TY - JOUR

T1 - Real-time bidirectional search

T2 - Coordinated problem solving in uncertain situations

AU - Ishida, Toru

PY - 1996

Y1 - 1996

N2 - This paper investigates real-time bidirectional search (RTBS) algorithms, where two problem solvers, starting from the initial and goal states, physically move toward each other. To evaluate the RTBS performance, two kinds of algorithms are proposed and are compared to real-time unidirectional search. One is called centralized RTBS where a supervisor always selects the best action from all possible moves of the two problem solvers. The other is called decoupled RTBS where no supervisor exists and the two problem solvers independently select their next moves. Experiments on mazes and n-puzzles show that 1) in clear situations decoupled RTBS performs better, while in uncertain situations, centralized RTBS becomes more efficient, and that 2) RTBS is more efficient than real-time unidirectional search for 15-and 24-puzzles but not for randomly generated mazes. It will be shown that the selection of the problem solving organization is the selection of the problem space, which determines the baseline of the organizational efficiency; once a difficult problem space is selected, the local coordination among problem solvers hardly overcome the deficit.

AB - This paper investigates real-time bidirectional search (RTBS) algorithms, where two problem solvers, starting from the initial and goal states, physically move toward each other. To evaluate the RTBS performance, two kinds of algorithms are proposed and are compared to real-time unidirectional search. One is called centralized RTBS where a supervisor always selects the best action from all possible moves of the two problem solvers. The other is called decoupled RTBS where no supervisor exists and the two problem solvers independently select their next moves. Experiments on mazes and n-puzzles show that 1) in clear situations decoupled RTBS performs better, while in uncertain situations, centralized RTBS becomes more efficient, and that 2) RTBS is more efficient than real-time unidirectional search for 15-and 24-puzzles but not for randomly generated mazes. It will be shown that the selection of the problem solving organization is the selection of the problem space, which determines the baseline of the organizational efficiency; once a difficult problem space is selected, the local coordination among problem solvers hardly overcome the deficit.

KW - Bidirectional search

KW - Heuristic depression

KW - Organizational problem solving

KW - Problem solving

KW - Real-time problem solving

KW - Real-time search

KW - Search

UR - http://www.scopus.com/inward/record.url?scp=0030168653&partnerID=8YFLogxK

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U2 - 10.1109/34.506412

DO - 10.1109/34.506412

M3 - Article

AN - SCOPUS:0030168653

VL - 18

SP - 617

EP - 628

JO - IEEE Transactions on Pattern Analysis and Machine Intelligence

JF - IEEE Transactions on Pattern Analysis and Machine Intelligence

SN - 0162-8828

IS - 6

ER -