make speed fading configurable

CHANGELOG.md

@@ -31,6 +31,7 @@
    * ADDED: the workflow to find landmarks in a graph tile, associate them with nearby edges, and update the graph tile to store the associations [#4278](https://github.com/valhalla/valhalla/pull/4278)
    * ADDED: update maneuver generation to add nearby landmarks to maneuvers as direction support [#4293](https://github.com/valhalla/valhalla/pull/4293)
    * CHANGED: the boost property tree config is now read into a singleton that doesn't need to be passed around anymore [#4220](https://github.com/valhalla/valhalla/pull/4220)
+   * ADDED: Make livespeed fading time configurable in valhalla.json [#4177](https://github.com/valhalla/valhalla/pull/4177)
 
 ## Release Date: 2023-05-11 Valhalla 3.4.0
 * **Removed**

scripts/valhalla_build_config

@@ -270,6 +270,9 @@ config = {
         'max_exclude_polygons_length': 10000,
         'max_distance_disable_hierarchy_culling': 0,
     },
+    'baldr': {
+        'live_speed_fading_sec': 3600
+    },
     'statsd': {
         'host': Optional(str),
         'port': 8125,
@@ -549,6 +552,9 @@ help_text = {
         'batch_size': 'Approximate maximum size in bytes of each batch of stats to send to statsd',
         'tags': 'List of tags to include with each metric',
     },
+    'baldr': {
+        'live_speed_fading_sec': 'The time (in seconds) over which the live speed will be faded into the traffic speed sources',
+    },
 }
 
 

src/baldr/graphtile.cc

@@ -6,6 +6,7 @@
 #include "baldr/sign.h"
 #include "baldr/tilehierarchy.h"
 #include "filesystem.h"
+#include "config.h"
 #include "midgard/aabb2.h"
 #include "midgard/pointll.h"
 #include "midgard/tiles.h"
@@ -368,6 +369,11 @@ void GraphTile::Initialize(const GraphId& graphid) {
     lane_connectivity_size_ = header_->end_offset() - header_->lane_connectivity_offset();
   }
 
+  try {
+    live_speed_fading_sec_ = config().get<float>("baldr.live_speed_fading_sec", 3600);
+  } catch (const ConfigUninitializedException &e){
+    live_speed_fading_sec_ = 3600;
+  }
   // For reference - how to use the end offset to set size of an object (that
   // is not fixed size and count).
   // example_size_ = header_->end_offset() - header_->example_offset();

valhalla/baldr/graphtile.h

@@ -640,12 +640,12 @@ class GraphTile {
     // TODO(danpat): for short-ish durations along the route, we should fade live
     //               speeds into any historic/predictive/average value we'd normally use
 
-    constexpr double LIVE_SPEED_FADE = 1. / 3600.;
+    double live_speed_fade = 1. / live_speed_fading_sec_;
     // This parameter describes the weight of live-traffic on a specific edge. In the beginning of the
     // route live-traffic gives more information about current congestion situation. But the further
     // we go the less consistent this traffic is. We prioritize predicted traffic in this case.
     // Want to have a smooth decrease function.
-    float live_traffic_multiplier = 1. - std::min(seconds_from_now * LIVE_SPEED_FADE, 1.);
+    float live_traffic_multiplier = 1. - std::min(seconds_from_now * live_speed_fade, 1.);
     uint32_t partial_live_speed = 0;
     float partial_live_pct = 0;
     if ((flow_mask & kCurrentFlowMask) && traffic_tile() && live_traffic_multiplier != 0.) {
@@ -872,6 +872,9 @@ class GraphTile {
   // Predicted speeds
   PredictedSpeeds predictedspeeds_;
 
+  // Time (in seconds) over which live speed will be faded into other traffic speed sources
+  float live_speed_fading_sec_;
+
   // Map of stop one stops in this tile.
   std::unordered_map<std::string, GraphId> stop_one_stops;