    def __init__(
        self,
        combine_method,
        tgt_dict,
        src_dict=None,
        beam_size=1,
        max_len_a=0,
        max_len_b=200,
        min_len=1,
        len_penalty=1.0,
        unk_penalty=0.0,
        retain_dropout=False,
        temperature=1.0,
        match_source_len=False,
        no_repeat_ngram_size=0,
        normalize_scores=True,
        channel_models=None,
        k2=10,
        ch_weight=1.0,
        channel_scoring_type='log_norm',
        top_k_vocab=0,
        lm_models=None,
        lm_dict=None,
        lm_weight=1.0,
        normalize_lm_scores_by_tgt_len=False,
    ):
        """Generates translations of a given source sentence,
           using beam search with noisy channel decoding.

        Args:
            combine_method (string, optional): Method to combine direct, LM and
                channel model scores (default: None)
            tgt_dict (~fairseq.data.Dictionary): target dictionary
            src_dict (~fairseq.data.Dictionary): source dictionary
            beam_size (int, optional): beam width (default: 1)
            max_len_a/b (int, optional): generate sequences of maximum length
                ax + b, where x is the source length
            min_len (int, optional): the minimum length of the generated output
                (not including end-of-sentence)
            len_penalty (float, optional): length penalty, where <1.0 favors
                shorter, >1.0 favors longer sentences (default: 1.0)
            unk_penalty (float, optional): unknown word penalty, where <0
                produces more unks, >0 produces fewer (default: 0.0)
            retain_dropout (bool, optional): use dropout when generating
                (default: False)
            temperature (float, optional): temperature, where values
                >1.0 produce more uniform samples and values <1.0 produce
                sharper samples (default: 1.0)
            match_source_len (bool, optional): outputs should match the source
                length (default: False)
            no_repeat_ngram_size (int, optional): Size of n-grams that we avoid
                repeating in the generation (default: 0)
            normalize_scores (bool, optional): normalize scores by the length
                of the output (default: True)
            channel_models (List[~fairseq.models.FairseqModel]): ensemble of models
                translating from the target to the source
            k2 (int, optional): Top K2 candidates to score per beam at each step (default:10)
            ch_weight (int, optional): Weight associated with the channel model score
                assuming that the direct model score has weight 1.0 (default: 1.0)
            channel_scoring_type (str, optional): String specifying how to score
                the channel model (default: 'log_norm')
            top_k_vocab (int, optional): If `channel_scoring_type` is `'src_vocab'` or
                `'src_vocab_batched'`, then this parameter specifies the number of
                most frequent tokens to include in the channel model output vocabulary,
                in addition to the source tokens in the input batch (default: 0)
            lm_models (List[~fairseq.models.FairseqModel]): ensemble of models
                generating text in the target language
            lm_dict (~fairseq.data.Dictionary): LM Model dictionary
            lm_weight (int, optional): Weight associated with the LM model score
                assuming that the direct model score has weight 1.0 (default: 1.0)
            normalize_lm_scores_by_tgt_len (bool, optional): Should we normalize LM scores
                by the target length? By default, we normalize the combination of
                LM and channel model scores by the source length
        """
        self.pad = tgt_dict.pad()
        self.unk = tgt_dict.unk()
        self.eos = tgt_dict.eos()
        self.vocab_size = len(tgt_dict)
        self.beam_size = beam_size
        # the max beam size is the dictionary size - 1, since we never select pad
        self.beam_size = min(beam_size, self.vocab_size - 1)
        self.max_len_a = max_len_a
        self.max_len_b = max_len_b
        self.min_len = min_len
        self.normalize_scores = normalize_scores
        self.len_penalty = len_penalty
        self.unk_penalty = unk_penalty
        self.retain_dropout = retain_dropout
        self.temperature = temperature
        self.match_source_len = match_source_len
        self.no_repeat_ngram_size = no_repeat_ngram_size
        self.channel_models = channel_models
        self.src_dict = src_dict
        self.tgt_dict = tgt_dict
        self.combine_method = combine_method
        self.k2 = k2
        self.ch_weight = ch_weight
        self.channel_scoring_type = channel_scoring_type
        self.top_k_vocab = top_k_vocab
        self.lm_models = lm_models
        self.lm_dict = lm_dict
        self.lm_weight = lm_weight
        self.log_softmax_fn = torch.nn.LogSoftmax(dim=1)
        self.normalize_lm_scores_by_tgt_len = normalize_lm_scores_by_tgt_len

        self.share_tgt_dict = (self.lm_dict == self.tgt_dict)
        self.tgt_to_lm = make_dict2dict(tgt_dict, lm_dict)

        self.ch_scoring_bsz = 3072

        assert temperature > 0, '--temperature must be greater than 0'

        self.search = NoisyChannelBeamSearch(tgt_dict)
Generates translations of a given source sentence,
using beam search with noisy channel decoding.

Args:
combine_method (string, optional): Method to combine direct, LM and
channel model scores (default: None)
tgt_dict (~fairseq.data.Dictionary): target dictionary
src_dict (~fairseq.data.Dictionary): source dictionary
beam_size (int, optional): beam width (default: 1)
max_len_a/b (int, optional): generate sequences of maximum length
ax + b, where x is the source length
min_len (int, optional): the minimum length of the generated output
(not including end-of-sentence)
len_penalty (float, optional): length penalty, where <1.0 favors
shorter, >1.0 favors longer sentences (default: 1.0)
unk_penalty (float, optional): unknown word penalty, where <0
produces more unks, >0 produces fewer (default: 0.0)
retain_dropout (bool, optional): use dropout when generating
(default: False)
temperature (float, optional): temperature, where values
>1.0 produce more uniform samples and values <1.0 produce
sharper samples (default: 1.0)
match_source_len (bool, optional): outputs should match the source
length (default: False)
no_repeat_ngram_size (int, optional): Size of n-grams that we avoid
repeating in the generation (default: 0)
normalize_scores (bool, optional): normalize scores by the length
of the output (default: True)
channel_models (List[~fairseq.models.FairseqModel]): ensemble of models
translating from the target to the source
k2 (int, optional): Top K2 candidates to score per beam at each step (default:10)
ch_weight (int, optional): Weight associated with the channel model score
assuming that the direct model score has weight 1.0 (default: 1.0)
channel_scoring_type (str, optional): String specifying how to score
the channel model (default: 'log_norm')
top_k_vocab (int, optional): If `channel_scoring_type` is `'src_vocab'` or
`'src_vocab_batched'`, then this parameter specifies the number of
most frequent tokens to include in the channel model output vocabulary,
in addition to the source tokens in the input batch (default: 0)
lm_models (List[~fairseq.models.FairseqModel]): ensemble of models
generating text in the target language
lm_dict (~fairseq.data.Dictionary): LM Model dictionary
lm_weight (int, optional): Weight associated with the LM model score
assuming that the direct model score has weight 1.0 (default: 1.0)
normalize_lm_scores_by_tgt_len (bool, optional): Should we normalize LM scores
by the target length? By default, we normalize the combination of
LM and channel model scores by the source length
examples/fast_noisy_channel/noisy_channel_sequence_generator.py