SRC/dla_porcond.f(3)

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version 3.12.1 · 7 versions
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💖 NAME 💖

okay so bestie, this is the Library Functions Manual page for SRC/dla_porcond.f — yes, the whole page is literally named after the file, and it's serving serious LAPACK main-character energy. 🎀

✨ SYNOPSIS ✨

Functions/Subroutines

  • double precision function dla_porcond (uplo, n, a, lda, af, ldaf, cmode, c, info, work, iwork) — DLA_PORCOND estimates the Skeel condition number for a symmetric positive-definite matrix. no cap, that's the whole vibe. 💅

🦋 Function/Subroutine Documentation 🦋

double precision function dla_porcond (character uplo, integer n, double
    precision, dimension( lda, * ) a, integer lda, double precision,
    dimension( ldaf, * ) af, integer ldaf, integer cmode, double precision,
    dimension( * ) c, integer info, double precision, dimension( * ) work,
    integer, dimension( * ) iwork)

DLA_PORCOND estimates the Skeel condition number for a symmetric positive-definite matrix. it's giving numerical linear algebra but make it cute. 🧚

🎀 Purpose 🎀

okay so here's the tea: DLA_PORCOND estimates the Skeel condition number of op(A) * op2(C), where op2 is determined by CMODE like this:

CMODE =  1    op2(C) = C
CMODE =  0    op2(C) = I
CMODE = -1    op2(C) = inv(C)

the Skeel condition number is literally:

cond(A) = norminf( |inv(A)||A| )

and it's computed by computing scaling factors R such that diag(R)*A*op2(C) is row equilibrated, then computing the standard infinity-norm condition number. highkey iconic. ✨

🌸 Parameters 🌸

  • UPLO — UPLO is CHARACTER*1. = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. bestie, pick a triangle, any triangle. 🫶
  • N — N is INTEGER. The number of linear equations, i.e., the order of the matrix A. N >= 0. math said be non-negative. 💀
  • A — A is DOUBLE PRECISION array, dimension (LDA,N). On entry, the N-by-N matrix A. the main character matrix fr fr. 👑
  • LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N). respect the leading dimension. 💅
  • AF — AF is DOUBLE PRECISION array, dimension (LDAF,N). The triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, as computed by DPOTRF. slay, Cholesky ate. 🔥
  • LDAF — LDAF is INTEGER. The leading dimension of the array AF. LDAF >= max(1,N). another leading dimension check, periodt. ✨
  • CMODE — CMODE is INTEGER. Determines op2(C) in the formula op(A) * op2(C) as follows: CMODE = 1 → op2(C) = C; CMODE = 0 → op2(C) = I; CMODE = -1 → op2(C) = inv(C). pick your op2 era. 🦋
  • C — C is DOUBLE PRECISION array, dimension (N). The vector C in the formula op(A) * op2(C). the C vector is lowkey doing bits. 🍓
  • INFO — INFO is INTEGER. = 0: Successful exit. i > 0: The ith argument is invalid. bestie, if INFO is not zero, something is giving invalid argument energy. 😭
  • WORK — WORK is DOUBLE PRECISION array, dimension (3*N). Workspace. it works so the function can work. 💜
  • IWORK — IWORK is INTEGER array, dimension (N). Workspace. integer workspace, we love to see it. 🎀

💖 Author 💖

shoutout to the author icons:

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

Definition at line 139 of file dla_porcond.f.

🫶 Author 🫶

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mwah 💋 — this cutie page is from LAPACK Version 3.12.0, and the footer tag says SRC/dla_porcond.f(3). periodt. 🎀🌈

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