--- /dev/null
+#include "clapack.h"
+
+/* Table of constant values */
+
+static integer c__1 = 1;
+static integer c_n1 = -1;
+static integer c__3 = 3;
+static integer c__2 = 2;
+static doublereal c_b22 = -1.;
+static doublereal c_b23 = 1.;
+
+/* Subroutine */ int dsytrd_(char *uplo, integer *n, doublereal *a, integer *
+ lda, doublereal *d__, doublereal *e, doublereal *tau, doublereal *
+ work, integer *lwork, integer *info)
+{
+ /* System generated locals */
+ integer a_dim1, a_offset, i__1, i__2, i__3;
+
+ /* Local variables */
+ integer i__, j, nb, kk, nx, iws;
+ extern logical lsame_(char *, char *);
+ integer nbmin, iinfo;
+ logical upper;
+ extern /* Subroutine */ int dsytd2_(char *, integer *, doublereal *,
+ integer *, doublereal *, doublereal *, doublereal *, integer *), dsyr2k_(char *, char *, integer *, integer *, doublereal
+ *, doublereal *, integer *, doublereal *, integer *, doublereal *,
+ doublereal *, integer *), dlatrd_(char *,
+ integer *, integer *, doublereal *, integer *, doublereal *,
+ doublereal *, doublereal *, integer *), xerbla_(char *,
+ integer *);
+ extern integer ilaenv_(integer *, char *, char *, integer *, integer *,
+ integer *, integer *);
+ integer ldwork, lwkopt;
+ logical lquery;
+
+
+/* -- LAPACK routine (version 3.1) -- */
+/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
+/* November 2006 */
+
+/* .. Scalar Arguments .. */
+/* .. */
+/* .. Array Arguments .. */
+/* .. */
+
+/* Purpose */
+/* ======= */
+
+/* DSYTRD reduces a real symmetric matrix A to real symmetric */
+/* tridiagonal form T by an orthogonal similarity transformation: */
+/* Q**T * A * Q = T. */
+
+/* Arguments */
+/* ========= */
+
+/* UPLO (input) CHARACTER*1 */
+/* = 'U': Upper triangle of A is stored; */
+/* = 'L': Lower triangle of A is stored. */
+
+/* N (input) INTEGER */
+/* The order of the matrix A. N >= 0. */
+
+/* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
+/* On entry, the symmetric matrix A. If UPLO = 'U', the leading */
+/* N-by-N upper triangular part of A contains the upper */
+/* triangular part of the matrix A, and the strictly lower */
+/* triangular part of A is not referenced. If UPLO = 'L', the */
+/* leading N-by-N lower triangular part of A contains the lower */
+/* triangular part of the matrix A, and the strictly upper */
+/* triangular part of A is not referenced. */
+/* On exit, if UPLO = 'U', the diagonal and first superdiagonal */
+/* of A are overwritten by the corresponding elements of the */
+/* tridiagonal matrix T, and the elements above the first */
+/* superdiagonal, with the array TAU, represent the orthogonal */
+/* matrix Q as a product of elementary reflectors; if UPLO */
+/* = 'L', the diagonal and first subdiagonal of A are over- */
+/* written by the corresponding elements of the tridiagonal */
+/* matrix T, and the elements below the first subdiagonal, with */
+/* the array TAU, represent the orthogonal matrix Q as a product */
+/* of elementary reflectors. See Further Details. */
+
+/* LDA (input) INTEGER */
+/* The leading dimension of the array A. LDA >= max(1,N). */
+
+/* D (output) DOUBLE PRECISION array, dimension (N) */
+/* The diagonal elements of the tridiagonal matrix T: */
+/* D(i) = A(i,i). */
+
+/* E (output) DOUBLE PRECISION array, dimension (N-1) */
