1 subroutine dpbfa(abd,lda,n,m,info)
4 double precision abd(lda,n)
6 c dpbfa factors a double precision symmetric positive definite
7 c matrix stored in band form.
9 c dpbfa is usually called by dpbco, but it can be called
10 c directly with a saving in time if rcond is not needed.
14 c abd double precision(lda, n)
15 c the matrix to be factored. the columns of the upper
16 c triangle are stored in the columns of abd and the
17 c diagonals of the upper triangle are stored in the
18 c rows of abd . see the comments below for details.
21 c the leading dimension of the array abd .
22 c lda must be .ge. m + 1 .
25 c the order of the matrix a .
28 c the number of diagonals above the main diagonal.
33 c abd an upper triangular matrix r , stored in band
34 c form, so that a = trans(r)*r .
37 c = 0 for normal return.
38 c = k if the leading minor of order k is not
43 c if a is a symmetric positive definite band matrix,
44 c the following program segment will set up the input.
46 c m = (band width above diagonal)
55 c linpack. this version dated 08/14/78 .
56 c cleve moler, university of new mexico, argonne national lab.
58 c subroutines and functions
65 double precision ddot,t, a(10), b(10), temp
68 c begin block with ...exits to 40
74 c PRINT *, 'a = ', a(i), 'i = ', i
75 c PRINT *, 'b = ', b(i)
78 temp = ddot(10,a,1,b,1)
86 if (m .lt. mu) go to 20
89 t = abd(k,j) - ddot(k-mu,abd(ik,jk),1,abd(mu,j),1)
100 if (s .le. 0.0d0) go to 40