zhico

NAME

zhico - (obsolete) compute the UDU factorization and condition number of a Hermitian matrix A. If the condition number is not needed then xHIFA is slightly faster. It is typical to follow a call to xHICO with a call to xHISL to solve Ax = b or to xHIDI to compute the determinant, inverse, and inertia of A.

SYNOPSIS

  SUBROUTINE ZHICO( A, LDA, N, IPIVOT, RCOND, WORK)
  DOUBLE COMPLEX A(LDA,*), WORK(*)
  INTEGER LDA, N
  INTEGER IPIVOT(*)
  DOUBLE PRECISION RCOND
 
  SUBROUTINE ZHICO_64( A, LDA, N, IPIVOT, RCOND, WORK)
  DOUBLE COMPLEX A(LDA,*), WORK(*)
  INTEGER*8 LDA, N
  INTEGER*8 IPIVOT(*)
  DOUBLE PRECISION RCOND

C INTERFACE

#include <sunperf.h>

void zhico(doublecomplex *a, int lda, int n, int *ipivot, double *rcond);

void zhico_64(doublecomplex *a, long lda, long n, long *ipivot, double *rcond);

ARGUMENTS

* A (input/output): On entry, the upper triangle of the matrix A. On exit, a UDU factorization of the matrix A. The strict lower triangle of A is not referenced.
* LDA (input): Leading dimension of the array A as specified in a dimension or type statement. LDA >= max(1,N).
* N (input): Order of the matrix A. N >= 0.
* IPIVOT (output): On exit, a vector of pivot indices.
* RCOND (output): On exit, an estimate of the reciprocal condition number of A. 0.0 >= RCOND >= 1.0. As the value of RCOND gets smaller, operations with A such as solving Ax = b may become less stable. If RCOND satisfies RCOND + 1.0 = 1.0 then A may be singular to working precision.
* WORK (workspace): Scratch array with a dimension of N.