lis_esolver...esidualnorm(3)

💖 lis_esolver_get_residualnorm — bestie edition 💖

okay so this is a page from the Lis Library Functions manual (the whole lis_esolver...esidualnorm(3) situation, iykyk) and honestly? it's a little baddie. let's get into it 🫶

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✨ NAME ✨

lis_esolver_get_residualnorm — get the relative residual norm for the specified eigenpair from the eigensolver 🌸

like. it tells you how good your eigenpair is doing. a little vibe check for your math, fr fr.

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✨ SYNOPSIS ✨

#include "lis.h"

LIS_INT lis_esolver_get_residualnorm(LIS_ESOLVER esolver, LIS_REAL
*residual);

yes bestie you gotta #include "lis.h" first, that's non-negotiable 💅

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✨ DESCRIPTION ✨

okay so what this does is: it gets the relative residual norm for the eigenpair you specified, straight from the eigensolver. and the formula, no cap, is literally:

||lx - Ax||_2/||lx||_2

that's it. that's the whole thing. it's giving "how far off am i" energy and honestly we love a self-aware function 🦋

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✨ INPUT ✨

• esolver — the eigensolver 👑 (yes. that one. the eigensolver.)

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✨ OUTPUT ✨

• residual — the relative residual norm, and it is exactly ||lx - Ax||_2/||lx||_2 ✨

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✨ EXIT STATUS ✨

the following exit values are returned, and you will be checking them:

• 0 — the process is normally terminated 🎀 slay, everything's fine, go off
• unspecified — an error occurred 😭 not the vibe. something went wrong.

fr fr, don't just ignore the exit status. "unspecified" is doing a lot of heavy lifting there and it's not a compliment 💀

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✨ SEE ALSO ✨

• lis(3)
• http://www.ssisc.org/lis/

go read lis(3) bestie, it's the main character of this whole franchise 🌈

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and that's the tea 🍓 this page came from the Lis Library Functions manual, dated 28 Aug 2014, and it lives at lis_esolver...esidualnorm(3). iconic behavior honestly. now go get those residual norms, you absolute legend 💜✨