#include "blaswrap.h"
/*  -- translated by f2c (version 19990503).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include "f2c.h"

/* Table of constant values */

static real c_b5 = 0.f;
static integer c__1 = 1;
static real c_b19 = 1.f;

/* Subroutine */ int sstt21_(integer *n, integer *kband, real *ad, real *ae, 
	real *sd, real *se, real *u, integer *ldu, real *work, real *result)
{
    /* System generated locals */
    integer u_dim1, u_offset, i__1;
    real r__1, r__2, r__3;

    /* Local variables */
    static real unfl;
    extern /* Subroutine */ int ssyr_(char *, integer *, real *, real *, 
	    integer *, real *, integer *);
    static real temp1, temp2;
    static integer j;
    extern /* Subroutine */ int ssyr2_(char *, integer *, real *, real *, 
	    integer *, real *, integer *, real *, integer *), sgemm_(
	    char *, char *, integer *, integer *, integer *, real *, real *, 
	    integer *, real *, integer *, real *, real *, integer *);
    static real anorm, wnorm;
    extern doublereal slamch_(char *), slange_(char *, integer *, 
	    integer *, real *, integer *, real *);
    extern /* Subroutine */ int slaset_(char *, integer *, integer *, real *, 
	    real *, real *, integer *);
    extern doublereal slansy_(char *, char *, integer *, real *, integer *, 
	    real *);
    static real ulp;


#define u_ref(a_1,a_2) u[(a_2)*u_dim1 + a_1]


/*  -- LAPACK test 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   
    =======   

    SSTT21 checks a decomposition of the form   

       A = U S U'   

    where ' means transpose, A is symmetric tridiagonal, U is orthogonal,   
    and S is diagonal (if KBAND=0) or symmetric tridiagonal (if KBAND=1).   
    Two tests are performed:   

       RESULT(1) = | A - U S U' | / ( |A| n ulp )   

       RESULT(2) = | I - UU' | / ( n ulp )   

    Arguments   
    =========   

    N       (input) INTEGER   
            The size of the matrix.  If it is zero, SSTT21 does nothing.   
            It must be at least zero.   

    KBAND   (input) INTEGER   
            The bandwidth of the matrix S.  It may only be zero or one.   
            If zero, then S is diagonal, and SE is not referenced.  If   
            one, then S is symmetric tri-diagonal.   

    AD      (input) REAL array, dimension (N)   
            The diagonal of the original (unfactored) matrix A.  A is   
            assumed to be symmetric tridiagonal.   

    AE      (input) REAL array, dimension (N-1)   
            The off-diagonal of the original (unfactored) matrix A.  A   
            is assumed to be symmetric tridiagonal.  AE(1) is the (1,2)   
            and (2,1) element, AE(2) is the (2,3) and (3,2) element, etc.   

    SD      (input) REAL array, dimension (N)   
            The diagonal of the (symmetric tri-) diagonal matrix S.   

    SE      (input) REAL array, dimension (N-1)   
            The off-diagonal of the (symmetric tri-) diagonal matrix S.   
            Not referenced if KBSND=0.  If KBAND=1, then AE(1) is the   
            (1,2) and (2,1) element, SE(2) is the (2,3) and (3,2)   
            element, etc.   

    U       (input) REAL array, dimension (LDU, N)   
            The orthogonal matrix in the decomposition.   

    LDU     (input) INTEGER   
            The leading dimension of U.  LDU must be at least N.   

    WORK    (workspace) REAL array, dimension (N*(N+1))   

    RESULT  (output) REAL array, dimension (2)   
            The values computed by the two tests described above.  The   
            values are currently limited to 1/ulp, to avoid overflow.   
            RESULT(1) is always modified.   

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


       1)      Constants   

       Parameter adjustments */
    --ad;
    --ae;
    --sd;
    --se;
    u_dim1 = *ldu;
    u_offset = 1 + u_dim1 * 1;
    u -= u_offset;
    --work;
    --result;

    /* Function Body */
    result[1] = 0.f;
    result[2] = 0.f;
    if (*n <= 0) {
	return 0;
    }

    unfl = slamch_("Safe minimum");
    ulp = slamch_("Precision");

/*     Do Test 1   

       Copy A & Compute its 1-Norm: */

    slaset_("Full", n, n, &c_b5, &c_b5, &work[1], n);

    anorm = 0.f;
    temp1 = 0.f;

    i__1 = *n - 1;
    for (j = 1; j <= i__1; ++j) {
	work[(*n + 1) * (j - 1) + 1] = ad[j];
	work[(*n + 1) * (j - 1) + 2] = ae[j];
	temp2 = (r__1 = ae[j], dabs(r__1));
/* Computing MAX */
	r__2 = anorm, r__3 = (r__1 = ad[j], dabs(r__1)) + temp1 + temp2;
	anorm = dmax(r__2,r__3);
	temp1 = temp2;
/* L10: */
    }

/* Computing 2nd power */
    i__1 = *n;
    work[i__1 * i__1] = ad[*n];
/* Computing MAX */
    r__2 = anorm, r__3 = (r__1 = ad[*n], dabs(r__1)) + temp1, r__2 = max(r__2,
	    r__3);
    anorm = dmax(r__2,unfl);

/*     Norm of A - USU' */

    i__1 = *n;
    for (j = 1; j <= i__1; ++j) {
	r__1 = -sd[j];
	ssyr_("L", n, &r__1, &u_ref(1, j), &c__1, &work[1], n);
/* L20: */
    }

    if (*n > 1 && *kband == 1) {
	i__1 = *n - 1;
	for (j = 1; j <= i__1; ++j) {
	    r__1 = -se[j];
	    ssyr2_("L", n, &r__1, &u_ref(1, j), &c__1, &u_ref(1, j + 1), &
		    c__1, &work[1], n);
/* L30: */
	}
    }

/* Computing 2nd power */
    i__1 = *n;
    wnorm = slansy_("1", "L", n, &work[1], n, &work[i__1 * i__1 + 1]);

    if (anorm > wnorm) {
	result[1] = wnorm / anorm / (*n * ulp);
    } else {
	if (anorm < 1.f) {
/* Computing MIN */
	    r__1 = wnorm, r__2 = *n * anorm;
	    result[1] = dmin(r__1,r__2) / anorm / (*n * ulp);
	} else {
/* Computing MIN */
	    r__1 = wnorm / anorm, r__2 = (real) (*n);
	    result[1] = dmin(r__1,r__2) / (*n * ulp);
	}
    }

/*     Do Test 2   

       Compute  UU' - I */

    sgemm_("N", "C", n, n, n, &c_b19, &u[u_offset], ldu, &u[u_offset], ldu, &
	    c_b5, &work[1], n);

    i__1 = *n;
    for (j = 1; j <= i__1; ++j) {
	work[(*n + 1) * (j - 1) + 1] += -1.f;
/* L40: */
    }

/* Computing MIN   
   Computing 2nd power */
    i__1 = *n;
    r__1 = (real) (*n), r__2 = slange_("1", n, n, &work[1], n, &work[i__1 * 
	    i__1 + 1]);
    result[2] = dmin(r__1,r__2) / (*n * ulp);

    return 0;

/*     End of SSTT21 */

} /* sstt21_ */

#undef u_ref


