Add ballistic integration as an option (#873)

* Add ballistic integration as an option

* bug fix

Co-authored-by: AboudyKreidieh <akreidieh@gmail.com>

examples/exp_configs/non_rl/i210_subnetwork.py

@@ -24,7 +24,7 @@
         lane_change_mode="strategic",
     ),
     acceleration_controller=(IDMController, {
-        "a": 0.3, "b": 2.0, "noise": 0.45
+        "a": 0.3, "b": 2.0, "noise": 0.5
     }),
 )
 
@@ -69,9 +69,10 @@
 
     # simulation-related parameters
     sim=SumoParams(
-        sim_step=0.8,
+        sim_step=0.5,
         render=False,
         color_by_speed=True,
+        use_ballistic=True
     ),
 
     # environment related parameters (see flow.core.params.EnvParams)

flow/core/kernel/simulation/traci.py

@@ -91,6 +91,10 @@ def start_simulation(self, network, sim_params):
                     "--step-length", str(sim_params.sim_step)
                 ]
 
+                # use a ballistic integration step (if request)
+                if sim_params.use_ballistic:
+                    sumo_call.append("--step-method.ballistic")
+
                 # add step logs (if requested)
                 if sim_params.no_step_log:
                     sumo_call.append("--no-step-log")

flow/core/params.py

@@ -566,6 +566,8 @@ class SumoParams(SimParams):
     color_by_speed : bool
         whether to color the vehicles by the speed they are moving at the
         current time step
+    use_ballistic: bool, optional
+        If true, use a ballistic integration step instead of an euler step
     """
 
     def __init__(self,
@@ -586,7 +588,8 @@ def __init__(self,
                  print_warnings=True,
                  teleport_time=-1,
                  num_clients=1,
-                 color_by_speed=False):
+                 color_by_speed=False,
+                 use_ballistic=False):
         """Instantiate SumoParams."""
         super(SumoParams, self).__init__(
             sim_step, render, restart_instance, emission_path, save_render,
@@ -600,6 +603,7 @@ def __init__(self,
         self.teleport_time = teleport_time
         self.num_clients = num_clients
         self.color_by_speed = color_by_speed
+        self.use_ballistic = use_ballistic
 
 
 class EnvParams:

flow/visualize/visualizer_rllib.py

@@ -74,6 +74,10 @@ def visualizer_rllib(args):
     sim_params = flow_params['sim']
     setattr(sim_params, 'num_clients', 1)
 
+    # for hacks for old pkl files TODO: remove eventually
+    if not hasattr(sim_params, 'use_ballistic'):
+        sim_params.use_ballistic = False
+
     # Determine agent and checkpoint
     config_run = config['env_config']['run'] if 'run' in config['env_config'] \
         else None