[PATCH] ipa: libipa: vector: Add matrix-vector multiplication

[Kieran Bingham]

Quoting Paul Elder (2024-06-10 15:25:01)
> On Mon, Jun 10, 2024 at 12:53:22PM +0100, Kieran Bingham wrote:
> > Quoting Paul Elder (2024-06-07 09:20:45)
> > > Add an operation for multiplying a matrix with a vector.
> > > 
> > > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> > > 
> > > ---
> > > Depends on v6 of "ipa: libipa: Add Matrix class" and v5 of "ipa: libipa:
> > > Add Vector class"
> > > ---
> > >  src/ipa/libipa/vector.cpp | 12 ++++++++++++
> > >  src/ipa/libipa/vector.h   | 22 ++++++++++++++++++++++
> > >  2 files changed, 34 insertions(+)
> > > 
> > > diff --git a/src/ipa/libipa/vector.cpp b/src/ipa/libipa/vector.cpp
> > > index bdc3c447c..e18426fe5 100644
> > > --- a/src/ipa/libipa/vector.cpp
> > > +++ b/src/ipa/libipa/vector.cpp
> > > @@ -145,6 +145,18 @@ namespace ipa {
> > >   * \return The length of the vector
> > >   */
> > >  
> > > +/**
> > > + * \fn Vector<T, R1> operator*(const Matrix<T, R1, C1> &m, const Vector<T, R2> &v)
> > > + * \brief Multiply a matrix by a vector
> > > + * \tparam T Numerical type of the contents of the matrix and vector
> > > + * \tparam R1 The number of rows in the matrix
> > > + * \tparam C1 The number of colums in the matrix
> > > + * \tparam R2 The number of elements in the vector
> > > + * \param m The matrix
> > > + * \param v The vector
> > > + * \return Product of matrix \a m and vector \a v
> > > + */
> > > +
> > >  /**
> > >   * \fn bool operator==(const Vector<T, R> &lhs, const Vector<T, R> &rhs)
> > >   * \brief Compare vectors for equality
> > > diff --git a/src/ipa/libipa/vector.h b/src/ipa/libipa/vector.h
> > > index 87aad28b5..934b44494 100644
> > > --- a/src/ipa/libipa/vector.h
> > > +++ b/src/ipa/libipa/vector.h
> > > @@ -17,6 +17,8 @@
> > >  
> > >  #include "libcamera/internal/yaml_parser.h"
> > >  
> > > +#include "matrix.h"
> > > +
> > >  namespace libcamera {
> > >  
> > >  LOG_DECLARE_CATEGORY(Vector)
> > > @@ -166,6 +168,26 @@ private:
> > >         std::array<T, R> data_;
> > >  };
> > >  
> > > +#ifndef __DOXYGEN__
> > > +template<typename T,
> > > +        unsigned int R1, unsigned int C1,
> > > +        unsigned int R2,
> > > +        std::enable_if_t<std::is_arithmetic_v<T> && C1 == R2> * = nullptr>
> > > +#endif /* __DOXYGEN__ */
> > > +Vector<T, R1> operator*(const Matrix<T, R1, C1> &m, const Vector<T, R2> &v)
> > > +{
> > > +       Vector<T, R1> result;
> > > +
> > 
> > Does this need to ASSERT(C1 == R2); or such?
> 
> It's in SFINAE... is that not sufficient?

Ah, you mean this line above:

       std::enable_if_t<std::is_arithmetic_v<T> && C1 == R2> * = nullptr>

I missed that. If it provides the compile time guarantees, then sure -
even better.

--
Kieran


> 
> > 
> > Other than that it looks ok to me, but I haven't seen the usage yet (or
> > tests :D)
> > 
> > 
> > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> 
> Thanks,
> 
> Paul
> 
> > 
> > 
> > > +       for (unsigned int i = 0; i < R1; i++) {
> > > +               T sum = 0;
> > > +               for (unsigned int j = 0; j < C1; j++)
> > > +                       sum += m[i][j] * v[j];
> > > +               result[i] = sum;
> > > +       }
> > > +
> > > +       return result;
> > > +}
> > > +
> > >  #ifndef __DOXYGEN__
> > >  template<typename T, unsigned int R,
> > >          std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
> > > -- 
> > > 2.39.2
> > >