[PATCH v6 1/4] ipa: libipa: Add Vector class

[Stefan Klug]

Hi Paul,

thank you for the patch.
Kieran already commented some points, which I won't repeat...
I only add a few more :-)

On Fri, Jun 07, 2024 at 05:42:58PM +0900, Paul Elder wrote:
> Add a vector class to libipa. The original purpose of this is to replace
> the floating-point Point class that Raspberry Pi used in their Pwl, as
> that implementation of Point seemed more akin to a Vector than a Point.
> 
> This is added to libipa instead of to geometry.h to avoid public API
> issues, plus this is not expected to be needed by applications.
> 
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> 
> ---
> No change in v6
> 
> New in v5
> ---
>  src/ipa/libipa/vector.cpp | 162 ++++++++++++++++++++++++++++++
>  src/ipa/libipa/vector.h   | 206 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 368 insertions(+)
>  create mode 100644 src/ipa/libipa/vector.cpp
>  create mode 100644 src/ipa/libipa/vector.h
> 
> diff --git a/src/ipa/libipa/vector.cpp b/src/ipa/libipa/vector.cpp
> new file mode 100644
> index 000000000..bdc3c447c
> --- /dev/null
> +++ b/src/ipa/libipa/vector.cpp
> @@ -0,0 +1,162 @@
> +/* SPDX-License-Identifier: BSD-2-Clause */
> +/*
> + * Copyright (C) 2019, Raspberry Pi Ltd
> + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> + *
> + * Vector and related operations
> + */
> +
> +#include "vector.h"
> +
> +#include <libcamera/base/log.h>
> +
> +/**
> + * \file vector.h
> + * \brief Vector class
> + */
> +
> +namespace libcamera {
> +
> +LOG_DEFINE_CATEGORY(Vector)
> +
> +namespace ipa {
> +
> +/**
> + * \class Vector
> + * \brief Vector class
> + * \tparam T Type of numerical values to be stored in the vector
> + * \tparam R Number of rows in the vector
> + */
> +
> +/**
> + * \fn Vector::Vector()
> + * \brief Construct an identity vector
> + */
> +
> +/**
> + * \fn Vector::Vector(const std::array<T, R> &data)
> + * \brief Construct vector from supplied data
> + * \param data Data from which to construct a vector
> + *
> + * \a data is a one-dimensional vector and will be turned into a vector in
> + * row-major order. The size of \a data must be equal to the product of the
> + * number of rows and columns of the vector (RxC).
> + */
> +
> +/**
> + * \fn Vector::readYaml
> + * \brief Populate the vector with yaml data
> + * \param yaml Yaml data to populate the vector with
> + *
> + * Any existing data in the vector 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 vector (RxC).
> + *
> + * The yaml data is expected to be a list with elements of type T.
> + *
> + * \return 0 on success, negative error code otherwise
> + */
> +
> +/**
> + * \fn Vector::toString
> + * \brief Assemble and return a string describing the vector
> + * \return A string describing the vector
> + */

Is this still needed when we have ostream << () ? I don't think we need
two functions with the same purpose. Maybe move the imple into ostream
<< ()?

> +
> +/**
> + * \fn T Vector::operator[](size_t i) const
> + * \brief Index to a row in the vector
> + * \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
> + * vector. Note that the lifetime of the Span returned by this first-level
> + * operator[] is bound to that of the Vector itself, so it is not recommended
> + * to save the Span that is the result of this operator[].
> + *
> + * \return Row \a i from the vector, as a Span
> + */
> +
> +/**
> + * \fn T &Vector::operator[](size_t i)
> + * \copydoc Vector::operator[](size_t i) const
> + */
> +
> +/**
> + * \fn Vector::x()
> + * \brief Convenience function to access the first element of the vector
> + */
> +
> +/**
> + * \fn Vector::y()
> + * \brief Convenience function to access the second element of the vector
> + */
> +
> +/**
> + * \fn Vector::operator-() const
> + * \brief Negate a Vector by negating both all of its coordinates
> + * \return The negated vector
> + */
> +
> +/**
> + * \fn Vector::operator-(Vector const &other) const
> + * \brief Subtract one vector from another
> + * \param[in] other The other vector
> + * \return The difference of \a other from this vector
> + */
> +
> +/**
> + * \fn Vector::operator+()
> + * \brief Add two vectors together
> + * \param[in] other The other vector
> + * \return The sum of the two vectors
> + */
> +
> +/**
> + * \fn Vector::operator*(const Vector<T, R> &other) const
> + * \brief Compute the dot product
> + * \param[in] other The other vector
> + * \return The dot product of the two vectors
> + */
> +
> +/**
> + * \fn Vector::operator*(T factor) const
> + * \brief Scale up the vector

