Subversion Repositories eco32

* Exercise 1.3.2'--18, Solution 2

      LOC #100

t IS $255

a00 GREG Data_Segment

a10 GREG Data_Segment+8

a20 GREG Data_Segment+8*2

ij  GREG  % element index

ii  GREG  % row index times 8

j   GREG  % column index

x   GREG  % current maximum

y   GREG  % current element

z   GREG  % current min max

ans IS $0 % return register

Phase1 SET j,8 Start at column 8.

       SET z,1000  $\.z\gets\infty$ (more or less).

3H     ADD ij,j,9*8-2*8

       LDB x,a20,ij

1H     LDB y,a10,ij

       CMP t,x,y    Is x

       CSN x,t,y   If so, update the maximum.

2H     SUB ij,ij,8  Move up one.

       PBP ij,1B

       STB x,a10,ij Store column maximum.

       CMP t,x,z    Is x

       CSN z,t,x   If so, update the min max.

       SUB  j,j,1   Move left a column.

       PBP  j,3B

Phase2 SET  ii,9*8-8 At this point $\.z=\min_jC(j)$

3H     ADD  ij,ii,8  Prepare to search a row.

       SET  j,8

1H     LDB  x,a10,ij

       SUB  t,z,x    Is $\.z>a_{ij}$?

       PBP  t,No     No saddle in this row

       PBN  t,2F

       LDB  x,a00,j  Is $a_{ij}=C(j)$?

       CMP  t,x,z

       CSZ  ans,t,ij If so, remember a possible saddle point.

2H     SUB  j,j,1    Move left in row.

       SUB  ij,ij,1

       PBP  j,1B

       LDA  ans,a10,ans  A saddle point was found here.

       POP  1,0

No     SUB  ii,ii,8

       PBP  ii,3B     Try another row.

       SET  ans,0

       POP  1,0     $\.{ans} = 0$; no saddle.\quad\slug

aaaa   GREG 6364136223846793005  C E Haynes's multiplier

Main   SET  ij,9*8      assume that $1 = seed

1H     MULU $1,$1,aaaa

       INCL $1,1

       MULU x,$1,5

       GET  x,rH

       SUB  x,x,2

       STB  x,a10,ij

       SUB  ij,ij,1

       PBP  ij,1B

       PUSHJ 2,Phase1

       JMP  Main