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

/* Subroutine */ int ssbgvd_(char *jobz, char *uplo, integer *n, integer *ka, 
	integer *kb, real *ab, integer *ldab, real *bb, integer *ldbb, real *
	w, real *z__, integer *ldz, real *work, integer *lwork, integer *
	iwork, integer *liwork, integer *info  	)
{
/*  -- LAPACK driver routine (version 3.1) --   
       Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..   
       November 2006   


    Purpose   
    =======   

    SSBGVD computes all the eigenvalues, and optionally, the eigenvectors   
    of a real generalized symmetric-definite banded eigenproblem, of the   
    form A*x=(lambda)*B*x.  Here A and B are assumed to be symmetric and   
    banded, and B is also positive definite.  If eigenvectors are   
    desired, it uses a divide and conquer algorithm.   

    The divide and conquer algorithm makes very mild assumptions about   
    floating point arithmetic. It will work on machines with a guard   
    digit in add/subtract, or on those binary machines without guard   
    digits which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or   
    Cray-2. It could conceivably fail on hexadecimal or decimal machines   
    without guard digits, but we know of none.   

    Arguments   
    =========   

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

    UPLO    (input) CHARACTER*1   
            = 'U':  Upper triangles of A and B are stored;   
            = 'L':  Lower triangles of A and B are stored.   

    N       (input) INTEGER   
            The order of the matrices A and B.  N >= 0.   

    KA      (input) INTEGER   
            The number of superdiagonals of the matrix A if UPLO = 'U',   
            or the number of subdiagonals if UPLO = 'L'.  KA >= 0.   

    KB      (input) INTEGER   
            The number of superdiagonals of the matrix B if UPLO = 'U',   
            or the number of subdiagonals if UPLO = 'L'.  KB >= 0.   

    AB      (input/output) REAL array, dimension (LDAB, N)   
            On entry, the upper or lower triangle of the symmetric band   
            matrix A, stored in the first ka+1 rows of the array.  The   
            j-th column of A is stored in the j-th column of the array AB   
            as follows:   
            if UPLO = 'U', AB(ka+1+i-j,j) = A(i,j) for max(1,j-ka)<=i<=j;   
            if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+ka).   

            On exit, the contents of AB are destroyed.   

    LDAB    (input) INTEGER   
            The leading dimension of the array AB.  LDAB >= KA+1.   

    BB      (input/output) REAL array, dimension (LDBB, N)   
            On entry, the upper or lower triangle of the symmetric band   
            matrix B, stored in the first kb+1 rows of the array.  The   
            j-th column of B is stored in the j-th column of the array BB   
            as follows:   
            if UPLO = 'U', BB(ka+1+i-j,j) = B(i,j) for max(1,j-kb)<=i<=j;   
            if UPLO = 'L', BB(1+i-j,j)    = B(i,j) for j<=i<=min(n,j+kb).   

            On exit, the factor S from the split Cholesky factorization   
            B = S**T*S, as returned by SPBSTF.   

    LDBB    (input) INTEGER   
            The leading dimension of the array BB.  LDBB >= KB+1.   

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

    Z       (output) REAL array, dimension (LDZ, N)   
            If JOBZ = 'V', then if INFO = 0, Z contains the matrix Z of   
            eigenvectors, with the i-th column of Z holding the   
            eigenvector associated with W(i).  The eigenvectors are   
            normalized so Z**T*B*Z = I.   
            If JOBZ = 'N', then Z is not referenced.   

    LDZ     (input) INTEGER   
            The leading dimension of the array Z.  LDZ >= 1, and if   
            JOBZ = 'V', LDZ >= max(1,N).   

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

    LWORK   (input) INTEGER   
            The dimension of the array WORK.   
            If N <= 1,               LWORK >= 1.   
            If JOBZ = 'N' and N > 1, LWORK >= 3*N.   
            If JOBZ = 'V' and N > 1, LWORK >= 1 + 5*N + 2*N**2.   

            If LWORK = -1, then a workspace query is assumed; the routine   
            only calculates the optimal sizes of the WORK and IWORK   
            arrays, returns these values as the first entries of the WORK   
            and IWORK arrays, and no error message related to LWORK or   
            LIWORK is issued by XERBLA.   

    IWORK   (workspace/output) INTEGER array, dimension (MAX(1,LIWORK))   
            On exit, if LIWORK > 0, IWORK(1) returns the optimal LIWORK.   

    LIWORK  (input) INTEGER   
            The dimension of the array IWORK.   
            If JOBZ  = 'N' or N <= 1, LIWORK >= 1.   
            If JOBZ  = 'V' and N > 1, LIWORK >= 3 + 5*N.   

            If LIWORK = -1, then a workspace query is assumed; the   
            routine only calculates the optimal sizes of the WORK and   
            IWORK arrays, returns these values as the first entries of   
            the WORK and IWORK arrays, and no error message related to   
            LWORK or LIWORK 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, and i is:   
               <= N:  the algorithm failed to converge:   
                      i off-diagonal elements of an intermediate   
                      tridiagonal form did not converge to zero;   
               > N:   if INFO = N + i, for 1 <= i <= N, then SPBSTF   
                      returned INFO = i: B is not positive definite.   
                      The factorization of B could not be completed and   
                      no eigenvalues or eigenvectors were computed.   

