--- /dev/null
+#include "clapack.h"
+
+/* Table of constant values */
+
+static integer c__9 = 9;
+static integer c__0 = 0;
+static integer c__2 = 2;
+static doublereal c_b23 = 1.;
+static doublereal c_b24 = 0.;
+static integer c__1 = 1;
+
+/* Subroutine */ int dlaed0_(integer *icompq, integer *qsiz, integer *n,
+ doublereal *d__, doublereal *e, doublereal *q, integer *ldq,
+ doublereal *qstore, integer *ldqs, doublereal *work, integer *iwork,
+ integer *info)
+{
+ /* System generated locals */
+ integer q_dim1, q_offset, qstore_dim1, qstore_offset, i__1, i__2;
+ doublereal d__1;
+
+ /* Builtin functions */
+ double log(doublereal);
+ integer pow_ii(integer *, integer *);
+
+ /* Local variables */
+ integer i__, j, k, iq, lgn, msd2, smm1, spm1, spm2;
+ doublereal temp;
+ integer curr;
+ extern /* Subroutine */ int dgemm_(char *, char *, integer *, integer *,
+ integer *, doublereal *, doublereal *, integer *, doublereal *,
+ integer *, doublereal *, doublereal *, integer *);
+ integer iperm;
+ extern /* Subroutine */ int dcopy_(integer *, doublereal *, integer *,
+ doublereal *, integer *);
+ integer indxq, iwrem;
+ extern /* Subroutine */ int dlaed1_(integer *, doublereal *, doublereal *,
+ integer *, integer *, doublereal *, integer *, doublereal *,
+ integer *, integer *);
+ integer iqptr;
+ extern /* Subroutine */ int dlaed7_(integer *, integer *, integer *,
+ integer *, integer *, integer *, doublereal *, doublereal *,
+ integer *, integer *, doublereal *, integer *, doublereal *,
+ integer *, integer *, integer *, integer *, integer *, doublereal
+ *, doublereal *, integer *, integer *);
+ integer tlvls;
+ extern /* Subroutine */ int dlacpy_(char *, integer *, integer *,
+ doublereal *, integer *, doublereal *, integer *);
+ integer igivcl;
+ extern /* Subroutine */ int xerbla_(char *, integer *);
+ extern integer ilaenv_(integer *, char *, char *, integer *, integer *,
+ integer *, integer *);
+ integer igivnm, submat, curprb, subpbs, igivpt;
+ extern /* Subroutine */ int dsteqr_(char *, integer *, doublereal *,
+ doublereal *, doublereal *, integer *, doublereal *, integer *);
+ integer curlvl, matsiz, iprmpt, smlsiz;
+
+
+/* -- LAPACK routine (version 3.1) -- */
+/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
+/* November 2006 */
+
+/* .. Scalar Arguments .. */
+/* .. */
+/* .. Array Arguments .. */
+/* .. */
+
+/* Purpose */
+/* ======= */
+
+/* DLAED0 computes all eigenvalues and corresponding eigenvectors of a */
+/* symmetric tridiagonal matrix using the divide and conquer method. */
+
+/* Arguments */
+/* ========= */
+
+/* ICOMPQ (input) INTEGER */
+/* = 0: Compute eigenvalues only. */
+/* = 1: Compute eigenvectors of original dense symmetric matrix */
+/* also. On entry, Q contains the orthogonal matrix used */
+/* to reduce the original matrix to tridiagonal form. */
+/* = 2: Compute eigenvalues and eigenvectors of tridiagonal */
+/* matrix. */
+
