Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?larrc
Computes the number of eigenvalues of the symmetric tridiagonal matrix.
Syntax
call slarrc(jobt, n, vl, vu, d, e, pivmin, eigcnt, lcnt, rcnt, info)
call dlarrc(jobt, n, vl, vu, d, e, pivmin, eigcnt, lcnt, rcnt, info)
Include Files
mkl.fi
Description
The routine finds the number of eigenvalues of the symmetric tridiagonal matrix T or of its factorization L*D*L^{T} in the specified interval.
Input Parameters
- jobt
-
CHARACTER*1 . = 'L' : computes Sturm count for matrix L*D*L^{T} .
- n
-
INTEGER . The order of the matrix. ( n > 1 ).
- vl , vu
-
REAL for slarrc DOUBLE PRECISION for dlarrc
- d
-
REAL for slarrc DOUBLE PRECISION for dlarrc Array, DIMENSION ( n ). If jobt= 'T' : contains the n diagonal elements of the tridiagonal matrix T . If jobt= 'L' : contains the n diagonal elements of the diagonal matrix D .
- e
-
REAL for slarrc DOUBLE PRECISION for dlarrc Array, DIMENSION ( n ). If jobt= 'T' : contains the (n-1) offdiagonal elements of the matrix T . If jobt= 'L' : contains the (n-1) offdiagonal elements of the matrix L .
- pivmin
-
REAL for slarrc DOUBLE PRECISION for dlarrc The minimum pivot in the Sturm sequence for the matrix T .
Output Parameters
- eigcnt
-
The number of eigenvalues of the symmetric tridiagonal matrix T that are in the half-open interval (vl,vu] .
- lcnt , rcnt
-
INTEGER . The left and right negcounts of the interval.
info
INTEGER .
Now it is not used and always is set to 0.