+/* The off-diagonal elements of the tridiagonal matrix T: */
+/* E(i) = A(i,i+1) if UPLO = 'U', E(i) = A(i+1,i) if UPLO = 'L'. */
+
+/* TAU (output) DOUBLE PRECISION array, dimension (N-1) */
+/* The scalar factors of the elementary reflectors (see Further */
+/* Details). */
+
+/* WORK (workspace/output) DOUBLE PRECISION array, dimension (MAX(1,LWORK)) */
+/* On exit, if INFO = 0, WORK(1) returns the optimal LWORK. */
+
+/* LWORK (input) INTEGER */
+/* The dimension of the array WORK. LWORK >= 1. */
+/* For optimum performance LWORK >= N*NB, where NB is the */
+/* optimal blocksize. */
+
+/* If LWORK = -1, then a workspace query is assumed; the routine */
+/* only calculates the optimal size of the WORK array, returns */
+/* this value as the first entry of the WORK array, and no error */
+/* message related to LWORK is issued by XERBLA. */
+
+/* INFO (output) INTEGER */
+/* = 0: successful exit */
+/* < 0: if INFO = -i, the i-th argument had an illegal value */
+
+/* Further Details */
+/* =============== */
+
+/* If UPLO = 'U', the matrix Q is represented as a product of elementary */
+/* reflectors */
+
+/* Q = H(n-1) . . . H(2) H(1). */
+
+/* Each H(i) has the form */
+
+/* H(i) = I - tau * v * v' */
+
+/* where tau is a real scalar, and v is a real vector with */
+/* v(i+1:n) = 0 and v(i) = 1; v(1:i-1) is stored on exit in */
+/* A(1:i-1,i+1), and tau in TAU(i). */
+
+/* If UPLO = 'L', the matrix Q is represented as a product of elementary */
+/* reflectors */
+
+/* Q = H(1) H(2) . . . H(n-1). */
+
+/* Each H(i) has the form */
+
+/* H(i) = I - tau * v * v' */
+
+/* where tau is a real scalar, and v is a real vector with */
+/* v(1:i) = 0 and v(i+1) = 1; v(i+2:n) is stored on exit in A(i+2:n,i), */
+/* and tau in TAU(i). */
+
+/* The contents of A on exit are illustrated by the following examples */
+/* with n = 5: */
+
+/* if UPLO = 'U': if UPLO = 'L': */
+
+/* ( d e v2 v3 v4 ) ( d ) */
+/* ( d e v3 v4 ) ( e d ) */
+/* ( d e v4 ) ( v1 e d ) */
+/* ( d e ) ( v1 v2 e d ) */
+/* ( d ) ( v1 v2 v3 e d ) */
+
+/* where d and e denote diagonal and off-diagonal elements of T, and vi */
+/* denotes an element of the vector defining H(i). */
+
+/* ===================================================================== */
+
+/* .. Parameters .. */
+/* .. */
+/* .. Local Scalars .. */
+/* .. */
+/* .. External Subroutines .. */
+/* .. */
+/* .. Intrinsic Functions .. */
+/* .. */
+/* .. External Functions .. */
+/* .. */
+/* .. Executable Statements .. */
+
+/* Test the input parameters */
+
+ /* Parameter adjustments */
+ a_dim1 = *lda;
+ a_offset = 1 + a_dim1;
+ a -= a_offset;
+ --d__;
+ --e;
+ --tau;
+ --work;
+
+ /* Function Body */
+ *info = 0;
+ upper = lsame_(uplo, "U");
+ lquery = *lwork == -1;
+ if (! upper && ! lsame_(uplo, "L")) {
+ *info = -1;
+ } else if (*n < 0) {
+ *info = -2;
+ } else if (*lda < max(1,*n)) {
+ *info = -4;
+ } else if (*lwork < 1 && ! lquery) {
+ *info = -9;
+ }
+
+ if (*info == 0) {
+
+/* Determine the block size. */
+
+ nb = ilaenv_(&c__1, "DSYTRD", uplo, n, &c_n1, &c_n1, &c_n1);
+ lwkopt = *n * nb;
+ work[1] = (doublereal) lwkopt;
+ }
+
+ if (*info != 0) {
+ i__1 = -(*info);
+ xerbla_("DSYTRD", &i__1);
+ return 0;
+ } else if (lquery) {
+ return 0;
+ }
+
+/* Quick return if possible */
+
+ if (*n == 0) {
+ work[1] = 1.;
