balanced m=1: time=8, utilization=0.250
balanced m=4: time=14, utilization=0.571
balanced m=16: time=38, utilization=0.842
imbalanced m=1: time=10, utilization=0.250
imbalanced m=4: time=22, utilization=0.455
imbalanced m=16: time=70, utilization=0.571
per-operation overhead=0.0: best tested microbatches=128, elapsed=65.500
per-operation overhead=0.1: best tested microbatches=32, elapsed=77.000
per-operation overhead=0.5: best tested microbatches=16, elapsed=95.000
per-operation overhead=1.0: best tested microbatches=8, elapsed=110.000
