rnnlm-example.h
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// rnnlm/rnnlm-example.h
// Copyright 2017 Johns Hopkins University (author: Daniel Povey)
// See ../../COPYING for clarification regarding multiple authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
// MERCHANTABLITY OR NON-INFRINGEMENT.
// See the Apache 2 License for the specific language governing permissions and
// limitations under the License.
#ifndef KALDI_RNNLM_RNNLM_EXAMPLE_H_
#define KALDI_RNNLM_RNNLM_EXAMPLE_H_
#include "base/kaldi-common.h"
#include "util/kaldi-thread.h"
#include "matrix/matrix-lib.h"
#include "cudamatrix/cu-matrix.h"
#include "cudamatrix/cu-vector.h"
#include "rnnlm/sampling-lm.h"
#include "rnnlm/sampler.h"
namespace kaldi {
namespace rnnlm {
// A single minibatch for training an RNNLM.
struct RnnlmExample {
int32 vocab_size; // The vocabulary size (defined as largest integer word-id
// plus one) for which this example was obtained; mostly
// used in bounds checking.
int32 num_chunks; // The number of parallel word sequences/chunks. [note:
// some of the word sequences may actually be made up of
// smaller subsequences appended together.
int32 chunk_length; // The length of each sequence in a minibatch,
// including any terminating </s> symbols, which are
// included explicitly in the sequences. Note:
// when </s> appears in the middle of sequences because
// we splice shorter word-sequences together, we
// will replace it with <s> on the input side of the network.
// Sentences, or pieces of sentences, that were shorter
// than 'chunk_length', will be padded as needed.
int32 sample_group_size; // derived from the sample_group_size option; this
// is the number of consecutive time-steps which
// form a single unit for sampling purposes. This
// number Will always divide chunk_length.
// Example: if sample_group_size=2, we'll sample one
// set of words for t={0,1}, another for t={2,3}, and
// so on. The sampling is for the denominator of
// the objective function.
int32 num_samples; // This is the number of words that we sample at the
// output of the nnet for each of the 'num_sample_groups'
// groups. If we didn't do sampling because the user
// didn't provide the ARPA language model, this will be
// zero (in this case we'll do the summation over all
// words in the vocab).
std::vector<int32> input_words; // Contains the input word symbols 0 <= i <
// vocab_size for each position in each
// chunk; dimension == chunk_length *
// num_chunks, where 0 <= t < chunk_length
// has larger stride than 0 <= n <
// num_chunks. In the common case these will
// be the same as the previous output symbol.
std::vector<int32> output_words; // The output (predicted) word symbols for
// each position in each chunk; indexed in
// the same way as 'input_words'. What this
// contains is different from 'input_words'
// in the sampling case (i.e. if
// !sampled_words.empty()). In this case,
// instead of the word-index it contains the
// relative index 0 <= i < num_samples
// within the block of sampled words. In
// the not-sampled case it contains actual
// word indexes 0 <= i < vocab_size.
// Weights for each of the output_words, indexed the same way as
// 'output_words'. These reflect any data-weighting we had in the original
// data, plus some zeros that relate to padding sequences of uneven length.
CuVector<BaseFloat> output_weights;
// This vector contains the word-indexes that we sampled for each position in
// the chunk and for each group of chunks. (It will be empty if the
// user didn't provide the ARPA language model). Its dimension is
// num_sample_groups * num_samples, where
// num_sample_groups == (chunk_length / sample_group_size).
// The sample-group index has the largest stride (you can think of the sample
// group index as the number i = t / sample_group_size, in integer division,
// where 0 <= t < chunk_length is the position in the chunk). The sampled
// words within each block of size 'num_samples' are sorted and unique.
std::vector<int32> sampled_words;
// This vector has the same dimension as 'sampled_words', and contains the
// inverses of the probabilities probability 0 < p <= 1 with which that word
// was included in the sampled set of words. These inverse probabilities
// appear in the objective function computation (it's related to importance
// sampling).