I stumbled over the wording "Scale up". I would just say "Multiply the
vector by a scalar"

> + * \param[in] factor The factor
> + * \return The vector scaled up by \a factor
> + */
> +
> +/**
> + * \fn Vector::operator/()
> + * \brief Scale down the vector

Maybe: Divide the vector by a scalar.

With the comments from Kieran resolved, I'm fine with it.

Reviewed-by: Stefan Klug <stefan.klug at ideasonboard.com> 

Cheers,
Stefan

> + * \param[in] factor The factor
> + * \return The vector scaled down by \a factor
> + */
> +
> +/**
> + * \fn Vector::len2()
> + * \brief Get the squared length of the vector
> + * \return The squared length of the vector
> + */
> +
> +/**
> + * \fn Vector::len()
> + * \brief Get the length of the vector
> + * \return The length of the vector
> + */
> +
> +/**
> + * \fn bool operator==(const Vector<T, R> &lhs, const Vector<T, R> &rhs)
> + * \brief Compare vectors for equality
> + * \return True if the two vectors are equal, false otherwise
> + */
> +
> +/**
> + * \fn bool operator!=(const Vector<T, R> &lhs, const Vector<T, R> &rhs)
> + * \brief Compare vectors for inequality
> + * \return True if the two vectors are not equal, false otherwise
> + */
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/vector.h b/src/ipa/libipa/vector.h
> new file mode 100644
> index 000000000..87aad28b5
> --- /dev/null
> +++ b/src/ipa/libipa/vector.h
> @@ -0,0 +1,206 @@
> +/* SPDX-License-Identifier: BSD-2-Clause */
> +/*
> + * Copyright (C) 2019, Raspberry Pi Ltd
> + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> + *
> + * Vector and related operations
> + */
> +#pragma once
> +
> +#include <algorithm>
> +#include <array>
> +#include <cmath>
> +#include <sstream>
> +
> +#include <libcamera/base/log.h>
> +#include <libcamera/base/span.h>
> +
> +#include "libcamera/internal/yaml_parser.h"
> +
> +namespace libcamera {
> +
> +LOG_DECLARE_CATEGORY(Vector)
> +
> +namespace ipa {
> +
> +#ifndef __DOXYGEN__
> +template<typename T, unsigned int R,
> +	 std::enable_if_t<std::is_arithmetic_v<T> && R >= 2> * = nullptr>
> +#else
> +template<typename T, unsigned int R>
> +#endif /* __DOXYGEN__ */
> +class Vector
> +{
> +public:
> +	Vector() = default;
> +
> +	Vector(const std::array<T, R> &data)
> +	{
> +		ASSERT(data.size() == R);
> +
> +		for (unsigned int i = 0; i < R; i++)
> +			data_[i] = data[i];
> +	}
> +
> +	~Vector() = default;
> +
> +	int readYaml(const libcamera::YamlObject &yaml)
> +	{
> +		if (yaml.size() != R) {
> +			LOG(Vector, Error)
> +				<< "Wrong number of values in vector: expected "
> +				<< R << ", got " << yaml.size();
> +			return -EINVAL;
> +		}
> +
> +		unsigned int i = 0;
> +		for (const auto &x : yaml.asList()) {
> +			auto value = x.get<T>();
> +			if (!value) {
> +				LOG(Vector, Error) << "Failed to read vector value";
> +				return -EINVAL;
> +			}
> +
> +			data_[i++] = *value;
> +		}
> +
> +		return 0;
> +	}
> +
