Make Waves2AMR routines deterministic by default

amr-wind/ocean_waves/relaxation_zones/waves2amr_ops.H

@@ -215,6 +215,10 @@ struct ReadInputsOp<W2AWaves>
             pp.query("HOS_init_time", wdata.t_winit);
         }
 
+        // Default fftw_plan is deterministic
+        std::string fftw_planner_flag{"estimate"};
+        pp.query("fftw_planner_flag", fftw_planner_flag);
+
         amrex::Vector<amrex::Real> prob_lo_input(AMREX_SPACEDIM);
         amrex::ParmParse pp_geom("geometry");
         pp_geom.getarr("prob_lo", prob_lo_input);
@@ -300,9 +304,22 @@ struct ReadInputsOp<W2AWaves>
         wdata.v_mptr = modes_hosgrid::allocate_complex(wdata.n0, wdata.n1);
         wdata.w_mptr = modes_hosgrid::allocate_complex(wdata.n0, wdata.n1);
 
+        // Set up planner flag based on input
+        auto plan_f = modes_hosgrid::planner_flags::estimate;
+        if (fftw_planner_flag == "patient") {
+            plan_f = modes_hosgrid::planner_flags::patient;
+        } else if (fftw_planner_flag == "exhaustive") {
+            plan_f = modes_hosgrid::planner_flags::exhaustive;
+        } else if (fftw_planner_flag == "measure") {
+            plan_f = modes_hosgrid::planner_flags::measure;
+        } else if (!(fftw_planner_flag == "estimate")) {
+            amrex::Print()
+                << "WARNING (waves2amr_ops): invalid fftw_planner_flag "
+                   "specified; defaulting to estimate (FFTW_ESTIMATE).\n";
+        }
         // Set up plan for FFTW
-        wdata.plan =
-            modes_hosgrid::plan_ifftw(wdata.n0, wdata.n1, wdata.eta_mptr);
+        wdata.plan = modes_hosgrid::plan_ifftw(
+            wdata.n0, wdata.n1, wdata.eta_mptr, plan_f);
 
         // Create height vector for velocity mode conversion before
         // interpolation, with prob_lo as bottom

docs/sphinx/user/inputs_ocean_waves.rst

@@ -118,6 +118,17 @@ The following input arguments are only valid for the W2AWaves wave type:
    This argument is only active if HOS_init_timestep is omitted. AMR-Wind will pick the
    time step in the modes closest to the specified time.
 
+.. input_param:: OceanWaves.label.fftw_planner_flag
+
+   **type:** String, optional, default = estimate
+
+   When setting up a plan for the inverse Fourier transform within the Waves2AMR library,
+   the FFTW algorithm can use different techniques to choose among available methods. Some of these
+   are faster than others, and the optimal choice can also depend on the architecture. The
+   default, "estimate", which corresponds to FFTW_ESTIMATE, is deterministic. The other
+   options are "exhaustive", "patient", and "measure". Variations from nondeterministic
+   approaches are tiny, on the order of machine precision.
+
 .. input_param:: OceanWaves.label.number_interp_points_in_z
 
    **type:** Integer, mandatory