CuVector<BaseFloat> sample_inv_probs;
RnnlmExample(): vocab_size(0), num_chunks(0), chunk_length(0),
sample_group_size(1), num_samples(0) { }
// Shallow swap.
void Swap(RnnlmExample *other);
void Write(std::ostream &os, bool binary) const;
void Read(std::istream &is, bool binary);
};
// The word symbols we train on are zero-based integers
// (although zero is reserved for <eps> so this won't appear
// as a word
// we reserve 0 and 1 for the BOS symbol (usually <s>)
// and the EOS symbol (usually </s>) respectively.
// There are some subtleties regarding how we prepare the
// sentences and arrange them into minibatches.
//
// Firstly, we prepare original data that looks like the following:
//
// 1.0 Hello there
// 1.0 How are you
//
// [All of these words will be turned into integers by sym2int.pl before the C++
// tools are run].
//
// We want the models to be able to take advantage of context from previous
// sentences (say, in a dialogue or a series of sentences). Therefore we allow
// the data preparation to create include multiple successive sentences on one
// line, as follows:
//
// 1.0 Hello there </s> How are you
//
// The immedate left-context which the RNNLM sees when predicting "How" above
// will be </s>, unlike the normal case at start-of-sentence where it would be
// <s>. So essentially </s>, when seen as left-context, means "we're beginning
// a new sentence here but the prior words were part of the same dialogue."
//
//
// We train on minibatches of a fixed size, so it may be necessary to split up
// or combine sentences to a fixed length. Internally (inside
// rnnlm-create-egs), we read these variable-length sentences, randomize the
// order using a buffer, and then split and combine them as necessary to
// obtain a fixed length.
//
// The first stage in processing the sentences is to add an initial <s> and
// final <s> and to associate each word with a weight (which is just the
// sentence weight, at this point (1.0 in the example), except for the initial
// <s> which has zero weight).
//
//
// Next we split sentences which (when the </s> is included but not the <s>) are
// longer than chunk_length, into multiple pieces. At the split points, to the
// RHS of each split we will add some left-context words, up to
// min_split_context (e.g. 3), and we'll give those words zero weight so the
// RNNLM doesn't try to predict them, they are just used as left-context to
// predict future words. (The reason for the zero weight is to avoid counting
// these words twice).
struct RnnlmEgsConfig {
int32 vocab_size; // The vocabulary size: or more specifically, the largest
// integer word-id plus one. Must be provided, as it
// gets included in each minibatch (mostly for checking
// purposes).
int32 num_chunks_per_minibatch;
int32 chunk_length;
int32 min_split_context;
int32 sample_group_size; // affects the sampling: if sample_group_size is 2,
// then we'll sample words once for (t=0, t=1), then
// again for (t=2, t=3), and so on. We support
// merging time-steps in this way (but not splitting
// them smaller), due to considerations of computing
// time if you assume we also have a network that
// learns word representation from their
// character-level features.
int32 num_samples; // the number of words we choose each time we do the
// sampling.
int32 chunk_buffer_size;
int32 bos_symbol; // must be set.
int32 eos_symbol; // must be set.
int32 brk_symbol; // must be set.
BaseFloat special_symbol_prob; // sampling probability at the output for
// words that aren't supposed to be predicted
// (<s>, <brk>)-- this ensures that the model
// makes their output probs small, which
// avoids hassle when computing the normalizer
// in test time (if we didn't sample them with
// some probability to ensure their probs are
// small, we'd have to exclude them from the
// denominator sum.
BaseFloat uniform_prob_mass; // this value should be < 1.0; it takes this
// proportion of the unigram distribution used
// for sampling and assigns it to uniformly
// predict all words. This may avoid certain
// pathologies during training, and ensuring
// that all words' probs are bounded away from
// zero might be necessary for the theory of
// importance sampling.
