Sync public subset from Flux (private)

include/numerics/matvec.h

@@ -0,0 +1,156 @@
+#ifndef _matvec_n_
+#define _matvec_n_
+
+
+#include "./utils/matrix.h"
+#include "./core/omp_config.h"
+
+namespace numerics{
+	
+// =================================================
+//   y = A * x    (Matrix–Vector product)
+// =================================================
+	template <typename T>
+	utils::Vector<T> matvec(const utils::Matrix<T>& A, const utils::Vector<T>& x) {
+	    if (A.cols() != x.size()) {
+	        throw std::runtime_error("matvec: dimension mismatch");
+	    }
+
+	    const uint64_t m = A.rows();
+	    const uint64_t n = A.cols();
+
+	    utils::Vector<T> y(m, T{0});
+
+	    for (uint64_t i = 0; i < m; ++i) {
+	        for (uint64_t j = 0; j < n; ++j) {
+	            y[i] += A(i, j) * x[j];
+	        }
+	    }
+	    return y;
+	}
+	// -------------- Collapse(2) OpenMP ----------------
+	template <typename T>
+	utils::Vector<T> matvec_omp(const utils::Matrix<T>& A, const utils::Vector<T>& x) {
+	    if (A.cols() != x.size()) {
+	        throw std::runtime_error("matvec: dimension mismatch");
+	    }
+
+	    const uint64_t m = A.rows();
+	    const uint64_t n = A.cols();
+
+	    utils::Vector<T> y(m, T{0}); // <-- y has length m (rows)
+
+
+        const T* xptr = x.data();
+        const T* Aptr = A.data();	// row-major: A(i,j) == Aptr[i*n + j]
+
+        // Each row i is an independent dot product: y[i] = dot(A[i,*], x)
+	    #pragma omp parallel for schedule(static)
+	    for (uint64_t i = 0; i < m; ++i) {
+            const T* row = Aptr + i * n;     // contiguous row i
+            T acc = T{0};
+            #pragma omp simd reduction(+:acc)
+	        for (uint64_t j = 0; j < n; ++j) {
+	            acc += row[j] * xptr[j];
+	        }
+	        y[i] = acc;
+		}
+
+	    return y;
+	}
+
+	// -------------- Auto OpenMP ----------------
+	template <typename T>
+	utils::Vector<T> matvec_auto(const utils::Matrix<T>& A,
+	                             const utils::Vector<T>& x) {
+
+	    
+	    uint64_t work = A.rows() * A.cols();
+
+	    bool can_parallel = omp_config::omp_parallel_allowed();
+		#ifdef _OPENMP
+		    int threads = omp_get_max_threads();
+		#else
+		    int threads = 1;
+		#endif
+
+	    if (can_parallel || work > static_cast<uint64_t>(threads) * 4ull) {
+	        return matvec_omp(A,x);
+	    }
+	    else{
+	    	// Safe fallback
+	    	return matvec(A,x);
+	    }
+	    
+	}
+
+// =================================================
+//   y = x * A    (Vector–Matrix product)
+// =================================================
+	template <typename T>
+	utils::Vector<T> vecmat(const utils::Vector<T>& x, const utils::Matrix<T>& A) {
+	    if (x.size() != A.rows()) {
+	        throw std::runtime_error("vecmat: dimension mismatch");
+	    }
+	    const uint64_t m = A.rows();
+	    const uint64_t n = A.cols();
+
+	    utils::Vector<T> y(n, T{0});
+
+	    for (uint64_t j = 0; j < n; ++j) {
+	        for (uint64_t i = 0; i < m; ++i) {
+	            y[j] += x[i] * A(i, j);
+	        }
+	    }
+	    return y;
+	}
+
+	// -------------- Collapse(2) OpenMP ----------------
+	template <typename T>
+	utils::Vector<T> vecmat_omp(const utils::Vector<T>& x, const utils::Matrix<T>& A) {
+	    if (x.size() != A.rows()) {
+	        throw std::runtime_error("vecmat: dimension mismatch");
+	    }
+	    const uint64_t m = A.rows();
+	    const uint64_t n = A.cols();
+
+	    utils::Vector<T> y(n, T{0});
+	    #pragma omp parallel for schedule(static)
+	    for (uint64_t j = 0; j < n; ++j) {
+	        T acc = T{0};
+	        for (uint64_t i = 0; i < m; ++i) {
+	            acc += x[i] * A(i, j);
+	        }
+	        y[j] = acc;
+	    }
+	    return y;
+	}
+
+	// -------------- Auto OpenMP ----------------
+	template <typename T>
+	utils::Vector<T> vecmat_auto(const utils::Vector<T>& x,
+								 const utils::Matrix<T>& A) {
+	    
+	    uint64_t work = A.rows() * A.cols();
+
+	    bool can_parallel = omp_config::omp_parallel_allowed();
+		#ifdef _OPENMP
+		    int threads = omp_get_max_threads();
+		#else
+		    int threads = 1;
+		#endif
+
+	    if (can_parallel || work > static_cast<uint64_t>(threads) * 4ull) {
+	        return vecmat_omp(x,A);
+	    }
+	    else{
+	    	// Safe fallback
+	    	return vecmat(x,A);
+	    }
+	    
+	}
+
+
+} // namespace numerics
+
+#endif // _matvec_n_