OnlineCacheFeature Class Reference

This feature type can be used to cache its input, to avoid repetition of computation in a multi-pass decoding context. More...

#include <online-feature.h>

Inheritance diagram for OnlineCacheFeature:

Collaboration diagram for OnlineCacheFeature:

Public Member Functions
virtual int32	Dim () const
virtual bool	IsLastFrame (int32 frame) const
	Returns true if this is the last frame. More...
virtual BaseFloat	FrameShiftInSeconds () const
virtual int32	NumFramesReady () const
	returns the feature dimension. More...
virtual void	GetFrame (int32 frame, VectorBase< BaseFloat > *feat)
	Gets the feature vector for this frame. More...
virtual void	GetFrames (const std::vector< int32 > &frames, MatrixBase< BaseFloat > *feats)
	This is like GetFrame() but for a collection of frames. More...
virtual	~OnlineCacheFeature ()
void	ClearCache ()
	OnlineCacheFeature (OnlineFeatureInterface *src)
Public Member Functions inherited from OnlineFeatureInterface
virtual	~OnlineFeatureInterface ()
	Virtual destructor. More...

Private Attributes
OnlineFeatureInterface *	src_
std::vector< Vector< BaseFloat > *>	cache_

Detailed Description

This feature type can be used to cache its input, to avoid repetition of computation in a multi-pass decoding context.

Definition at line 564 of file online-feature.h.

Constructor & Destructor Documentation

~OnlineCacheFeature()

virtual ~OnlineCacheFeature ( )

inlinevirtual

Definition at line 582 of file online-feature.h.

{ ClearCache(); }

OnlineCacheFeature()

OnlineCacheFeature ( OnlineFeatureInterface *  src )

inlineexplicit

Definition at line 589 of file online-feature.h.

: src_(src) { }

Member Function Documentation

ClearCache()

void ClearCache

(

)

Definition at line 662 of file online-feature.cc.

References rnnlm::i.

Referenced by kaldi::GetOutput().

                                    {
  for (size_t i = 0; i < cache_.size(); i++)
    delete cache_[i];
  cache_.resize(0);
}

Dim()

virtual int32 Dim ( ) const

inlinevirtual

Implements OnlineFeatureInterface.

Definition at line 566 of file online-feature.h.

{ return src_->Dim(); }

FrameShiftInSeconds()

virtual BaseFloat FrameShiftInSeconds ( ) const

inlinevirtual

Implements OnlineFeatureInterface.

Definition at line 571 of file online-feature.h.

                                                {
    return src_->FrameShiftInSeconds();
  }

GetFrame()

void GetFrame ( int32  frame, VectorBase< BaseFloat > *  feat  )

virtual

Gets the feature vector for this frame.

Before calling this for a given frame, it is assumed that you called NumFramesReady() and it returned a number greater than "frame". Otherwise this call will likely crash with an assert failure. This function is not declared const, in case there is some kind of caching going on, but most of the time it shouldn't modify the class.

Implements OnlineFeatureInterface.

Definition at line 604 of file online-feature.cc.

References VectorBase< Real >::CopyFromVec(), OnlineDeltaFeature::Dim(), OnlineFeatureInterface::GetFrame(), KALDI_ASSERT, and OnlineDeltaFeature::src_.

Referenced by kaldi::GetOutput().

                                                                          {
  KALDI_ASSERT(frame >= 0);
  if (static_cast<size_t>(frame) < cache_.size() && cache_[frame] != NULL) {
    feat->CopyFromVec(*(cache_[frame]));
  } else {
    if (static_cast<size_t>(frame) >= cache_.size())
      cache_.resize(frame + 1, NULL);
    int32 dim = this->Dim();
    cache_[frame] = new Vector<BaseFloat>(dim);
    // The following call will crash if frame "frame" is not ready.
    src_->GetFrame(frame, cache_[frame]);
    feat->CopyFromVec(*(cache_[frame]));
  }
}

GetFrames()

void GetFrames ( const std::vector< int32 > &  frames, MatrixBase< BaseFloat > *  feats  )

virtual

This is like GetFrame() but for a collection of frames.

