/* Copyright (c) 1992-2008 The University of Tennessee.  All rights reserved.
 * See file COPYING in this directory for details. */

#ifdef __cplusplus
extern "C" {
#endif

#include "f2c.h"
#include "hypre_lapack.h"

/* Subroutine */ integer dsyev_(const char *jobz,const char *uplo, integer *n, doublereal *a,
	 integer *lda, doublereal *w, doublereal *work, integer *lwork,
	integer *info)
{
/*  -- LAPACK driver routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       June 30, 1999


    Purpose
    =======

    DSYEV computes all eigenvalues and, optionally, eigenvectors of a
    real symmetric matrix A.

    Arguments
    =========

    JOBZ    (input) CHARACTER*1
            = 'N':  Compute eigenvalues only;
            = 'V':  Compute eigenvalues and eigenvectors.

    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) DOUBLE PRECISION array, dimension (LDA, N)
            On entry, the symmetric matrix A.  If UPLO = 'U', the
            leading N-by-N upper triangular part of A contains the
            upper triangular part of the matrix A.  If UPLO = 'L',
            the leading N-by-N lower triangular part of A contains
            the lower triangular part of the matrix A.
            On exit, if JOBZ = 'V', then if INFO = 0, A contains the
            orthonormal eigenvectors of the matrix A.
            If JOBZ = 'N', then on exit the lower triangle (if UPLO='L')
            or the upper triangle (if UPLO='U') of A, including the
            diagonal, is destroyed.

    LDA     (input) INTEGER
            The leading dimension of the array A.  LDA >= max(1,N).

    W       (output) DOUBLE PRECISION array, dimension (N)
            If INFO = 0, the eigenvalues in ascending order.

    WORK    (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
            On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

    LWORK   (input) INTEGER
            The length of the array WORK.  LWORK >= max(1,3*N-1).
            For optimal efficiency, LWORK >= (NB+2)*N,
            where NB is the blocksize for DSYTRD returned by ILAENV.

            If LWORK = -1, then a workspace query is assumed; the routine
            only calculates the optimal size of the WORK array, returns
            this value as the first entry of the WORK array, and no error
            message related to LWORK is issued by XERBLA.

    INFO    (output) INTEGER
            = 0:  successful exit
            < 0:  if INFO = -i, the i-th argument had an illegal value
            > 0:  if INFO = i, the algorithm failed to converge; i
                  off-diagonal elements of an intermediate tridiagonal
                  form did not converge to zero.

    =====================================================================


       Test the input parameters.

       Parameter adjustments */
    /* Table of constant values */
    integer c__1 = 1;
    integer c_n1 = -1;
    integer c__0 = 0;
    doublereal c_b17 = 1.;

    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2;
    doublereal d__1;
    /* Local variables */
    integer inde;
    doublereal anrm;
    integer imax;
    doublereal rmin, rmax;
/*** integer lopt;***/
    extern /* Subroutine */ integer dscal_(integer *, doublereal *, doublereal *,
	    integer *);
    doublereal sigma;
    extern logical lsame_(const char *,const char *);
    integer iinfo;
    logical lower, wantz;
    integer nb;
    extern doublereal dlamch_(const char *);
    integer iscale;
    extern /* Subroutine */ integer dlascl_(const char *, integer *, integer *,
	    doublereal *, doublereal *, integer *, integer *, doublereal *,
	    integer *, integer *);
    doublereal safmin;
    extern integer ilaenv_(integer *,const char *,const char *, integer *, integer *,
	    integer *, integer *, ftnlen, ftnlen);
    extern /* Subroutine */ integer xerbla_(const char *, integer *);
    doublereal bignum;
    integer indtau;
    extern /* Subroutine */ integer dsterf_(integer *, doublereal *, doublereal *,
	     integer *);
    extern doublereal dlansy_(const char *,const char *, integer *, doublereal *,
	    integer *, doublereal *);
    integer indwrk;
    extern /* Subroutine */ integer dorgtr_(const char *, integer *, doublereal *,
	    integer *, doublereal *, doublereal *, integer *, integer *), dsteqr_(const char *, integer *, doublereal *, doublereal *,
	    doublereal *, integer *, doublereal *, integer *),
	    dsytrd_(const char *, integer *, doublereal *, integer *, doublereal *,
	    doublereal *, doublereal *, doublereal *, integer *, integer *);
    integer llwork;
    doublereal smlnum;
    integer lwkopt;
    logical lquery;
    doublereal eps;
#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]


