#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int sspevd_(char *jobz, char *uplo, integer *n, real *ap, real *w, real *z__, integer *ldz, real *work, integer *lwork, integer *iwork, integer *liwork, integer *info ) { /* -- LAPACK driver routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= SSPEVD computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage. If eigenvectors are desired, it uses a divide and conquer algorithm. The divide and conquer algorithm 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 X-MP, Cray Y-MP, Cray C-90, or Cray-2. It could conceivably fail on hexadecimal or decimal machines without guard digits, but we know of none. Arguments ========= JOBZ (input) CHARACTER*1 = 'N': Compute eigenvalues only; = 'V': Compute eigenvalues and eigenvectors. 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. AP (input/output) REAL array, dimension (N*(N+1)/2) On entry, the upper or lower triangle of the symmetric matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n. On exit, AP is overwritten by values generated during the reduction to tridiagonal form. If UPLO = 'U', the diagonal and first superdiagonal of the tridiagonal matrix T overwrite the corresponding elements of A, and if UPLO = 'L', the diagonal and first subdiagonal of T overwrite the corresponding elements of A. W (output) REAL array, dimension (N) If INFO = 0, the eigenvalues in ascending order. Z (output) REAL array, dimension (LDZ, N) If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal eigenvectors of the matrix A, with the i-th column of Z holding the eigenvector associated with W(i). If JOBZ = 'N', then Z is not referenced. LDZ (input) INTEGER The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N). WORK (workspace/output) REAL array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the required LWORK. LWORK (input) INTEGER The dimension of the array WORK. If N <= 1, LWORK must be at least 1. If JOBZ = 'N' and N > 1, LWORK must be at least 2*N. If JOBZ = 'V' and N > 1, LWORK must be at least 1 + 6*N + N**2. If LWORK = -1, then a workspace query is assumed; the routine only calculates the required sizes of the WORK and IWORK arrays, returns these values as the first entries of the WORK and IWORK arrays, and no error message related to LWORK or LIWORK is issued by XERBLA. IWORK (workspace/output) INTEGER array, dimension (MAX(1,LIWORK)) On exit, if INFO = 0, IWORK(1) returns the required LIWORK. LIWORK (input) INTEGER The dimension of the array IWORK. If JOBZ = 'N' or N <= 1, LIWORK must be at least 1. If JOBZ = 'V' and N > 1, LIWORK must be at least 3 + 5*N. If LIWORK = -1, then a workspace query is assumed; the routine only calculates the required sizes of the WORK and IWORK arrays, returns these values as the first entries of the WORK and IWORK arrays, and no error message related to LWORK or LIWORK is issued by XERBLA. INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value. > 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of an intermediate tridiagonal form did not converge to zero. ===================================================================== Test the input parameters. Parameter adjustments */ /* Table of constant values */ static integer c__1 = 1; /* System generated locals */ integer z_dim1, z_offset, i__1; real r__1; /* Builtin functions */ double sqrt(doublereal); /* Local variables */ static real eps; static integer inde; static real anrm, rmin, rmax, sigma; extern logical lsame_(char *, char *); static integer iinfo; extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *); static integer lwmin; static logical wantz; static integer iscale; extern doublereal slamch_(char *); static real safmin; extern /* Subroutine */ int xerbla_(char *, integer *); static real bignum; static integer indtau; extern /* Subroutine */ int sstedc_(char *, integer *, real *, real *, real *, integer *, real *, integer *, integer *, integer *, integer *); static integer indwrk, liwmin; extern doublereal slansp_(char *, char *, integer *, real *, real *); extern /* Subroutine */ int ssterf_(integer *, real *, real *, integer *); static integer llwork; static real smlnum; extern /* Subroutine */ int ssptrd_(char *, integer *, real *, real *, real *, real *, integer *); static logical lquery; extern /* Subroutine */ int sopmtr_(char *, char *, char *, integer *, integer *, real *, real *, real *, integer *, real *, integer *); --ap; --w; z_dim1 = *ldz; z_offset = 1 + z_dim1; z__ -= z_offset; --work; --iwork; /* Function Body */ wantz = lsame_(jobz, "V"); lquery = *lwork == -1 || *liwork == -1; *info = 0; if (! (wantz || lsame_(jobz, "N"))) { *info = -1; } else if (! (lsame_(uplo, "U") || lsame_(uplo, "L"))) { *info = -2; } else if (*n < 0) { *info = -3; } else if (*ldz < 1 || wantz && *ldz < *n) { *info = -7; } if (*info == 0) { if (*n <= 1) { liwmin = 1; lwmin = 1; } else { if (wantz) { liwmin = *n * 5 + 3; /* Computing 2nd power */ i__1 = *n; lwmin = *n * 6 + 1 + i__1 * i__1; } else { liwmin = 1; lwmin = *n << 1; } } iwork[1] = liwmin; work[1] = (real) lwmin; if (*lwork < lwmin && ! lquery) { *info = -9; } else if (*liwork < liwmin && ! lquery) { *info = -11; } } if (*info != 0) { i__1 = -(*info); xerbla_("SSPEVD", &i__1); return 0; } else if (lquery) { return 0; } /* Quick return if possible */ if (*n == 0) { return 0; } if (*n == 1) { w[1] = ap[1]; if (wantz) { z__[z_dim1 + 1] = 1.f; } return 0; } /* Get machine constants. */ safmin = slamch_("Safe minimum"); eps = slamch_("Precision"); smlnum = safmin / eps; bignum = 1.f / smlnum; rmin = sqrt(smlnum); rmax = sqrt(bignum); /* Scale matrix to allowable range, if necessary. */ anrm = slansp_("M", uplo, n, &ap[1], &work[1]); iscale = 0; if (anrm > 0.f && anrm < rmin) { iscale = 1; sigma = rmin / anrm; } else if (anrm > rmax) { iscale = 1; sigma = rmax / anrm; } if (iscale == 1) { i__1 = *n * (*n + 1) / 2; sscal_(&i__1, &sigma, &ap[1], &c__1); } /* Call SSPTRD to reduce symmetric packed matrix to tridiagonal form. */ inde = 1; indtau = inde + *n; ssptrd_(uplo, n, &ap[1], &w[1], &work[inde], &work[indtau], &iinfo); /* For eigenvalues only, call SSTERF. For eigenvectors, first call SSTEDC to generate the eigenvector matrix, WORK(INDWRK), of the tridiagonal matrix, then call SOPMTR to multiply it by the Householder transformations represented in AP. */ if (! wantz) { ssterf_(n, &w[1], &work[inde], info); } else { indwrk = indtau + *n; llwork = *lwork - indwrk + 1; sstedc_("I", n, &w[1], &work[inde], &z__[z_offset], ldz, &work[indwrk] , &llwork, &iwork[1], liwork, info); sopmtr_("L", uplo, "N", n, n, &ap[1], &work[indtau], &z__[z_offset], ldz, &work[indwrk], &iinfo); } /* If matrix was scaled, then rescale eigenvalues appropriately. */ if (iscale == 1) { r__1 = 1.f / sigma; sscal_(n, &r__1, &w[1], &c__1); } work[1] = (real) lwmin; iwork[1] = liwmin; return 0; /* End of SSPEVD */ } /* sspevd_ */