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␈↓ ↓H␈↓␈↓βS␈↓∧ Artificial Intelligence Laboratory, STANFORD UNIVERSITY, Stanford, California 94305

␈↓ ↓H␈↓∧Telephone 415 497-4430␈↓ 
,May 9, 1980 




␈↓ ↓H␈↓Prof. Judea Pearl
␈↓ ↓H␈↓Cognitive Systems Laboratory
␈↓ ↓H␈↓School of Engineering and Applied Science
␈↓ ↓H␈↓U.C.L.A.
␈↓ ↓H␈↓Los Angeles, CA  90024

␈↓ ↓H␈↓Dear Judea:

␈↓ ↓H␈↓        Thanks␈α
for␈αyour␈α
paper␈αabout␈α
alpha-beta.␈α As␈α
the␈α"father"␈α
of␈αthe␈α
algorithm,␈αI␈α
must␈αprotest
␈↓ ↓H␈↓that␈αyou␈αhave␈αsolved␈αthe␈αwrong␈αproblem.␈α The␈αpoint␈α
of␈αthe␈αalgorithm␈αis␈αthat␈αit␈αis␈αto␈αbe␈αused␈α
with
␈↓ ↓H␈↓a␈α⊃move-ordering␈α⊃heuristic␈α⊃that␈α⊃tries␈α⊃to␈α⊃examine␈α⊃the␈α⊃best␈α⊃move␈α⊃≡rst.␈α⊃ Results␈α∩about␈α⊃randomly
␈↓ ↓H␈↓generated trees seem to me unmotivated.

␈↓ ↓H␈↓        Interesting␈α
results␈α
would␈α∞involve␈α
making␈α
assumptions␈α
about␈α∞how␈α
often␈α
the␈α
best␈α∞move␈α
was
␈↓ ↓H␈↓examined ≡rst, second, etc. and then determining the expected number of positions examined.

␈↓ ↓H␈↓        Is␈α∂there␈α∞something␈α∂I␈α∞don't␈α∂understand␈α∞about␈α∂the␈α∞question␈α∂you␈α∞have␈α∂investigated␈α∂and␈α∞the
␈↓ ↓H␈↓other questions mentioned in the paper that makes my qualms irrelevant?


␈↓ ↓H␈↓Best regards,



␈↓ ↓H␈↓John McCarthy
␈↓ ↓H␈↓Director
␈↓ ↓H␈↓Professor of Computer Science