DPPT02(3)

okay so bestie, this is the dppt02.f(3) page from the Library Functions Manual 💖 — and it’s all about computing a residual, no cap. The header path energy is /home/abui...IN/dppt02.f(3), and we’re gonna get into it.

🌸 NAME 🌸

The NAME line is literally this source file path, bestie:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/dppt02.f

✨ SYNOPSIS ✨

Functions/Subroutines

   subroutine DPPT02 (uplo, n, nrhs, a, x, ldx, b, ldb, rwork, resid)
       DPPT02

💖 Function/Subroutine Documentation 💖

The signature is giving “I know my types” energy:

   subroutine DPPT02 (character uplo, integer n, integer nrhs, double
       precision, dimension( * ) a, double precision, dimension( ldx, * ) x,
       integer ldx, double precision, dimension( ldb, * ) b, integer ldb,
       double precision, dimension( * ) rwork, double precision resid)
       DPPT02

And yes, the routine name is DPPT02. Periodt. 💅

🎀 Purpose 🎀

DPPT02 computes the residual in the solution of a symmetric system of linear equations A*x = b when packed storage is used for the coefficient matrix. The ratio computed is:

   RESID = norm(B - A*X) / ( norm(A) * norm(X) * EPS),

where EPS is the machine precision. 🫶

🧚 Parameters 🧚

• UPLO — is CHARACTER*1. It specifies whether the upper or lower triangular part of the symmetric matrix A is stored: = 'U': Upper triangular, = 'L': Lower triangular. iconic ✨
• N — is INTEGER. The number of rows and columns of the matrix A. N >= 0.
• NRHS — is INTEGER. The number of columns of B, the matrix of right hand sides. NRHS >= 0.
• A — is DOUBLE PRECISION array, dimension (N*(N+1)/2). The original symmetric matrix A, stored as a packed triangular matrix.
• X — is DOUBLE PRECISION array, dimension (LDX,NRHS). The computed solution vectors for the system of linear equations.
• LDX — is INTEGER. The leading dimension of the array X. LDX >= max(1,N).
• 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.
• LDB — is INTEGER. The leading dimension of the array B. LDB >= max(1,N).
• RWORK — is DOUBLE PRECISION array, dimension (N).
• RESID — is DOUBLE PRECISION. The maximum over the number of right hand sides of norm(B - A*X) / ( norm(A) * norm(X) * EPS ).

👑 Author 👑

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

📌 Definition at line 120 of file dppt02.f. 📌

That’s the exact line, bestie.

🤖 Author (auto-generated) 🤖

Generated automatically by Doxygen for LAPACK from the source code.

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okay that’s the whole page! LAPACK Version 3.12.0, source path /home/abui...IN/dppt02.f(3) — no date listed in the footer, so that’s the whole tea. 💅✨