See also Training for an overview of the relevant aspects.


An integer defining the batch size in data items (frames, words, subwords, etc.) per batch. A mini-batch has at least a time-dimension and a batch-dimension (or sequence-dimension), and depending on dense or sparse, also a feature-dimension. batch_size is the upper limit for time * sequences during creation of the mini-batches.


Defines the default value for seq_ordering across all datasets. It is recommended to not use this parameter, but rather define seq_ordering explicitly in the datasets for better readability. Possible values are:

  • default: Keep the sequences as is

  • reverse: Use the default sequences in reversed order

  • random: Shuffle the data with a predefined fixed seed

  • random:<seed>: Shuffle the data with the seed given

  • sorted: Sort by length (only if available), beginning with shortest sequences

  • sorted_reverse: Sort by length, beginning with longest sequences

  • laplace:<n_buckets>: Sort by length with n laplacian buckets (one bucket means going from shortest to longest and back with 1/n of the data).

  • laplace:.<n_sequences>: sort by length with n sequences per laplacian bucket.

Note that not all sequence order modes are available for all datasets, and some datasets may provide additional modes.


You can chunk sequences of your data into parts, which will greatly reduce the amount of needed zero-padding. This option is a string of two numbers, separated by a comma, i.e. chunk_size:chunk_step, where chunk_size is the size of a chunk, and chunk_step is the step after which we create the next chunk. I.e. the chunks will overlap by chunk_size - chunk_step frames. Set this to 0 to disable it, or for example 100:75 to enable it.


If set to True, checkpoints are removed based on their score on the dev set. Per default, 2 recent, 4 best, and the checkpoints 20,40,80,160,240 are kept. Can be set as a dictionary to specify additional options.

  • keep_last_n: integer defining how many recent checkpoints to keep

  • keep_best_n: integer defining how many best checkpoints to keep

  • keep: list or set of integers defining which checkpoints to keep


A dict with string:integer pairs. The string must be a valid data key, and the integer specifies the upper bound for this data object. During batch construction any sequence where the specified data object exceeds the upper bound are discarded. Note that some datasets (e.g OggZipDataset) load and process the data to determine the length, so even for discarded sequences data processing might be performed.


An integer specifying the upper limit of sequences in a batch (can be used in addition to batch_size).


An integer specifying the number of epochs to train.


An integer specifying after how many epochs the model is saved.


An integer or string specifying the epoch to start the training at. The default is ‘auto’.


If set to False, the training will not be interrupted if a single update step has a loss with NaN of Inf