#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_b2 = 1.f;
static real c_b3 = 0.f;
static integer c__1 = 1;

/* Subroutine */ int slarfy_(char *uplo, integer *n, real *v, integer *incv, 
	real *tau, real *c__, integer *ldc, real *work)
{
    /* System generated locals */
    integer c_dim1, c_offset;
    real r__1;

    /* Local variables */
    extern doublereal sdot_(integer *, real *, integer *, real *, integer *);
    extern /* Subroutine */ int ssyr2_(char *, integer *, real *, real *, 
	    integer *, real *, integer *, real *, integer *);
    static real alpha;
    extern /* Subroutine */ int saxpy_(integer *, real *, real *, integer *, 
	    real *, integer *), ssymv_(char *, integer *, real *, real *, 
	    integer *, real *, integer *, real *, real *, integer *);


/*  -- LAPACK auxiliary test routine (version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       February 29, 1992   


    Purpose   
    =======   

    SLARFY applies an elementary reflector, or Householder matrix, H,   
    to an n x n symmetric matrix C, from both the left and the right.   

    H is represented in the form   

       H = I - tau * v * v'   

    where  tau  is a scalar and  v  is a vector.   

    If  tau  is  zero, then  H  is taken to be the unit matrix.   

    Arguments   
    =========   

    UPLO    (input) CHARACTER*1   
            Specifies whether the upper or lower triangular part of the   
            symmetric matrix C is stored.   
            = 'U':  Upper triangle   
            = 'L':  Lower triangle   

    N       (input) INTEGER   
            The number of rows and columns of the matrix C.  N >= 0.   

    V       (input) REAL array, dimension   
                    (1 + (N-1)*abs(INCV))   
            The vector v as described above.   

    INCV    (input) INTEGER   
            The increment between successive elements of v.  INCV must   
            not be zero.   

    TAU     (input) REAL   
            The value tau as described above.   

    C       (input/output) REAL array, dimension (LDC, N)   
            On entry, the matrix C.   
            On exit, C is overwritten by H * C * H'.   

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

    WORK    (workspace) REAL array, dimension (N)   

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


       Parameter adjustments */
    --v;
    c_dim1 = *ldc;
    c_offset = 1 + c_dim1 * 1;
    c__ -= c_offset;
    --work;

    /* Function Body */
    if (*tau == 0.f) {
	return 0;
    }

/*     Form  w:= C * v */

    ssymv_(uplo, n, &c_b2, &c__[c_offset], ldc, &v[1], incv, &c_b3, &work[1], 
	    &c__1);

    alpha = *tau * -.5f * sdot_(n, &work[1], &c__1, &v[1], incv);
    saxpy_(n, &alpha, &v[1], incv, &work[1], &c__1);

/*     C := C - v * w' - w * v' */

    r__1 = -(*tau);
    ssyr2_(uplo, n, &r__1, &v[1], incv, &work[1], &c__1, &c__[c_offset], ldc);

    return 0;

/*     End of SLARFY */

} /* slarfy_ */


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