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

/* Subroutine */ int ssygst_(integer *itype, char *uplo, integer *n, real *a, 
	integer *lda, real *b, integer *ldb, integer *info)
{
/*  -- LAPACK routine (version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       September 30, 1994   


    Purpose   
    =======   

    SSYGST reduces a real symmetric-definite generalized eigenproblem   
    to standard form.   

    If ITYPE = 1, the problem is A*x = lambda*B*x,   
    and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)   

    If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or   
    B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.   

    B must have been previously factorized as U**T*U or L*L**T by SPOTRF.   

    Arguments   
    =========   

    ITYPE   (input) INTEGER   
            = 1: compute inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T);   
            = 2 or 3: compute U*A*U**T or L**T*A*L.   

    UPLO    (input) CHARACTER   
            = 'U':  Upper triangle of A is stored and B is factored as   
                    U**T*U;   
            = 'L':  Lower triangle of A is stored and B is factored as   
                    L*L**T.   

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

    A       (input/output) REAL 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, 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, if INFO = 0, the transformed matrix, stored in the   
            same format as A.   

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

    B       (input) REAL array, dimension (LDB,N)   
            The triangular factor from the Cholesky factorization of B,   
            as returned by SPOTRF.   

    LDB     (input) INTEGER   
            The leading dimension of the array B.  LDB >= max(1,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;
    static integer c_n1 = -1;
    static real c_b14 = 1.f;
    static real c_b16 = -.5f;
    static real c_b19 = -1.f;
    static real c_b52 = .5f;
    
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, i__1, i__2, i__3;
    /* Local variables */
    static integer k;
    extern logical lsame_(char *, char *);
    static logical upper;
    extern /* Subroutine */ int strmm_(char *, char *, char *, char *, 
	    integer *, integer *, real *, real *, integer *, real *, integer *
	    ), ssymm_(char *, char *, integer 
	    *, integer *, real *, real *, integer *, real *, integer *, real *
	    , real *, integer *), strsm_(char *, char *, char 
	    *, char *, integer *, integer *, real *, real *, integer *, real *
	    , integer *);
    static integer kb, nb;
    extern /* Subroutine */ int ssygs2_(integer *, char *, integer *, real *, 
	    integer *, real *, integer *, integer *), ssyr2k_(char *, 
	    char *, integer *, integer *, real *, real *, integer *, real *, 
	    integer *, real *, real *, integer *), xerbla_(
	    char *, integer *);
    extern integer ilaenv_(integer *, char *, char *, integer *, integer *, 
	    integer *, integer *, ftnlen, ftnlen);
#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]
#define b_ref(a_1,a_2) b[(a_2)*b_dim1 + a_1]


    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1 * 1;
    b -= b_offset;

    /* Function Body */
    *info = 0;
    upper = lsame_(uplo, "U");
    if (*itype < 1 || *itype > 3) {
	*info = -1;
    } else if (! upper && ! lsame_(uplo, "L")) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*lda < max(1,*n)) {
	*info = -5;
    } else if (*ldb < max(1,*n)) {
	*info = -7;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("SSYGST", &i__1);
	return 0;
    }

/*     Quick return if possible */

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

/*     Determine the block size for this environment. */

    nb = ilaenv_(&c__1, "SSYGST", uplo, n, &c_n1, &c_n1, &c_n1, (ftnlen)6, (
	    ftnlen)1);

    if (nb <= 1 || nb >= *n) {

/*        Use unblocked code */

	ssygs2_(itype, uplo, n, &a[a_offset], lda, &b[b_offset], ldb, info);
    } else {

/*        Use blocked code */

	if (*itype == 1) {
	    if (upper) {

/*              Compute inv(U')*A*inv(U) */

		i__1 = *n;
		i__2 = nb;
		for (k = 1; i__2 < 0 ? k >= i__1 : k <= i__1; k += i__2) {
/* Computing MIN */
		    i__3 = *n - k + 1;
		    kb = min(i__3,nb);

/*                 Update the upper triangle of A(k:n,k:n) */

		    ssygs2_(itype, uplo, &kb, &a_ref(k, k), lda, &b_ref(k, k),
			     ldb, info);
		    if (k + kb <= *n) {
			i__3 = *n - k - kb + 1;
			strsm_("Left", uplo, "Transpose", "Non-unit", &kb, &
				i__3, &c_b14, &b_ref(k, k), ldb, &a_ref(k, k 
				+ kb), lda);
			i__3 = *n - k - kb + 1;
			ssymm_("Left", uplo, &kb, &i__3, &c_b16, &a_ref(k, k),
				 lda, &b_ref(k, k + kb), ldb, &c_b14, &a_ref(
				k, k + kb), lda);
			i__3 = *n - k - kb + 1;
			ssyr2k_(uplo, "Transpose", &i__3, &kb, &c_b19, &a_ref(
				k, k + kb), lda, &b_ref(k, k + kb), ldb, &
				c_b14, &a_ref(k + kb, k + kb), lda);
			i__3 = *n - k - kb + 1;
			ssymm_("Left", uplo, &kb, &i__3, &c_b16, &a_ref(k, k),
				 lda, &b_ref(k, k + kb), ldb, &c_b14, &a_ref(
				k, k + kb), lda);
			i__3 = *n - k - kb + 1;
			strsm_("Right", uplo, "No transpose", "Non-unit", &kb,
				 &i__3, &c_b14, &b_ref(k + kb, k + kb), ldb, &
				a_ref(k, k + kb), lda);
		    }
/* L10: */
		}
	    } else {

