SRC/dsptri.f(3)

💖 SRC/dsptri.f(3) 💖

From the Library Functions Manual — okay bestie, this is the DSPTRI page and it is lowkey iconic. 💅✨

🌸 NAME 🌸

SRC/dsptri.f

✨ SYNOPSIS ✨

Functions/Subroutines

• subroutine dsptri (uplo, n, ap, ipiv, work, info) — this is DSPTRI, periodt. 🫶

🛠️ Function/Subroutine Documentation 🛠️

subroutine dsptri (character uplo, integer n, double precision, dimension( * ) ap, integer, dimension( * ) ipiv, double precision, dimension( * ) work, integer info)

DSPTRI

💫 Purpose

DSPTRI computes the inverse of a real symmetric indefinite matrix A in packed storage using the factorization A = U*D*U**T or A = L*D*L**T computed by DSPTRF. No cap, that's the whole glow-up. 🔥

🧚 Parameters 🧚

💅 UPLO

UPLO is CHARACTER*1. It specifies whether the details of the factorization are stored as an upper or lower triangular matrix.

• = 'U': Upper triangular, form is A = U*D*U**T;
• = 'L': Lower triangular, form is A = L*D*L**T.

💅 N

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

💅 AP

AP is DOUBLE PRECISION array, dimension (N*(N+1)/2).

On entry, the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by DSPTRF, stored as a packed triangular matrix.

On exit, if INFO = 0, the (symmetric) inverse of the original matrix, stored as a packed triangular matrix. The j-th column of inv(A) is stored in the array AP as follows:

• if UPLO = 'U', AP(i + (j-1)*j/2) = inv(A)(i,j) for 1<=i<=j;
• if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = inv(A)(i,j) for j<=i<=n.

💅 IPIV

IPIV is INTEGER array, dimension (N). Details of the interchanges and the block structure of D as determined by DSPTRF.

💅 WORK

WORK is DOUBLE PRECISION array, dimension (N).

💅 INFO

INFO is INTEGER.

• = 0: successful exit
• < 0: if INFO = -i, the i-th argument had an illegal value
• > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its inverse could not be computed.

👑 Author 👑

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 108 of file dsptri.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

---

💖 And that's the cute sign-off, bestie: LAPACK Version 3.12.0, SRC/dsptri.f(3) — no date shown in the footer, so that's the whole vibe. Stay iconic! 💖🎀