#include "blaswrap.h"
#include "f2c.h"
/* Subroutine */ int chetrf_(char *uplo, integer *n, complex *a, integer *lda, integer *ipiv, complex *work, integer *lwork, integer *info )
{
/* -- LAPACK routine (version 3.1) --
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
Purpose
=======
CHETRF computes the factorization of a complex Hermitian matrix A
using the Bunch-Kaufman diagonal pivoting method. The form of the
factorization is
A = U*D*U**H or A = L*D*L**H
where U (or L) is a product of permutation and unit upper (lower)
triangular matrices, and D is Hermitian and block diagonal with
1-by-1 and 2-by-2 diagonal blocks.
This is the blocked version of the algorithm, calling Level 3 BLAS.
Arguments
=========
UPLO (input) CHARACTER*1
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input/output) COMPLEX array, dimension (LDA,N)
On entry, the Hermitian matrix A. If UPLO = 'U', the leading
N-by-N upper triangular part of A contains the upper
triangular part of the matrix A, and the strictly lower
triangular part of A is not referenced. If UPLO = 'L', the
leading N-by-N lower triangular part of A contains the lower
triangular part of the matrix A, and the strictly upper
triangular part of A is not referenced.
On exit, the block diagonal matrix D and the multipliers used
to obtain the factor U or L (see below for further details).
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
IPIV (output) INTEGER array, dimension (N)
Details of the interchanges and the block structure of D.
If IPIV(k) > 0, then rows and columns k and IPIV(k) were
interchanged and D(k,k) is a 1-by-1 diagonal block.
If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and
columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k)
is a 2-by-2 diagonal block. If UPLO = 'L' and IPIV(k) =
IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were
interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
WORK (workspace/output) COMPLEX array, dimension (MAX(1,LWORK))
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
LWORK (input) INTEGER
The length of WORK. LWORK >=1. For best performance
LWORK >= N*NB, where NB is the block size returned by ILAENV.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, D(i,i) is exactly zero. The factorization
has been completed, but the block diagonal matrix D is
exactly singular, and division by zero will occur if it
is used to solve a system of equations.
Further Details
===============
If UPLO = 'U', then A = U*D*U', where
U = P(n)*U(n)* ... *P(k)U(k)* ...,
i.e., U is a product of terms P(k)*U(k), where k decreases from n to
1 in steps of 1 or 2, and D is a block diagonal matrix with 1-by-1
and 2-by-2 diagonal blocks D(k). P(k) is a permutation matrix as
defined by IPIV(k), and U(k) is a unit upper triangular matrix, such
that if the diagonal block D(k) is of order s (s = 1 or 2), then
( I v 0 ) k-s
U(k) = ( 0 I 0 ) s
( 0 0 I ) n-k
k-s s n-k
If s = 1, D(k) overwrites A(k,k), and v overwrites A(1:k-1,k).
If s = 2, the upper triangle of D(k) overwrites A(k-1,k-1), A(k-1,k),
and A(k,k), and v overwrites A(1:k-2,k-1:k).
If UPLO = 'L', then A = L*D*L', where
L = P(1)*L(1)* ... *P(k)*L(k)* ...,
i.e., L is a product of terms P(k)*L(k), where k increases from 1 to
n in steps of 1 or 2, and D is a block diagonal matrix with 1-by-1
and 2-by-2 diagonal blocks D(k). P(k) is a permutation matrix as
defined by IPIV(k), and L(k) is a unit lower triangular matrix, such
that if the diagonal block D(k) is of order s (s = 1 or 2), then
( I 0 0 ) k-1
L(k) = ( 0 I 0 ) s
( 0 v I ) n-k-s+1
k-1 s n-k-s+1
If s = 1, D(k) overwrites A(k,k), and v overwrites A(k+1:n,k).
If s = 2, the lower triangle of D(k) overwrites A(k,k), A(k+1,k),
and A(k+1,k+1), and v overwrites A(k+2:n,k:k+1).
=====================================================================
Test the input parameters.
