SRC/stptri.f(3)

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version 3.12.1 · 4 versions
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💖 SRC/stptri.f 💖

okay bestie, this is the SRC/stptri.f(3) page from the Library Functions Manual, and it's literally all about one little subroutine. let's get into it 🫶

✨ NAME ✨

SRC/stptri.f

🦋 SYNOPSIS 🦋

Functions/Subroutines

  • subroutine stptri (uplo, diag, n, ap, info) — STPTRI

🎀 Function/Subroutine Documentation 🎀

subroutine stptri (character uplo, character diag, integer n, real, dimension( * ) ap, integer info)

STPTRI

💖 Purpose 💖

STPTRI computes the inverse of a real upper or lower triangular matrix A stored in packed format. periodt. ✨

🌟 Parameters 🌟

  • UPLO — UPLO is CHARACTER*1. = 'U': A is upper triangular; = 'L': A is lower triangular.
  • DIAG — DIAG is CHARACTER*1. = 'N': A is non-unit triangular; = 'U': A is unit triangular.
  • 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 upper or lower triangular matrix A, stored columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*((2*n-j)/2) = A(i,j) for j<=i<=n. See below for further details. On exit, the (triangular) inverse of the original matrix, in the same packed storage format.
  • INFO — INFO is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. > 0: if INFO = i, A(i,i) is exactly zero. The triangular matrix is singular and its inverse can not be computed.

👑 Author 👑

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

🔍 Further Details 🔍

A triangular matrix A can be transferred to packed storage using one of the following program segments:

!>  UPLO = 'U':                      UPLO = 'L':
!>
!>        JC = 1                           JC = 1
!>        DO 2 J = 1, N                    DO 2 J = 1, N
!>           DO 1 I = 1, J                    DO 1 I = J, N
!>              AP(JC+I-1) = A(I,J)              AP(JC+I-J) = A(I,J)
!>      1    CONTINUE                    1    CONTINUE
!>           JC = JC + J                      JC = JC + N - J + 1
!>      2 CONTINUE                       2 CONTINUE
!>

Definition at line 116 of file stptri.f.

🪄 Author 🪄

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and that's a wrap, bestie! huge shoutout to LAPACK Version 3.12.0 and the source page SRC/stptri.f(3) — footer vibes only, and there's no date on this one, so we're not inventing one 💅✨💖

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