binomiq

In your benchmarks, KDB's max on longs takes twice as long as sum on longs. I am not able to replicate this with the most recent version of KDB (2020.03.30).

    $QHOME/l64/q -s 4
    KDB+ 4.0 2020.03.30 Copyright (C) 1993-2020 Kx Systems
    l64/ 4()core 516718MB <snip>

    q)zz:1000000000?1000j
    q)0.01*system"t do[100;max zz]"
    257.52
    q)0.01*system"t do[100;sum zz]"
    251.95

There's a marginal difference here rather than double.

For the version of KDB with the regression bug:

    q)0.01*system"t do[100;max zz]"
    512.21
    q)0.01*system"t do[100;sum zz]"
    254.24

Which starts to look more like your numbers.

KDB works around this by storing the nanos in 64 bits but only for a particular time range.

1707.09.22D00:12:43.145224194 (max negative) to 2292.04.10D23:47:16.854775806 (max positive)

With 0 at 2000.01.01D00:00:00.000000000

Were these benchmarks before or after 2020.03.26? There was a bug that caused max operations to take twice as long.

From the KDB+ 4.0 release notes:

2020.03.26 FIX fixed performance regression for max. e.g. q)x:100000000?100;system"ts:10 max x"