RnnlmEgsConfig(): vocab_size(-1),
num_chunks_per_minibatch(128),
chunk_length(32),
min_split_context(3),
sample_group_size(2),
num_samples(512),
chunk_buffer_size(20000),
bos_symbol(1), // we use standardized values in the scripts,
eos_symbol(2), // so these are sensible defaults.
brk_symbol(3),
special_symbol_prob(1.0e-05),
uniform_prob_mass(0.05) { }
void Register(OptionsItf *po) {
po->Register("vocab-size", &vocab_size,
"Size of the vocabulary (more specifically: the largest integer "
"word-id plus one).");
po->Register("chunk-length", &chunk_length,
"Length of sequences that we train on (actual sentences will be "
"split up and re-combined as necessary to achieve this legnth");
po->Register("num-chunks-per-minibatch", &num_chunks_per_minibatch,
"Number of distinct sequences/chunks per minibatch.");
po->Register("min-split-context", &min_split_context,
"Minimum left-context that we supply after breaking up "
"a training sequence into pieces.");
po->Register("sample-group-size", &sample_group_size,
"Number of time-steps for which we draw a single sample of words. "
"Must divide chunk-length.");
po->Register("num-samples", &num_samples,
"Number of words we sample, each time we sample (importance sampling). "
"Must be at least num-chunks-per-minibatch * sample-group-size. "
"If you don't supply the ARPA LM to the program, or you set "
"num-samples to zero, or num-samples exceeds the number of words "
"with nonzero probability, the no sampling will be done.");
po->Register("chunk-buffer-size", &chunk_buffer_size,
"Number of chunks of sentence that we buffer while "
"processing the input. Larger means more complete "
"randomization but also more I/O before we produce any "
"output, and more memory used.");
po->Register("bos-symbol", &bos_symbol,
"Integer id of the beginning-of-sentence symbol <s>. "
"Must be specified.");
po->Register("eos-symbol", &eos_symbol,
"Integer id of the beginning-of-sentence symbol <s>. "
"Must be specified.");
po->Register("brk-symbol", &brk_symbol,
"Integer id of the 'break' symbol <brk> (only used "
"during training, most likely); used to tell the network "
"that the context is partial. Must be specified.");
po->Register("special-symbol-prob", &special_symbol_prob,
"Probability with which we sample the special symbols "
"<s> and <brk> on each minibatch. See code for reason.");
po->Register("uniform-prob-mass", &uniform_prob_mass,
"We replace this proportion of the unigram distribution's "
"probability mass with a uniform distribution over words. "
"Probably not necessary or important.");
}
// Checks that the config makes sense, and dies if not.
void Check() const {
KALDI_ASSERT(chunk_length > min_split_context * 4 &&
num_chunks_per_minibatch > 0 &&
min_split_context >= 0 &&
sample_group_size >= 1 &&
chunk_length % sample_group_size == 0);
if (vocab_size <= 0) {
KALDI_ERR << "The --vocab-size option must be provided.";
}
if (!(bos_symbol > 0 && eos_symbol > 0 && brk_symbol > 0 &&
bos_symbol != eos_symbol && brk_symbol != eos_symbol &&
brk_symbol != bos_symbol)) {
KALDI_ERR << "--bos-symbol, --eos-symbol and --brk-symbol "
"must be specified, >0, and all different.";
}
KALDI_ASSERT(num_samples == 0 ||
num_samples >= num_chunks_per_minibatch * sample_group_size);
KALDI_ASSERT(special_symbol_prob >= 0.0 && special_symbol_prob <= 1.0);
KALDI_ASSERT(uniform_prob_mass >= 0.0 && uniform_prob_mass < 1.0);
}
};
/**
Class RnnlmExampleSampler encapsulates the logic for sampling words
for a minibatch. (the words at the output of the RNNLM are sampled and
we train with an importance-sampling algorithm).
*/
class RnnlmExampleSampler {
public:
RnnlmExampleSampler(const RnnlmEgsConfig &config,
const SamplingLm &arpa_sampling);
// Does the sampling for 'minibatch'. 'minibatch' is expected to already
// have all fields populated except for 'sampled_words' and 'sample_probs'.
// This function does the sampling and sets those fields.
void SampleForMinibatch(RnnlmExample *minibatch) const;
~RnnlmExampleSampler() { delete sampler_; }
int32 VocabSize() const {
return arpa_sampling_.GetUnigramDistribution().size();
}
private:
// does the part of the sampling for group 'g' (note: 'g' is the
// same as the position 0 <= t < chunk_length in the sequence if
// config_.sample_group_size == 1, and otherwise, each group
// encompasses several successive 't' values.
void SampleForGroup(int32 g, RnnlmExample *minibatch) const;
// This function gets the combination of histories to be sampled from for the g'th
// group of 't' values, for this minibatch.
