# sgtt01.f - Man Page

TESTING/LIN/sgtt01.f

## Synopsis

### Functions/Subroutines

subroutine sgtt01 (n, dl, d, du, dlf, df, duf, du2, ipiv, work, ldwork, rwork, resid)
SGTT01

## Function/Subroutine Documentation

### subroutine sgtt01 (integer n, real, dimension( * ) dl, real, dimension( * ) d, real, dimension( * ) du, real, dimension( * ) dlf, real, dimension( * ) df, real, dimension( * ) duf, real, dimension( * ) du2, integer, dimension( * ) ipiv, real, dimension( ldwork, * ) work, integer ldwork, real, dimension( * ) rwork, real resid)

SGTT01

Purpose:

``` SGTT01 reconstructs a tridiagonal matrix A from its LU factorization
and computes the residual
norm(L*U - A) / ( norm(A) * EPS ),
where EPS is the machine epsilon.```
Parameters

N

```          N is INTEGER
The order of the matrix A.  N >= 0.```

DL

```          DL is REAL array, dimension (N-1)
The (n-1) sub-diagonal elements of A.```

D

```          D is REAL array, dimension (N)
The diagonal elements of A.```

DU

```          DU is REAL array, dimension (N-1)
The (n-1) super-diagonal elements of A.```

DLF

```          DLF is REAL array, dimension (N-1)
The (n-1) multipliers that define the matrix L from the
LU factorization of A.```

DF

```          DF is REAL array, dimension (N)
The n diagonal elements of the upper triangular matrix U from
the LU factorization of A.```

DUF

```          DUF is REAL array, dimension (N-1)
The (n-1) elements of the first super-diagonal of U.```

DU2

```          DU2 is REAL array, dimension (N-2)
The (n-2) elements of the second super-diagonal of U.```

IPIV

```          IPIV is INTEGER array, dimension (N)
The pivot indices; for 1 <= i <= n, row i of the matrix was
interchanged with row IPIV(i).  IPIV(i) will always be either
i or i+1; IPIV(i) = i indicates a row interchange was not
required.```

WORK

`          WORK is REAL array, dimension (LDWORK,N)`

LDWORK

```          LDWORK is INTEGER
The leading dimension of the array WORK.  LDWORK >= max(1,N).```

RWORK

`          RWORK is REAL array, dimension (N)`

RESID

```          RESID is REAL
The scaled residual:  norm(L*U - A) / (norm(A) * EPS)```
Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 132 of file sgtt01.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page sgtt01(3) is an alias of sgtt01.f(3).

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