DGET08(3)

💅 DGET08(3) 💅

okay so this is the Library Functions Manual entry for DGET08, from that LAPACK source tree — you know the one, it lives at /home/abui...IN/dget08.f(3). welcome to the group chat, bestie 🫶

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✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/dget08.f

that's it. that's the name. it's a whole path and honestly it's giving "my mom named me after the street she grew up on" 😭 but we move.

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🦋 SYNOPSIS 🦋

Functions/Subroutines 🌸

subroutine DGET08 (trans, m, n, nrhs, a, lda, x, ldx, b, ldb, rwork,
    resid)

DGET08

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👑 Function/Subroutine Documentation 👑

🎀 subroutine DGET08 🎀

subroutine DGET08 (character trans, integer m, integer n, integer nrhs,
    double precision, dimension( lda, * ) a, integer lda, double precision,
    dimension( ldx, * ) x, integer ldx, double precision, dimension( ldb, *
    ) b, integer ldb, double precision, dimension( * ) rwork, double
    precision resid)

DGET08

💖 Purpose: 💖

!> !> DGET08 computes the residual for a solution of a system of linear !> equations A*x = b or A'*x = b: !> RESID = norm(B - A*X,inf) / ( norm(A,inf) * norm(X,inf) * EPS ), !> where EPS is the machine epsilon. !>

like, it's a vibe check for your linear solver. it looks at how far off B - A*X is and normalizes it by norm(A,inf), norm(X,inf) and EPS. iconic behavior ngl ✨

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💅 Parameters 💅

• TRANS — TRANS is CHARACTER*1, no cap. it specifies the form of the system of equations:
  • = 'N': A *x = b
  • = 'T': A'*x = b, where A' is the transpose of A
  • = 'C': A'*x = b, where A' is the transpose of A
• M — M is INTEGER. the number of rows of the matrix A. M >= 0. simple as that, bestie 🍓
• N — N is INTEGER. the number of columns of the matrix A. N >= 0. slay.
• NRHS — NRHS is INTEGER. the number of columns of B, the matrix of right hand sides. NRHS >= 0. three non-negativity constraints in a row, we love a consistent queen 👑
• A — A is DOUBLE PRECISION array, dimension (LDA,N). the original M x N matrix A. the main character, literally.
• LDA — LDA is INTEGER. the leading dimension of the array A. LDA >= max(1,M). respect the constraint or suffer 🙈
• X — X is DOUBLE PRECISION array, dimension (LDX,NRHS). the computed solution vectors for the system of linear equations. the whole reason we're here fr fr.
• LDX — LDX is INTEGER. the leading dimension of the array X. it's conditional, keep up: if TRANS = 'N', LDX >= max(1,N); if TRANS = 'T' or 'C', LDX >= max(1,M). conditional logic, we stay flexible 💅
• B — B is DOUBLE PRECISION array, dimension (LDB,NRHS). on entry, the right hand side vectors for the system of linear equations. on exit, B is overwritten with the difference B - A*X. so yeah, she gets wrecked on the way out — do NOT expect your original B to still be there 😭💀
• LDB — LDB is INTEGER. the leading dimension of the array B. watch the caps and the conditionals: IF TRANS = 'N', LDB >= max(1,M); if TRANS = 'T' or 'C', LDB >= max(1,N). note it flips compared to LDX, iykyk.
• RWORK — RWORK is DOUBLE PRECISION array, dimension (M). that's it. that's the whole description. it's a workspace, she works, we respect her privacy 🧚
• RESID — RESID is DOUBLE PRECISION. the maximum over the number of right hand sides of norm(B - A*X) / ( norm(A) * norm(X) * EPS ). the final girl. the number you actually came for. the grade. the vibe check result ⭐

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🌈 Author 🌈

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

take a bow, legends 🫶

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🌸 Definition at line 131 of file dget08.f. 🌸

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💜 Author 💜

Generated automatically by Doxygen for LAPACK from the source code. not a human, not a bestie, just a little robot doing her best 🤖✨

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and that's the whole thing, bestie — LAPACK, Version 3.12.0, straight outta /home/abui...IN/dget08.f(3). go compute some residuals and text me when you're done 💖🎀🦋