// It outputs to 'history_states' the the weighted
// combination of history-states, as a list of pair (history, weight)
// [with each history repeated only once], where for example
// history == [] is the unigram backoff state, history=[10] means
// we saw the word 10 as left-context, history[20, 10] means 10 is
// the immediate left-contxt and 20 is before that. The weight
// 'weight' will be > 0 and will be a sum of the weights of the
// output words in the minibatch that have that history.
void GetHistoriesForGroup(
int32 g, const RnnlmExample &minibatch,
std::vector<std::pair<std::vector<int32>, BaseFloat> > *hist_weights) const;
// This function renumbers 'output_words' so that instead of being
// numbers 0 <= i < vocab_size, they are numbered as indexes into the
// relevant block of the vector 'output_words'.
void RenumberOutputWordsForGroup(
int32 g, RnnlmExample *minibatch) const;
// This function is used to obtain the history (of maximum length
// 'max_history_length') used when predicting the t'th output word in the n'th
// sequence of this minibatch. The history is output to 'history'. Note: the
// only situation where the history-length would be less than
// 'max_history_length' is due to edge effects.
//
// As an example of a normal case: if max_history_length is 2, and for the
// provided n, the input words in 'minibatch.input_words[..]' for t values up
// to and including 't' are '.. the day of', then 'history' would be set to [
// day of ] (obviously in integer form).
//
// As an example of edge effects: if this is the
// first word of a chunk that's part of the sequence and max_history_length >
// 1; in this case the history would either be [<s>] or [<brk>].
void GetHistory(int32 t, int32 n,
const RnnlmExample &minibatch,
int32 max_history_length,
std::vector<int32> *history) const;
RnnlmEgsConfig config_;
// arpa_ stores the n-gram language model that we use for importance sampling.
const SamplingLm &arpa_sampling_;
// class Sampler does some of the lower-level aspects of sampling.
Sampler *sampler_;
};
/// This class takes care of all of the logic of creating minibatches for RNNLM
/// training, including the sampling aspect. It implements the bulk of the
/// functionality of the binary rnnlm-get-egs.
class RnnlmExampleCreator {
public:
// This constructor is for when you are using importance sampling from
// an ARPA language model (the normal case).
RnnlmExampleCreator(const RnnlmEgsConfig &config,
const TaskSequencerConfig &sequencer_config,
const RnnlmExampleSampler &minibatch_sampler,
TableWriter<KaldiObjectHolder<RnnlmExample> > *writer):
config_(config), minibatch_sampler_(&minibatch_sampler),
sampling_sequencer_(sequencer_config),
writer_(writer), num_sequences_processed_(0), num_chunks_processed_(0),
num_words_processed_(0), num_minibatches_written_(0) { Check(); }
// This constructor is for when you are not using importance sampling,
// so no samples will be stored in the minibatch and the training code
// will presumably evaluate all the words each time. This is intended
// to be used for testing purposes.
RnnlmExampleCreator(const RnnlmEgsConfig &config,
TableWriter<KaldiObjectHolder<RnnlmExample> > *writer):
config_(config), minibatch_sampler_(NULL),
sampling_sequencer_(TaskSequencerConfig()),
writer_(writer), num_sequences_processed_(0),
num_chunks_processed_(0), num_words_processed_(0),
num_minibatches_written_(0) { Check(); }
// The user calls this to provide a single sequence (a sentence; or multiple
// sentences that are part of a continuous stream or dialogue, separated
// by </s>), to this class. This class will write out minibatches when
// it's ready.
// This will normally be the result of reading a line of text with the format:
// <weight> <word1> <word2> ....
// e.g.:
// 1.0 Hello there
// [although the "hello there" would have been converted to integers
// by the time it was read in, via sym2int.pl, so it would look like:
// 1.0 7620 12309
// We also allow:
// 1.0 Hello there </s> Hi </s> My name is Bob
// if you want to train the model to predict sentences given
// the history of the conversation.
void AcceptSequence(BaseFloat weight,
const std::vector<int32> &words);
// Reads the lines from this input stream, calling AcceptSequence() on each
// one. Lines will be of the format:
// <weight> <possibly-empty-sequence-of-integers>
// e.g.:
// 1.0 2560 8991
void Process(std::istream &is);
// Flush out any pending minibatches.
void Flush() {
while (ProcessOneMinibatch());
sampling_sequencer_.Wait();
}
~RnnlmExampleCreator();
private:
void Check() const;
// Attempts to create a minibatch. Returns true if it successfully did so,
// and false if it could not do so because there was insufficient data.
