LAPACK  3.5.0
LAPACK: Linear Algebra PACKage
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dstect.f File Reference

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Functions/Subroutines

subroutine dstect (N, A, B, SHIFT, NUM)
 DSTECT More...
 

Function/Subroutine Documentation

subroutine dstect ( integer  N,
double precision, dimension( * )  A,
double precision, dimension( * )  B,
double precision  SHIFT,
integer  NUM 
)

DSTECT

Purpose:
    DSTECT counts the number NUM of eigenvalues of a tridiagonal
    matrix T which are less than or equal to SHIFT. T has
    diagonal entries A(1), ... , A(N), and offdiagonal entries
    B(1), ..., B(N-1).
    See W. Kahan "Accurate Eigenvalues of a Symmetric Tridiagonal
    Matrix", Report CS41, Computer Science Dept., Stanford
    University, July 21, 1966
Parameters
[in]N
          N is INTEGER
          The dimension of the tridiagonal matrix T.
[in]A
          A is DOUBLE PRECISION array, dimension (N)
          The diagonal entries of the tridiagonal matrix T.
[in]B
          B is DOUBLE PRECISION array, dimension (N-1)
          The offdiagonal entries of the tridiagonal matrix T.
[in]SHIFT
          SHIFT is DOUBLE PRECISION
          The shift, used as described under Purpose.
[out]NUM
          NUM is INTEGER
          The number of eigenvalues of T less than or equal
          to SHIFT.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
November 2011

Definition at line 83 of file dstect.f.

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