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/* -- translated by f2c (version 19940927).
You must link the resulting object file with the libraries:
-lf2c -lm (in that order)
*/
#include "f2c.h"
/* Table of constant values */
static integer c__3 = 3;
static integer c__1 = 1;
static doublereal c_b8 = 1.;
static doublereal c_b10 = 0.;
/* Subroutine */ int dlarge_(integer *n, doublereal *a, integer *lda, integer
*iseed, doublereal *work, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1;
doublereal d__1;
/* Builtin functions */
double d_sign(doublereal *, doublereal *);
/* Local variables */
extern /* Subroutine */ int dger_(integer *, integer *, doublereal *,
doublereal *, integer *, doublereal *, integer *, doublereal *,
integer *);
extern doublereal dnrm2_(integer *, doublereal *, integer *);
static integer i;
extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *,
integer *), dgemv_(char *, integer *, integer *, doublereal *,
doublereal *, integer *, doublereal *, integer *, doublereal *,
doublereal *, integer *);
static doublereal wa, wb, wn;
extern /* Subroutine */ int xerbla_(char *, integer *), dlarnv_(
integer *, integer *, integer *, doublereal *);
static doublereal tau;
/* -- LAPACK auxiliary test routine (version 2.0)
Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
Courant Institute, Argonne National Lab, and Rice University
February 29, 1992
Purpose
=======
DLARGE pre- and post-multiplies a real general n by n matrix A
with a random orthogonal matrix: A = U*D*U'.
Arguments
=========
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the original n by n matrix A.
On exit, A is overwritten by U*A*U' for some random
orthogonal matrix U.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= N.
ISEED (input/output) INTEGER array, dimension (4)
On entry, the seed of the random number generator; the array
elements must be between 0 and 4095, and ISEED(4) must be
odd.
On exit, the seed is updated.
WORK (workspace) DOUBLE PRECISION array, dimension (2*N)
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
=====================================================================
Test the input arguments
Parameter adjustments */
a_dim1 = *lda;
a_offset = a_dim1 + 1;
a -= a_offset;
--iseed;
--work;
/* Function Body */
*info = 0;
if (*n < 0) {
*info = -1;
} else if (*lda < max(1,*n)) {
*info = -3;
}
if (*info < 0) {
i__1 = -(*info);
xerbla_("DLARGE", &i__1);
return 0;
}
/* pre- and post-multiply A by random orthogonal matrix */
for (i = *n; i >= 1; --i) {
/* generate random reflection */
i__1 = *n - i + 1;
dlarnv_(&c__3, &iseed[1], &i__1, &work[1]);
i__1 = *n - i + 1;
wn = dnrm2_(&i__1, &work[1], &c__1);
wa = d_sign(&wn, &work[1]);
if (wn == 0.) {
tau = 0.;
} else {
wb = work[1] + wa;
i__1 = *n - i;
d__1 = 1. / wb;
dscal_(&i__1, &d__1, &work[2], &c__1);
work[1] = 1.;
tau = wb / wa;
}
/* multiply A(i:n,1:n) by random reflection from the left */
i__1 = *n - i + 1;
dgemv_("Transpose", &i__1, n, &c_b8, &a[i + a_dim1], lda, &work[1], &
c__1, &c_b10, &work[*n + 1], &c__1);
i__1 = *n - i + 1;
d__1 = -tau;
dger_(&i__1, n, &d__1, &work[1], &c__1, &work[*n + 1], &c__1, &a[i +
a_dim1], lda);
/* multiply A(1:n,i:n) by random reflection from the right */
i__1 = *n - i + 1;
dgemv_("No transpose", n, &i__1, &c_b8, &a[i * a_dim1 + 1], lda, &
work[1], &c__1, &c_b10, &work[*n + 1], &c__1);
i__1 = *n - i + 1;
d__1 = -tau;
dger_(n, &i__1, &d__1, &work[*n + 1], &c__1, &work[1], &c__1, &a[i *
a_dim1 + 1], lda);
/* L10: */
}
return 0;
/* End of DLARGE */
} /* dlarge_ */
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