// If we are not doing sampling, this function will write
// the minibatch to 'writer_' directly; if we are doing sampling, it will
// give it to a background thread to be processed and written.
bool ProcessOneMinibatch();
struct SequenceChunk {
// 'sequence' is a pointer to the word sequence (without initial <s>, but with
// final </s> added by us, and possibly with </s> in the middle to demarcate
// sentences that are part of a single conversation or piece of text.
std::shared_ptr<std::vector<int32> > sequence;
// 'weight' is the weight on this chunk of sequence, i.e. the
// corpus weighting the user chose to apply on the
// original sequences.
BaseFloat weight;
int32 begin; // beginning position in the sequence, of the first predicted
// word (begin >= 0).
int32 end; // one past the end of the last predicted word; will be <= sequence->size().
int32 context_begin; // context_begin <= begin is the first word in
// the sequence that is seen as left-context. This will
// be the same as 'begin' if begin == 0, but will be less
// by up to config_.min_split_context if begin > 0.
// note: we actually see one more word of left-context, namely
// <s> if context_begin==0 or <brk> otherwise, but this
// doesn't affect how many 't' values this sequence uses
// up because we get it 'for free' (since we see one word
// of left-context even without recurrence).
SequenceChunk(const RnnlmEgsConfig &config,
const std::shared_ptr<std::vector<int32> > &seq,
BaseFloat w, int32 b, int32 e):
sequence(seq), weight(w), begin(b), end(e),
context_begin(std::max<int32>(0, b - config.min_split_context)) { }
// The length (in 't' values) that this chunk of a sequence takes up.
int32 Length() const { return end - context_begin; }
};
class SingleMinibatchCreator {
public:
SingleMinibatchCreator(const RnnlmEgsConfig &config);
// The user calls this to ask it to accept a chunk into this
// minibatch. It returns true if it can do so, and false if it
// can't do so because it's too big for any space that remains
// in this minibatch.
// If it returns true it will have taken ownership of 'chunk'
// from a memory management point of view.
bool AcceptChunk(SequenceChunk *chunk);
// You call this when you've provided all the data you're going to provide
// (usually because it already rejected a bunch of chunks due to no space
// left), and you want to create a minibatch. You will let this object go
// out of scope or delete it right after this.
// This function does everything but the sampling aspect of creating
// the object 'minibatch'; the caller is responsible for that.
void CreateMinibatch(RnnlmExample *minibatch);
~SingleMinibatchCreator();
private:
// called from CreateMinibatch, handles a single sequence
void CreateMinibatchOneSequence(int32 n, RnnlmExample *minibatch);
// This function writes to the minibatch for the n'th sequence,
// (with 0 <= n < config_.minibatch_size), the t'th position
// (with 0 <= t < config_.chunk_length).
// 'input_word' is the word the RNNLM sees as its input;
// 'output_word' is the word the RNNLM predicts as its output
// (and this will normally be the same as the 'input_word'
// for t+1, except at chunk boundaries);
// 'weight' is the weight in the objective, for predicting the word
// 'output_word'. This is normally the same as the corpus weight for
// this data-source, but it could be zero for words that are only used
// for context after a split, or for where we are padding a sequence.
void Set(int32 n, int32 t, int32 input_word, int32 output_word,
BaseFloat weight, RnnlmExample *minibatch) const;
const RnnlmEgsConfig &config_;
// Indexed by 0 < n < config_.num_chunks_per_minibatch, and then a list of
// SequenceChunk*. It's a list instead of just one SequenceChunk* because
// each chunk of the eg we write may actually contain more than one
// sequence, or fragment of a sequence. The pointers are owned here.
std::vector<std::vector<SequenceChunk*> > eg_chunks_;
// lists all eg_chunks 0 <= n < config_.num_chunks_per_minibatch that
// are completely empty (i.e. eg_chunks[i].empty()).
std::vector<int32> empty_eg_chunks_;
// Lists all eg_chunks that are not empty but not completely full,
// giving the amount of space left in the eg_chunk, as an unordered list
// of pairs (n, space_left).
