Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

ID 766686
Date 7/13/2023
Public

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?larrr

Performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

Syntax

call slarrr( n, d, e, info )

call dlarrr( n, d, e, info )

Include Files

  • mkl.fi

Description

The routine performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

Input Parameters

n

INTEGER. The order of the matrix T. (n> 0).

d

REAL for slarrr

DOUBLE PRECISION for dlarrr

Array, DIMENSION (n).

Contains n diagonal elements of the matrix T.

e

REAL for slarrr

DOUBLE PRECISION for dlarrr

Array, DIMENSION (n).

The first (n-1) entries contain sub-diagonal elements of the tridiagonal matrix T; e(n) is set to 0.

Output Parameters

info

INTEGER.

= 0: the matrix warrants computations preserving relative accuracy (default value).

= -1: the matrix warrants computations guaranteeing only absolute accuracy.