zungl2.c File Reference

(r)

Functions
int	zungl2_fla (integer *m, integer *n, integer *k, doublecomplex *a, integer *lda, doublecomplex *tau, doublecomplex *work, integer *info)

Function Documentation

zungl2_fla()

int zungl2_fla	(	integer *	m,
		integer *	n,
		integer *	k,
		doublecomplex *	a,
		integer *	lda,
		doublecomplex *	tau,
		doublecomplex *	work,
		integer *	info
	)

{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3;
    doublecomplex z__1, z__2;
    /* Builtin functions */
    void d_cnjg(doublecomplex *, doublecomplex *);
    /* Local variables */
    integer i__, j, l;
    extern /* Subroutine */
    int zscal_(integer *, doublecomplex *, doublecomplex *, integer *), zlarf_(char *, integer *, integer *, doublecomplex *, integer *, doublecomplex *, doublecomplex *, integer *, doublecomplex *), xerbla_(char *, integer *), zlacgv_(integer *, doublecomplex *, integer *);
    /* -- LAPACK computational routine (version 3.4.2) -- */
    /* -- LAPACK is a software package provided by Univ. of Tennessee, -- */
    /* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
    /* September 2012 */
    /* .. Scalar Arguments .. */
    /* .. */
    /* .. Array Arguments .. */
    /* .. */
    /* ===================================================================== */
    /* .. Parameters .. */
    /* .. */
    /* .. Local Scalars .. */
    /* .. */
    /* .. External Subroutines .. */
    /* .. */
    /* .. Intrinsic Functions .. */
    /* .. */
    /* .. Executable Statements .. */
    /* Test the input arguments */
    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    --tau;
    --work;
    /* Function Body */
    *info = 0;
    if (*m < 0)
    {
        *info = -1;
    }
    else if (*n < *m)
    {
        *info = -2;
    }
    else if (*k < 0 || *k > *m)
    {
        *info = -3;
    }
    else if (*lda < max(1,*m))
    {
        *info = -5;
    }
    if (*info != 0)
    {
        i__1 = -(*info);
        xerbla_("ZUNGL2", &i__1);
        return 0;
    }
    /* Quick return if possible */
    if (*m <= 0)
    {
        return 0;
    }
    if (*k < *m)
    {
        /* Initialise rows k+1:m to rows of the unit matrix */
        i__1 = *n;
        for (j = 1;
                j <= i__1;
                ++j)
        {
            i__2 = *m;
            for (l = *k + 1;
                    l <= i__2;
                    ++l)
            {
                i__3 = l + j * a_dim1;
                a[i__3].r = 0.;
                a[i__3].i = 0.; // , expr subst
                /* L10: */
            }
            if (j > *k && j <= *m)
            {
                i__2 = j + j * a_dim1;
                a[i__2].r = 1.;
                a[i__2].i = 0.; // , expr subst
            }
            /* L20: */
        }
    }
    for (i__ = *k;
            i__ >= 1;
            --i__)
    {
        /* Apply H(i)**H to A(i:m,i:n) from the right */
        if (i__ < *n)
        {
            i__1 = *n - i__;
            zlacgv_(&i__1, &a[i__ + (i__ + 1) * a_dim1], lda);
            if (i__ < *m)
            {
                i__1 = i__ + i__ * a_dim1;
                a[i__1].r = 1.;
                a[i__1].i = 0.; // , expr subst
                i__1 = *m - i__;
                i__2 = *n - i__ + 1;
                d_cnjg(&z__1, &tau[i__]);
                zlarf_("Right", &i__1, &i__2, &a[i__ + i__ * a_dim1], lda, & z__1, &a[i__ + 1 + i__ * a_dim1], lda, &work[1]);
            }
            i__1 = *n - i__;
            i__2 = i__;
            z__1.r = -tau[i__2].r;
            z__1.i = -tau[i__2].i; // , expr subst
            zscal_(&i__1, &z__1, &a[i__ + (i__ + 1) * a_dim1], lda);
            i__1 = *n - i__;
            zlacgv_(&i__1, &a[i__ + (i__ + 1) * a_dim1], lda);
        }
        i__1 = i__ + i__ * a_dim1;
        d_cnjg(&z__2, &tau[i__]);
        z__1.r = 1. - z__2.r;
        z__1.i = 0. - z__2.i; // , expr subst
        a[i__1].r = z__1.r;
        a[i__1].i = z__1.i; // , expr subst
        /* Set A(i,1:i-1) to zero */
        i__1 = i__ - 1;
        for (l = 1;
                l <= i__1;
                ++l)
        {
            i__2 = i__ + l * a_dim1;
            a[i__2].r = 0.;
            a[i__2].i = 0.; // , expr subst
            /* L30: */
        }
        /* L40: */
    }
    return 0;
    /* End of ZUNGL2 */
}

References i.

Referenced by zunglq_fla().