// What this means specifically is as follows:
// Let SpaceUsed(n) be equal to \sum_i eg_chunks[n][i]->MinLength(config_),
// then partial_eg_chunks_ will contain a pair
// (n, k) where k = config_.chunk_length - SpaceUsed(n),
// wherever this would give us 0 < k < config_.chunk_length.
// 'k' represents the largest MinLength() of a SequenceChunk that we
// would be able to fit in this eg_chunk.
std::vector<std::pair<int32, int32> > partial_eg_chunks_;
};
// This class is a wrapper class that, when provided to class TaskSequencer, allows us to
// run the call 'sampler.SampleForMinibatch(minibatch)' in multiple threads, followed by
// sequentially calling writer->Write(key, *minibatch) and deleting minibatch.
class SamplerTask {
public:
SamplerTask(const RnnlmExampleSampler &sampler,
const std::string &key,
TableWriter<KaldiObjectHolder<RnnlmExample> > *writer,
RnnlmExample *minibatch):
sampler_(sampler), key_(key), writer_(writer), minibatch_(minibatch) { }
void operator () () {
sampler_.SampleForMinibatch(minibatch_);
}
~SamplerTask() {
writer_->Write(key_, *minibatch_);
delete minibatch_;
}
private:
const RnnlmExampleSampler &sampler_;
std::string key_;
TableWriter<KaldiObjectHolder<RnnlmExample> > *writer_;
RnnlmExample *minibatch_; // owned here.
};
// Checks an input sequence, as read directly from the user.
// Checks that weight > 0.0, that 'words' does not contain
// <s> or <brk> (see bos_symbol and brk_symbol in the config).
// Note: it may contain </s> internally to separate sentences
// that are part of a sequence of utterances, such as a conversation.
// It's not expected to contain </s> at the end, but this is
// not checked for, because it's not absolutely disallowed.
// (it would get processed into </s> </s> which would be an empty
// turn in a multi-sentence conversation).
// Also, while we don't expect to see empty 'words' often, it's
// not disallowed because you might legitimately want the LM
// to be able to generate the empty sequence in an ASR application.
void CheckSequence(BaseFloat weight,
const std::vector<int32> &words);
// This function splits a sequence into one or more
// objects of type SequenceChunk, and appends them to 'chunks_'.j
void SplitSequenceIntoChunks(BaseFloat weight,
const std::vector<int32> &words);
// for a provided sequence_length > config_.chunk_length,
// randomly chooses a list of chunk lengths with the following
// properties:
// The chunk lengths sum to 'sequence_length'.
// (*chunk_lengths)[0] <= config_.chunk_length
// (*chunk_lengths)[i] <= config_.chunk_length - config_.min_split_context
// for i > 0
// All but one of the chunk_lenghhs have the maximum possible
// value (depending on their position).
void ChooseChunkLengths(int32 sequence_length,
std::vector<int32> *chunk_lengths);
// Removes, and returns, a randomly chosen SequenceChunk* from 'chunks_'.
// Transfers ownership to caller.
SequenceChunk *GetRandomChunk();
// This stores pending chunks that we have not yet processed
// into a minibatch. The pointers are owned here.
std::vector<SequenceChunk*> chunks_;
const RnnlmEgsConfig &config_;
const RnnlmExampleSampler *minibatch_sampler_;
TaskSequencer<SamplerTask> sampling_sequencer_;
TableWriter<KaldiObjectHolder<RnnlmExample> > *writer_;
int32 num_sequences_processed_;
int32 num_chunks_processed_;
int32 num_words_processed_;
int32 num_minibatches_written_;
};
typedef TableWriter<KaldiObjectHolder<RnnlmExample> > RnnlmExampleWriter;
typedef SequentialTableReader<KaldiObjectHolder<RnnlmExample> > SequentialRnnlmExampleReader;
} // namespace rnnlm
} // namespace kaldi
#endif // KALDI_RNNLM_RNNLM_EXAMPLE_H_