dorgtr.c File Reference

(r)

Functions
int	dorgtr_fla (char *uplo, integer *n, doublereal *a, integer *lda, doublereal *tau, doublereal *work, integer *lwork, integer *info)

Function Documentation

dorgtr_fla()

int dorgtr_fla	(	char *	uplo,
		integer *	n,
		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, nb;
    extern logical lsame_(char *, char *);
    integer iinfo;
    logical upper;
    extern /* Subroutine */
    int xerbla_(char *, integer *);
    extern integer ilaenv_(integer *, char *, char *, integer *, integer *, integer *, integer *);
    extern /* Subroutine */
    int dorgql_(integer *, integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, integer *, integer *), dorgqr_fla(integer *, integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, integer *, integer *);
    integer 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 Functions .. */
    /* .. */
    /* .. 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;
    lquery = *lwork == -1;
    upper = lsame_(uplo, "U");
    if (! upper && ! lsame_(uplo, "L"))
    {
        *info = -1;
    }
    else if (*n < 0)
    {
        *info = -2;
    }
    else if (*lda < max(1,*n))
    {
        *info = -4;
    }
    else /* if(complicated condition) */
    {
        /* Computing MAX */
        i__1 = 1;
        i__2 = *n - 1; // , expr subst
        if (*lwork < max(i__1,i__2) && ! lquery)
        {
            *info = -7;
        }
    }
    if (*info == 0)
    {
        if (upper)
        {
            i__1 = *n - 1;
            i__2 = *n - 1;
            i__3 = *n - 1;
            nb = ilaenv_(&c__1, "DORGQL", " ", &i__1, &i__2, &i__3, &c_n1);
        }
        else
        {
            i__1 = *n - 1;
            i__2 = *n - 1;
            i__3 = *n - 1;
            nb = ilaenv_(&c__1, "DORGQR", " ", &i__1, &i__2, &i__3, &c_n1);
        }
        /* Computing MAX */
        i__1 = 1;
        i__2 = *n - 1; // , expr subst
        lwkopt = max(i__1,i__2) * nb;
        work[1] = (doublereal) lwkopt;
    }
    if (*info != 0)
    {
        i__1 = -(*info);
        xerbla_("DORGTR", &i__1);
        return 0;
    }
    else if (lquery)
    {
        return 0;
    }
    /* Quick return if possible */
    if (*n == 0)
    {
        work[1] = 1.;
        return 0;
    }
    if (upper)
    {
        /* Q was determined by a call to DSYTRD with UPLO = 'U' */
        /* Shift the vectors which define the elementary reflectors one */
        /* column to the left, and set the last row and column of Q to */
        /* those of the unit matrix */
        i__1 = *n - 1;
        for (j = 1;
                j <= i__1;
                ++j)
        {
            i__2 = j - 1;
            for (i__ = 1;
                    i__ <= i__2;
                    ++i__)
            {
                a[i__ + j * a_dim1] = a[i__ + (j + 1) * a_dim1];
                /* L10: */
            }
            a[*n + j * a_dim1] = 0.;
            /* L20: */
        }
        i__1 = *n - 1;
        for (i__ = 1;
                i__ <= i__1;
                ++i__)
        {
            a[i__ + *n * a_dim1] = 0.;
            /* L30: */
        }
        a[*n + *n * a_dim1] = 1.;
        /* Generate Q(1:n-1,1:n-1) */
        i__1 = *n - 1;
        i__2 = *n - 1;
        i__3 = *n - 1;
        dorgql_(&i__1, &i__2, &i__3, &a[a_offset], lda, &tau[1], &work[1], lwork, &iinfo);
    }
    else
    {
        /* Q was determined by a call to DSYTRD with UPLO = 'L'. */
        /* Shift the vectors which define the elementary reflectors one */
        /* column to the right, and set the first row and column of Q to */
        /* those of the unit matrix */
        for (j = *n;
                j >= 2;
                --j)
        {
            a[j * a_dim1 + 1] = 0.;
            i__1 = *n;
            for (i__ = j + 1;
                    i__ <= i__1;
                    ++i__)
            {
                a[i__ + j * a_dim1] = a[i__ + (j - 1) * a_dim1];
                /* L40: */
            }
            /* L50: */
        }
        a[a_dim1 + 1] = 1.;
        i__1 = *n;
        for (i__ = 2;
                i__ <= i__1;
                ++i__)
        {
            a[i__ + a_dim1] = 0.;
            /* L60: */
        }
        if (*n > 1)
        {
            /* Generate Q(2:n,2:n) */
            i__1 = *n - 1;
            i__2 = *n - 1;
            i__3 = *n - 1;
            dorgqr_fla(&i__1, &i__2, &i__3, &a[(a_dim1 << 1) + 2], lda, &tau[1], &work[1], lwork, &iinfo);
        }
    }
    work[1] = (doublereal) lwkopt;
    return 0;
    /* End of DORGTR */
}

References dorgqr_fla(), and i.