[Algorit] Use a reasonable initial iterate, not 0

This was only a temporary workaround for problems that no longer exist.

src/timestepping/backward_euler.cc

@@ -70,8 +70,7 @@ void BackwardEuler<Vector, Matrix, Function, dim>::setup(
     Arithmetic::subtractProduct(rhs, A, u_o);
   }
 
-  // v_o makes a good initial iterate; we could use anything, though
-  iterate = 0.0;
+  iterate = v_o;
 
   for (size_t i = 0; i < dirichletNodes.size(); ++i)
     for (size_t j = 0; j < dim; ++j)

src/timestepping/newmark.cc

@@ -80,8 +80,7 @@ void Newmark<Vector, Matrix, Function, dim>::setup(Vector const &ell,
     Arithmetic::subtractProduct(rhs, A, u_o);
   }
 
-  // v_o makes a good initial iterate; we could use anything, though
-  iterate = 0.0;
+  iterate = v_o;
 
   for (size_t i = 0; i < dirichletNodes.size(); ++i)
     for (size_t j = 0; j < dim; ++j)