Package ai.djl.training.dataset

Class Batch

  • All Implemented Interfaces:
    java.lang.AutoCloseable
    public class Batch
extends java.lang.Object
implements java.lang.AutoCloseable
    A Batch is used to hold multiple items (data and label pairs) from a Dataset.

    When training and performing inference, it is often more efficient to run multiple items through a network simultaneously rather than one at a time. For this reason, much of the API is oriented around the Batch class.

    In a Batch, data and label are each an NDList. The data NDList represents the data for each input in the batch. The number of NDArrays in the NDList is based on the number of different kinds of inputs, not the batch size. Similarly, the label NDList represents the labels for each kind of output.

    For example, an Image Question and Answer dataset has two inputs: an image and a question. In this case, the data in the Batch will be an NDList containing an NCHW image NDArray and an NTC question NDArray. The label will be an NDList containing only an NTC answer NDArray.

    In order to differentiate a batch vs a single record (despite them both consisting of two NDLists), we have the Batch and the Record respectively.

    • Constructor Summary

      Constructors 
      Constructor Description
      Batch​(NDManager manager, NDList data, NDList labels, int size, Batchifier dataBatchifier, Batchifier labelBatchifier, long progress, long progressTotal)
      Creates a new instance of Batch with the given manager, data and labels.
      Batch​(NDManager manager, NDList data, NDList labels, int size, Batchifier dataBatchifier, Batchifier labelBatchifier, long progress, long progressTotal, java.util.List<?> indices)
      Creates a new instance of Batch with the given manager, data and labels.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void close()
      NDList getData()
      Gets the data of this Batch.
      java.util.List<?> getIndices()
      Returns the indices used to extract the data and labels from the Dataset.
      NDList getLabels()
      Gets the labels corresponding to the data of this Batch.
      NDManager getManager()
      Gets the NDManager that is attached to this Batch.
      long getProgress()
      Returns the progress of the batch if it is part of some kind of iteration like a dataset iteration.
      long getProgressTotal()
      Returns the total or end value for the progress of the batch if it is part of some kind of iteration like a dataset iteration.
      int getSize()
      Returns the batchSize.
      Batch[] split​(Device[] devices, boolean evenSplit)
      Splits the data and labels in the Batch across the given devices.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • Batch

        public Batch​(NDManager manager,
             NDList data,
             NDList labels,
             int size,
             Batchifier dataBatchifier,
             Batchifier labelBatchifier,
             long progress,
             long progressTotal)
        Creates a new instance of Batch with the given manager, data and labels.
        Parameters:
        manager - the manager for the Batch
        data - the NDList containing the data
        labels - the NDList containing the labels
        size - (batchSize) the number of Records in the batch
        dataBatchifier - the Batchifier that is used to split data
        labelBatchifier - the Batchifier that is used for split labels
        progress - the progress of the batch if it is part of some kind of iteration like a dataset iteration. Returns 0 if there is no iteration.
        progressTotal - the total or end value for the progress of the batch if it is part of

      • Batch

        public Batch​(NDManager manager,
             NDList data,
             NDList labels,
             int size,
             Batchifier dataBatchifier,
             Batchifier labelBatchifier,
             long progress,
             long progressTotal,
             java.util.List<?> indices)
        Creates a new instance of Batch with the given manager, data and labels.
        Parameters:
        manager - the manager for the Batch
        data - the NDList containing the data
        labels - the NDList containing the labels
        size - (batchSize) the number of Records in the batch
        dataBatchifier - the Batchifier that is used to split data
        labelBatchifier - the Batchifier that is used for split labels
        progress - the progress of the batch if it is part of some kind of iteration like a dataset iteration. Returns 0 if there is no iteration.
        progressTotal - the total or end value for the progress of the batch if it is part of
        indices - the indices used to extract the data and labels

    • Method Detail

      • getManager

        public NDManager getManager()
        Gets the NDManager that is attached to this Batch.
        Returns:
        the NDManager attached to this Batch

      • getData

        public NDList getData()
        Gets the data of this Batch.
        Returns:
        an NDList that contains the data

      • getLabels

        public NDList getLabels()
        Gets the labels corresponding to the data of this Batch.
        Returns:
        an NDList that contains the labels

      • getSize

        public int getSize()
        Returns the batchSize.
        Returns:
        the batchSize or number of Records in the batch

      • getProgress

        public long getProgress()
        Returns the progress of the batch if it is part of some kind of iteration like a dataset iteration.
        Returns:
        the progress of the batch if it is part of some kind of iteration like a dataset iteration. Returns 0 if there is no iteration

      • getProgressTotal

        public long getProgressTotal()
        Returns the total or end value for the progress of the batch if it is part of some kind of iteration like a dataset iteration.
        Returns:
        the total or end value for the progress of the batch if it is part of some kind of iteration like a dataset iteration. Returns 0 if there is no iteration

      • close

        public void close()
        Specified by:
        close in interface java.lang.AutoCloseable

      • split

        public Batch[] split​(Device[] devices,
                     boolean evenSplit)
        Splits the data and labels in the Batch across the given devices.

        if evenSplit is false, that last device may have a smaller batch than the rest.

        Parameters:
        devices - an array of Device across which the data must be split
        evenSplit - whether each slice must have the same shape
        Returns:
        an array of Batch, each of which corresponds to a Device

      • getIndices

        public java.util.List<?> getIndices()
        Returns the indices used to extract the data and labels from the Dataset.
        Returns:
        a list of Long if the Dataset is a RandomAccessDataset, otherwise may return null.