DPOT02(3)

okay bestie, welcome to the dpot02.f(3) page from the Library Functions Manual — LAPACK routine realness, but make it cute. 💅✨

NAME 🎀

the whole name situation is literally this source file path:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/dpot02.f

no extra nickname, no secret identity. it’s giving “my name is my path” energy. 🫶

SYNOPSIS 🦋

Functions/Subroutines

subroutine DPOT02 (uplo, n, nrhs, a, lda, x, ldx, b, ldb, rwork, resid)
           DPOT02

Function/Subroutine Documentation 🔥

here’s the full signature, copied exactly because we do not mess with function signatures in this house:

subroutine DPOT02 (character uplo, 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)
       DPOT02

and yes, DPOT02 appears again on its own line. iconic. 👑

Purpose 🎯

!>
!> DPOT02 computes the residual for the solution of a symmetric system
!> of linear equations  A*x = b:
!>
!>    RESID = norm(B - A*X) / ( norm(A) * norm(X) * EPS ),
!>
!> where EPS is the machine epsilon.
!>

so basically DPOT02 computes the residual for the solution of a symmetric system of linear equations A*x = b, and the residual formula is right there: RESID = norm(B - A*X) / ( norm(A) * norm(X) * EPS ), where EPS is the machine epsilon. no cap, that’s the whole purpose. 💖

Parameters 🌸

every parameter, every type, every constraint — no skipping, bestie:

• UPLO — CHARACTER*1. Specifies whether the upper or lower triangular part of the symmetric matrix A is stored: = 'U': Upper triangular, = 'L': Lower triangular. choose your triangle, bestie. 💅
• N — INTEGER. The number of rows and columns of the matrix A. N >= 0.
• NRHS — INTEGER. The number of columns of B, the matrix of right hand sides. NRHS >= 0.
• A — DOUBLE PRECISION array, dimension (LDA,N). The original symmetric matrix A.
• LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N)
• X — DOUBLE PRECISION array, dimension (LDX,NRHS). The computed solution vectors for the system of linear equations.
• LDX — INTEGER. The leading dimension of the array X. LDX >= max(1,N).
• B — 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. this is important: it gets changed, so don’t act surprised. 😭
• LDB — INTEGER. The leading dimension of the array B. LDB >= max(1,N)
• RWORK — DOUBLE PRECISION array, dimension (N).
• RESID — DOUBLE PRECISION. The maximum over the number of right hand sides of norm(B - A*X) / ( norm(A) * norm(X) * EPS ).

Author 👑

the author lineup, exactly as listed:

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

Definition at line 125 of file dpot02.f.

Author 🫶

and the Doxygen-generated author note says: Generated automatically by Doxygen for LAPACK from the source code. periodt.

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shoutout to LAPACK Version 3.12.0, the source path /home/abui...IN/dpot02.f(3), and the date — which this footer literally didn’t print, so we’re calling it a mystery date 🕵️‍♀️💖