dlalsd.c

提供矩阵类的函数库

#include "blaswrap.h"
/*  -- translated by f2c (version 19990503).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include "f2c.h"

/* Common Block Declarations */

struct {
    doublereal ops, itcnt;
} latime_;

#define latime_1 latime_

/* Table of constant values */

static integer c__1 = 1;
static doublereal c_b6 = 0.;
static integer c__0 = 0;
static doublereal c_b11 = 1.;

/* Subroutine */ int dlalsd_(char *uplo, integer *smlsiz, integer *n, integer 
	*nrhs, doublereal *d__, doublereal *e, doublereal *b, integer *ldb, 
	doublereal *rcond, integer *rank, doublereal *work, integer *iwork, 
	integer *info)
{
    /* System generated locals */
    integer b_dim1, b_offset, i__1, i__2;
    doublereal d__1;

    /* Builtin functions */
    double log(doublereal), d_sign(doublereal *, doublereal *);

    /* Local variables */
    static integer difl, difr, perm, nsub;
    extern /* Subroutine */ int drot_(integer *, doublereal *, integer *, 
	    doublereal *, integer *, doublereal *, doublereal *);
    static integer nlvl, sqre, bxst, c__, i__, j, k;
    static doublereal r__;
    static integer s, u;
    extern /* Subroutine */ int dgemm_(char *, char *, integer *, integer *, 
	    integer *, doublereal *, doublereal *, integer *, doublereal *, 
	    integer *, doublereal *, doublereal *, integer *);
    static integer z__;
    extern /* Subroutine */ int dcopy_(integer *, doublereal *, integer *, 
	    doublereal *, integer *);
    static integer poles, sizei, nsize, nwork;
    extern doublereal dopbl3_(char *, integer *, integer *, integer *)
	    ;
    static integer icmpq1, icmpq2;
    static doublereal cs;
    extern /* Subroutine */ int dlasda_(integer *, integer *, integer *, 
	    integer *, doublereal *, doublereal *, doublereal *, integer *, 
	    doublereal *, integer *, doublereal *, doublereal *, doublereal *,
	     doublereal *, integer *, integer *, integer *, integer *, 
	    doublereal *, doublereal *, doublereal *, doublereal *, integer *,
	     integer *);
    extern doublereal dlamch_(char *);
    static integer bx;
    extern /* Subroutine */ int dlalsa_(integer *, integer *, integer *, 
	    integer *, doublereal *, integer *, doublereal *, integer *, 
	    doublereal *, integer *, doublereal *, integer *, doublereal *, 
	    doublereal *, doublereal *, doublereal *, integer *, integer *, 
	    integer *, integer *, doublereal *, doublereal *, doublereal *, 
	    doublereal *, integer *, integer *);
    static doublereal sn;
    extern /* Subroutine */ int dlascl_(char *, integer *, integer *, 
	    doublereal *, doublereal *, integer *, integer *, doublereal *, 
	    integer *, integer *);
    extern integer idamax_(integer *, doublereal *, integer *);
    static integer st;
    extern /* Subroutine */ int dlasdq_(char *, integer *, integer *, integer 
	    *, integer *, integer *, doublereal *, doublereal *, doublereal *,
	     integer *, doublereal *, integer *, doublereal *, integer *, 
	    doublereal *, integer *);
    static integer vt;
    extern /* Subroutine */ int dlacpy_(char *, integer *, integer *, 
	    doublereal *, integer *, doublereal *, integer *), 
	    dlartg_(doublereal *, doublereal *, doublereal *, doublereal *, 
	    doublereal *), dlaset_(char *, integer *, integer *, doublereal *,
	     doublereal *, doublereal *, integer *), xerbla_(char *, 
	    integer *);
    static integer givcol;
    extern doublereal dlanst_(char *, integer *, doublereal *, doublereal *);
    extern /* Subroutine */ int dlasrt_(char *, integer *, doublereal *, 
	    integer *);
    static doublereal orgnrm;
    static integer givnum, givptr, nm1, smlszp, st1;
    static doublereal eps;
    static integer iwk;
    static doublereal tol;


#define b_ref(a_1,a_2) b[(a_2)*b_dim1 + a_1]


/*  -- LAPACK routine (instrumented to count ops, version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       October 31, 1999   


    Purpose   
    =======   

    DLALSD uses the singular value decomposition of A to solve the least   
    squares problem of finding X to minimize the Euclidean norm of each   
    column of A*X-B, where A is N-by-N upper bidiagonal, and X and B   
    are N-by-NRHS. The solution X overwrites B.   

    The singular values of A smaller than RCOND times the largest   
    singular value are treated as zero in solving the least squares   
    problem; in this case a minimum norm solution is returned.   
    The actual singular values are returned in D in ascending order.   

    This code makes very mild assumptions about floating point   
    arithmetic. It will work on machines with a guard digit in   
    add/subtract, or on those binary machines without guard digits   
    which subtract like the Cray XMP, Cray YMP, Cray C 90, or Cray 2.   
    It could conceivably fail on hexadecimal or decimal machines   
    without guard digits, but we know of none.   

    Arguments   
    =========   

    UPLO   (input) CHARACTER*1   
           = 'U': D and E define an upper bidiagonal matrix.   
           = 'L': D and E define a  lower bidiagonal matrix.   

    SMLSIZ (input) INTEGER   
           The maximum size of the subproblems at the bottom of the   
           computation tree.   

    N      (input) INTEGER   
           The dimension of the  bidiagonal matrix.  N >= 0.   

    NRHS   (input) INTEGER   
           The number of columns of B. NRHS must be at least 1.   

    D      (input/output) DOUBLE PRECISION array, dimension (N)   
           On entry D contains the main diagonal of the bidiagonal   
           matrix. On exit, if INFO = 0, D contains its singular values.   

    E      (input) DOUBLE PRECISION array, dimension (N-1)   
           Contains the super-diagonal entries of the bidiagonal matrix.   
           On exit, E has been destroyed.   

    B      (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)   
           On input, B contains the right hand sides of the least   
           squares problem. On output, B contains the solution X.   

    LDB    (input) INTEGER   
           The leading dimension of B in the calling subprogram.   
           LDB must be at least max(1,N).   

    RCOND  (input) DOUBLE PRECISION   
           The singular values of A less than or equal to RCOND times   
           the largest singular value are treated as zero in solving   
           the least squares problem. If RCOND is negative,   
           machine precision is used instead.   
           For example, if diag(S)*X=B were the least squares problem,   
           where diag(S) is a diagonal matrix of singular values, the   
           solution would be X(i) = B(i) / S(i) if S(i) is greater than   
           RCOND*max(S), and X(i) = 0 if S(i) is less than or equal to   
           RCOND*max(S).   

    RANK   (output) INTEGER   
           The number of singular values of A greater than RCOND times   
           the largest singular value.   

    WORK   (workspace) DOUBLE PRECISION array, dimension at least   
           (9*N + 2*N*SMLSIZ + 8*N*NLVL + N*NRHS + (SMLSIZ+1)**2),   
           where NLVL = max(0, INT(log_2 (N/(SMLSIZ+1))) + 1).   

    IWORK  (workspace) INTEGER array, dimension at least   
           (3*N*NLVL + 11*N)   

    INFO   (output) INTEGER   
           = 0:  successful exit.   
           < 0:  if INFO = -i, the i-th argument had an illegal value.   
           > 0:  The algorithm failed to compute an singular value while   
                 working on the submatrix lying in rows and columns   
                 INFO/(N+1) through MOD(INFO,N+1).   

    =====================================================================   


       Test the input parameters.   

       Parameter adjustments */
    --d__;
    --e;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1 * 1;
    b -= b_offset;
    --work;
    --iwork;

    /* Function Body */
    *info = 0;

    if (*n < 0) {
	*info = -3;
    } else if (*nrhs < 1) {
	*info = -4;
    } else if (*ldb < 1 || *ldb < *n) {
	*info = -8;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DLALSD", &i__1);
	return 0;
    }

    eps = dlamch_("Epsilon");

/*     Set up the tolerance. */

    if (*rcond <= 0. || *rcond >= 1.) {
	*rcond = eps;
    }

    *rank = 0;

/*     Quick return if possible. */

    if (*n == 0) {
	return 0;
    } else if (*n == 1) {
	if (d__[1] == 0.) {
	    dlaset_("A", &c__1, nrhs, &c_b6, &c_b6, &b[b_offset], ldb);
	} else {
	    *rank = 1;
	    latime_1.ops += (doublereal) (*nrhs << 1);
	    dlascl_("G", &c__0, &c__0, &d__[1], &c_b11, &c__1, nrhs, &b[
		    b_offset], ldb, info);
	    d__[1] = abs(d__[1]);
	}
	return 0;
    }

/*     Rotate the matrix if it is lower bidiagonal. */

    if (*(unsigned char *)uplo == 'L') {
	latime_1.ops += (doublereal) ((*n - 1) * 6);
	i__1 = *n - 1;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    dlartg_(&d__[i__], &e[i__], &cs, &sn, &r__);
	    d__[i__] = r__;
	    e[i__] = sn * d__[i__ + 1];
	    d__[i__ + 1] = cs * d__[i__ + 1];
	    if (*nrhs == 1) {
		latime_1.ops += 6.;
		drot_(&c__1, &b_ref(i__, 1), &c__1, &b_ref(i__ + 1, 1), &c__1,
			 &cs, &sn);
	    } else {
		work[(i__ << 1) - 1] = cs;
		work[i__ * 2] = sn;
	    }
/* L10: */
	}
	if (*nrhs > 1) {
	    latime_1.ops += (doublereal) ((*n - 1) * 6 * *nrhs);
	    i__1 = *nrhs;
	    for (i__ = 1; i__ <= i__1; ++i__) {