In Elegance vs. performance RS et al bring up some interesting results, and a nice graph widget to visualise them.
Here's the widget:
pack [canvas .c -bg white -width 600 -height 500] -expand 1 array set color { 1 red 2 blue 3 green 4 yellow } foreach idx {1 2 3} { .c create line 0 500 0 500 -fill $color($idx) -tag sum$idx } for {set i 1} {$i<600} {incr i} { set list [lrange [string repeat "1 " [expr {$i*2}]] 0 end] foreach idx {1 2 3} { set t [lindex [time {sum$idx $list}] 0] .c coords sum$idx [concat [.c coords sum$idx] $i [expr {500-$t/40}]] } update }