johnu, on 2018-October-26, 14:36, said:
I've been reading Bird and Anthias's Winning Notrump Leads. Surprisingly, or maybe not, the winning double dummy lead is frequently a passive lead through dummy's suit in the absence of a clear cut sequence lead, and one of the worst leads is frequently a broken suit lead into one of declarer's presumed long suits. Of course, double dummy assumes you will make the right switch and continuations after the opening lead.
I ran my own simulation and a spade, club and heart lead were all about the same, with a diamond lead was clearly worst. The results were a little insignificant because 6NT was such a heavy favorite to make (95+%) in my simulation (South having 12+ HCP and relatively balanced).
In any case, I would lead a heart through dummy's possible 4 card heart suit, and not a diamond or club when there is a good chance declarer has a 4 (or 5) card suit.
Did your simulation score the leads only by trick expectancy?
While I chose a heart, my second choice would be a diamond. Whether your simulation would dissuade me depends on how it ranked the various possibilities.
My expectation, against reasonably good players and bearing in mind my hand, is that they will make 6N most of the time and that grand would be at best a borderline proposition....I'd not be surprised if it made, but it probably needs a little luck, such as a finesse or two.
If they have 12 winners on any lead, the diamond is the one lead that is the most likely to give them 13.
So the question is: does the simulation rank the diamond as the worst because it gives rise to the highest trick expectancy for declarer or because is gives rise to the highest likelihood that 6N makes?
Unless playing BAM or mps, I'd cheerfully give them 13 tricks 9 times out of 10, if I hold them to 11 tricks that other time.
That would mean the diamond lead generated a trick expectancy of 12.8, yet at imps or rubber, that one 'beat' outweighs all those overtricks.
I know it is more complicated than that, but I think you'll get the point.
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari