#include "blaswrap.h"
#include "f2c.h"

/* Subroutine */ int ssycon_(char *uplo, integer *n, real *a, integer *lda, 
	integer *ipiv, real *anorm, real *rcond, real *work, integer *iwork, 
	integer *info)
{
/*  -- LAPACK routine (version 3.1) --   
       Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..   
       November 2006   

       Modified to call SLACN2 in place of SLACON, 7 Feb 03, SJH.   


    Purpose   
    =======   

    SSYCON estimates the reciprocal of the condition number (in the   
    1-norm) of a real symmetric matrix A using the factorization   
    A = U*D*U**T or A = L*D*L**T computed by SSYTRF.   

    An estimate is obtained for norm(inv(A)), and the reciprocal of the   
    condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).   

    Arguments   
    =========   

    UPLO    (input) CHARACTER*1   
            Specifies whether the details of the factorization are stored   
            as an upper or lower triangular matrix.   
            = 'U':  Upper triangular, form is A = U*D*U**T;   
            = 'L':  Lower triangular, form is A = L*D*L**T.   

    N       (input) INTEGER   
            The order of the matrix A.  N >= 0.   

    A       (input) REAL array, dimension (LDA,N)   
            The block diagonal matrix D and the multipliers used to   
            obtain the factor U or L as computed by SSYTRF.   

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

    IPIV    (input) INTEGER array, dimension (N)   
            Details of the interchanges and the block structure of D   
            as determined by SSYTRF.   

    ANORM   (input) REAL   
            The 1-norm of the original matrix A.   

    RCOND   (output) REAL   
            The reciprocal of the condition number of the matrix A,   
            computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an   
            estimate of the 1-norm of inv(A) computed in this routine.   

    WORK    (workspace) REAL array, dimension (2*N)   

    IWORK    (workspace) INTEGER array, dimension (N)   

    INFO    (output) INTEGER   
            = 0:  successful exit   
            < 0:  if INFO = -i, the i-th argument had an illegal value   

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


       Test the input parameters.   

       Parameter adjustments */
    /* Table of constant values */
    static integer c__1 = 1;
    
    /* System generated locals */
    integer a_dim1, a_offset, i__1;
    /* Local variables */
    static integer i__, kase;
    extern logical lsame_(char *, char *);
    static integer isave[3];
    static logical upper;
    extern /* Subroutine */ int slacn2_(integer *, real *, real *, integer *, 
	    real *, integer *, integer *), xerbla_(char *, integer *);
    static real ainvnm;
    extern /* Subroutine */ int ssytrs_(char *, integer *, integer *, real *, 
	    integer *, integer *, real *, integer *, integer *);


    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    --ipiv;
    --work;
    --iwork;

    /* Function Body */
    *info = 0;
    upper = lsame_(uplo, "U");
    if (! upper && ! lsame_(uplo, "L")) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*lda < max(1,*n)) {
	*info = -4;
    } else if (*anorm < 0.f) {
	*info = -6;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("SSYCON", &i__1);
	return 0;
    }

/*     Quick return if possible */

    *rcond = 0.f;
    if (*n == 0) {
	*rcond = 1.f;
	return 0;
    } else if (*anorm <= 0.f) {
	return 0;
    }

/*     Check that the diagonal matrix D is nonsingular. */

    if (upper) {

/*        Upper triangular storage: examine D from bottom to top */

	for (i__ = *n; i__ >= 1; --i__) {
	    if (ipiv[i__] > 0 && a[i__ + i__ * a_dim1] == 0.f) {
		return 0;
	    }
/* L10: */
	}
    } else {

/*        Lower triangular storage: examine D from top to bottom. */

	i__1 = *n;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    if (ipiv[i__] > 0 && a[i__ + i__ * a_dim1] == 0.f) {
		return 0;
	    }
/* L20: */
	}
    }

/*     Estimate the 1-norm of the inverse. */

    kase = 0;
L30:
    slacn2_(n, &work[*n + 1], &work[1], &iwork[1], &ainvnm, &kase, isave);
    if (kase != 0) {

/*        Multiply by inv(L*D*L') or inv(U*D*U'). */

	ssytrs_(uplo, n, &c__1, &a[a_offset], lda, &ipiv[1], &work[1], n, 
		info);
	goto L30;
    }

/*     Compute the estimate of the reciprocal condition number. */

    if (ainvnm != 0.f) {
	*rcond = 1.f / ainvnm / *anorm;
    }

    return 0;

/*     End of SSYCON */

} /* ssycon_ */