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

[Paul Elder]

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;
+
+	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