnetV2101,
                   epoch: 100,
                   batchSize: 300,
                   testOnTrainSet: false,
                   metricsCallback: (metrics) => Console.WriteLine(metrics),
                   validationSet: transformedTestData,
                   reuseTrainSetBottleneckCachedValues: true,
                   reuseValidationSetBottleneckCachedValues: true));

Output:

Number of rows 182
Phase: Training, Dataset used: Validation, Batch Processed Count:   0, Epoch:  93, Accuracy:        NaN
Phase: Training, Dataset used: Validation, Batch Processed Count:   0, Epoch:  94, Accuracy:        NaN
Phase: Training, Dataset used: Validation, Batch Processed Count:   0, Epoch:  95, Accuracy:        NaN
Phase: Training, Dataset used: Validation, Batch Processed Count:   0, Epoch:  96, Accuracy:        NaN
Phase: Training, Dataset used: Validation, Batch Processed Count:   0, Epoch:  97, Accuracy:        NaN
Phase: Training, Dataset used: Validation, Batch Processed Count:   0, Epoch:  98, Accuracy:        NaN
Phase: Training, Dataset used: Validation, Batch Processed Count:   0, Epoch:  99, Accuracy:        NaN

When the batchSize is set equal to the number of rows (in this case 182), this is the output:

Phase: Training, Dataset used: Validation, Batch Processed Count:   1, Epoch:  95, Accuracy:          1
Phase: Training, Dataset used: Validation, Batch Processed Count:   1, Epoch:  96, Accuracy:          1
Phase: Training, Dataset used: Validation, Batch Processed Count:   1, Epoch:  97, Accuracy:          1
Phase: Training, Dataset used: Validation, Batch Processed Count:   1, Epoch:  98, Accuracy:          1
Phase: Training, Dataset used: Validation, Batch Processed Count:   1, Epoch:  99, Accuracy:          1

dotnet / machinelearning