+/* QSIZ (input) INTEGER */
+/* The dimension of the orthogonal matrix used to reduce */
+/* the full matrix to tridiagonal form. QSIZ >= N if ICOMPQ = 1. */
+
+/* N (input) INTEGER */
+/* The dimension of the symmetric tridiagonal matrix. N >= 0. */
+
+/* D (input/output) DOUBLE PRECISION array, dimension (N) */
+/* On entry, the main diagonal of the tridiagonal matrix. */
+/* On exit, its eigenvalues. */
+
+/* E (input) DOUBLE PRECISION array, dimension (N-1) */
+/* The off-diagonal elements of the tridiagonal matrix. */
+/* On exit, E has been destroyed. */
+
+/* Q (input/output) DOUBLE PRECISION array, dimension (LDQ, N) */
+/* On entry, Q must contain an N-by-N orthogonal matrix. */
+/* If ICOMPQ = 0 Q is not referenced. */
+/* If ICOMPQ = 1 On entry, Q is a subset of the columns of the */
+/* orthogonal matrix used to reduce the full */
+/* matrix to tridiagonal form corresponding to */
+/* the subset of the full matrix which is being */
+/* decomposed at this time. */
+/* If ICOMPQ = 2 On entry, Q will be the identity matrix. */
+/* On exit, Q contains the eigenvectors of the */
+/* tridiagonal matrix. */
+
+/* LDQ (input) INTEGER */
+/* The leading dimension of the array Q. If eigenvectors are */
+/* desired, then LDQ >= max(1,N). In any case, LDQ >= 1. */
+
+/* QSTORE (workspace) DOUBLE PRECISION array, dimension (LDQS, N) */
+/* Referenced only when ICOMPQ = 1. Used to store parts of */
+/* the eigenvector matrix when the updating matrix multiplies */
+/* take place. */
+
+/* LDQS (input) INTEGER */
+/* The leading dimension of the array QSTORE. If ICOMPQ = 1, */
+/* then LDQS >= max(1,N). In any case, LDQS >= 1. */
+
+/* WORK (workspace) DOUBLE PRECISION array, */
+/* If ICOMPQ = 0 or 1, the dimension of WORK must be at least */
+/* 1 + 3*N + 2*N*lg N + 2*N**2 */
+/* ( lg( N ) = smallest integer k */
+/* such that 2^k >= N ) */
+/* If ICOMPQ = 2, the dimension of WORK must be at least */
+/* 4*N + N**2. */
+
+/* IWORK (workspace) INTEGER array, */
+/* If ICOMPQ = 0 or 1, the dimension of IWORK must be at least */
+/* 6 + 6*N + 5*N*lg N. */
+/* ( lg( N ) = smallest integer k */
+/* such that 2^k >= N ) */
+/* If ICOMPQ = 2, the dimension of IWORK must be at least */
+/* 3 + 5*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 eigenvalue while */
+/* working on the submatrix lying in rows and columns */
+/* INFO/(N+1) through mod(INFO,N+1). */
+
+/* Further Details */
+/* =============== */
+
+/* Based on contributions by */
+/* Jeff Rutter, Computer Science Division, University of California */
+/* at Berkeley, USA */
+
+/* ===================================================================== */
+
+/* .. Parameters .. */
+/* .. */
+/* .. Local Scalars .. */
+/* .. */
+/* .. External Subroutines .. */
+/* .. */
+/* .. External Functions .. */
+/* .. */
+/* .. Intrinsic Functions .. */
+/* .. */
+/* .. Executable Statements .. */
+
+/* Test the input parameters. */
+
+ /* Parameter adjustments */
