grass.benchmark: shuffle runs for benchmarking by number of cores (#2152)

To avoid bias when other processes are running at the same time

python/grass/benchmark/runners.py

@@ -15,6 +15,7 @@
 """Basic functions for benchmarking modules"""
 
 import shutil
+import random
 from types import SimpleNamespace
 
 import grass.script as gs
@@ -68,7 +69,7 @@ def benchmark_single(module, label, repeat=5):
     )
 
 
-def benchmark_nprocs(module, label, max_nprocs, repeat=5):
+def benchmark_nprocs(module, label, max_nprocs, repeat=5, shuffle=True):
     """Benchmark module using values of nprocs up to *max_nprocs*.
 
     *module* is an instance of PyGRASS Module class or any object which
@@ -82,6 +83,8 @@ def benchmark_nprocs(module, label, max_nprocs, repeat=5):
     to generate a continuous range of integer values from 1 up to *max_nprocs*.
     *repeat* sets how many times the each run is repeated.
     So, the module will run ``max_nprocs * repeat`` times.
+    Runs are executed in random order, set *shuffle* to false if they
+    need to be executed in order based on number of threads.
 
     *label* is a text to add to the result (for user-facing display).
     Optional *nprocs* is passed to the module if present.
@@ -102,27 +105,28 @@ def benchmark_nprocs(module, label, max_nprocs, repeat=5):
     avg_times = []
     all_times = []
     nprocs_list = list(range(1, max_nprocs + 1))
-    for nprocs in nprocs_list:
-        print("\u2500" * term_size.columns)
-        print(f"Benchmark with {nprocs} thread(s)...\n")
-        time_sum = 0
-        measured_times = []
-        for _ in range(repeat):
-            module.update(nprocs=nprocs)
-            module.run()
-            print(f"{module.time}s")
-            time_sum += module.time
-            measured_times.append(module.time)
-
-        avg = time_sum / repeat
+    nprocs_list_shuffled = sorted(nprocs_list * repeat)
+    if shuffle:
+        random.shuffle(nprocs_list_shuffled)
+    times = {}
+    print("\u2500" * term_size.columns)
+    for nprocs in nprocs_list_shuffled:
+        module.update(nprocs=nprocs)
+        module.run()
+        print(f"Run with {nprocs} thread(s) took {module.time}s\n")
+        if nprocs in times:
+            times[nprocs] += [module.time]
+        else:
+            times[nprocs] = [module.time]
+    for nprocs in sorted(times):
+        avg = sum(times[nprocs]) / repeat
         avg_times.append(avg)
-        all_times.append(measured_times)
+        all_times.append(times[nprocs])
         if nprocs == 1:
             serial_avg = avg
         if avg < min_avg:
             min_avg = avg
             min_time = nprocs
-        print(f"\nResult - {avg}s")
 
     print("\u2500" * term_size.columns)
     if serial_avg is not None: