ICODE-ADC/lammps
4
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
1e8b2ad5a07fd32e63b55d7d52e1264829b96bb4
lammps/lib/linalg/dgebd2.cpp
Axel Kohlmeyer 1e8b2ad5a0 whitespace fixes
2022-12-28 13:48:43 -05:00

394 lines
13 KiB
C++
Raw Blame History

/* fortran/dgebd2.f -- translated by f2c (version 20200916).
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
*/
#ifdef __cplusplus
extern "C" {
#endif
#include "lmp_f2c.h"
/* Table of constant values */
static integer c__1 = 1;
/* > \brief \b DGEBD2 reduces a general matrix to bidiagonal form using an unblocked algorithm. */
/* =========== DOCUMENTATION =========== */
/* Online html documentation available at */
/* http://www.netlib.org/lapack/explore-html/ */
/* > \htmlonly */
/* > Download DGEBD2 + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dgebd2.
f"> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dgebd2.
f"> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dgebd2.
f"> */
/* > [TXT]</a> */
/* > \endhtmlonly */
/* Definition: */
/* =========== */
/* SUBROUTINE DGEBD2( M, N, A, LDA, D, E, TAUQ, TAUP, WORK, INFO ) */
/* .. Scalar Arguments .. */
/* INTEGER INFO, LDA, M, N */
/* .. */
/* .. Array Arguments .. */
/* DOUBLE PRECISION A( LDA, * ), D( * ), E( * ), TAUP( * ), */
/* $ TAUQ( * ), WORK( * ) */
/* .. */
/* > \par Purpose: */
/* ============= */
/* > */
/* > \verbatim */
/* > */
/* > DGEBD2 reduces a real general m by n matrix A to upper or lower */
/* > bidiagonal form B by an orthogonal transformation: Q**T * A * P = B. */
/* > */
/* > If m >= n, B is upper bidiagonal; if m < n, B is lower bidiagonal. */
/* > \endverbatim */
/* Arguments: */
/* ========== */
/* > \param[in] M */
/* > \verbatim */
/* > M is INTEGER */
/* > The number of rows in the matrix A. M >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in] N */
/* > \verbatim */
/* > N is INTEGER */
/* > The number of columns in the matrix A. N >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in,out] A */
/* > \verbatim */
/* > A is DOUBLE PRECISION array, dimension (LDA,N) */
/* > On entry, the m by n general matrix to be reduced. */
/* > On exit, */
/* > if m >= n, the diagonal and the first superdiagonal are */
/* > overwritten with the upper bidiagonal matrix B; the */
/* > elements below the diagonal, with the array TAUQ, represent */
/* > the orthogonal matrix Q as a product of elementary */
/* > reflectors, and the elements above the first superdiagonal, */
/* > with the array TAUP, represent the orthogonal matrix P as */
/* > a product of elementary reflectors; */
/* > if m < n, the diagonal and the first subdiagonal are */
/* > overwritten with the lower bidiagonal matrix B; the */
/* > elements below the first subdiagonal, with the array TAUQ, */
/* > represent the orthogonal matrix Q as a product of */
/* > elementary reflectors, and the elements above the diagonal, */
/* > with the array TAUP, represent the orthogonal matrix P as */
/* > a product of elementary reflectors. */
/* > See Further Details. */
/* > \endverbatim */
/* > */
/* > \param[in] LDA */
/* > \verbatim */
/* > LDA is INTEGER */
/* > The leading dimension of the array A. LDA >= max(1,M). */
/* > \endverbatim */
/* > */
/* > \param[out] D */
/* > \verbatim */
/* > D is DOUBLE PRECISION array, dimension (min(M,N)) */
/* > The diagonal elements of the bidiagonal matrix B: */
/* > D(i) = A(i,i). */
/* > \endverbatim */
/* > */
/* > \param[out] E */