+ --d__;
+ --e;
+ q_dim1 = *ldq;
+ q_offset = 1 + q_dim1;
+ q -= q_offset;
+ qstore_dim1 = *ldqs;
+ qstore_offset = 1 + qstore_dim1;
+ qstore -= qstore_offset;
+ --work;
+ --iwork;
+
+ /* Function Body */
+ *info = 0;
+
+ if (*icompq < 0 || *icompq > 2) {
+ *info = -1;
+ } else if (*icompq == 1 && *qsiz < max(0,*n)) {
+ *info = -2;
+ } else if (*n < 0) {
+ *info = -3;
+ } else if (*ldq < max(1,*n)) {
+ *info = -7;
+ } else if (*ldqs < max(1,*n)) {
+ *info = -9;
+ }
+ if (*info != 0) {
+ i__1 = -(*info);
+ xerbla_("DLAED0", &i__1);
+ return 0;
+ }
+
+/* Quick return if possible */
+
+ if (*n == 0) {
+ return 0;
+ }
+
+ smlsiz = ilaenv_(&c__9, "DLAED0", " ", &c__0, &c__0, &c__0, &c__0);
+
+/* Determine the size and placement of the submatrices, and save in */
+/* the leading elements of IWORK. */
+
+ iwork[1] = *n;
+ subpbs = 1;
+ tlvls = 0;
+L10:
+ if (iwork[subpbs] > smlsiz) {
+ for (j = subpbs; j >= 1; --j) {
+ iwork[j * 2] = (iwork[j] + 1) / 2;
+ iwork[(j << 1) - 1] = iwork[j] / 2;
+/* L20: */
+ }
+ ++tlvls;
+ subpbs <<= 1;
+ goto L10;
+ }
+ i__1 = subpbs;
+ for (j = 2; j <= i__1; ++j) {
+ iwork[j] += iwork[j - 1];
+/* L30: */
+ }
+
+/* Divide the matrix into SUBPBS submatrices of size at most SMLSIZ+1 */
+/* using rank-1 modifications (cuts). */
+
+ spm1 = subpbs - 1;
+ i__1 = spm1;
+ for (i__ = 1; i__ <= i__1; ++i__) {
+ submat = iwork[i__] + 1;
+ smm1 = submat - 1;
+ d__[smm1] -= (d__1 = e[smm1], abs(d__1));
+ d__[submat] -= (d__1 = e[smm1], abs(d__1));
+/* L40: */
+ }
+
+ indxq = (*n << 2) + 3;
+ if (*icompq != 2) {
+
+/* Set up workspaces for eigenvalues only/accumulate new vectors */
+/* routine */
+
+ temp = log((doublereal) (*n)) / log(2.);
+ lgn = (integer) temp;
+ if (pow_ii(&c__2, &lgn) < *n) {
+ ++lgn;
+ }
+ if (pow_ii(&c__2, &lgn) < *n) {
+ ++lgn;
+ }
+ iprmpt = indxq + *n + 1;
+ iperm = iprmpt + *n * lgn;
+ iqptr = iperm + *n * lgn;
+ igivpt = iqptr + *n + 2;
+ igivcl = igivpt + *n * lgn;
+
+ igivnm = 1;
+ iq = igivnm + (*n << 1) * lgn;
+/* Computing 2nd power */
+ i__1 = *n;
+ iwrem = iq + i__1 * i__1 + 1;
+
+/* Initialize pointers */
+
+ i__1 = subpbs;
+ for (i__ = 0; i__ <= i__1; ++i__) {
+ iwork[iprmpt + i__] = 1;
+ iwork[igivpt + i__] = 1;
+/* L50: */
+ }
+ iwork[iqptr] = 1;
+ }
+
+/* Solve each submatrix eigenproblem at the bottom of the divide and */
+/* conquer tree. */
+
+ curr = 0;
+ i__1 = spm1;
+ for (i__ = 0; i__ <= i__1; ++i__) {
+ if (i__ == 0) {
+ submat = 1;
+ matsiz = iwork[1];
+ } else {
+ submat = iwork[i__] + 1;
+ matsiz = iwork[i__ + 1] - iwork[i__];
+ }
+ if (*icompq == 2) {
+ dsteqr_("I", &matsiz, &d__[submat], &e[submat], &q[submat +
+ submat * q_dim1], ldq, &work[1], info);
+ if (*info != 0) {
+ goto L130;
+ }
+ } else {
+ dsteqr_("I", &matsiz, &d__[submat], &e[submat], &work[iq - 1 +
+ iwork[iqptr + curr]], &matsiz, &work[1], info);
+ if (*info != 0) {
+ goto L130;
+ }
+ if (*icompq == 1) {
+ dgemm_("N", "N", qsiz, &matsiz, &matsiz, &c_b23, &q[submat *
