SRC/dlapmt.f(3)

🌸 SRC/dlapmt.f(3) — from the Library Functions Manual 🌸

okay bestie, buckle up, because this is the LAPACK page for SRC/dlapmt.f and it's honestly kind of a vibe 💅

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✨ NAME ✨

SRC/dlapmt.f — like, that's the file, that's the name, no notes 🎀

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🦋 SYNOPSIS 🦋

Functions/Subroutines

• subroutine dlapmt (forwrd, m, n, x, ldx, k) — DLAPMT performs a forward or backward permutation of the columns of a matrix. that's the whole personality tbh 💫

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💖 Function/Subroutine Documentation 💖

subroutine dlapmt (logical forwrd, integer m, integer n, double precision, dimension( ldx, * ) x, integer ldx, integer, dimension( * ) k)

DLAPMT performs a forward or backward permutation of the columns of a matrix. periodt. 👑

🌈 Purpose

!>
!> DLAPMT rearranges the columns of the M by N matrix X as specified
!> by the permutation K(1),K(2),...,K(N) of the integers 1,...,N.
!> If FORWRD = .TRUE.,  forward permutation:
!>
!>      X(*,K(J)) is moved X(*,J) for J = 1,2,...,N.
!>
!> If FORWRD = .FALSE., backward permutation:
!>
!>      X(*,J) is moved to X(*,K(J)) for J = 1,2,...,N.
!>

so literally: you hand it a permutation K(1),K(2),...,K(N) of the integers 1,...,N and it shuffles the columns of your M by N matrix X around according to it. forward mode, backward mode, whichever, she's flexible 🧚

🎀 Parameters

• FORWRD — FORWRD is LOGICAL

!>          FORWRD is LOGICAL
!>          = .TRUE., forward permutation
!>          = .FALSE., backward permutation
!>

so .TRUE. = forward permutation, .FALSE. = backward permutation. pick your fighter 💅

• M — M is INTEGER

!>          M is INTEGER
!>          The number of rows of the matrix X. M >= 0.
!>

the number of rows of X, and the constraint is M >= 0. zero rows is allowed, iconic of her honestly 😌

• N — N is INTEGER

!>          N is INTEGER
!>          The number of columns of the matrix X. N >= 0.
!>

the number of columns of X, with N >= 0. same energy, same rule 🫶

• X — X is DOUBLE PRECISION array, dimension (LDX,N)

!>          X is DOUBLE PRECISION array, dimension (LDX,N)
!>          On entry, the M by N matrix X.
!>          On exit, X contains the permuted matrix X.
!>

on entry it's your M by N matrix X, on exit it holds the permuted matrix X. yes she edits in place, she's efficient like that 🔥

• LDX — LDX is INTEGER

!>          LDX is INTEGER
!>          The leading dimension of the array X, LDX >= MAX(1,M).
!>

the leading dimension of the array X, and it must satisfy LDX >= MAX(1,M). don't test her on this 🙈

• K — K is INTEGER array, dimension (N)

!>          K is INTEGER array, dimension (N)
!>          On entry, K contains the permutation vector. K is used as
!>          internal workspace, but reset to its original value on
!>          output.
!>

on entry, K holds the permutation vector. she does use K as internal workspace mid-swing (scandalous, I know), but it gets reset to its original value on output, so no harm no foul 💀✨

👑 Author

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

⭐ Definition

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

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💜 Author (of the page itself, lol)

Generated automatically by Doxygen for LAPACK from the source code. she didn't even write her own about-me, queen behavior 😭

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ngl bestie, if you're passing K around expecting it to stay scrambled — it won't. it resets. that's the whole warning, no cap 🌸

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anyway that's the whole page 💖 this was SRC/dlapmt.f(3) from LAPACK, Version 3.12.0, generated automatically by Doxygen for LAPACK from the source code — slay, go permute some columns, mwah 🎀🦋💅