ZPOT02(3)

💅 ZPOT02(3) — bestie edition

okay so this is a page from the Library Functions Manual (the LAPACK one, yeah that LAPACK), and it's all about a lil Fortran subroutine called ZPOT02. it lives at this absolute unit of a path, no cap:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/zpot02.f

---

✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/zpot02.f

like. that's the whole name. it's giving "i am the file and the file is me." iconic behavior honestly 🎀

---

🦋 SYNOPSIS 🦋

Functions/Subroutines

subroutine ZPOT02 (uplo, n, nrhs, a, lda, x, ldx, b, ldb, rwork, resid)

ZPOT02 — that's her. that's the girl. 💖

---

🌸 Function/Subroutine Documentation 🌸

subroutine ZPOT02 (character uplo, integer n, integer nrhs, complex*16,
    dimension( lda, * ) a, integer lda, complex*16, dimension( ldx, * ) x,
    integer ldx, complex*16, dimension( ldb, * ) b, integer ldb, double
    precision, dimension( * ) rwork, double precision resid)

ZPOT02 — yes she's back, we love a repeat appearance 👑

🧚 Purpose 🧚

okay so here's the whole point of her existence, and it's literally written in the source as a doc comment:

!>
!> ZPOT02 computes the residual for the solution of a Hermitian system
!> of linear equations  A*x = b:
!>
!>    RESID = norm(B - A*X) / ( norm(A) * norm(X) * EPS ),
!>
!> where EPS is the machine epsilon.
!>

so she computes the residual for the solution of a Hermitian system of linear equations A*x = b, and the formula is right there ↑. EPS is the machine epsilon, periodt. 🔥

---

💜 Parameters 💜

every single one, in order, nothing skipped, we do NOT leave the girlies out:

• UPLO — UPLO is CHARACTER*1. specifies whether the upper or lower triangular part of the Hermitian matrix A is stored:
  • = 'U': Upper triangular
  • = 'L': Lower triangular
• N — N is INTEGER. the number of rows and columns of the matrix A. N >= 0.
• NRHS — NRHS is INTEGER. the number of columns of B, the matrix of right hand sides. NRHS >= 0.
• A — A is COMPLEX*16 array, dimension (LDA,N). the original Hermitian matrix A. 🫶
• LDA — LDA is INTEGER. the leading dimension of the array A. LDA >= max(1,N)
• X — X is COMPLEX*16 array, dimension (LDX,NRHS). the computed solution vectors for the system of linear equations. main character energy fr fr.
• LDX — LDX is INTEGER. the leading dimension of the array X. LDX >= max(1,N).
• B — B is COMPLEX*16 array, dimension (LDB,NRHS). 👀 listen:
  • On entry, the right hand side vectors for the system of linear equations.
  • On exit, B is overwritten with the difference B - A*X. (she's not a storage girlie, she replaces.)
• LDB — LDB is INTEGER. the leading dimension of the array B. LDB >= max(1,N).
• RWORK — RWORK is DOUBLE PRECISION array, dimension (N)
• RESID — RESID is DOUBLE PRECISION. the maximum over the number of right hand sides of norm(B - A*X) / ( norm(A) * norm(X) * EPS ). 💀 she's the final boss of the whole routine honestly.

---

👑 Author 👑

the credit roll, respect to everyone here:

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

Definition at line 125 of file zpot02.f. ⭐

---

🌈 Author (again, but the meta one) 🌈

Generated automatically by Doxygen for LAPACK from the source code. 🙈 so nobody hand-wrote this page, a robot did, and we thank her for her service.

---

that's the whole thing bestie, you ate. go forth and compute residuals 🍓

LAPACK — Version 3.12.0 · /home/abui...IN/zpot02.f(3) · mwah, see u in the next manpage 💅✨🦋