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src/matrix/compressed-matrix.h
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// matrix/compressed-matrix.h
// Copyright 2012 Johns Hopkins University (author: Daniel Povey)
// Frantisek Skala, Wei Shi
// 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_MATRIX_COMPRESSED_MATRIX_H_
#define KALDI_MATRIX_COMPRESSED_MATRIX_H_ 1
#include "matrix/kaldi-matrix.h"
namespace kaldi {
/// \addtogroup matrix_group
/// @{
/*
The enum CompressionMethod is used when creating a CompressedMatrix (a lossily
compressed matrix) from a regular Matrix. It dictates how we choose the
compressed format and how we choose the ranges of floats that are represented
by particular integers.
kAutomaticMethod = 1 This is the default when you don't specify the
compression method. It is a shorthand for using
kSpeechFeature if the num-rows is more than 8, and
kTwoByteAuto otherwise.
kSpeechFeature = 2 This is the most complicated of the compression methods,
and was designed for speech features which have a roughly
Gaussian distribution with different ranges for each
dimension. Each element is stored in one byte, but there
is an 8-byte header per column; the spacing of the
integer values is not uniform but is in 3 ranges.
kTwoByteAuto = 3 Each element is stored in two bytes as a uint16, with
the representable range of values chosen automatically
with the minimum and maximum elements of the matrix as
its edges.
kTwoByteSignedInteger = 4
Each element is stored in two bytes as a uint16, with
the representable range of value chosen to coincide with
what you'd get if you stored signed integers, i.e.
[-32768.0, 32767.0]. Suitable for waveform data that
was previously stored as 16-bit PCM.
kOneByteAuto = 5 Each element is stored in one byte as a uint8, with the
representable range of values chosen automatically with
the minimum and maximum elements of the matrix as its
edges.
kOneByteUnsignedInteger = 6 Each element is stored in
one byte as a uint8, with the representable range of
values equal to [0.0, 255.0].
kOneByteZeroOne = 7 Each element is stored in
one byte as a uint8, with the representable range of
values equal to [0.0, 1.0]. Suitable for image data
that has previously been compressed as int8.
// We can add new methods here as needed: if they just imply different ways
// of selecting the min_value and range, and a num-bytes = 1 or 2, they will
// be trivial to implement.
*/
enum CompressionMethod {
kAutomaticMethod = 1,
kSpeechFeature = 2,
kTwoByteAuto = 3,
kTwoByteSignedInteger = 4,
kOneByteAuto = 5,
kOneByteUnsignedInteger = 6,
kOneByteZeroOne = 7
};
/*
This class does lossy compression of a matrix. It supports various compression
methods, see enum CompressionMethod.
*/
class CompressedMatrix {
public:
CompressedMatrix(): data_(NULL) { }
~CompressedMatrix() { Clear(); }
template<typename Real>
explicit CompressedMatrix(const MatrixBase<Real> &mat,
CompressionMethod method = kAutomaticMethod):
data_(NULL) { CopyFromMat(mat, method); }
/// Initializer that can be used to select part of an existing
/// CompressedMatrix without un-compressing and re-compressing (note: unlike
/// similar initializers for class Matrix, it doesn't point to the same memory
/// location).
///
/// This creates a CompressedMatrix with the size (num_rows, num_cols)
/// starting at (row_offset, col_offset).
///
/// If you specify allow_padding = true,
/// it is permitted to have row_offset < 0 and
/// row_offset + num_rows > mat.NumRows(), and the result will contain
/// repeats of the first and last rows of 'mat' as necessary.
CompressedMatrix(const CompressedMatrix &mat,
const MatrixIndexT row_offset,
const MatrixIndexT num_rows,
const MatrixIndexT col_offset,
const MatrixIndexT num_cols,
bool allow_padding = false);
void *Data() const { return this->data_; }
/// This will resize *this and copy the contents of mat to *this.
template<typename Real>
void CopyFromMat(const MatrixBase<Real> &mat,
CompressionMethod method = kAutomaticMethod);
CompressedMatrix(const CompressedMatrix &mat);
CompressedMatrix &operator = (const CompressedMatrix &mat); // assignment operator.
template<typename Real>
CompressedMatrix &operator = (const MatrixBase<Real> &mat); // assignment operator.
/// Copies contents to matrix. Note: mat must have the correct size.
