[PATCH v7 1/3] ipa: libipa: Add Matrix class
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Wed Jun 12 11:32:43 CEST 2024
On Wed, Jun 12, 2024 at 04:59:39PM +0900, Paul Elder wrote:
> On Wed, Jun 12, 2024 at 02:33:33AM +0300, Laurent Pinchart wrote:
> > On Tue, Jun 11, 2024 at 11:02:05PM +0900, Paul Elder wrote:
> > > Add a class to represent a Matrix object and operations for adding
> > > matrices, multipling a matrix by a scalar, and multiplying two matrices.
> > >
> > > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> > > Reviewed-by: Stefan Klug <stefan.klug at ideasonboard.com>
> > > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > >
> > > ---
> > > Changes in v7:
> > > - fix copyright and license
> > >
> > > Changes in v6:
> > > - fix doxygen
> > >
> > > Changes in v5:
> > > - add documentation
> > >
> > > Changes in v4:
> > > - remove stray semicolons
> > > - add operator<<
> > > - clean up/optimize constructor
> > > - replace get() and set() with operator[] (and a second [] can be used
> > > as operator[] returns a Span)
> > >
> > > Changes in v3:
> > > - fix template parameters of operator* to allow different types for the
> > > scalar multiplier and the matrix's number type
> > > - clear data in constructors
> > > - fix assert in constructor
> > >
> > > Changes v2:
> > > - make rows and columns into template arguments
> > > - initialize to identity matrix on construction
> > > - add getter and setter
> > > - change from struct to class
> > > - fix matrix multiplication
> > > - clean up unused includes
> > > - avoid dereferencing an absent std::optional
> > > ---
> > > src/ipa/libipa/matrix.cpp | 123 ++++++++++++++++++++++++++
> > > src/ipa/libipa/matrix.h | 172 +++++++++++++++++++++++++++++++++++++
> > > src/ipa/libipa/meson.build | 2 +
> > > 3 files changed, 297 insertions(+)
> > > create mode 100644 src/ipa/libipa/matrix.cpp
> > > create mode 100644 src/ipa/libipa/matrix.h
> > >
> > > diff --git a/src/ipa/libipa/matrix.cpp b/src/ipa/libipa/matrix.cpp
> > > new file mode 100644
> > > index 000000000000..02091a0b4ce1
> > > --- /dev/null
> > > +++ b/src/ipa/libipa/matrix.cpp
> > > @@ -0,0 +1,123 @@
> > > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > > +/*
> > > + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> > > + *
> > > + * Matrix and related operations
> > > + */
> > > +
> > > +#include "matrix.h"
> > > +
> > > +#include <libcamera/base/log.h>
> > > +
> > > +/**
> > > + * \file matrix.h
> > > + * \brief Matrix class
> > > + */
> > > +
> > > +namespace libcamera {
> > > +
> > > +LOG_DEFINE_CATEGORY(Matrix)
> > > +
> > > +namespace ipa {
> > > +
> > > +/**
> > > + * \class Matrix
> > > + * \brief Matrix class
> > > + * \tparam T Type of numerical values to be stored in the matrix
> > > + * \tparam R Number of rows in the matrix
> > > + * \tparam C Number of columns in the matrix
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix::Matrix()
> > > + * \brief Construct an identity matrix
> >
> > I would have expected the default constructor to construct a zero
> > matrix. Is there a reason to go for identity instead ?
> >
> > As identity matrices are useful too, I would add a static
> > Matrix::identity() function that constructs and returns an identity
> > matrix.
> >
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix::Matrix(const std::vector<T> &data)
> >
> > Turning the argument into a Span would allow passing any type of
> > contiguous data (vector, array, C array, ...) without requiring the
> > caller to construct a std::vector.
>
> That's what I wanted to do but it was refusing to work.
Show me the failure and I'll help :-)
> > > + * \brief Construct matrix from supplied data
> >
> > s/matrix/a matrix/
> >
> > > + * \param data Data from which to construct a matrix
> >
> > \param[in]
> >
> > Same below.
> >
> > > + *
> > > + * \a data is a one-dimensional vector and will be turned into a matrix in
> > > + * row-major order. The size of \a data must be equal to the product of the
> > > + * number of rows and columns of the matrix (RxC).
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix::readYaml
> >
> > s/$/()/
> >
> > Same below.
