slasda.c

著名的LAPACK矩阵计算软件包, 是比较新的版本, 一般用到矩阵分解的朋友也许会用到

    difr -= difr_offset;
    difl_dim1 = *ldu;
    difl_offset = 1 + difl_dim1 * 1;
    difl -= difl_offset;
    vt_dim1 = *ldu;
    vt_offset = 1 + vt_dim1 * 1;
    vt -= vt_offset;
    u_dim1 = *ldu;
    u_offset = 1 + u_dim1 * 1;
    u -= u_offset;
    --k;
    --givptr;
    perm_dim1 = *ldgcol;
    perm_offset = 1 + perm_dim1 * 1;
    perm -= perm_offset;
    givcol_dim1 = *ldgcol;
    givcol_offset = 1 + givcol_dim1 * 1;
    givcol -= givcol_offset;
    --c__;
    --s;
    --work;
    --iwork;

    /* Function Body */
    *info = 0;

    if (*icompq < 0 || *icompq > 1) {
	*info = -1;
    } else if (*smlsiz < 3) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*sqre < 0 || *sqre > 1) {
	*info = -4;
    } else if (*ldu < *n + *sqre) {
	*info = -8;
    } else if (*ldgcol < *n) {
	*info = -17;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("SLASDA", &i__1);
	return 0;
    }

    m = *n + *sqre;

/*     If the input matrix is too small, call SLASDQ to find the SVD. */

    if (*n <= *smlsiz) {
	if (*icompq == 0) {
	    slasdq_("U", sqre, n, &c__0, &c__0, &c__0, &d__[1], &e[1], &vt[
		    vt_offset], ldu, &u[u_offset], ldu, &u[u_offset], ldu, &
		    work[1], info);
	} else {
	    slasdq_("U", sqre, n, &m, n, &c__0, &d__[1], &e[1], &vt[vt_offset]
		    , ldu, &u[u_offset], ldu, &u[u_offset], ldu, &work[1], 
		    info);
	}
	return 0;
    }

/*     Book-keeping and  set up the computation tree. */

    inode = 1;
    ndiml = inode + *n;
    ndimr = ndiml + *n;
    idxq = ndimr + *n;
    iwk = idxq + *n;

    ncc = 0;
    nru = 0;

    smlszp = *smlsiz + 1;
    vf = 1;
    vl = vf + m;
    nwork1 = vl + m;
    nwork2 = nwork1 + smlszp * smlszp;

    slasdt_(n, &nlvl, &nd, &iwork[inode], &iwork[ndiml], &iwork[ndimr], 
	    smlsiz);

/*     for the nodes on bottom level of the tree, solve   
       their subproblems by SLASDQ. */

    latime_1.ops += 1.f;
    ndb1 = (nd + 1) / 2;
    i__1 = nd;
    for (i__ = ndb1; i__ <= i__1; ++i__) {

/*        IC : center row of each node   
          NL : number of rows of left  subproblem   
          NR : number of rows of right subproblem   
          NLF: starting row of the left   subproblem   
          NRF: starting row of the right  subproblem */

