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such that g i ↔ C i , where 1 ≤ i ≤ m + n− 1 (see Fig. 2). We can construct a 2-D
CA N =( Q, δ 2 ,w ) such that all cells in g i simulate the i th cell C i in real-time
and N can fire any m×n arrays at time t = T ( m + n− 1) if and only if M fires
1-D arrays of length m + n − 1 at time t = T ( m + n − 1), where δ 2 : Q 5 → Q
is the transition function, and w ∈ Q is the border state of the array. Note that
the set of internal states of N is the same as M . The transition function δ 2 is
constructed as follows:
Type (II): U pper-left corner cell
For any state b,c,d
Type (I): Inner cell
For any state a,b,c,d
2
{Q-{w}}
2
{Q-{w}}
such that
δ
1 (w, b, c) = d :
w
such that
δ
1 (a, b, c) = d :
a
(1)
w
b
c
d
(1)
a
b
c
d
c
c
w
w
w
b
c
d
(2)
(2)
a
b
c
d
w
c
w
a
w
b
w
d
(3)
(3)
a
b
c
d
c
w
a
(4)
w
b
c
d
Type (III): Lower-right corner cell
For any state a, b, d
c
2
{Q-{w}}
such that
δ
1 (a, b, w) = d:
a
(5)
a
b
w
d
a
c
(1)
a
b
w
d
w
a
(6)
w
b
c
d
w
w
a
b
w
d
(2)
w
w
(7)
a
b
w
d
a
c
w
b
w
d
(3)
w
w
(8)
a
b
c
d
w
a
(9)
w
b
w
d
c
Fig. 3. Construction of transition rules for 2-D firing squad synchronization algorithm
Let δ 1 ( a, b, c )= d be any transition rule of M , where a, b, c, d ∈{Q−{w}} .
Then, N has nine transition rules, as shown in Fig. 3 Type (I). The first rule (1)
in Type (I) is used by an inner cell that does not include border cells amongst
its four neighbors. Rules (2)-(7) are used by an inner cell that has a border cell
as its upper, lower, left, right, lower left, or upper right neighbor, respectively.
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