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Diffstat (limited to 'math/deboor/subfor.f')
| -rw-r--r-- | math/deboor/subfor.f | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/math/deboor/subfor.f b/math/deboor/subfor.f new file mode 100644 index 00000000..344aff0c --- /dev/null +++ b/math/deboor/subfor.f @@ -0,0 +1,45 @@ + 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 |