---
name: "sppt01.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/sppt01.f"
---

# sppt01.f(3)

## NAME

TESTING/LIN/sppt01.f

## SYNOPSIS

### Functions/Subroutines

subroutine **sppt01** (uplo, n, a, afac, rwork, resid)\
 **SPPT01**

## Function/Subroutine Documentation

### subroutine sppt01 (character uplo, integer n, real, dimension( \* ) a, real, dimension( \* ) afac, real, dimension( \* ) rwork, real resid)

**SPPT01**

**Purpose:**

```
!>
!> SPPT01 reconstructs a symmetric positive definite packed matrix A
!> from its L*L' or U'*U factorization and computes the residual
!>    norm( L*L' - A ) / ( N * norm(A) * EPS ) or
!>    norm( U'*U - A ) / ( N * norm(A) * EPS ),
!> where EPS is the machine epsilon.
!>
```

**Parameters**

*UPLO*

```
!>          UPLO is CHARACTER*1
!>          Specifies whether the upper or lower triangular part of the
!>          symmetric matrix A is stored:
!>          = 'U':  Upper triangular
!>          = 'L':  Lower triangular
!>
```

*N*

```
!>          N is INTEGER
!>          The number of rows and columns of the matrix A.  N >= 0.
!>
```

*A*

```
!>          A is REAL array, dimension (N*(N+1)/2)
!>          The original symmetric matrix A, stored as a packed
!>          triangular matrix.
!>
```

*AFAC*

```
!>          AFAC is REAL array, dimension (N*(N+1)/2)
!>          On entry, the factor L or U from the L*L' or U'*U
!>          factorization of A, stored as a packed triangular matrix.
!>          Overwritten with the reconstructed matrix, and then with the
!>          difference L*L' - A (or U'*U - A).
!>
```

*RWORK*

```
!>          RWORK is REAL array, dimension (N)
!>
```

*RESID*

```
!>          RESID is REAL
!>          If UPLO = 'L', norm(L*L' - A) / ( N * norm(A) * EPS )
!>          If UPLO = 'U', norm(U'*U - A) / ( N * norm(A) * EPS )
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **92** of file **sppt01.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.