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/* dopgtr.f -- translated by f2c (version 20061008).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#include "f2c.h"
#include "blaswrap.h"
/* Subroutine */ int dopgtr_(char *uplo, integer *n, doublereal *ap,
doublereal *tau, doublereal *q, integer *ldq, doublereal *work,
integer *info)
{
/* System generated locals */
integer q_dim1, q_offset, i__1, i__2, i__3;
/* Local variables */
integer i__, j, ij;
extern logical lsame_(char *, char *);
integer iinfo;
logical upper;
extern /* Subroutine */ int dorg2l_(integer *, integer *, integer *,
doublereal *, integer *, doublereal *, doublereal *, integer *),
dorg2r_(integer *, integer *, integer *, doublereal *, integer *,
doublereal *, doublereal *, integer *), xerbla_(char *, integer *);
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DOPGTR generates a real orthogonal matrix Q which is defined as the */
/* product of n-1 elementary reflectors H(i) of order n, as returned by */
/* DSPTRD using packed storage: */
/* if UPLO = 'U', Q = H(n-1) . . . H(2) H(1), */
/* if UPLO = 'L', Q = H(1) H(2) . . . H(n-1). */
/* Arguments */
/* ========= */
/* UPLO (input) CHARACTER*1 */
/* = 'U': Upper triangular packed storage used in previous */
/* call to DSPTRD; */
/* = 'L': Lower triangular packed storage used in previous */
/* call to DSPTRD. */
/* N (input) INTEGER */
/* The order of the matrix Q. N >= 0. */
/* AP (input) DOUBLE PRECISION array, dimension (N*(N+1)/2) */
/* The vectors which define the elementary reflectors, as */
/* returned by DSPTRD. */
/* TAU (input) DOUBLE PRECISION array, dimension (N-1) */
/* TAU(i) must contain the scalar factor of the elementary */
/* reflector H(i), as returned by DSPTRD. */
/* Q (output) DOUBLE PRECISION array, dimension (LDQ,N) */
/* The N-by-N orthogonal matrix Q. */
/* LDQ (input) INTEGER */
/* The leading dimension of the array Q. LDQ >= max(1,N). */
/* WORK (workspace) DOUBLE PRECISION array, dimension (N-1) */
/* INFO (output) INTEGER */
/* = 0: successful exit */
/* < 0: if INFO = -i, the i-th argument had an illegal value */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input arguments */
/* Parameter adjustments */
--ap;
--tau;
q_dim1 = *ldq;
q_offset = 1 + q_dim1;
q -= q_offset;
--work;
/* Function Body */
*info = 0;
upper = lsame_(uplo, "U");
if (! upper && ! lsame_(uplo, "L")) {
*info = -1;
} else if (*n < 0) {
*info = -2;
} else if (*ldq < max(1,*n)) {
*info = -6;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("DOPGTR", &i__1);
return 0;
}
/* Quick return if possible */
if (*n == 0) {
return 0;
}
if (upper) {
/* Q was determined by a call to DSPTRD with UPLO = 'U' */
/* Unpack the vectors which define the elementary reflectors and */
/* set the last row and column of Q equal to those of the unit */
/* matrix */
ij = 2;
i__1 = *n - 1;
for (j = 1; j <= i__1; ++j) {
i__2 = j - 1;
for (i__ = 1; i__ <= i__2; ++i__) {
q[i__ + j * q_dim1] = ap[ij];
++ij;
/* L10: */
}
ij += 2;
q[*n + j * q_dim1] = 0.;
/* L20: */
}
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
q[i__ + *n * q_dim1] = 0.;
/* L30: */
}
q[*n + *n * q_dim1] = 1.;
/* Generate Q(1:n-1,1:n-1) */
i__1 = *n - 1;
i__2 = *n - 1;
i__3 = *n - 1;
dorg2l_(&i__1, &i__2, &i__3, &q[q_offset], ldq, &tau[1], &work[1], &
iinfo);
} else {
/* Q was determined by a call to DSPTRD with UPLO = 'L'. */
/* Unpack the vectors which define the elementary reflectors and */
/* set the first row and column of Q equal to those of the unit */
/* matrix */
q[q_dim1 + 1] = 1.;
i__1 = *n;
for (i__ = 2; i__ <= i__1; ++i__) {
q[i__ + q_dim1] = 0.;
/* L40: */
}
ij = 3;
i__1 = *n;
for (j = 2; j <= i__1; ++j) {
q[j * q_dim1 + 1] = 0.;
i__2 = *n;
for (i__ = j + 1; i__ <= i__2; ++i__) {
q[i__ + j * q_dim1] = ap[ij];
++ij;
/* L50: */
}
ij += 2;
/* L60: */
}
if (*n > 1) {
/* Generate Q(2:n,2:n) */
i__1 = *n - 1;
i__2 = *n - 1;
i__3 = *n - 1;
dorg2r_(&i__1, &i__2, &i__3, &q[(q_dim1 << 1) + 2], ldq, &tau[1],
&work[1], &iinfo);
}
}
return 0;
/* End of DOPGTR */
} /* dopgtr_ */
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