SUBROUTINE DSBEVD( JOBZ, UPLO, N, KD, AB, LDAB, W, Z, LDZ, WORK, * LWORK, IWORK, LIWORK, INFO) CHARACTER * 1 JOBZ, UPLO INTEGER N, KD, LDAB, LDZ, LWORK, LIWORK, INFO INTEGER IWORK(*) DOUBLE PRECISION AB(LDAB,*), W(*), Z(LDZ,*), WORK(*) SUBROUTINE DSBEVD_64( JOBZ, UPLO, N, KD, AB, LDAB, W, Z, LDZ, WORK, * LWORK, IWORK, LIWORK, INFO) CHARACTER * 1 JOBZ, UPLO INTEGER*8 N, KD, LDAB, LDZ, LWORK, LIWORK, INFO INTEGER*8 IWORK(*) DOUBLE PRECISION AB(LDAB,*), W(*), Z(LDZ,*), WORK(*)
SUBROUTINE SBEVD( JOBZ, UPLO, [N], KD, AB, [LDAB], W, Z, [LDZ], * [WORK], [LWORK], [IWORK], [LIWORK], [INFO]) CHARACTER(LEN=1) :: JOBZ, UPLO INTEGER :: N, KD, LDAB, LDZ, LWORK, LIWORK, INFO INTEGER, DIMENSION(:) :: IWORK REAL(8), DIMENSION(:) :: W, WORK REAL(8), DIMENSION(:,:) :: AB, Z SUBROUTINE SBEVD_64( JOBZ, UPLO, [N], KD, AB, [LDAB], W, Z, [LDZ], * [WORK], [LWORK], [IWORK], [LIWORK], [INFO]) CHARACTER(LEN=1) :: JOBZ, UPLO INTEGER(8) :: N, KD, LDAB, LDZ, LWORK, LIWORK, INFO INTEGER(8), DIMENSION(:) :: IWORK REAL(8), DIMENSION(:) :: W, WORK REAL(8), DIMENSION(:,:) :: AB, Z
void dsbevd(char jobz, char uplo, int n, int kd, double *ab, int ldab, double *w, double *z, int ldz, int *info);
void dsbevd_64(char jobz, char uplo, long n, long kd, double *ab, long ldab, double *w, double *z, long ldz, long *info);
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.
On exit, AB is overwritten by values generated during the reduction to tridiagonal form. If UPLO = 'U', the first superdiagonal and the diagonal of the tridiagonal matrix T are returned in rows KD and KD+1 of AB, and if UPLO = 'L', the diagonal and first subdiagonal of T are returned in the first two rows of AB.
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.
If LIWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the IWORK array, returns this value as the first entry of the IWORK array, and no error message related to LIWORK is issued by XERBLA.