# k=20 queries=1000000 median of 5, ns per op
       n   veb_succ   hbm_succ   set_succ    veb_ins    hbm_ins    set_ins
     256       20.2        6.5       25.1       13.1        2.9       32.1
    1024       19.6        5.8       35.7       22.1        3.0       50.3
    4096       21.8        4.0       51.4       27.2        2.8       61.3
   16384       31.3        5.7       73.7       39.0        4.4       85.2
   65536       43.5        5.2      121.4       66.7        2.7      121.3
  262144       71.5        2.1      297.1       83.1        1.3      181.4