INSTALL/dlamch.f(3)

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version 3.12.1 · 4 versions
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INSTALL/dlamch.f 💅✨

okay bestie, this page lives in the Library Functions Manual, and it’s all about INSTALL/dlamch.f — the .f file manual for dlamch and dlamc3. It’s giving numerical machine-parameters realness, no cap. 🎀

✨ NAME ✨

INSTALL/dlamch.f — that’s the name, bestie. Periodt. 🌸

🎀 SYNOPSIS 🎀

Functions/Subroutines

double precision function dlamch (cmach)
    DLAMCH
double precision function dlamc3 (a, b)
    DLAMC3

💖 Function/Subroutine Documentation 💖

double precision function dlamc3 (double precision a, double precision b)

DLAMC3 Purpose:

so DLAMC3 is here to force A and B to be stored before the addition of A and B happens. Why? For situations where optimizers might hold one of these in a register. That’s the whole vibe. 🧚

Author

LAPACK is a software package provided by Univ. of Tennessee, Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd.. 🫶

Parameters

  • A — A is a DOUBLE PRECISION.
  • B — B is a DOUBLE PRECISION. The values A and B.

📍 Definition at line 171 of file dlamch.f.

double precision function dlamch (character cmach)

DLAMCH

Purpose:

DLAMCH determines double precision machine parameters. That’s it, that’s the job. ✨

Parameters

CMACH — CMACH is CHARACTER*1. It specifies the value to be returned by DLAMCH, like a lil’ menu of machine-parameter treats:

  • = 'E' or 'e', — DLAMCH := eps
  • = 'S' or 's , — DLAMCH := sfmin
  • = 'B' or 'b', — DLAMCH := base
  • = 'P' or 'p', — DLAMCH := eps*base
  • = 'N' or 'n', — DLAMCH := t
  • = 'R' or 'r', — DLAMCH := rnd
  • = 'M' or 'm', — DLAMCH := emin
  • = 'U' or 'u', — DLAMCH := rmin
  • = 'L' or 'l', — DLAMCH := emax
  • = 'O' or 'o', — DLAMCH := rmax

and where these lil’ cuties mean:

  • eps = relative machine precision
  • sfmin = safe minimum, such that 1/sfmin does not overflow
  • base = base of the machine
  • prec = eps*base
  • t = number of (base) digits in the mantissa
  • rnd = 1.0 when rounding occurs in addition, 0.0 otherwise
  • emin = minimum exponent before (gradual) underflow
  • rmin = underflow threshold - base**(emin-1)
  • emax = largest exponent before overflow
  • rmax = overflow threshold - (base**emax)*(1-eps)

Author

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

📍 Definition at line 68 of file dlamch.f.

🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code. 💖

okay bestie, that’s the whole INSTALL/dlamch.f(3) page. The footer is giving source/version realness: LAPACK, Version 3.12.0, and INSTALL/dlamch.f(3). Slay. 💅✨

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