> >
> > > + * \brief Populate the matrix with yaml data
> > > + * \param yaml Yaml data to populate the matrix with
> > > + *
> > > + * Any existing data in the matrix will be overwritten. The size of the data
> > > + * read from \a yaml must be equal to the product of the number of rows and
> > > + * columns of the matrix (RxC).
> > > + *
> > > + * The yaml data is expected to be a list with elements of type T.
> >
> > in row-major order.
> >
> > > + *
> > > + * \return 0 on success, negative error code otherwise
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix::toString
> > > + * \brief Assemble and return a string describing the matrix
> > > + * \return A string describing the matrix
> > > + */
> > > +
> > > +/**
> > > + * \fn Span<const T, C> Matrix::operator[](size_t i) const
> > > + * \brief Index to a row in the matrix
> > > + * \param i Index of row to retrieve
> > > + *
> > > + * This operator[] returns a Span, which can then be indexed into again with
> > > + * another operator[], allowing a convenient m[i][j] to access elements of the
> > > + * matrix. Note that the lifetime of the Span returned by this first-level
> > > + * operator[] is bound to that of the Matrix itself, so it is not recommended
> > > + * to save the Span that is the result of this operator[].
> >
> > That's a clever idea, I like it.
> >
> > Longer term we may need a different (and
> > unfortunately much more complex) implementation to allow using Matrix[i]
> > in APIs that expect a Vector (which itself may need to be reimplemented
> > as a matrix with a single column). And the next thing we know is that
> > we'll reimplement uBLAS or Eigen3 :-) I'll cross my fingers and wish we
> > won't reach that point.
> >
> > https://stackoverflow.com/questions/1380371/what-are-the-most-widely-used-c-vector-matrix-math-linear-algebra-libraries-a
> >
> > "It seems that many projects slowly come upon a need to do matrix math,
> > and fall into the trap of first building some vector classes and slowly
> > adding in functionality until they get caught building a half-assed
> > custom linear algebra library, and depending on it."
>
> Oops... :)
>
> > > + *
> > > + * \return Row \a i from the matrix, as a Span
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix::operator[](size_t i)
> > > + * \copydoc Matrix::operator[](size_t i) const
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix::Matrix<U, R, C> operator*(T d, const Matrix<U, R, C> &m)
> > > + * \brief Scalar product
> > > + * \tparam T Type of the numerical scalar value
> > > + * \tparam U Type of numerical values in the matrix
> > > + * \tparam R Number of rows in the matrix
> > > + * \tparam C Number of columns in the matrix
> > > + * \param d Scalar
> > > + * \param m Matrix
> > > + * \return Product of scalar \a d and matrix \a m
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix<T, R1, C2> operator*(const Matrix<T, R1, C1> &m1, const Matrix<T, R2, C2> &m2)
> > > + * \brief Matrix multiplication
> > > + * \tparam T Type of numerical values in the matrices
> > > + * \tparam R1 Number of rows in the first matrix
> > > + * \tparam C1 Number of columns in the first matrix
> > > + * \tparam R2 Number of rows in the second matrix
> > > + * \tparam C2 Number of columns in the second matrix
> > > + * \param m1 Multiplicand matrix
> > > + * \param m2 Multiplier matrix
> > > + * \return Matrix product of matrices \a m1 and \a m2
> > > + */
> > > +
> > > +/**
> > > + * \fn Matrix<T, R, C> operator+(const Matrix<T, R, C> &m1, const Matrix<T, R, C> &m2)
> > > + * \brief Matrix addition
> > > + * \tparam T Type of numerical values in the matrices
> > > + * \tparam R Number of rows in the matrices
> > > + * \tparam C Number of columns in the matrices
> > > + * \param m1 Summand matrix
> > > + * \param m2 Summand matrix
> > > + * \return Matrix sum of matrices \a m1 and \a m2
> > > + */
> > > +
> > > +} /* namespace ipa */
> > > +
> > > +} /* namespace libcamera */
> > > diff --git a/src/ipa/libipa/matrix.h b/src/ipa/libipa/matrix.h
> > > new file mode 100644
> > > index 000000000000..90eaea03bd14
> > > --- /dev/null
> > > +++ b/src/ipa/libipa/matrix.h
> > > @@ -0,0 +1,172 @@
> > > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > > +/*
> > > + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> > > + *
> > > + * Matrix and related operations
> > > + */
> > > +#pragma once
> > > +
> > > +#include <algorithm>
> > > +#include <cmath>
> > > +#include <sstream>
> > > +#include <vector>
> > > +
> > > +#include <libcamera/base/log.h>
> > > +#include <libcamera/base/span.h>
> > > +
> > > +#include "libcamera/internal/yaml_parser.h"
> > > +
> > > +namespace libcamera {
> > > +
> > > +LOG_DECLARE_CATEGORY(Matrix)
> > > +
> > > +namespace ipa {
> > > +
> > > +#ifndef __DOXYGEN__
> > > +template<typename T, unsigned int R, unsigned int C,
> >
> > Following the Vector class,
> >
> > template<typename T, unsigned int Rows, unsigned int Cols,
> >
> > > + std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
> > > +#else
> > > +template<typename T, unsigned int R, unsigned int C>
> > > +#endif /* __DOXYGEN__ */
> > > +class Matrix
> > > +{
> > > +public:
> > > + Matrix()
> > > + : data_(R * C, static_cast<T>(false))
> >
> > false ? That's a strange one, anything wrong with 0 ?
