Finishing up and starting lu decomp

include/decomp/lu.h

@@ -0,0 +1,61 @@
+#pragma once
+
+#include "./utils/vector.h"
+#include "./utils/matrix.h"
+
+namespace decomp{
+
+	// Stores PA = LU with partial pivoting (row permutations).
+	template <typename T>
+	struct LU{
+		utils::Matrix<T> LUmat; 	// combined L (unit diagonal implied) and U
+		std::vector<uint64_t> piv;	// pivot indices (row permutations)
+		bool singular= false;		// set true if zero (or near-zero) pivots encountered
+
+		LU() = default;
+
+    	explicit LU(const utils::Matrix<T>& A) {
+        	factor(A);
+        }
+
+    	void factor(const utils::Matrix<T>&A){
+
+    		const uint64_t rows = A.rows();
+    		if (rows != A.cols()){
+    			throw std::runtime_error("LU: factor non-square");
+    		}
+
+    		if (rows == 0){
+    			LUmat = A;
+    			piv.clear();
+    			singular = false;
+    			return;
+    		}
+
+    		T big, tmp;
+
+    		LUmat = A;
+    		piv.resize(rows);		// piv stores the implicit scaling of each row.
+    		//double d = 1.0;			// No row interchanges yet.
+
+    		for (uint64_t i = 0; i < rows; ++i){	// Loop over rows to get the implicit scaling information.
+    			big = T{0};
+    			for (uint64_t j = 0; j < rows; ++j){
+    				tmp=std::abs(LUmat(i,j));
+    				if (tmp > big){
+    					big = tmp;
+    				}
+    			}
+    			if (big == T{0}){
+    				throw std::runtime_error("Singular matrix in LU.factor()");
+    			}
+    		}
+    	}
+
+	}; // struct LU
+
+	typedef LU<float> LUf;
+	typedef LU<double> LUd;
+
+
+} // namespace decomp