SPEC CPU2006 Benchmark Description

Benchmark Name


Benchmark Authors

Gian-Carlo Pascutto <gcp [at] sjeng.org>
Vincent Diepeveen <diep [at] xs4all.nl>

Benchmark Program General Category

Artificial Intelligence (game tree search & pattern recognition)

Benchmark Description

458.sjeng is based on Sjeng 11.2, which is a program that plays chess and several chess variants, such as drop-chess (similar to Shogi), and 'losing' chess.

It attempts to find the best move via a combination of alpha-beta or priority proof number tree searches, advanced move ordering, positional evaluation and heuristic forward pruning. Practically, it will explore the tree of variations resulting from a given position to a given base depth, extending interesting variations but discarding doubtful or irrelevant ones. From this tree the optimal line of play for both players ("principle variation") is determined, as well as a score reflecting the balance of power between the two.

The SPEC version is an enhanced version of the free Sjeng 11.2 program, modified to be more portable and more accurately reflect the workload of current professional programs.

Input Description

458.sjeng's input consists of a textfile containing alternations of

  1. a chess position in the standard Forsyth-Edwards Notation (FEN)
  2. the depth to which this position should be analyzed, in half-moves (ply depth)

The SPEC reference input consists of 9 positions belonging to various phases of the game.

Output Description

458.sjeng's output consists, per position, of some side information (textual display of the chessboard, phase of the game, used parameters...) followed by the output from the tree searching module as it progresses. This is formatted as follows:

  1. Attained depth in half-moves (plies)
  2. Score for the player that is to move, in equivalents of 1 pawn
  3. Number of positions investigated
  4. The optimal line of play ("principle variation")

Programming Language


Known portability issues

Requires that "int" is at least 32 bits wide.


Last updated: 27 July 2006