> >
> > > + {
> > > + for (size_t i = 0; i < std::min(R, C); i++)
> > > + (*this)[i][i] = static_cast<T>(true);
> >
> > And 1 here.
> >
> > > + }
> > > +
> > > + Matrix(const std::vector<T> &data)
> > > + {
> > > + ASSERT(data.size() == R * C);
> > > +
> > > + data_.clear();
> > > + for (const T &x : data)
> > > + data_.push_back(x);
> >
> > That will perform quite a few reallocations. I think you can simply
> > write
> >
> > std::copy(data.begin(), data.end(), data_.begin());
> >
> > > + }
> > > +
> > > + ~Matrix() = default;
> > > +
> > > + int readYaml(const libcamera::YamlObject &yaml)
> > > + {
> > > + if (yaml.size() != R * C) {
> > > + LOG(Matrix, Error)
> > > + << "Wrong number of values in matrix: expected "
> > > + << R * C << ", got " << yaml.size();
> > > + return -EINVAL;
> > > + }
> > > +
> > > + unsigned int i = 0;
> > > + for (const auto &x : yaml.asList()) {
> > > + auto value = x.get<T>();
> > > + if (!value) {
> > > + LOG(Matrix, Error) << "Failed to read matrix value";
> > > + return -EINVAL;
> > > + }
> > > +
> > > + data_[i++] = *value;
> > > + }
> > > +
> > > + return 0;
> > > + }
> > > +
> > > + const std::string toString() const
> > > + {
> > > + std::stringstream out;
> > > +
> > > + out << "Matrix { ";
> > > + for (unsigned int i = 0; i < R; i++) {
> > > + out << "[ ";
> > > + for (unsigned int j = 0; j < C; j++) {
> > > + out << (*this)[i][j];
> > > + out << ((j + 1 < C) ? ", " : " ");
> > > + }
> > > + out << ((i + 1 < R) ? "], " : "]");
> > > + }
> > > + out << " }";
> > > +
> > > + return out.str();
> > > + }
> > > +
> > > + Span<const T, C> operator[](size_t i) const
> > > + {
> > > + return Span<const T, C>{ &data_.data()[i * C], C };
> > > + }
> > > +
> > > + Span<T, C> operator[](size_t i)
> > > + {
> > > + return Span<T, C>{ &data_.data()[i * C], C };
> > > + }
> > > +
> > > +private:
> > > + std::vector<T> data_;
> >
> > Should this be a std::array<T, Rows * Cols>, like for the Vector class ?
> >
> > > +};
> > > +
> > > +#ifndef __DOXYGEN__
> > > +template<typename T, typename U, unsigned int R, unsigned int C,
> > > + std::enable_if_t<std::is_arithmetic_v<T> && std::is_arithmetic_v<U>> * = nullptr>
> >
> > The latter is ensured by the Matrix class.
> >
> > You need an
> >
> > #else
> > template<typename T, typename U, unsigned int R, unsigned int C>
> >
> > Same below.