    Further Details   
    ===============   

    Based on contributions by   
       Mark Fahey, Department of Mathematics, Univ. of Kentucky, USA   

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


       Test the input parameters.   

       Parameter adjustments */
    /* Table of constant values */
    static real c_b12 = 1.f;
    static real c_b13 = 0.f;
    
    /* System generated locals */
    integer ab_dim1, ab_offset, bb_dim1, bb_offset, z_dim1, z_offset, i__1;
    /* Local variables */
    static integer inde;
    static char vect[1];
    extern logical lsame_(char *, char *);
    static integer iinfo;
    extern /* Subroutine */ int sgemm_(char *, char *, integer *, integer *, 
	    integer *, real *, real *, integer *, real *, integer *, real *, 
	    real *, integer *);
    static integer lwmin;
    static logical upper, wantz;
    static integer indwk2, llwrk2;
    extern /* Subroutine */ int xerbla_(char *, integer *), sstedc_(
	    char *, integer *, real *, real *, real *, integer *, real *, 
	    integer *, integer *, integer *, integer *), slacpy_(char 
	    *, integer *, integer *, real *, integer *, real *, integer *);
    static integer indwrk, liwmin;
    extern /* Subroutine */ int spbstf_(char *, integer *, integer *, real *, 
	    integer *, integer *), ssbtrd_(char *, char *, integer *, 
	    integer *, real *, integer *, real *, real *, real *, integer *, 
	    real *, integer *), ssbgst_(char *, char *, 
	    integer *, integer *, integer *, real *, integer *, real *, 
	    integer *, real *, integer *, real *, integer *), 
	    ssterf_(integer *, real *, real *, integer *);
    static logical lquery;


    ab_dim1 = *ldab;
    ab_offset = 1 + ab_dim1;
    ab -= ab_offset;
    bb_dim1 = *ldbb;
    bb_offset = 1 + bb_dim1;
    bb -= bb_offset;
    --w;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1;
    z__ -= z_offset;
    --work;
    --iwork;

    /* Function Body */
    wantz = lsame_(jobz, "V");
    upper = lsame_(uplo, "U");
    lquery = *lwork == -1 || *liwork == -1;

    *info = 0;
    if (*n <= 1) {
	liwmin = 1;
	lwmin = 1;
    } else if (wantz) {
	liwmin = *n * 5 + 3;
/* Computing 2nd power */
	i__1 = *n;
	lwmin = *n * 5 + 1 + (i__1 * i__1 << 1);
    } else {
	liwmin = 1;
	lwmin = *n << 1;
    }

    if (! (wantz || lsame_(jobz, "N"))) {
	*info = -1;
    } else if (! (upper || lsame_(uplo, "L"))) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*ka < 0) {
	*info = -4;
    } else if (*kb < 0 || *kb > *ka) {
	*info = -5;
    } else if (*ldab < *ka + 1) {
	*info = -7;
    } else if (*ldbb < *kb + 1) {
	*info = -9;
    } else if (*ldz < 1 || wantz && *ldz < *n) {
	*info = -12;
    }

    if (*info == 0) {
	work[1] = (real) lwmin;
	iwork[1] = liwmin;

	if (*lwork < lwmin && ! lquery) {
	    *info = -14;
	} else if (*liwork < liwmin && ! lquery) {
	    *info = -16;
	}
    }

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

/*     Quick return if possible */

    if (*n == 0) {
	return 0;
    }

/*     Form a split Cholesky factorization of B. */

    spbstf_(uplo, n, kb, &bb[bb_offset], ldbb, info);
    if (*info != 0) {
	*info = *n + *info;
	return 0;
    }

/*     Transform problem to standard eigenvalue problem. */

    inde = 1;
    indwrk = inde + *n;
    indwk2 = indwrk + *n * *n;
    llwrk2 = *lwork - indwk2 + 1;
    ssbgst_(jobz, uplo, n, ka, kb, &ab[ab_offset], ldab, &bb[bb_offset], ldbb,
	     &z__[z_offset], ldz, &work[indwrk], &iinfo)
	    ;

/*     Reduce to tridiagonal form. */

    if (wantz) {
	*(unsigned char *)vect = 'U';
    } else {
	*(unsigned char *)vect = 'N';
    }
    ssbtrd_(vect, uplo, n, ka, &ab[ab_offset], ldab, &w[1], &work[inde], &z__[
	    z_offset], ldz, &work[indwrk], &iinfo);

/*     For eigenvalues only, call SSTERF. For eigenvectors, call SSTEDC. */

    if (! wantz) {
	ssterf_(n, &w[1], &work[inde], info);
    } else {
	sstedc_("I", n, &w[1], &work[inde], &work[indwrk], n, &work[indwk2], &
		llwrk2, &iwork[1], liwork, info);
	sgemm_("N", "N", n, n, n, &c_b12, &z__[z_offset], ldz, &work[indwrk], 
		n, &c_b13, &work[indwk2], n);
	slacpy_("A", n, n, &work[indwk2], n, &z__[z_offset], ldz);
    }

    work[1] = (real) lwmin;
    iwork[1] = liwmin;

    return 0;

/*     End of SSBGVD */

} /* ssbgvd_ */