	i1 = i__ - 1;
	ic = iwork[inode + i1];
	nl = iwork[ndiml + i1];
	nlp1 = nl + 1;
	nr = iwork[ndimr + i1];
	nlf = ic - nl;
	nrf = ic + 1;
	idxqi = idxq + nlf - 2;
	vfi = vf + nlf - 1;
	vli = vl + nlf - 1;
	sqrei = 1;
	if (*icompq == 0) {
	    slaset_("A", &nlp1, &nlp1, &c_b11, &c_b12, &work[nwork1], &smlszp);
	    slasdq_("U", &sqrei, &nl, &nlp1, &nru, &ncc, &d__[nlf], &e[nlf], &
		    work[nwork1], &smlszp, &work[nwork2], &nl, &work[nwork2], 
		    &nl, &work[nwork2], info);
	    itemp = nwork1 + nl * smlszp;
	    scopy_(&nlp1, &work[nwork1], &c__1, &work[vfi], &c__1);
	    scopy_(&nlp1, &work[itemp], &c__1, &work[vli], &c__1);
	} else {
	    slaset_("A", &nl, &nl, &c_b11, &c_b12, &u_ref(nlf, 1), ldu);
	    slaset_("A", &nlp1, &nlp1, &c_b11, &c_b12, &vt_ref(nlf, 1), ldu);
	    slasdq_("U", &sqrei, &nl, &nlp1, &nl, &ncc, &d__[nlf], &e[nlf], &
		    vt_ref(nlf, 1), ldu, &u_ref(nlf, 1), ldu, &u_ref(nlf, 1), 
		    ldu, &work[nwork1], info);
	    scopy_(&nlp1, &vt_ref(nlf, 1), &c__1, &work[vfi], &c__1);
	    scopy_(&nlp1, &vt_ref(nlf, nlp1), &c__1, &work[vli], &c__1);
	}
	if (*info != 0) {
	    return 0;
	}
	i__2 = nl;
	for (j = 1; j <= i__2; ++j) {
	    iwork[idxqi + j] = j;
/* L10: */
	}
	if (i__ == nd && *sqre == 0) {
	    sqrei = 0;
	} else {
	    sqrei = 1;
	}
	idxqi += nlp1;
	vfi += nlp1;
	vli += nlp1;
	nrp1 = nr + sqrei;
	if (*icompq == 0) {
	    slaset_("A", &nrp1, &nrp1, &c_b11, &c_b12, &work[nwork1], &smlszp);
	    slasdq_("U", &sqrei, &nr, &nrp1, &nru, &ncc, &d__[nrf], &e[nrf], &
		    work[nwork1], &smlszp, &work[nwork2], &nr, &work[nwork2], 
		    &nr, &work[nwork2], info);
	    itemp = nwork1 + (nrp1 - 1) * smlszp;
	    scopy_(&nrp1, &work[nwork1], &c__1, &work[vfi], &c__1);
	    scopy_(&nrp1, &work[itemp], &c__1, &work[vli], &c__1);
	} else {
	    slaset_("A", &nr, &nr, &c_b11, &c_b12, &u_ref(nrf, 1), ldu);
	    slaset_("A", &nrp1, &nrp1, &c_b11, &c_b12, &vt_ref(nrf, 1), ldu);
	    slasdq_("U", &sqrei, &nr, &nrp1, &nr, &ncc, &d__[nrf], &e[nrf], &
		    vt_ref(nrf, 1), ldu, &u_ref(nrf, 1), ldu, &u_ref(nrf, 1), 
		    ldu, &work[nwork1], info);
	    scopy_(&nrp1, &vt_ref(nrf, 1), &c__1, &work[vfi], &c__1);
	    scopy_(&nrp1, &vt_ref(nrf, nrp1), &c__1, &work[vli], &c__1);
	}
	if (*info != 0) {
	    return 0;
	}
	i__2 = nr;
	for (j = 1; j <= i__2; ++j) {
	    iwork[idxqi + j] = j;
/* L20: */
	}
/* L30: */
    }

/*     Now conquer each subproblem bottom-up. */

    j = pow_ii(&c__2, &nlvl);
    for (lvl = nlvl; lvl >= 1; --lvl) {
	lvl2 = (lvl << 1) - 1;

/*        Find the first node LF and last node LL on   
          the current level LVL. */

	if (lvl == 1) {
	    lf = 1;
	    ll = 1;
	} else {
	    i__1 = lvl - 1;
	    lf = pow_ii(&c__2, &i__1);
	    ll = (lf << 1) - 1;
	}
	i__1 = ll;
	for (i__ = lf; i__ <= i__1; ++i__) {
	    im1 = i__ - 1;
	    ic = iwork[inode + im1];
	    nl = iwork[ndiml + im1];
	    nr = iwork[ndimr + im1];
	    nlf = ic - nl;
	    nrf = ic + 1;
	    if (i__ == ll) {
		sqrei = *sqre;
	    } else {
		sqrei = 1;
	    }
	    vfi = vf + nlf - 1;
	    vli = vl + nlf - 1;
	    idxqi = idxq + nlf - 1;
	    alpha = d__[ic];
	    beta = e[ic];
	    if (*icompq == 0) {
		slasd6_(icompq, &nl, &nr, &sqrei, &d__[nlf], &work[vfi], &
			work[vli], &alpha, &beta, &iwork[idxqi], &perm[
			perm_offset], &givptr[1], &givcol[givcol_offset], 
			ldgcol, &givnum[givnum_offset], ldu, &poles[
			poles_offset], &difl[difl_offset], &difr[difr_offset],
			 &z__[z_offset], &k[1], &c__[1], &s[1], &work[nwork1],
			 &iwork[iwk], info);
	    } else {
		--j;
		slasd6_(icompq, &nl, &nr, &sqrei, &d__[nlf], &work[vfi], &
			work[vli], &alpha, &beta, &iwork[idxqi], &perm_ref(
			nlf, lvl), &givptr[j], &givcol_ref(nlf, lvl2), ldgcol,
			 &givnum_ref(nlf, lvl2), ldu, &poles_ref(nlf, lvl2), &
			difl_ref(nlf, lvl), &difr_ref(nlf, lvl2), &z___ref(
			nlf, lvl), &k[j], &c__[j], &s[j], &work[nwork1], &
			iwork[iwk], info);
	    }
	    if (*info != 0) {
		return 0;
	    }
/* L40: */
	}
/* L50: */
    }

    return 0;

/*     End of SLASDA */

} /* slasda_ */

#undef givnum_ref
#undef givcol_ref
#undef vt_ref
#undef poles_ref
#undef z___ref
#undef u_ref
#undef perm_ref
#undef difr_ref
#undef difl_ref