dorg2r.c File Reference

(r)

Functions
int	dorg2r_fla (integer *m, integer *n, integer *k, doublereal *a, integer *lda, doublereal *tau, doublereal *work, integer *info)

Function Documentation

dorg2r_fla()

int dorg2r_fla	(	integer *	m,
		integer *	n,
		integer *	k,
		doublereal *	a,
		integer *	lda,
		doublereal *	tau,
		doublereal *	work,
		integer *	info
	)

{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2;
    doublereal d__1;
    /* Local variables */
    integer i__, j, l;
    extern /* Subroutine */
    int dscal_(integer *, doublereal *, doublereal *, integer *), dlarf_(char *, integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, integer *, doublereal *), xerbla_(char *, 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 < 0 || *n > *m)
    {
        *info = -2;
    }
    else if (*k < 0 || *k > *n)
    {
        *info = -3;
    }
    else if (*lda < max(1,*m))
    {
        *info = -5;
    }
    if (*info != 0)
    {
        i__1 = -(*info);
        xerbla_("DORG2R", &i__1);
        return 0;
    }
    /* Quick return if possible */
    if (*n <= 0)
    {
        return 0;
    }
    /* Initialise columns k+1:n to columns of the unit matrix */
    i__1 = *n;
    for (j = *k + 1;
            j <= i__1;
            ++j)
    {
        i__2 = *m;
        for (l = 1;
                l <= i__2;
                ++l)
        {
            a[l + j * a_dim1] = 0.;
            /* L10: */
        }
        a[j + j * a_dim1] = 1.;
        /* L20: */
    }
    for (i__ = *k;
            i__ >= 1;
            --i__)
    {
        /* Apply H(i) to A(i:m,i:n) from the left */
        if (i__ < *n)
        {
            a[i__ + i__ * a_dim1] = 1.;
            i__1 = *m - i__ + 1;
            i__2 = *n - i__;
            dlarf_("Left", &i__1, &i__2, &a[i__ + i__ * a_dim1], &c__1, &tau[ i__], &a[i__ + (i__ + 1) * a_dim1], lda, &work[1]);
        }
        if (i__ < *m)
        {
            i__1 = *m - i__;
            d__1 = -tau[i__];
            dscal_(&i__1, &d__1, &a[i__ + 1 + i__ * a_dim1], &c__1);
        }
        a[i__ + i__ * a_dim1] = 1. - tau[i__];
        /* Set A(1:i-1,i) to zero */
        i__1 = i__ - 1;
        for (l = 1;
                l <= i__1;
                ++l)
        {
            a[l + i__ * a_dim1] = 0.;
            /* L30: */
        }
        /* L40: */
    }
    return 0;
    /* End of DORG2R */
}

References i.

Referenced by dopgtr_(), and dorgqr_fla().