There is a default implementation that just gets the frames one by one, but it may be overridden for efficiency by child classes (since sometimes it's more efficient to do things in a batch).

Reimplemented from OnlineFeatureInterface.

Definition at line 619 of file online-feature.cc.

References OnlineDeltaFeature::Dim(), OnlineFeatureInterface::GetFrames(), rnnlm::i, kaldi::kUndefined, MatrixBase< Real >::Row(), and OnlineDeltaFeature::src_.

                                                                  {
  int32 num_frames = frames.size();
  // non_cached_frames will be the subset of 't' values in 'frames' which were
  // not previously cached, which we therefore need to get from src_.
  std::vector<int32> non_cached_frames;
  // 'non_cached_indexes' stores the indexes 'i' into 'frames' corresponding to
  // the corresponding frames in 'non_cached_frames'.
  std::vector<int32> non_cached_indexes;
  non_cached_frames.reserve(frames.size());
  non_cached_indexes.reserve(frames.size());
  for (int32 i = 0; i < num_frames; i++) {
    int32 t = frames[i];
    if (static_cast<size_t>(t) < cache_.size() && cache_[t] != NULL) {
      feats->Row(i).CopyFromVec(*(cache_[t]));
    } else {
      non_cached_frames.push_back(t);
      non_cached_indexes.push_back(i);
    }
  }
  if (non_cached_frames.empty())
    return;
  int32 num_non_cached_frames = non_cached_frames.size(),
      dim = this->Dim();
  Matrix<BaseFloat> non_cached_feats(num_non_cached_frames, dim,
                                     kUndefined);
  src_->GetFrames(non_cached_frames, &non_cached_feats);
  for (int32 i = 0; i < num_non_cached_frames; i++) {
    int32 t = non_cached_frames[i];
    if (static_cast<size_t>(t) < cache_.size() && cache_[t] != NULL) {
      // We can reach this point due to repeat indexes in 'non_cached_frames'.
      feats->Row(non_cached_indexes[i]).CopyFromVec(*(cache_[t]));
    } else {
      SubVector<BaseFloat> this_feat(non_cached_feats, i);
      feats->Row(non_cached_indexes[i]).CopyFromVec(this_feat);
      if (static_cast<size_t>(t) >= cache_.size())
        cache_.resize(t + 1, NULL);
      cache_[t] = new Vector<BaseFloat>(this_feat);
    }
  }
}

IsLastFrame()

virtual bool IsLastFrame ( int32  frame ) const

inlinevirtual

Returns true if this is the last frame.

Frame indices are zero-based, so the first frame is zero. IsLastFrame(-1) will return false, unless the file is empty (which is a case that I'm not sure all the code will handle, so be careful). This function may return false for some frame if we haven't yet decided to terminate decoding, but later true if we decide to terminate decoding. This function exists mainly to correctly handle end effects in feature extraction, and is not a mechanism to determine how many frames are in the decodable object (as it used to be, and for backward compatibility, still is, in the Decodable interface).

Implements OnlineFeatureInterface.

Definition at line 568 of file online-feature.h.

Referenced by kaldi::GetOutput().

                                              {
    return src_->IsLastFrame(frame);
  }

NumFramesReady()

virtual int32 NumFramesReady ( ) const

inlinevirtual

returns the feature dimension.

Returns the total number of frames, since the start of the utterance, that are now available. In an online-decoding context, this will likely increase with time as more data becomes available.

Implements OnlineFeatureInterface.

Definition at line 575 of file online-feature.h.

{ return src_->NumFramesReady(); }

Member Data Documentation

cache_

std::vector<Vector<BaseFloat>* > cache_

private

Definition at line 593 of file online-feature.h.

src_

OnlineFeatureInterface* src_

private

Definition at line 592 of file online-feature.h.

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The documentation for this class was generated from the following files:

• feat/online-feature.h
• feat/online-feature.cc