> +	const std::string toString() const
> +	{
> +		std::stringstream out;
> +
> +		out << "Vector { ";
> +		for (unsigned int i = 0; i < R; i++) {
> +			out << (*this)[i];
> +			out << ((i + 1 < R) ? ", " : " ");
> +		}
> +		out << " }";
> +
> +		return out.str();
> +	}
> +
> +	const T operator[](size_t i) const
> +	{
> +		return data_[i];
> +	}
> +
> +	T &operator[](size_t i)
> +	{
> +		return data_[i];
> +	}
> +
> +	const T x() const
> +	{
> +		return data_[0];
> +	}
> +
> +	const T y() const
> +	{
> +		return data_[1];
> +	}
> +
> +	constexpr Vector<T, R> operator-() const
> +	{
> +		Vector<T, R> ret;
> +		for (unsigned int i = 0; i < R; i++)
> +			ret[i] = -data_[i];
> +		return ret;
> +	}
> +
> +	constexpr Vector<T, R> operator-(const Vector<T, R> &other) const
> +	{
> +		Vector<T, R> ret;
> +		for (unsigned int i = 0; i < R; i++)
> +			ret[i] = data_[i] - other[i];
> +		return ret;
> +	}
> +
> +	constexpr Vector<T, R> operator+(const Vector<T, R> &other) const
> +	{
> +		Vector<T, R> ret;
> +		for (unsigned int i = 0; i < R; i++)
> +			ret[i] = data_[i] + other[i];
> +		return ret;
> +	}
> +
> +	constexpr T operator*(const Vector<T, R> &other) const
> +	{
> +		T ret = 0;
> +		for (unsigned int i = 0; i < R; i++)
> +			ret += data_[i] * other[i];
> +		return ret;
> +	}
> +
> +	constexpr Vector<T, R> operator*(T factor) const
> +	{
> +		Vector<T, R> ret;
> +		for (unsigned int i = 0; i < R; i++)
> +			ret[i] = data_[i] * factor;
> +		return ret;
> +	}
> +
> +	constexpr Vector<T, R> operator/(T factor) const
> +	{
> +		Vector<T, R> ret;
> +		for (unsigned int i = 0; i < R; i++)
> +			ret[i] = data_[i] / factor;
> +		return ret;
> +	}
> +
> +	constexpr T len2() const
> +	{
> +		T ret = 0;
> +		for (unsigned int i = 0; i < R; i++)
> +			ret += data_[i] * data_[i];
> +		return ret;
> +	}
> +
> +	constexpr double len() const
> +	{
> +		return std::sqrt(len2());
> +	}
> +
> +private:
> +	std::array<T, R> data_;
> +};
> +
> +#ifndef __DOXYGEN__
> +template<typename T, unsigned int R,
> +	 std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
> +#endif /* __DOXYGEN__ */
> +bool operator==(const Vector<T, R> &lhs, const Vector<T, R> &rhs)
> +{
> +	for (unsigned int i = 0; i < R; i++)
> +		if (lhs[i] != rhs[i])
> +			return false;
> +
> +	return true;
> +}
> +
> +#ifndef __DOXYGEN__
> +template<typename T, unsigned int R,
> +	 std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
> +#endif /* __DOXYGEN__ */
> +bool operator!=(const Vector<T, R> &lhs, const Vector<T, R> &rhs)
> +{
> +	for (unsigned int i = 0; i < R; i++)
> +		if (lhs[i] != rhs[i])
> +			return true;
> +
> +	return false;
> +}
> +
> +} /* namespace ipa */
> +
> +#ifndef __DOXYGEN__
> +template<typename T, unsigned int R>
> +std::ostream &operator<<(std::ostream &out, const ipa::Vector<T, R> &v)
> +{
> +	out << v.toString();
> +	return out;
> +}
> +#endif /* __DOXYGEN__ */
> +
> +} /* namespace libcamera */
> -- 
> 2.39.2
>