+ q_dim1 + 1], ldq, &work[iq - 1 + iwork[iqptr + curr]],
+ &matsiz, &c_b24, &qstore[submat * qstore_dim1 + 1],
+ ldqs);
+ }
+/* Computing 2nd power */
+ i__2 = matsiz;
+ iwork[iqptr + curr + 1] = iwork[iqptr + curr] + i__2 * i__2;
+ ++curr;
+ }
+ k = 1;
+ i__2 = iwork[i__ + 1];
+ for (j = submat; j <= i__2; ++j) {
+ iwork[indxq + j] = k;
+ ++k;
+/* L60: */
+ }
+/* L70: */
+ }
+
+/* Successively merge eigensystems of adjacent submatrices */
+/* into eigensystem for the corresponding larger matrix. */
+
+/* while ( SUBPBS > 1 ) */
+
+ curlvl = 1;
+L80:
+ if (subpbs > 1) {
+ spm2 = subpbs - 2;
+ i__1 = spm2;
+ for (i__ = 0; i__ <= i__1; i__ += 2) {
+ if (i__ == 0) {
+ submat = 1;
+ matsiz = iwork[2];
+ msd2 = iwork[1];
+ curprb = 0;
+ } else {
+ submat = iwork[i__] + 1;
+ matsiz = iwork[i__ + 2] - iwork[i__];
+ msd2 = matsiz / 2;
+ ++curprb;
+ }
+
+/* Merge lower order eigensystems (of size MSD2 and MATSIZ - MSD2) */
+/* into an eigensystem of size MATSIZ. */
+/* DLAED1 is used only for the full eigensystem of a tridiagonal */
+/* matrix. */
+/* DLAED7 handles the cases in which eigenvalues only or eigenvalues */
+/* and eigenvectors of a full symmetric matrix (which was reduced to */
+/* tridiagonal form) are desired. */
+
+ if (*icompq == 2) {
+ dlaed1_(&matsiz, &d__[submat], &q[submat + submat * q_dim1],
+ ldq, &iwork[indxq + submat], &e[submat + msd2 - 1], &
+ msd2, &work[1], &iwork[subpbs + 1], info);
+ } else {
+ dlaed7_(icompq, &matsiz, qsiz, &tlvls, &curlvl, &curprb, &d__[
+ submat], &qstore[submat * qstore_dim1 + 1], ldqs, &
+ iwork[indxq + submat], &e[submat + msd2 - 1], &msd2, &
+ work[iq], &iwork[iqptr], &iwork[iprmpt], &iwork[iperm]
+, &iwork[igivpt], &iwork[igivcl], &work[igivnm], &
+ work[iwrem], &iwork[subpbs + 1], info);
+ }
+ if (*info != 0) {
+ goto L130;
+ }
+ iwork[i__ / 2 + 1] = iwork[i__ + 2];
+/* L90: */
+ }
+ subpbs /= 2;
+ ++curlvl;
+ goto L80;
+ }
+
+/* end while */
+
+/* Re-merge the eigenvalues/vectors which were deflated at the final */
+/* merge step. */
+
+ if (*icompq == 1) {
+ i__1 = *n;
+ for (i__ = 1; i__ <= i__1; ++i__) {
+ j = iwork[indxq + i__];
+ work[i__] = d__[j];
+ dcopy_(qsiz, &qstore[j * qstore_dim1 + 1], &c__1, &q[i__ * q_dim1
+ + 1], &c__1);
+/* L100: */
+ }
+ dcopy_(n, &work[1], &c__1, &d__[1], &c__1);
+ } else if (*icompq == 2) {
+ i__1 = *n;
+ for (i__ = 1; i__ <= i__1; ++i__) {
+ j = iwork[indxq + i__];
+ work[i__] = d__[j];
+ dcopy_(n, &q[j * q_dim1 + 1], &c__1, &work[*n * i__ + 1], &c__1);
+/* L110: */
+ }
+ dcopy_(n, &work[1], &c__1, &d__[1], &c__1);
+ dlacpy_("A", n, n, &work[*n + 1], n, &q[q_offset], ldq);
+ } else {
+ i__1 = *n;
+ for (i__ = 1; i__ <= i__1; ++i__) {
+ j = iwork[indxq + i__];
+ work[i__] = d__[j];
+/* L120: */
+ }
+ dcopy_(n, &work[1], &c__1, &d__[1], &c__1);
+ }
+ goto L140;
+
+L130:
+ *info = submat * (*n + 1) + submat + matsiz - 1;
+
+L140:
+ return 0;
+
+/* End of DLAED0 */
+
+} /* dlaed0_ */