dorgqr.c File Reference

(r)

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

Function Documentation

dorgqr_fla()

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

{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3;
    /* Local variables */
    integer i__, j, l, ib, nb, ki, kk, nx, iws, nbmin, iinfo;
    extern /* Subroutine */
    int dorg2r_fla(integer *, integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, integer *), dlarfb_(char *, char *, char *, char *, integer *, integer *, integer *, doublereal *, integer *, doublereal *, integer *, doublereal *, integer *, doublereal *, integer *), dlarft_(char *, char *, integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, integer *), xerbla_(char *, integer *);
    extern integer ilaenv_(integer *, char *, char *, integer *, integer *, integer *, integer *);
    integer ldwork, lwkopt;
    logical lquery;
    /* -- LAPACK computational routine (version 3.4.0) -- */
    /* -- LAPACK is a software package provided by Univ. of Tennessee, -- */
    /* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
    /* November 2011 */
    /* .. Scalar Arguments .. */
    /* .. */
    /* .. Array Arguments .. */
    /* .. */
    /* ===================================================================== */
    /* .. Parameters .. */
    /* .. */
    /* .. Local Scalars .. */
    /* .. */
    /* .. External Subroutines .. */
    /* .. */
    /* .. Intrinsic Functions .. */
    /* .. */
    /* .. External 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;
    nb = ilaenv_(&c__1, "DORGQR", " ", m, n, k, &c_n1);
    lwkopt = max(1,*n) * nb;
    work[1] = (doublereal) lwkopt;
    lquery = *lwork == -1;
    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;
    }
    else if (*lwork < max(1,*n) && ! lquery)
    {
        *info = -8;
    }
    if (*info != 0)
    {
        i__1 = -(*info);
        xerbla_("DORGQR", &i__1);
        return 0;
    }
    else if (lquery)
    {
        return 0;
    }
    /* Quick return if possible */
    if (*n <= 0)
    {
        work[1] = 1.;
        return 0;
    }
    nbmin = 2;
    nx = 0;
    iws = *n;
    if (nb > 1 && nb < *k)
    {
        /* Determine when to cross over from blocked to unblocked code. */
        /* Computing MAX */
        i__1 = 0;
        i__2 = ilaenv_(&c__3, "DORGQR", " ", m, n, k, &c_n1); // , expr subst
        nx = max(i__1,i__2);
        if (nx < *k)
        {
            /* Determine if workspace is large enough for blocked code. */
            ldwork = *n;
            iws = ldwork * nb;
            if (*lwork < iws)
            {
                /* Not enough workspace to use optimal NB: reduce NB and */
                /* determine the minimum value of NB. */
                nb = *lwork / ldwork;
                /* Computing MAX */
                i__1 = 2;
                i__2 = ilaenv_(&c__2, "DORGQR", " ", m, n, k, &c_n1); // , expr subst
                nbmin = max(i__1,i__2);
            }
        }
    }
    if (nb >= nbmin && nb < *k && nx < *k)
    {
        /* Use blocked code after the last block. */
        /* The first kk columns are handled by the block method. */
        ki = (*k - nx - 1) / nb * nb;
        /* Computing MIN */
        i__1 = *k;
        i__2 = ki + nb; // , expr subst
        kk = min(i__1,i__2);
        /* Set A(1:kk,kk+1:n) to zero. */
        i__1 = *n;
        for (j = kk + 1;
                j <= i__1;
                ++j)
        {
            i__2 = kk;
            for (i__ = 1;
                    i__ <= i__2;
                    ++i__)
            {
                a[i__ + j * a_dim1] = 0.;
                /* L10: */
            }
            /* L20: */
        }
    }
    else
    {
        kk = 0;
    }
    /* Use unblocked code for the last or only block. */
    if (kk < *n)
    {
        i__1 = *m - kk;
        i__2 = *n - kk;
        i__3 = *k - kk;
        dorg2r_fla(&i__1, &i__2, &i__3, &a[kk + 1 + (kk + 1) * a_dim1], lda, & tau[kk + 1], &work[1], &iinfo);
    }
    if (kk > 0)
    {
        /* Use blocked code */
        i__1 = -nb;
        for (i__ = ki + 1;
                i__1 < 0 ? i__ >= 1 : i__ <= 1;
                i__ += i__1)
        {
            /* Computing MIN */
            i__2 = nb;
            i__3 = *k - i__ + 1; // , expr subst
            ib = min(i__2,i__3);
            if (i__ + ib <= *n)
            {
                /* Form the triangular factor of the block reflector */
                /* H = H(i) H(i+1) . . . H(i+ib-1) */
                i__2 = *m - i__ + 1;
                dlarft_("Forward", "Columnwise", &i__2, &ib, &a[i__ + i__ * a_dim1], lda, &tau[i__], &work[1], &ldwork);
                /* Apply H to A(i:m,i+ib:n) from the left */
                i__2 = *m - i__ + 1;
                i__3 = *n - i__ - ib + 1;
                dlarfb_("Left", "No transpose", "Forward", "Columnwise", & i__2, &i__3, &ib, &a[i__ + i__ * a_dim1], lda, &work[ 1], &ldwork, &a[i__ + (i__ + ib) * a_dim1], lda, & work[ib + 1], &ldwork);
            }
            /* Apply H to rows i:m of current block */
            i__2 = *m - i__ + 1;
            dorg2r_fla(&i__2, &ib, &ib, &a[i__ + i__ * a_dim1], lda, &tau[i__], & work[1], &iinfo);
            /* Set rows 1:i-1 of current block to zero */
            i__2 = i__ + ib - 1;
            for (j = i__;
                    j <= i__2;
                    ++j)
            {
                i__3 = i__ - 1;
                for (l = 1;
                        l <= i__3;
                        ++l)
                {
                    a[l + j * a_dim1] = 0.;
                    /* L30: */
                }
                /* L40: */
            }
            /* L50: */
        }
    }
    work[1] = (doublereal) iws;
    return 0;
    /* End of DORGQR */
}

References dorg2r_fla().

Referenced by dorcsd2by1_(), dorcsd_(), dorghr_(), and dorgtr_fla().