/* > \verbatim */
/* > E is DOUBLE PRECISION array, dimension (min(M,N)-1) */
/* > The off-diagonal elements of the bidiagonal matrix B: */
/* > if m >= n, E(i) = A(i,i+1) for i = 1,2,...,n-1; */
/* > if m < n, E(i) = A(i+1,i) for i = 1,2,...,m-1. */
/* > \endverbatim */
/* > */
/* > \param[out] TAUQ */
/* > \verbatim */
/* > TAUQ is DOUBLE PRECISION array, dimension (min(M,N)) */
/* > The scalar factors of the elementary reflectors which */
/* > represent the orthogonal matrix Q. See Further Details. */
/* > \endverbatim */
/* > */
/* > \param[out] TAUP */
/* > \verbatim */
/* > TAUP is DOUBLE PRECISION array, dimension (min(M,N)) */
/* > The scalar factors of the elementary reflectors which */
/* > represent the orthogonal matrix P. See Further Details. */
/* > \endverbatim */
/* > */
/* > \param[out] WORK */
/* > \verbatim */
/* > WORK is DOUBLE PRECISION array, dimension (max(M,N)) */
/* > \endverbatim */
/* > */
/* > \param[out] INFO */
/* > \verbatim */
/* > INFO is INTEGER */
/* > = 0: successful exit. */
/* > < 0: if INFO = -i, the i-th argument had an illegal value. */
/* > \endverbatim */
/* Authors: */
/* ======== */
/* > \author Univ. of Tennessee */
/* > \author Univ. of California Berkeley */
/* > \author Univ. of Colorado Denver */
/* > \author NAG Ltd. */
/* > \ingroup doubleGEcomputational */
/* > \par Further Details: */
/* ===================== */
/* > */
/* > \verbatim */
/* > */
/* > The matrices Q and P are represented as products of elementary */
/* > reflectors: */
/* > */
/* > If m >= n, */
/* > */
/* > Q = H(1) H(2) . . . H(n) and P = G(1) G(2) . . . G(n-1) */
/* > */
/* > Each H(i) and G(i) has the form: */
/* > */
/* > H(i) = I - tauq * v * v**T and G(i) = I - taup * u * u**T */
/* > */
/* > where tauq and taup are real scalars, and v and u are real vectors; */
/* > v(1:i-1) = 0, v(i) = 1, and v(i+1:m) is stored on exit in A(i+1:m,i); */
/* > u(1:i) = 0, u(i+1) = 1, and u(i+2:n) is stored on exit in A(i,i+2:n); */
/* > tauq is stored in TAUQ(i) and taup in TAUP(i). */
/* > */
/* > If m < n, */
/* > */
/* > Q = H(1) H(2) . . . H(m-1) and P = G(1) G(2) . . . G(m) */
/* > */
/* > Each H(i) and G(i) has the form: */
/* > */
/* > H(i) = I - tauq * v * v**T and G(i) = I - taup * u * u**T */
/* > */
/* > where tauq and taup are real scalars, and v and u are real vectors; */
/* > v(1:i) = 0, v(i+1) = 1, and v(i+2:m) is stored on exit in A(i+2:m,i); */
/* > u(1:i-1) = 0, u(i) = 1, and u(i+1:n) is stored on exit in A(i,i+1:n); */
/* > tauq is stored in TAUQ(i) and taup in TAUP(i). */
/* > */
/* > The contents of A on exit are illustrated by the following examples: */
/* > */
/* > m = 6 and n = 5 (m > n): m = 5 and n = 6 (m < n): */
/* > */
/* > ( d e u1 u1 u1 ) ( d u1 u1 u1 u1 u1 ) */
/* > ( v1 d e u2 u2 ) ( e d u2 u2 u2 u2 ) */
/* > ( v1 v2 d e u3 ) ( v1 e d u3 u3 u3 ) */
/* > ( v1 v2 v3 d e ) ( v1 v2 e d u4 u4 ) */
/* > ( v1 v2 v3 v4 d ) ( v1 v2 v3 e d u5 ) */
/* > ( v1 v2 v3 v4 v5 ) */
/* > */
/* > where d and e denote diagonal and off-diagonal elements of B, vi */
/* > denotes an element of the vector defining H(i), and ui an element of */
/* > the vector defining G(i). */
/* > \endverbatim */
/* > */
/* ===================================================================== */
/* Subroutine */ int dgebd2_(integer *m, integer *n, doublereal *a, integer *
lda, doublereal *d__, doublereal *e, doublereal *tauq, doublereal *
