eigen/doc/snippets/Tutorial_solve_reuse_decomposition.cpp

Matrix3f A(3, 3);
A << 1, 2, 3, 4, 5, 6, 7, 8, 10;
PartialPivLU<Matrix3f> luOfA(A);  // compute LU decomposition of A
Vector3f b;
b << 3, 3, 4;
Vector3f x;
x = luOfA.solve(b);
cout << "The solution with right-hand side (3,3,4) is:" << endl;
cout << x << endl;
b << 1, 1, 1;
x = luOfA.solve(b);
cout << "The solution with right-hand side (1,1,1) is:" << endl;
cout << x << endl;