subroutine zposl(a,lda,n,b) integer lda,n complex*16 a(lda,1),b(1) c c zposl solves the complex*16 hermitian positive definite system c a * x = b c using the factors computed by zpoco or zpofa. c c on entry c c a complex*16(lda, n) c the output from zpoco or zpofa. c c lda integer c the leading dimension of the array a . c c n integer c the order of the matrix a . c c b complex*16(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 zpoco(a,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 zposl(a,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 zaxpy,zdotc c c internal variables c complex*16 zdotc,t integer k,kb double precision dreal,dimag complex*16 zdumr,zdumi dreal(zdumr) = zdumr dimag(zdumi) = (0.0d0,-1.0d0)*zdumi c c solve ctrans(r)*y = b c do 10 k = 1, n t = zdotc(k-1,a(1,k),1,b(1),1) b(k) = (b(k) - t)/a(k,k) 10 continue c c solve r*x = y c do 20 kb = 1, n k = n + 1 - kb b(k) = b(k)/a(k,k) t = -b(k) call zaxpy(k-1,t,a(1,k),1,b(1),1) 20 continue return end