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[/] [eco32/] [trunk/] [fp/] [implementation/] [mmix/] [saddle2.mms] - Rev 197
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* 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<y?
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<z?
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
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