+ return 0;
+ }
+
+ nx = *n;
+ iws = 1;
+ if (nb > 1 && nb < *n) {
+
+/* Determine when to cross over from blocked to unblocked code */
+/* (last block is always handled by unblocked code). */
+
+/* Computing MAX */
+ i__1 = nb, i__2 = ilaenv_(&c__3, "DSYTRD", uplo, n, &c_n1, &c_n1, &
+ c_n1);
+ nx = max(i__1,i__2);
+ if (nx < *n) {
+
+/* Determine if workspace is large enough for blocked code. */
+
+ ldwork = *n;
+ iws = ldwork * nb;
+ if (*lwork < iws) {
+
+/* Not enough workspace to use optimal NB: determine the */
+/* minimum value of NB, and reduce NB or force use of */
+/* unblocked code by setting NX = N. */
+
+/* Computing MAX */
+ i__1 = *lwork / ldwork;
+ nb = max(i__1,1);
+ nbmin = ilaenv_(&c__2, "DSYTRD", uplo, n, &c_n1, &c_n1, &c_n1);
+ if (nb < nbmin) {
+ nx = *n;
+ }
+ }
+ } else {
+ nx = *n;
+ }
+ } else {
+ nb = 1;
+ }
+
+ if (upper) {
+
+/* Reduce the upper triangle of A. */
+/* Columns 1:kk are handled by the unblocked method. */
+
+ kk = *n - (*n - nx + nb - 1) / nb * nb;
+ i__1 = kk + 1;
+ i__2 = -nb;
+ for (i__ = *n - nb + 1; i__2 < 0 ? i__ >= i__1 : i__ <= i__1; i__ +=
+ i__2) {
+
+/* Reduce columns i:i+nb-1 to tridiagonal form and form the */
+/* matrix W which is needed to update the unreduced part of */
+/* the matrix */
+
+ i__3 = i__ + nb - 1;
+ dlatrd_(uplo, &i__3, &nb, &a[a_offset], lda, &e[1], &tau[1], &
+ work[1], &ldwork);
+
+/* Update the unreduced submatrix A(1:i-1,1:i-1), using an */
+/* update of the form: A := A - V*W' - W*V' */
+
+ i__3 = i__ - 1;
+ dsyr2k_(uplo, "No transpose", &i__3, &nb, &c_b22, &a[i__ * a_dim1
+ + 1], lda, &work[1], &ldwork, &c_b23, &a[a_offset], lda);
+
+/* Copy superdiagonal elements back into A, and diagonal */
+/* elements into D */
+
+ i__3 = i__ + nb - 1;
+ for (j = i__; j <= i__3; ++j) {
+ a[j - 1 + j * a_dim1] = e[j - 1];
+ d__[j] = a[j + j * a_dim1];
+/* L10: */
+ }
+/* L20: */
+ }
+
+/* Use unblocked code to reduce the last or only block */
+
+ dsytd2_(uplo, &kk, &a[a_offset], lda, &d__[1], &e[1], &tau[1], &iinfo);
+ } else {
+
+/* Reduce the lower triangle of A */
+
+ i__2 = *n - nx;
+ i__1 = nb;
+ for (i__ = 1; i__1 < 0 ? i__ >= i__2 : i__ <= i__2; i__ += i__1) {
+
+/* Reduce columns i:i+nb-1 to tridiagonal form and form the */
+/* matrix W which is needed to update the unreduced part of */
+/* the matrix */
+
+ i__3 = *n - i__ + 1;
+ dlatrd_(uplo, &i__3, &nb, &a[i__ + i__ * a_dim1], lda, &e[i__], &
+ tau[i__], &work[1], &ldwork);
+
+/* Update the unreduced submatrix A(i+ib:n,i+ib:n), using */
+/* an update of the form: A := A - V*W' - W*V' */
+
+ i__3 = *n - i__ - nb + 1;
+ dsyr2k_(uplo, "No transpose", &i__3, &nb, &c_b22, &a[i__ + nb +
+ i__ * a_dim1], lda, &work[nb + 1], &ldwork, &c_b23, &a[
+ i__ + nb + (i__ + nb) * a_dim1], lda);
+
+/* Copy subdiagonal elements back into A, and diagonal */
+/* elements into D */
+
+ i__3 = i__ + nb - 1;
+ for (j = i__; j <= i__3; ++j) {
+ a[j + 1 + j * a_dim1] = e[j];
+ d__[j] = a[j + j * a_dim1];
+/* L30: */
+ }
+/* L40: */
+ }
+
+/* Use unblocked code to reduce the last or only block */
+
+ i__1 = *n - i__ + 1;
+ dsytd2_(uplo, &i__1, &a[i__ + i__ * a_dim1], lda, &d__[i__], &e[i__],
+ &tau[i__], &iinfo);
+ }
+
+ work[1] = (doublereal) lwkopt;
+ return 0;
+
+/* End of DSYTRD */
+
+} /* dsytrd_ */
projects / opencv / blobdiff