lis_esolve...sidualnorm(3f)

✨ NAME ✨

okay so bestie, this is lis_esolver_get_residualnorm from the Lis Library Functions — it calculates the relative residual norm from the eigenvector 💅 lowkey a whole vibe check for your eigensolver's answer.

🎀 SYNOPSIS 🎀

subroutine lis_esolver_get_residualnorm(LIS_ESOLVER esolver, LIS_INTEGER
*residual, LIS_INTEGER ierr);

that's it, that's the whole signature, no cap 🫶

🌸 DESCRIPTION 🌸

So like, this subroutine calculates the relative residual norm ||lx - Ax||_2/l from the eigenvector x 💖

Translation? It's giving "how close is my answer to actually being an eigenvector," and the way that matters is literally everything when you're checking if your solve slayed or flopped 😭

🦋 INPUT 🦋

• esolver — The eigensolver 👑 (yes queen, your eigensolver, that one)

💜 OUTPUT 💜

• residual — The relative residual norm ||lx - Ax||_2/l ✨

💀 SEE ALSO 💀

• lis(3)
• http://www.ssisc.org/lis/

go peek at lis(3) if you're nosy, the docs are right there bestie, no gatekeeping 🙈

man page, 6 Sep 2012 — Lis Library Functions era, and she's still iconic 💖✨