# dptt01.f - Man Page

TESTING/LIN/dptt01.f

## Synopsis

### Functions/Subroutines

subroutine dptt01 (n, d, e, df, ef, work, resid)
DPTT01

## Function/Subroutine Documentation

### subroutine dptt01 (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, double precision, dimension( * ) df, double precision, dimension( * ) ef, double precision, dimension( * ) work, double precision resid)

DPTT01

Purpose:

``` DPTT01 reconstructs a tridiagonal matrix A from its L*D*L'
factorization and computes the residual
norm(L*D*L' - A) / ( n * norm(A) * EPS ),
where EPS is the machine epsilon.```
Parameters

N

```          N is INTEGER
The order of the matrix A.```

D

```          D is DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the tridiagonal matrix A.```

E

```          E is DOUBLE PRECISION array, dimension (N-1)
The (n-1) subdiagonal elements of the tridiagonal matrix A.```

DF

```          DF is DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the factor L from the L*D*L'
factorization of A.```

EF

```          EF is DOUBLE PRECISION array, dimension (N-1)
The (n-1) subdiagonal elements of the factor L from the
L*D*L' factorization of A.```

WORK

`          WORK is DOUBLE PRECISION array, dimension (2*N)`

RESID

```          RESID is DOUBLE PRECISION
norm(L*D*L' - A) / (n * norm(A) * EPS)```
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 90 of file dptt01.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dptt01(3) is an alias of dptt01.f(3).

Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK