subroutine cpbsl(abd,lda,n,m,b) integer lda,n,m complex abd(lda,1),b(1) c c cpbsl solves the complex hermitian positive definite band c system a*x = b c using the factors computed by cpbco or cpbfa. c c on entry c c abd complex(lda, n) c the output from cpbco or cpbfa. c c lda integer c the leading dimension of the array abd . c c n integer c the order of the matrix a . c c m integer c the number of diagonals above the main diagonal. c c b complex(n) c the right hand side vector. c c on return c c b the solution vector x . c c error condition c c a division by zero will occur if the input factor contains c a zero on the diagonal. technically this indicates c singularity but it is usually caused by improper subroutine c arguments. it will not occur if the subroutines are called c correctly and info .eq. 0 . c c to compute inverse(a) * c where c is a matrix c with p columns c call cpbco(abd,lda,n,rcond,z,info) c if (rcond is too small .or. info .ne. 0) go to ... c do 10 j = 1, p c call cpbsl(abd,lda,n,c(1,j)) c 10 continue c c linpack. this version dated 08/14/78 . c cleve moler, university of new mexico, argonne national lab. c c subroutines and functions c c blas caxpy,cdotc c fortran min0 c c internal variables c complex cdotc,t integer k,kb,la,lb,lm c c solve ctrans(r)*y = b c do 10 k = 1, n lm = min0(k-1,m) la = m + 1 - lm lb = k - lm t = cdotc(lm,abd(la,k),1,b(lb),1) b(k) = (b(k) - t)/abd(m+1,k) 10 continue c c solve r*x = y c do 20 kb = 1, n k = n + 1 - kb lm = min0(k-1,m) la = m + 1 - lm lb = k - lm b(k) = b(k)/abd(m+1,k) t = -b(k) call caxpy(lm,t,abd(la,k),1,b(lb),1) 20 continue return end