# dptt02.f - Man Page

TESTING/LIN/dptt02.f

## Synopsis

### Functions/Subroutines

subroutine dptt02 (n, nrhs, d, e, x, ldx, b, ldb, resid)
DPTT02

## Function/Subroutine Documentation

### subroutine dptt02 (integer n, integer nrhs, double precision, dimension( * ) d, double precision, dimension( * ) e, double precision, dimension( ldx, * ) x, integer ldx, double precision, dimension( ldb, * ) b, integer ldb, double precision resid)

DPTT02

Purpose:

``` DPTT02 computes the residual for the solution to a symmetric
tridiagonal system of equations:
RESID = norm(B - A*X) / (norm(A) * norm(X) * EPS),
where EPS is the machine epsilon.```
Parameters

N

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

NRHS

```          NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrices B and X.  NRHS >= 0.```

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.```

X

```          X is DOUBLE PRECISION array, dimension (LDX,NRHS)
The n by nrhs matrix of solution vectors X.```

LDX

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

B

```          B is DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the n by nrhs matrix of right hand side vectors B.
On exit, B is overwritten with the difference B - A*X.```

LDB

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

RESID

```          RESID is DOUBLE PRECISION
norm(B - A*X) / (norm(A) * norm(X) * EPS)```
Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 103 of file dptt02.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dptt02(3) is an alias of dptt02.f(3).

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