Ibm's deep blue chess grandmaster chips

IBM’S DEEP BLUE
CHESS
GRANDMASTER CHIPS
DESIGN PHILOSOPHY, GENERAL ARCHITECTURE,
AND PERFORMANCE OF THE CHESS CHIPS

 Ujitha Iroshan
 Nadeeshaan Gunasinghe
 Dulanga Sashika
Presenters

 Introduction
 History
 Origin of IBM’s Chess Grandmaster
 Task and Design Philosophy
Journey

 General Architecture
 Common chess machine Overview
 System Configuration
 Chip Overview
 Move Generator
 Evaluation Function
 Smart Move stack
 Search Control
 Performance
Journey Cont..

IBM Deep Blue World chess champion
Garry Kasparov in 1997
What is Deep Blue ?
Vs

Creating the first world champion class chess
computer is one of the oldest challenge in
computer science.
 Blitz chip won against grand master in
shortened time chess game in 1977
 Cray Blitz computer is defeated by
International master David Levy in shortened
time chess game in 1984
History

 PC programmed in Blitz won against 2nd rank chess
player in 1988 under faster time controls.
 Deep blue early version(Deep thought) was defeated
by the Champion Garry Kasparov in 1996 under
regular time control.
 Finally in 1997 Deep Blue won against the World
Champion Garry Kasparov under regular time control
History Ctd...

Winning a match against the human World
chess champion under regulation time control
The game had to play out no faster than three
minutes per move
Task description of Deep Blue

Regular time control
 Standard chess tournament time control
Faster time control (Shortened time)
 Limited time for entire match and for the each
moves
Task Description Ctd...

 Integrate level
 Integrate the maximally possible amount of
software-modifiable chess knowledge on to the
chess chip.
 Computational Speed
 Assign weights to positional features
Design Philosophy

Common chess machine Overview
 Follows the design outlined by Claud Shanon in
1949
 Chess 4.5 is the earliest and the first
successful chess machine design
 Today Chess Machines in one way or another
way, are the grandchildren of this Chess 4.5
General Architecture

Choosing the next move
 Shannon’s basic design uses a min-max tree
 The evaluation function is designed from the
computer player’s viewpoint
Common chess machine Overview Ctd...

 Assign numerical values for evaluation
function
■ +1- Computer Player Wins
■ -1- Computer Player Loses
■ 0- Drawn position
Choosing the next move Ctd..

Can regular Min-Max search be used in a
Chess Game?
Common chess machine Overview cont..

 New developments in Chess 4.5
 A hardware move generator
 Quiescence search (Capture Search) and
Alpha beta Pruning algorithm
Common chess machine Overview cont..

 1997 version of DB included 480 chess chips
 each chess chip could search 2 to 2.5 million
chess positions/s
 More software work could increase the speed.
But applied software work in chess knowledge
area
System Configuration

 Search goes parallelly in two levels
 One over IBM RS/6000 SP switching network
 The other over Micro Channel bus inside a
workstation node
 Partitioning the search provided a great deal
of design flexibility and increased the search
speed
 SW handled a 1% of the search, but the ⅔
search depth was reduced by SW
System Configuration

Block diagram of the Chess Chip
Chip Overview
The chip’s cycle time
lies between 40 and
50 nanoseconds in a
0.6-micron, three-
metal
layer, 5-V CMOS
process. The
average number
of cycles per position
searched is about
10;
power dissipation is
about one watt

 Each chess Chip works as a chess machine
 Why Chess chips rather than software
algorithm for the competing?
 Provided design possibilities unacceptable by SW
 Time-scaling factor dropped from instruction cycle
time to gate delay
 Only thing required was reexamine of the time
complexity of the competing algorithm
Chip Overview

Inside of a chess chip
Chess
Chip
Smart
Move
stack
Evaluation
Function
Search
Move
generator

 What is move generator?
 Used to decide the next best move of a
chess piece
 An 8x8 array of combinational logic
 Move generation is controlled by a
hardwired finite state machine
Move Generator

Why Deep Blue’s move generator special?
 Generate check and check evasion Moves
 Generates attacking moves
 Hardware pruning of irrelevant chess moves
Move Generator Ctd..

A chip cell
The combinational logic array is a silicon chess
board
Each has four major components
 Find victim transmitter
 Find Attacker Transmitter
 Receiver
 Distributed arbiter
 Four-bit piece register

Find Victim and Find Attacker

As described earlier, move generator computes
all the moves implicitly for a single move.
What if SW is used for this task?...

Generating moves from a partially
generated position
 Need to mask the already searched moves
 Belle design used 2-bit disable-stack for
masking
 What is used in Deep Blue?

Other moves generated by Move generator
 checking moves
 check-evasion moves
 Detect Hung Pieces
 Measures the forcefulness of checks

Evaluation Function
What is Evaluation Function?
 Evaluation function is a function used by game-
playing programs to estimate the value or
goodness of a position in the minimax and related
algorithms.
Evaluation Function of “Deep Blue”
 Contain about 66,000 gates not including RAMs
and ROMs.
 All sub blocks of the evaluation function divided
into two sections
• Lower sub blocks provide fast evaluation
• Upper sub blocks provide slow evaluation

The piece placement table
computes a position’s incremental
evaluation.
Uses three RAMs.

The Game Phase Control
 Contains a piece count register
 Maintain an XORed piece-location register
 The piece-count register addresses game phase
control RAMs
 The game phase control RAMs produce several
control values
 simply a bonus or penalty to be added to the
evaluation based on the material left on the
board.
 The most important game phase control value is
the king safety relevance
 tells the chess chip how to adjust the penalty for
bad pawn structure and the bonus for passed
pawns

The king-and-pawn array
mainly detects the “pawn can run” condition

The Endgame logic and ROMs
Mainly recognizes unusual endgame conditions

This is the single most complicated element
on the chip, occupying close to half of the
chip core.
Slow evaluation has a three-stage pipeline
 8 X 1 systolic array
 40-plus synchronous RAMs
 adder tree
Computes values for chess concepts such as,
 square control, pins, x-rays, king safety, pawn
structure, passed pawns, ray control, outposts,
pawn majority, rook on the 7th, blockade,
restraint and etc.
Slow evaluation

This doesn’t exist in the chess chip’s older
release.
Repetition detector
 Contains a 32-entry circular buffer of the last 32
plies of moves.
 Use hardware content addressable memory
algorithm
 Does this detects just simple repetition?
 Time complexity is O(n)
Smart move stack

implements a minimum-window alpha-beta
search algorithm
This search can only tell us whether the position
searched is better or worse than a single test
value.
Efficiency- wise, minimum-window-based search
seems about the same as the regular alpha-beta
search
Search Control

In early 1997, used a single chip running at
70% clock speed
A hardware bug reduced the chip to 7% to
14% of its regular speed
Deep Blue Jr. against the commercial chess
programs played 40 games and chess chip
score 95% against PC program
Performance

The 1997 version of Deep Blue only played six
games
Deep blue won the match by the score of 3.5 to
2.5
Kasparov is rated around 2815, which placed
Deep Blue’s performance at about 2875

Ibm's deep blue chess grandmaster chips

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