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"
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"
$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
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
KDB+ 4.0 2020.03.17 Copyright (C) 1993-2020 Kx Systems
l64/ 12(16)core 63960MB
EXPIRE 2021.03.26