SRC/ztrttp.f(3)

💜 SRC/ztrttp.f — LAPACK, bestie edition

okay so this is a page out of the LAPACK manual, specifically the SRC/ztrttp.f one, and it's genuinely so cute because it does exactly one thing and does it well ✨

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🌸 SYNOPSIS

Functions/Subroutines

• subroutine ztrttp (uplo, n, a, lda, ap, info) — ZTRTTP copies a triangular matrix from the standard full format (TR) to the standard packed format (TP). that's it, that's the whole slay 💅

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🎀 Function/Subroutine Documentation

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

ZTRTTP copies a triangular matrix from the standard full format (TR) to the standard packed format (TP). no cap, it's a glow-up for your matrix — same vibes, smaller closet 🦋

✨ Purpose

!>
!> ZTRTTP copies a triangular matrix A from full format (TR) to standard
!> packed format (TP).
!>

literally just moving your girl from the spacious walk-in (full format) into a compact little bag (packed format) and she looks just as good 💖

💅 Parameters

• UPLO

!>          UPLO is CHARACTER*1
!>          = 'U':  A is upper triangular;
!>          = 'L':  A is lower triangular.
!>

picks which half of the matrix is the main character — 'U' for upper triangular, 'L' for lower triangular 👑

• N

!>          N is INTEGER
!>          The order of the matrices AP and A.  N >= 0.
!>

the order of AP and A, and it's gotta be N >= 0. no negatives allowed, we don't do that here 🙈

• A

!>          A is COMPLEX*16 array, dimension (LDA,N)
!>          On entry, the triangular matrix A.  If UPLO = 'U', the leading
!>          N-by-N upper triangular part of A contains the upper
!>          triangular part of the matrix A, and the strictly lower
!>          triangular part of A is not referenced.  If UPLO = 'L', the
!>          leading N-by-N lower triangular part of A contains the lower
!>          triangular part of the matrix A, and the strictly upper
!>          triangular part of A is not referenced.
!>

COMPLEX*16 array, dimension (LDA,N). on entry it holds your triangular matrix A. if UPLO = 'U', the leading N-by-N upper triangular part of A holds the upper triangular part of the matrix, and the strictly lower triangular part is not referenced (it said "not me", it's not in this scene 😭). if UPLO = 'L', flip it: the leading N-by-N lower triangular part holds the lower triangular part, and the strictly upper triangular part is not referenced. iykyk 🫶

• LDA

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

the leading dimension of array A, and it has to be LDA >= max(1,N). rules are rules, bestie 🎀

• AP

!>          AP is COMPLEX*16 array, dimension ( N*(N+1)/2 ),
!>          On exit, the upper or lower triangular matrix A, packed
!>          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)*(2n-j)/2) = A(i,j) for j<=i<=n.
!>

COMPLEX*16 array, dimension ( N*(N+1)/2 ). on exit it's your upper or lower triangular matrix A, packed columnwise in a linear array — the compression is giving ✨effortless✨. the j-th column of A lands in AP like this:

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

formulas ate, ngl 🔥

• INFO

!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!>

the vibe check at the end 💀 = 0 means successful exit (we love a clean run 🌈). < 0 means if INFO = -i, the i-th argument had an illegal value — so check your args before you come for her 🙈

👑 Author

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

the whole friend group contributed, we stan a collaborative effort 💖

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Definition at line 103 of file ztrttp.f. go look, it's right there 👀

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⭐ Author

Generated automatically by Doxygen for LAPACK from the source code. so it's not even a human writing this, it's a bot doing its little task and honestly? respect 🫡

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and that's the whole page, bestie — every flag, every bound, every formula, all present and accounted for 💜

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kisses and good vibes from the LAPACK girlies — Version 3.12.0, wrapped up and ready for you, periodt** 🎀✨