Parameter adjustments */
/* Table of constant values */
static integer c__1 = 1;
static integer c_n1 = -1;
static integer c__2 = 2;
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
/* Local variables */
static integer j, k, kb, nb, iws;
extern logical lsame_(char *, char *);
static integer nbmin, iinfo;
static logical upper;
extern /* Subroutine */ int chetf2_(char *, integer *, complex *, integer
*, integer *, integer *), clahef_(char *, integer *,
integer *, integer *, complex *, integer *, integer *, complex *,
integer *, integer *), xerbla_(char *, integer *);
extern integer ilaenv_(integer *, char *, char *, integer *, integer *,
integer *, integer *, ftnlen, ftnlen);
static integer ldwork, lwkopt;
static logical lquery;
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--ipiv;
--work;
/* Function Body */
*info = 0;
upper = lsame_(uplo, "U");
lquery = *lwork == -1;
if (! upper && ! lsame_(uplo, "L")) {
*info = -1;
} else if (*n < 0) {
*info = -2;
} else if (*lda < max(1,*n)) {
*info = -4;
} else if (*lwork < 1 && ! lquery) {
*info = -7;
}
if (*info == 0) {
/* Determine the block size */
nb = ilaenv_(&c__1, "CHETRF", uplo, n, &c_n1, &c_n1, &c_n1, (ftnlen)6,
(ftnlen)1);
lwkopt = *n * nb;
work[1].r = (real) lwkopt, work[1].i = 0.f;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("CHETRF", &i__1);
return 0;
} else if (lquery) {
return 0;
}
nbmin = 2;
ldwork = *n;
if (nb > 1 && nb < *n) {
iws = ldwork * nb;
if (*lwork < iws) {
/* Computing MAX */
i__1 = *lwork / ldwork;
nb = max(i__1,1);
/* Computing MAX */
i__1 = 2, i__2 = ilaenv_(&c__2, "CHETRF", uplo, n, &c_n1, &c_n1, &
c_n1, (ftnlen)6, (ftnlen)1);
nbmin = max(i__1,i__2);
}
} else {
iws = 1;
}
if (nb < nbmin) {
nb = *n;
}
if (upper) {
/* Factorize A as U*D*U' using the upper triangle of A
K is the main loop index, decreasing from N to 1 in steps of
KB, where KB is the number of columns factorized by CLAHEF;
KB is either NB or NB-1, or K for the last block */
k = *n;
L10:
/* If K < 1, exit from loop */
if (k < 1) {
goto L40;
}
if (k > nb) {
/* Factorize columns k-kb+1:k of A and use blocked code to
update columns 1:k-kb */
clahef_(uplo, &k, &nb, &kb, &a[a_offset], lda, &ipiv[1], &work[1],
n, &iinfo);
} else {
/* Use unblocked code to factorize columns 1:k of A */
chetf2_(uplo, &k, &a[a_offset], lda, &ipiv[1], &iinfo);
kb = k;
}
/* Set INFO on the first occurrence of a zero pivot */
if (*info == 0 && iinfo > 0) {
*info = iinfo;
}
/* Decrease K and return to the start of the main loop */
k -= kb;
goto L10;
} else {
/* Factorize A as L*D*L' using the lower triangle of A
K is the main loop index, increasing from 1 to N in steps of
KB, where KB is the number of columns factorized by CLAHEF;
KB is either NB or NB-1, or N-K+1 for the last block */
k = 1;
L20:
/* If K > N, exit from loop */
if (k > *n) {
goto L40;
}
if (k <= *n - nb) {
/* Factorize columns k:k+kb-1 of A and use blocked code to
update columns k+kb:n */
i__1 = *n - k + 1;
clahef_(uplo, &i__1, &nb, &kb, &a[k + k * a_dim1], lda, &ipiv[k],
&work[1], n, &iinfo);
} else {
/* Use unblocked code to factorize columns k:n of A */
i__1 = *n - k + 1;
chetf2_(uplo, &i__1, &a[k + k * a_dim1], lda, &ipiv[k], &iinfo);
kb = *n - k + 1;
}
/* Set INFO on the first occurrence of a zero pivot */
if (*info == 0 && iinfo > 0) {
*info = iinfo + k - 1;
}
/* Adjust IPIV */
i__1 = k + kb - 1;
for (j = k; j <= i__1; ++j) {
if (ipiv[j] > 0) {
ipiv[j] = ipiv[j] + k - 1;
} else {
ipiv[j] = ipiv[j] - k + 1;
}
/* L30: */
}
/* Increase K and return to the start of the main loop */
k += kb;
goto L20;
}
L40:
work[1].r = (real) lwkopt, work[1].i = 0.f;
return 0;
/* End of CHETRF */
} /* chetrf_ */