    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    --w;
    --work;

    /* Function Body */
    wantz = lsame_(jobz, "V");
    lower = lsame_(uplo, "L");
    lquery = *lwork == -1;

    *info = 0;
    if (! (wantz || lsame_(jobz, "N"))) {
	*info = -1;
    } else if (! (lower || lsame_(uplo, "U"))) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*lda < max(1,*n)) {
	*info = -5;
    } else /* if(complicated condition) */ {
/* Computing MAX */
	i__1 = 1, i__2 = *n * 3 - 1;
	if (*lwork < max(i__1,i__2) && ! lquery) {
	    *info = -8;
	}
    }

    if (*info == 0) {
	nb = ilaenv_(&c__1, "DSYTRD", uplo, n, &c_n1, &c_n1, &c_n1, (ftnlen)6,
		 (ftnlen)1);
/* Computing MAX */
	i__1 = 1, i__2 = (nb + 2) * *n;
	lwkopt = max(i__1,i__2);
	work[1] = (doublereal) lwkopt;
    }

    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DSYEV ", &i__1);
	return 0;
    } else if (lquery) {
	return 0;
    }

/*     Quick return if possible */

    if (*n == 0) {
	work[1] = 1.;
	return 0;
    }

    if (*n == 1) {
	w[1] = a_ref(1, 1);
	work[1] = 3.;
	if (wantz) {
	    a_ref(1, 1) = 1.;
	}
	return 0;
    }

/*     Get machine constants. */

    safmin = dlamch_("Safe minimum");
    eps = dlamch_("Precision");
    smlnum = safmin / eps;
    bignum = 1. / smlnum;
    rmin = sqrt(smlnum);
    rmax = sqrt(bignum);

/*     Scale matrix to allowable range, if necessary. */

    anrm = dlansy_("M", uplo, n, &a[a_offset], lda, &work[1]);
    iscale = 0;
    if (anrm > 0. && anrm < rmin) {
	iscale = 1;
	sigma = rmin / anrm;
    } else if (anrm > rmax) {
	iscale = 1;
	sigma = rmax / anrm;
    }
    if (iscale == 1) {
	dlascl_(uplo, &c__0, &c__0, &c_b17, &sigma, n, n, &a[a_offset], lda,
		info);
    }

/*     Call DSYTRD to reduce symmetric matrix to tridiagonal form. */

    inde = 1;
    indtau = inde + *n;
    indwrk = indtau + *n;
    llwork = *lwork - indwrk + 1;
    dsytrd_(uplo, n, &a[a_offset], lda, &w[1], &work[inde], &work[indtau], &
	    work[indwrk], &llwork, &iinfo);
/***lopt = (integer) ((*n << 1) + work[indwrk]);***/

/*     For eigenvalues only, call DSTERF.  For eigenvectors, first call
       DORGTR to generate the orthogonal matrix, then call DSTEQR. */

    if (! wantz) {
	dsterf_(n, &w[1], &work[inde], info);
    } else {
	dorgtr_(uplo, n, &a[a_offset], lda, &work[indtau], &work[indwrk], &
		llwork, &iinfo);
	dsteqr_(jobz, n, &w[1], &work[inde], &a[a_offset], lda, &work[indtau],
		 info);
    }

/*     If matrix was scaled, then rescale eigenvalues appropriately. */

    if (iscale == 1) {
	if (*info == 0) {
	    imax = *n;
	} else {
	    imax = *info - 1;
	}
	d__1 = 1. / sigma;
	dscal_(&imax, &d__1, &w[1], &c__1);
    }

/*     Set WORK(1) to optimal workspace size. */

    work[1] = (doublereal) lwkopt;

    return 0;

/*     End of DSYEV */

} /* dsyev_ */

#undef a_ref

#ifdef __cplusplus
}
#endif