/*              Compute inv(L)*A*inv(L') */

		i__2 = *n;
		i__1 = nb;
		for (k = 1; i__1 < 0 ? k >= i__2 : k <= i__2; k += i__1) {
/* Computing MIN */
		    i__3 = *n - k + 1;
		    kb = min(i__3,nb);

/*                 Update the lower triangle of A(k:n,k:n) */

		    ssygs2_(itype, uplo, &kb, &a_ref(k, k), lda, &b_ref(k, k),
			     ldb, info);
		    if (k + kb <= *n) {
			i__3 = *n - k - kb + 1;
			strsm_("Right", uplo, "Transpose", "Non-unit", &i__3, 
				&kb, &c_b14, &b_ref(k, k), ldb, &a_ref(k + kb,
				 k), lda);
			i__3 = *n - k - kb + 1;
			ssymm_("Right", uplo, &i__3, &kb, &c_b16, &a_ref(k, k)
				, lda, &b_ref(k + kb, k), ldb, &c_b14, &a_ref(
				k + kb, k), lda);
			i__3 = *n - k - kb + 1;
			ssyr2k_(uplo, "No transpose", &i__3, &kb, &c_b19, &
				a_ref(k + kb, k), lda, &b_ref(k + kb, k), ldb,
				 &c_b14, &a_ref(k + kb, k + kb), lda);
			i__3 = *n - k - kb + 1;
			ssymm_("Right", uplo, &i__3, &kb, &c_b16, &a_ref(k, k)
				, lda, &b_ref(k + kb, k), ldb, &c_b14, &a_ref(
				k + kb, k), lda);
			i__3 = *n - k - kb + 1;
			strsm_("Left", uplo, "No transpose", "Non-unit", &
				i__3, &kb, &c_b14, &b_ref(k + kb, k + kb), 
				ldb, &a_ref(k + kb, k), lda);
		    }
/* L20: */
		}
	    }
	} else {
	    if (upper) {

/*              Compute U*A*U' */

		i__1 = *n;
		i__2 = nb;
		for (k = 1; i__2 < 0 ? k >= i__1 : k <= i__1; k += i__2) {
/* Computing MIN */
		    i__3 = *n - k + 1;
		    kb = min(i__3,nb);

/*                 Update the upper triangle of A(1:k+kb-1,1:k+kb-1) */

		    i__3 = k - 1;
		    strmm_("Left", uplo, "No transpose", "Non-unit", &i__3, &
			    kb, &c_b14, &b[b_offset], ldb, &a_ref(1, k), lda);
		    i__3 = k - 1;
		    ssymm_("Right", uplo, &i__3, &kb, &c_b52, &a_ref(k, k), 
			    lda, &b_ref(1, k), ldb, &c_b14, &a_ref(1, k), lda);
		    i__3 = k - 1;
		    ssyr2k_(uplo, "No transpose", &i__3, &kb, &c_b14, &a_ref(
			    1, k), lda, &b_ref(1, k), ldb, &c_b14, &a[
			    a_offset], lda);
		    i__3 = k - 1;
		    ssymm_("Right", uplo, &i__3, &kb, &c_b52, &a_ref(k, k), 
			    lda, &b_ref(1, k), ldb, &c_b14, &a_ref(1, k), lda);
		    i__3 = k - 1;
		    strmm_("Right", uplo, "Transpose", "Non-unit", &i__3, &kb,
			     &c_b14, &b_ref(k, k), ldb, &a_ref(1, k), lda);
		    ssygs2_(itype, uplo, &kb, &a_ref(k, k), lda, &b_ref(k, k),
			     ldb, info);
/* L30: */
		}
	    } else {

/*              Compute L'*A*L */

		i__2 = *n;
		i__1 = nb;
		for (k = 1; i__1 < 0 ? k >= i__2 : k <= i__2; k += i__1) {
/* Computing MIN */
		    i__3 = *n - k + 1;
		    kb = min(i__3,nb);

/*                 Update the lower triangle of A(1:k+kb-1,1:k+kb-1) */

		    i__3 = k - 1;
		    strmm_("Right", uplo, "No transpose", "Non-unit", &kb, &
			    i__3, &c_b14, &b[b_offset], ldb, &a_ref(k, 1), 
			    lda);
		    i__3 = k - 1;
		    ssymm_("Left", uplo, &kb, &i__3, &c_b52, &a_ref(k, k), 
			    lda, &b_ref(k, 1), ldb, &c_b14, &a_ref(k, 1), lda);
		    i__3 = k - 1;
		    ssyr2k_(uplo, "Transpose", &i__3, &kb, &c_b14, &a_ref(k, 
			    1), lda, &b_ref(k, 1), ldb, &c_b14, &a[a_offset], 
			    lda);
		    i__3 = k - 1;
		    ssymm_("Left", uplo, &kb, &i__3, &c_b52, &a_ref(k, k), 
			    lda, &b_ref(k, 1), ldb, &c_b14, &a_ref(k, 1), lda);
		    i__3 = k - 1;
		    strmm_("Left", uplo, "Transpose", "Non-unit", &kb, &i__3, 
			    &c_b14, &b_ref(k, k), ldb, &a_ref(k, 1), lda);
		    ssygs2_(itype, uplo, &kb, &a_ref(k, k), lda, &b_ref(k, k),
			     ldb, info);
/* L40: */
		}
	    }
	}
    }
    return 0;

/*     End of SSYGST */

} /* ssygst_ */

#undef b_ref
#undef a_ref


