allow single-step backward Euler

integration/BackwardEuler/be_integrator.H

@@ -181,6 +181,15 @@ int be_integrator (BurnT& state, BeT& be)
 
     int ierr;
 
+		if (be.atol_enuc < 0.0_rt) {
+			// Do a single step to the final time
+    	const amrex::Real dt_single_step = be.tout - be.t;
+			ierr = single_step(state, be, dt_single_step);
+			be.t = be.tout;
+			++be.n_step;
+			return ierr;
+		}
+
     // estimate the timestep
 
     amrex::Array1D<amrex::Real, 1, int_neqs> ydot;