SRC/ztptri.f(3)

💅 SRC/ztptri.f(3) 💅

from the LAPACK Library Functions Manual

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🌸 NAME 🌸

SRC/ztptri.f — the source page for ztptri, bestie. That's the whole name section, no cap.

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✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

• subroutine ztptri (uplo, diag, n, ap, info) — ZTPTRI, the main character subroutine.

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🦋 Function/Subroutine Documentation 🦋

subroutine ztptri (character uplo, character diag, integer n, complex*16,
     dimension( * ) ap, integer info)

ZTPTRI — yes, that's her name, periodt.

💫 Purpose: 💫

okay so ZTPTRI computes the inverse of a complex upper or lower triangular matrix A stored in packed format. Literally iconic.

🌈 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 COMPLEX*16 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: 🔥

Here's the exact transfer tea from the page, !> markers and all:

!>
!>  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 ztptri.f.

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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💖 That's the whole page, bestie — footer tea: LAPACK Version 3.12.0 and page SRC/ztptri.f(3). No date in this footer, just those two icons. Slay and goodbye! 🫶✨