TESTING/LIN/dqrt12.f(3)

💜 TESTING/LIN/dqrt12.f

okay bestie, welcome to the TESTING/LIN corner of the Library Functions Manual — this is where LAPACK checks its own homework, and honestly? icon behavior. ✨

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🦋 SYNOPSIS

Functions/Subroutines

double precision function dqrt12 (m, n, a, lda, s, work, lwork)

DQRT12 — say it with me, it's giving main character energy 👑

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🌸 Function/Subroutine Documentation

double precision function dqrt12 (integer m, integer n, double precision,
    dimension( lda, * ) a, integer lda, double precision, dimension( * ) s,
    double precision, dimension( lwork ) work, integer lwork)

DQRT12 ✨ (yes that's the whole description, she's mysterious, she's booked and busy, we respect it)

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💅 Purpose

No cap, here's the whole vibe:

!>
!> DQRT12 computes the singular values `svlues' of the upper trapezoid
!> of A(1:M,1:N) and returns the ratio
!>
!>      || svlues - s ||/(||s||*eps*max(M,N))
!>

so basically she grabs the singular values of the upper trapezoid of A(1:M,1:N), does a little comparison dance with s, and hands you back that ratio. it's a whole accuracy-check moment 🫶 (and yes, svlues is spelled like that in the source — we keep it exactly, literally not touching it 😭)

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🎀 Parameters

• M

!>          M is INTEGER
!>          The number of rows of the matrix A.
!>

how many rows A has. that's it, that's the whole job 🍓

• N

!>          N is INTEGER
!>          The number of columns of the matrix A.
!>

how many columns A has. iconic, we love a symmetric description 💫

• A

!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          The M-by-N matrix A. Only the upper trapezoid is referenced.
!>

the star of the show 🌟 an M-by-N DOUBLE PRECISION array — but heads up, only the upper trapezoid gets referenced, the rest of her is literally just vibing in the background 💀

• LDA

!>          LDA is INTEGER
!>          The leading dimension of the array A.
!>

the leading dimension of A, aka the stride situation. crucial, don't skip 🎯

• S

!>          S is DOUBLE PRECISION array, dimension (min(M,N))
!>          The singular values of the matrix A.
!>

DOUBLE PRECISION array of size min(M,N) holding the singular values of A — the actual facts she's comparing against 💖

• WORK

!>          WORK is DOUBLE PRECISION array, dimension (LWORK)
!>

scratch space, DOUBLE PRECISION, dimension (LWORK). she works hard so you don't have to 🧚

• LWORK

!>          LWORK is INTEGER
!>          The length of the array WORK. LWORK >= max(M*N + 4*min(M,N) +
!>          max(M,N), M*N+2*MIN( M, N )+4*N).
!>

the length of WORK, and bestie please respect the minimum:

LWORK >= max(M*N + 4*min(M,N) + max(M,N), M*N+2*MIN( M, N )+4*N)

⚠️ too small and it's not a vibe. give WORK the room she deserves fr fr.

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👑 Author

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

the whole squad showed up for this one 🌈

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⭐ Details

Definition at line 88 of file dqrt12.f.

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💀 Author (again, yes really)

Generated automatically by Doxygen for LAPACK from the source code. she's not hand-written, she's machine-born and still slaying 🤖✨

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and that's the whole page, bestie! 📖 from LAPACK, Version 3.12.0 — one file, TESTING/LIN/dqrt12.f(3), delivered with love, no date on the footer so we're just gonna say it dropped whenever the source said so 🫶💖 mwah, go check those singular values ✨