> >
> > > +#endif /* __DOXYGEN__ */
> > > +Matrix<U, R, C> operator*(T d, const Matrix<U, R, C> &m)
> >
> > I'm surprised by the order of the operands, as I would have expected
> > users to write
> >
> > Matrix m;
> > Matrix r = m * factor;
> >
> > and not
> >
> > Matrix m;
> > Matrix r = factor * m;
> >
> > I recommend supporting both, you can easily implement one based on the
> > other.
> >
> > It would also be useful to support the following with a member operator:
> >
> > Matrix m;
> > Matrix r;
> > r *= factor;
> >
> > > +{
> > > + Matrix<U, R, C> result;
> > > +
> > > + for (unsigned int i = 0; i < R; i++)
> > > + for (unsigned int j = 0; j < C; j++)
> > > + result[i][j] = d * m[i][j];
> >
> > I think
> >
> > for (unsigned int i = 0; i < R * C; i++)
> > result.data_[i] = d * m.data_[i];
> >
> > would be more efficient.
>
> Yeah but data_ is private...
You can add a friend statement to make it accessible to the out-of-class
operators. See the other Vector class I shared with you recently.
> > > +
> > > + return result;
> > > +}
> > > +
> > > +#ifndef __DOXYGEN__
> > > +template<typename T,
> > > + unsigned int R1, unsigned int C1,
> > > + unsigned int R2, unsigned int C2,
> > > + std::enable_if_t<std::is_arithmetic_v<T> && C1 == R2> * = nullptr>
> > > +#endif /* __DOXYGEN__ */
> > > +Matrix<T, R1, C2> operator*(const Matrix<T, R1, C1> &m1, const Matrix<T, R2, C2> &m2)
> >
> > This can also be simplified in a similar way as above.
> >
> > > +{
> > > + Matrix<T, R1, C2> result;
> > > +
> > > + for (unsigned int i = 0; i < R1; i++) {
> > > + for (unsigned int j = 0; j < C2; j++) {
> > > + T sum = 0;
> > > +
> > > + for (unsigned int k = 0; k < C1; k++)
> > > + sum += m1[i][k] * m2[k][j];
> > > +
> > > + result[i][j] = sum;
> > > + }
> > > + }
> > > +
> > > + return result;
> > > +}
> > > +
> > > +#ifndef __DOXYGEN__
> > > +template<typename T, unsigned int R, unsigned int C,
> > > + std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
> >
> > Ensured by the Matrix type.
> >
> > > +#endif /* __DOXYGEN__ */
> > > +Matrix<T, R, C> operator+(const Matrix<T, R, C> &m1, const Matrix<T, R, C> &m2)
> > > +{
> > > + Matrix<T, R, C> result;
> > > +
> > > + for (unsigned int i = 0; i < R; i++)
> > > + for (unsigned int j = 0; j < C; j++)
> > > + result[i][j] = m1[i][j] + m2[i][j];
> >
> > I think
> >
> > for (unsigned int i = 0; i < R * C; i++)
> > result.data_[i] = m1.data_[i] + m2.data_[i];
> >
> > would be more efficient.
> >
> > > +
> > > + return result;
> > > +}
> > > +
> > > +} /* namespace ipa */
> > > +
> > > +#ifndef __DOXYGEN__
> > > +template<typename T, unsigned int R, unsigned int C>
> > > +std::ostream &operator<<(std::ostream &out, const ipa::Matrix<T, R, C> &m)
> > > +{
> > > + out << m.toString();
> > > + return out;
> > > +}
> > > +#endif /* __DOXYGEN__ */
> > > +
> > > +} /* namespace libcamera */
> > > diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> > > index b663afc7d9fe..067d0d273e0a 100644
> > > --- a/src/ipa/libipa/meson.build
> > > +++ b/src/ipa/libipa/meson.build
> > > @@ -7,6 +7,7 @@ libipa_headers = files([
> > > 'exposure_mode_helper.h',
> > > 'fc_queue.h',
> > > 'histogram.h',
> > > + 'matrix.h',
> > > 'module.h',
> > > ])
> > >
> > > @@ -17,6 +18,7 @@ libipa_sources = files([
> > > 'exposure_mode_helper.cpp',
> > > 'fc_queue.cpp',
> > > 'histogram.cpp',
> > > + 'matrix.cpp',
> > > 'module.cpp',
> > > ])
> > >
--
Regards,
Laurent Pinchart
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