.TH CPTTRF 1 "November 2006" " LAPACK routine (version 3.1) " " LAPACK routine (version 3.1) " .SH NAME CPTTRF - the L*D*L\(aq factorization of a complex Hermitian positive definite tridiagonal matrix A .SH SYNOPSIS .TP 19 SUBROUTINE CPTTRF( N, D, E, INFO ) .TP 19 .ti +4 INTEGER INFO, N .TP 19 .ti +4 REAL D( * ) .TP 19 .ti +4 COMPLEX E( * ) .SH PURPOSE CPTTRF computes the L*D*L\(aq factorization of a complex Hermitian positive definite tridiagonal matrix A. The factorization may also be regarded as having the form A = U\(aq*D*U. .br .SH ARGUMENTS .TP 8 N (input) INTEGER The order of the matrix A. N >= 0. .TP 8 D (input/output) REAL array, dimension (N) On entry, the n diagonal elements of the tridiagonal matrix A. On exit, the n diagonal elements of the diagonal matrix D from the L*D*L\(aq factorization of A. .TP 8 E (input/output) COMPLEX array, dimension (N-1) On entry, the (n-1) subdiagonal elements of the tridiagonal matrix A. On exit, the (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L\(aq factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the U\(aq*D*U factorization of A. .TP 8 INFO (output) INTEGER = 0: successful exit .br < 0: if INFO = -k, the k-th argument had an illegal value .br > 0: if INFO = k, the leading minor of order k is not positive definite; if k < N, the factorization could not be completed, while if k = N, the factorization was completed, but D(N) <= 0.