What program first made decisions by node-type?

[lkaufman]

Which is the first program known to make distinctions in its search algorithms between PV nodes and non-PV nodes? This could be different extensions or different reductions based on node type. I don't recall hearing of this prior to the 2000s, but I could well be wrong.

[Daniel Shawul]

AFAIK Fruit. I believe Fabian did it to get a stable search and PV.
No null_move at PV, no transposition cut off at PV, no futility at PV, no lmr at pv, more extensions at pv..
In general no selectivity at pv except for the extensions. Most of them have some elo cost associated with them it seems (however tiny).
Almost everybody does LMR at pv now, while I did it from the very beginning..

[michiguel]

AFAIK Fruit. I believe Fabian did it to get a stable search and PV.
No null_move at PV, no transposition cut off at PV, no futility at PV, no lmr at pv, more extensions at pv..
In general no selectivity at pv except for the extensions. Most of them have some elo cost associated with them it seems (however tiny).
Almost everybody does LMR at pv now, while I did it from the very beginning..

This is much older. Averno, according to his author, had different search functions for PV and non-PV circa 2001 and I am sure there were precedents for it.

Miguel

[Daniel Shawul]

If parallel search counts , then it is way back. PV-split comes to mind.
I am sure Knuth's PV,CUT and ALL node classification have been used in many programs in different ways.
But none in a way Fruit did it to take care of its PV. I believe this is more of a style than substance. But the fact that Fruit did less extensions did boost its elo a lot IMO.
The OP's question has to more specific . Also published material paper , source code or even a forum post would be good to have when discussing things of historical matter.

Daniel

[JuLieN]

Second question on computer chess history, Larry. Are you writing a book?

[lkaufman]

No, I'm just curious about who should get credit for these ideas. I am writing a chess book, but not on computer chess.

[Gerd Isenberg]

Which is the first program known to make distinctions in its search algorithms between PV nodes and non-PV nodes? This could be different extensions or different reductions based on node type. I don't recall hearing of this prior to the 2000s, but I could well be wrong.

Implicit the first programs using PVS/Negascout with some forward pruning near the tips, in PVS implementations often with different PVS/NWS routines.

Using explicit different extensions and later reductions, I don't know. Probably already early Type-B programs like Awit and Chaos, and Lang programs or even Henne/Nitsche. Levy, Broughton and Taylor did not mention node types explicitly in their 1989 SEX paper, but probability that a terminal node becomes part of the PV.