---
name: "spptri.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/spptri.f"
---

# spptri.f(3)

## NAME

SRC/spptri.f

## SYNOPSIS

### Functions/Subroutines

subroutine **spptri** (uplo, n, ap, info)\
 **SPPTRI**

## Function/Subroutine Documentation

### subroutine spptri (character uplo, integer n, real, dimension( \* ) ap, integer info)

**SPPTRI**

**Purpose:**

```
!>
!> SPPTRI computes the inverse of a real symmetric positive definite
!> matrix A using the Cholesky factorization A = U**T*U or A = L*L**T
!> computed by SPPTRF.
!>
```

**Parameters**

*UPLO*

```
!>          UPLO is CHARACTER*1
!>          = 'U':  Upper triangular factor is stored in AP;
!>          = 'L':  Lower triangular factor is stored in AP.
!>
```

*N*

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

*AP*

```
!>          AP is REAL array, dimension (N*(N+1)/2)
!>          On entry, the triangular factor U or L from the Cholesky
!>          factorization A = U**T*U or A = L*L**T, packed columnwise as
!>          a linear array.  The j-th column of U or L is stored in the
!>          array AP as follows:
!>          if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j;
!>          if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n.
!>
!>          On exit, the upper or lower triangle of the (symmetric)
!>          inverse of A, overwriting the input factor U or L.
!>
```

*INFO*

```
!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!>          > 0:  if INFO = i, the (i,i) element of the factor U or L is
!>                zero, and the inverse could not be computed.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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

## Author

Generated automatically by Doxygen for LAPACK from the source code.