PSLABAD(l)

📦 version 1.5, in ubuntu jammy

✨ PSLABAD — LAPACK auxiliary routine (version 1.5) ✨

okay bestie, welcome to PSLABAD, a lil LAPACK auxiliary routine from the l (that's the local / scalar-ish family, iykyk) 💅

🌸 NAME 🌸

PSLABAD — takes as input the values computed by PSLAMCH for underflow and overflow, and returns the square root of each of these values if the log of LARGE is sufficiently large 🎀

✨ SYNOPSIS ✨

SUBROUTINE PSLABAD( ICTXT, SMALL, LARGE )

    INTEGER         ICTXT

    REAL            LARGE, SMALL

💖 PURPOSE 💖

So here's the vibe: PSLABAD takes as input the values computed by PSLAMCH for underflow and overflow, and returns the square root of each of these values if the log of LARGE is sufficiently large. 🫶

This subroutine is intended to identify machines with a large exponent range, such as the Crays, and redefine the underflow and overflow limits to be the square roots of the values computed by PSLAMCH. It's needed because PSLAMCH does not compensate for poor arithmetic in the upper half of the exponent range, as is found on a Cray. no cap, that's just how it is 😭

In addition, this routine performs a global minimization and maximization on these values, to support heterogeneous computing networks. networking era fr fr 🌐✨

👑 ARGUMENTS 👑

  • ICTXT — (global input) INTEGER The BLACS context handle in which the computation takes place. basically the group chat this whole operation happens in 💬
  • SMALL — (local input/local output) REAL On entry, the underflow threshold as computed by PSLAMCH. On exit, if LOG10(LARGE) is sufficiently large, the square root of SMALL, otherwise unchanged. she either glows up or stays exactly the same 💅
  • LARGE — (local input/local output) REAL On entry, the overflow threshold as computed by PSLAMCH. On exit, if LOG10(LARGE) is sufficiently large, the square root of LARGE, otherwise unchanged. same deal, iconic behavior ⭐
heads up bestie: both SMALL and LARGE are local input / local output — so every process in the context brings its own values, and the routine does that global minimization/maximization thing to keep everybody on the same page. 🌈

LAPACK version 1.5 🌸 12 May 1997 🎀 — yeah she's an old queen but she still slays, mwah 💖 bye bestie!! 🦋

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