/// The kTrans case uses a temporary.
template<typename Real>
void CopyToMat(MatrixBase<Real> *mat,
MatrixTransposeType trans = kNoTrans) const;
void Write(std::ostream &os, bool binary) const;
void Read(std::istream &is, bool binary);
/// Returns number of rows (or zero for emtpy matrix).
inline MatrixIndexT NumRows() const { return (data_ == NULL) ? 0 :
(*reinterpret_cast<GlobalHeader*>(data_)).num_rows; }
/// Returns number of columns (or zero for emtpy matrix).
inline MatrixIndexT NumCols() const { return (data_ == NULL) ? 0 :
(*reinterpret_cast<GlobalHeader*>(data_)).num_cols; }
/// Copies row #row of the matrix into vector v.
/// Note: v must have same size as #cols.
template<typename Real>
void CopyRowToVec(MatrixIndexT row, VectorBase<Real> *v) const;
/// Copies column #col of the matrix into vector v.
/// Note: v must have same size as #rows.
template<typename Real>
void CopyColToVec(MatrixIndexT col, VectorBase<Real> *v) const;
/// Copies submatrix of compressed matrix into matrix dest.
/// Submatrix starts at row row_offset and column column_offset and its size
/// is defined by size of provided matrix dest
template<typename Real>
void CopyToMat(int32 row_offset,
int32 column_offset,
MatrixBase<Real> *dest) const;
void Swap(CompressedMatrix *other) { std::swap(data_, other->data_); }
void Clear();
/// scales all elements of matrix by alpha.
/// It scales the floating point values in GlobalHeader by alpha.
void Scale(float alpha);
friend class Matrix<float>;
friend class Matrix<double>;
private:
// This enum describes the different compressed-data formats: these are
// distinct from the compression methods although all of the methods apart
// from kAutomaticMethod dictate a particular compressed-data format.
//
// kOneByteWithColHeaders means there is a GlobalHeader and each
// column has a PerColHeader; the actual data is stored in
// one byte per element, in column-major order (the mapping
// from integers to floats is a little complicated).
// kTwoByte means there is a global header but no PerColHeader;
// the actual data is stored in two bytes per element in
// row-major order; it's decompressed as:
// uint16 i; GlobalHeader g;
// float f = g.min_value + i * (g.range / 65535.0)
// kOneByte means there is a global header but not PerColHeader;
// the data is stored in one byte per element in row-major
// order and is decompressed as:
// uint8 i; GlobalHeader g;
// float f = g.min_value + i * (g.range / 255.0)
enum DataFormat {
kOneByteWithColHeaders = 1,
kTwoByte = 2,
kOneByte = 3
};
// allocates data using new [], ensures byte alignment
// sufficient for float.
static void *AllocateData(int32 num_bytes);
struct GlobalHeader {
int32 format; // Represents the enum DataFormat.
float min_value; // min_value and range represent the ranges of the integer
// data in the kTwoByte and kOneByte formats, and the
// range of the PerColHeader uint16's in the
// kOneByteWithColheaders format.
float range;
int32 num_rows;
int32 num_cols;
};
// This function computes the global header for compressing this data.
template<typename Real>
static inline void ComputeGlobalHeader(const MatrixBase<Real> &mat,
CompressionMethod method,
GlobalHeader *header);
// The number of bytes we need to request when allocating 'data_'.
static MatrixIndexT DataSize(const GlobalHeader &header);
// This struct is only used in format kOneByteWithColHeaders.
struct PerColHeader {
uint16 percentile_0;
uint16 percentile_25;
uint16 percentile_75;
uint16 percentile_100;
};
template<typename Real>
static void CompressColumn(const GlobalHeader &global_header,
const Real *data, MatrixIndexT stride,
int32 num_rows, PerColHeader *header,
uint8 *byte_data);
template<typename Real>
static void ComputeColHeader(const GlobalHeader &global_header,
const Real *data, MatrixIndexT stride,
int32 num_rows, PerColHeader *header);
static inline uint16 FloatToUint16(const GlobalHeader &global_header,
float value);
// this is used only in the kOneByte compression format.
static inline uint8 FloatToUint8(const GlobalHeader &global_header,
float value);
static inline float Uint16ToFloat(const GlobalHeader &global_header,
uint16 value);
// this is used only in the kOneByteWithColHeaders compression format.
static inline uint8 FloatToChar(float p0, float p25,
float p75, float p100,
float value);
// this is used only in the kOneByteWithColHeaders compression format.
static inline float CharToFloat(float p0, float p25,
float p75, float p100,
uint8 value);
void *data_; // first GlobalHeader, then PerColHeader (repeated), then
// the byte data for each column (repeated). Note: don't intersperse
// the byte data with the PerColHeaders, because of alignment issues.
};
/// @} end of \addtogroup matrix_group
} // namespace kaldi
#endif // KALDI_MATRIX_COMPRESSED_MATRIX_H_
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