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fitpack/fpback.f

@@ -0,0 +1,32 @@
+      recursive subroutine fpback(a,z,n,k,c,nest)
+      implicit none
+c  subroutine fpback calculates the solution of the system of
+c  equations a*c = z with a a n x n upper triangular matrix
+c  of bandwidth k.
+c  ..
+c  ..scalar arguments..
+      integer n,k,nest
+c  ..array arguments..
+      real*8 a(nest,k),z(n),c(n)
+c  ..local scalars..
+      real*8 store
+      integer i,i1,j,k1,l,m
+c  ..
+      k1 = k-1
+      c(n) = z(n)/a(n,1)
+      i = n-1
+      if(i.eq.0) go to 30
+      do 20 j=2,n
+        store = z(i)
+        i1 = k1
+        if(j.le.k1) i1 = j-1
+        m = i
+        do 10 l=1,i1
+          m = m+1
+          store = store-c(m)*a(i,l+1)
+  10    continue
+        c(i) = store/a(i,1)
+        i = i-1
+  20  continue
+  30  return
+      end