Port the Go experiment to Python

book/src/dev/api.md

@@ -10,9 +10,11 @@ This
 [Python example](https://github.com/dabreegster/abstreet/blob/master/headless/examples/python_client.py)
 has everything you need to get started.
 
-Also check out the
-[Go example](https://github.com/dabreegster/abstreet/blob/master/headless/examples/go_client.go),
-which demonstrates just a few of the API calls.
+There's an experiment to cancel different percentages of trips and quantify the
+trip time savings on the remaining trips. The experiment is written in both
+[Go](https://github.com/dabreegster/abstreet/blob/master/headless/examples/go_client.go)
+and
+[Python](https://github.com/dabreegster/abstreet/blob/master/headless/examples/cancel_experiment.py).
 
 ## API details
 

headless/examples/cancel_experiment.py

@@ -0,0 +1,111 @@
+#!/usr/bin/python3
+# This example runs the same scenario repeatedly, each time cancelling a
+# different number of trips uniformly at random. The eventual goal is to
+# quantify how many trips need to be cancelled to substantially speed up
+# remaining ones.
+#
+# Before running this script, start the API server:
+#
+# > cargo run --release --bin headless -- --port=1234 data/system/scenarios/montlake/weekday.bin
+#
+# You may need to install https://requests.readthedocs.io
+# Keep this script formatted with autopep8 -i
+
+import argparse
+import json
+import requests
+import statistics
+import sys
+import time
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--api', default='http://localhost:1234')
+    parser.add_argument('--map_name', default='montlake')
+    parser.add_argument('--hours', type=int, default=24)
+    parser.add_argument('--cmp1', type=int, default=None)
+    parser.add_argument('--cmp2', type=int, default=None)
+    args = parser.parse_args()
+    if args.cmp1 and args.cmp2 and args.cmp1 > args.cmp2:
+        sys.exit(
+            '--cmp1={} --cmp2={} invalid, --cmp1 is the baseline'.format(args.cmp1, args.cmp2))
+    print('Simulating {} hours of data/system/scenarios/{}/weekday.bin'.format(args.hours, args.map_name))
+    print('')
+
+    num_succeeded_last = 0
+    results2 = None
+    for pct in range(100, 0, -10):
+        start = time.time()
+        results = run_sim(args, modifiers=[{'CancelPeople': pct}])
+        print('{}% of people cancelled: {:,} trips aborted, {:,} trips succeeded. Simulation took {:.1f}s'.format(
+            pct, results.num_aborted, len(results.trip_times), time.time() - start))
+        if len(results.trip_times) < num_succeeded_last:
+            print('--> less trips succeeded this round, so likely hit gridlock')
+            break
+        num_succeeded_last = len(results.trip_times)
+
+        if args.cmp2 == pct:
+            results2 = results
+        if args.cmp1 == pct:
+            print('')
+            print('Baseline cancelled {}%, experimental cancelled {}%'.format(
+                args.cmp1, args.cmp2))
+            compare_results(results, results2)
+            print('')
+
+
+# Returns Results
+def run_sim(args, modifiers=[]):
+    requests.post(args.api + '/sim/load', json={
+        'load': 'data/system/scenarios/{}/weekday.bin'.format(args.map_name),
+        'modifiers': modifiers,
+    })
+    requests.get(args.api + '/sim/goto-time',
+                 params={'t': '{}:00:00'.format(args.hours)})
+    raw_trips = requests.get(
+        args.api + '/data/get-finished-trips').json()['trips']
+
+    # Map trip ID to the duration (in seconds) of the trip. Filter out aborted
+    # (failed) trips.
+    num_aborted = 0
+    trip_times = {}
+    for (_, trip, mode, duration) in raw_trips:
+        if mode is None:
+            num_aborted += 1
+        else:
+            trip_times[trip] = duration
+
+    return Results(num_aborted, trip_times)
+
+
+class Results:
+    def __init__(self, num_aborted, trip_times):
+        self.num_aborted = num_aborted
+        # Maps trip ID to seconds
+        self.trip_times = trip_times
+
+
+def compare_results(results1, results2):
+    faster = []
+    slower = []
+
+    for trip, after_dt in results2.trip_times.items():
+        before_dt = results1.trip_times.get(trip)
+        if not before_dt:
+            # The trip didn't finish in time in the baseline run
+            continue
+        if before_dt:
+            if before_dt > after_dt:
+                faster.append(before_dt - after_dt)
+            elif after_dt > before_dt:
+                slower.append(after_dt - before_dt)
+
+    print('{:,} trips faster, average {:.1f}s savings'.format(
+        len(faster), statistics.mean(faster)))
+    print('{:,} trips slower, average {:.1f}s loss'.format(
+        len(slower), statistics.mean(slower)))
+
+
+if __name__ == '__main__':
+    main()