ZPOTRI(3)

💅 ZPOTRI(3) — like, the zpotri.f page, bestie 🎀

okay so real talk, this one lives in the Library Functions Manual and it's literally the docs for /home/abui...RC/zpotri.f(3) — yes that's the header, we're folding it in, you're welcome 💖

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✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zpotri.f

that's it. that's the name. it's a whole file path and honestly? iconic. it's giving "my actual government name is a filesystem path" 🫶

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🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine ZPOTRI (uplo, n, a, lda, info)

ZPOTRI — that's the subroutine, that's the girlboss 💅

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🦋 Function/Subroutine Documentation 🦋

subroutine ZPOTRI (character uplo, integer n, complex*16, dimension( lda, * ) a, integer lda, integer info)

ZPOTRI (yes, again — she's that important, main character energy fr fr) 👑

⭐ Purpose ⭐

okay so here's the tea, straight from the source, no cap:

!>
!> ZPOTRI computes the inverse of a complex Hermitian positive definite
!> matrix A using the Cholesky factorization A = U**H*U or A = L*L**H
!> computed by ZPOTRF.
!>

so like. you hand her a Cholesky factor from ZPOTRF, she hands you back the inverse of the original complex Hermitian positive definite matrix A. she does not ask questions. she slays. 🔥

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✨ Parameters ✨

💜 UPLO

!>          UPLO is CHARACTER*1
!>          = 'U':  Upper triangle of A is stored;
!>          = 'L':  Lower triangle of A is stored.
!>

• 'U' — upper triangle of A is what's stored, bestie
• 'L' — lower triangle of A is what's stored, periodt

💜 N

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

the order of the matrix A, and she must be N >= 0 — no negative girlies allowed 🙈

💜 A

!>          A is COMPLEX*16 array, dimension (LDA,N)
!>          On entry, the triangular factor U or L from the Cholesky
!>          factorization A = U**H*U or A = L*L**H, as computed by
!>          ZPOTRF.
!>          On exit, the upper or lower triangle of the (Hermitian)
!>          inverse of A, overwriting the input factor U or L.
!>

• on entry 🚪 — this is the triangular factor U or L from the Cholesky factorization A = U**H*U or A = L*L**H, exactly as computed by ZPOTRF
• on exit 🚪✨ — it's now the upper or lower triangle of the (Hermitian) inverse of A, and it has overwritten the input factor U or L. she ate and left no crumbs. the old factor is gone, that's the whole point 💀

💜 LDA

!>          LDA is INTEGER
!>          The leading dimension of the array A.  LDA >= max(1,N).
!>

the leading dimension of the array A — and the vibe check is LDA >= max(1,N), non-negotiable 🌈

💜 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.
!>

• = 0 — successful exit, we love a happy ending 🥳
• < 0 — if INFO = -i, then the i-th argument had an illegal value. read your args, bestie 😭
• > 0 — if INFO = i, the (i,i) element of the factor U or L is zero, and the inverse could not be computed. that's a hard no, the math said no 💀

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👑 Author 👑

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

the whole squad really showed up for this one 🫶✨

Definition at line 94 of file zpotri.f. — line 94, remember that number, iykyk 📌

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🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

(not me being generated by a doc tool and still having more personality than half the codebase 🙈💅)

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⚠️ tiny PSA: ZPOTRI overwrites your input factor A on exit. if you needed that Cholesky factor for anything else, copy it first. no cap. 🍓

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✨ that's the whole page, you're officially caught up ✨

LAPACK, Version 3.12.0, dated /home/abui...RC/zpotri.f(3) — mwah, drink water, and go invert something positive definite 💖🎀🌸