1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
|
subroutine subfor ( w, ipivot, nrow, last, b, x )
c carries out the forward pass of substitution for the current block,
c i.e., the action on the right side corresponding to the elimination
c carried out in f a c t r b for this block.
c at the end, x(j) contains the right side of the transformed
c ipivot(j)-th equation in this block, j=1,...,nrow. then, since
c for i=1,...,nrow-last, b(nrow+i) is going to be used as the right
c side of equation i in the next block (shifted over there from
c this block during factorization), it is set equal to x(last+i) here.
c
c parameters
c w, ipivot, nrow, last are as on return from factrb.
c b(j) is expected to contain, on input, the right side of j-th
c equation for this block, j=1,...,nrow.
c b(nrow+j) contains, on output, the appropriately modified right
c side for equation j in next block, j=1,...,nrow-last.
c x(j) contains, on output, the appropriately modified right
c side of equation ipivot(j) in this block, j=1,...,last (and
c even for j=last+1,...,nrow).
c
integer nrow
integer ipivot(nrow), ip,jmax,k, j
integer last, nrowml, lastp1
c dimension b(nrow + nrow-last)
real w(nrow,last),b(1),x(nrow),sum
ip = ipivot(1)
x(1) = b(ip)
if (nrow .eq. 1) go to 99
do 15 k=2,nrow
ip = ipivot(k)
jmax = amin0(k-1,last)
sum = 0.
do 14 j=1,jmax
14 sum = w(ip,j)*x(j) + sum
15 x(k) = b(ip) - sum
c
c transfer modified right sides of equations ipivot(last+1),...,
c ipivot(nrow) to next block.
nrowml = nrow - last
if (nrowml .eq. 0) go to 99
lastp1 = last+1
do 25 k=lastp1,nrow
25 b(nrowml+k) = x(k)
99 return
end
|