taup, doublereal *work, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
/* Local variables */
integer i__;
extern /* Subroutine */ int dlarf_(char *, integer *, integer *,
doublereal *, integer *, doublereal *, doublereal *, integer *,
doublereal *, ftnlen), dlarfg_(integer *, doublereal *,
doublereal *, integer *, doublereal *), xerbla_(char *, integer *,
ftnlen);
/* -- LAPACK computational routine -- */
/* -- LAPACK is a software package provided by Univ. of Tennessee, -- */
/* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--d__;
--e;
--tauq;
--taup;
--work;
/* Function Body */
*info = 0;
if (*m < 0) {
*info = -1;
} else if (*n < 0) {
*info = -2;
} else if (*lda < max(1,*m)) {
*info = -4;
}
if (*info < 0) {
i__1 = -(*info);
xerbla_((char *)"DGEBD2", &i__1, (ftnlen)6);
return 0;
}
if (*m >= *n) {
/* Reduce to upper bidiagonal form */
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Generate elementary reflector H(i) to annihilate A(i+1:m,i) */
i__2 = *m - i__ + 1;
/* Computing MIN */
i__3 = i__ + 1;
dlarfg_(&i__2, &a[i__ + i__ * a_dim1], &a[min(i__3,*m) + i__ *
a_dim1], &c__1, &tauq[i__]);
d__[i__] = a[i__ + i__ * a_dim1];
a[i__ + i__ * a_dim1] = 1.;
/* Apply H(i) to A(i:m,i+1:n) from the left */
if (i__ < *n) {
i__2 = *m - i__ + 1;
i__3 = *n - i__;
dlarf_((char *)"Left", &i__2, &i__3, &a[i__ + i__ * a_dim1], &c__1, &
tauq[i__], &a[i__ + (i__ + 1) * a_dim1], lda, &work[1]
, (ftnlen)4);
}
a[i__ + i__ * a_dim1] = d__[i__];
if (i__ < *n) {
/* Generate elementary reflector G(i) to annihilate */
/* A(i,i+2:n) */
i__2 = *n - i__;
/* Computing MIN */
i__3 = i__ + 2;
dlarfg_(&i__2, &a[i__ + (i__ + 1) * a_dim1], &a[i__ + min(
i__3,*n) * a_dim1], lda, &taup[i__]);
e[i__] = a[i__ + (i__ + 1) * a_dim1];
a[i__ + (i__ + 1) * a_dim1] = 1.;
/* Apply G(i) to A(i+1:m,i+1:n) from the right */
i__2 = *m - i__;
i__3 = *n - i__;
dlarf_((char *)"Right", &i__2, &i__3, &a[i__ + (i__ + 1) * a_dim1],
lda, &taup[i__], &a[i__ + 1 + (i__ + 1) * a_dim1],
lda, &work[1], (ftnlen)5);
a[i__ + (i__ + 1) * a_dim1] = e[i__];
} else {
taup[i__] = 0.;
}
/* L10: */
}
} else {
/* Reduce to lower bidiagonal form */
i__1 = *m;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Generate elementary reflector G(i) to annihilate A(i,i+1:n) */
i__2 = *n - i__ + 1;
/* Computing MIN */
i__3 = i__ + 1;
dlarfg_(&i__2, &a[i__ + i__ * a_dim1], &a[i__ + min(i__3,*n) *
a_dim1], lda, &taup[i__]);
d__[i__] = a[i__ + i__ * a_dim1];
a[i__ + i__ * a_dim1] = 1.;
/* Apply G(i) to A(i+1:m,i:n) from the right */
if (i__ < *m) {
i__2 = *m - i__;
i__3 = *n - i__ + 1;
dlarf_((char *)"Right", &i__2, &i__3, &a[i__ + i__ * a_dim1], lda, &
taup[i__], &a[i__ + 1 + i__ * a_dim1], lda, &work[1],
(ftnlen)5);
}
a[i__ + i__ * a_dim1] = d__[i__];
if (i__ < *m) {
/* Generate elementary reflector H(i) to annihilate */
/* A(i+2:m,i) */
i__2 = *m - i__;
/* Computing MIN */
i__3 = i__ + 2;
dlarfg_(&i__2, &a[i__ + 1 + i__ * a_dim1], &a[min(i__3,*m) +
i__ * a_dim1], &c__1, &tauq[i__]);
e[i__] = a[i__ + 1 + i__ * a_dim1];
a[i__ + 1 + i__ * a_dim1] = 1.;
/* Apply H(i) to A(i+1:m,i+1:n) from the left */
i__2 = *m - i__;
i__3 = *n - i__;
dlarf_((char *)"Left", &i__2, &i__3, &a[i__ + 1 + i__ * a_dim1], &
c__1, &tauq[i__], &a[i__ + 1 + (i__ + 1) * a_dim1],
lda, &work[1], (ftnlen)4);
a[i__ + 1 + i__ * a_dim1] = e[i__];
} else {
tauq[i__] = 0.;
}
/* L20: */
}
}
return 0;
/* End of DGEBD2 */
} /* dgebd2_ */
#ifdef __cplusplus
}
#endif
Reference in New Issue View Git Blame Copy Permalink