lanl/singularity-eos

Add extrapolation to rho = 0 for spiner tables

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#541 opened on Aug 15, 2025

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enhancementgood first issuehelp wanted

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Description

Right now spiner's logarithmic interpolation means that it can never extrapolate to exactly rho = 0. An easy fix would be to check if rho < the minimum density on the table, and if it is compute pressure as $P(rho, T) = \rho \Gamma(\rho_m, T)$ where here $\rho_m$ is the minimum density and $\Gamma$ is the Gruneisen coefficient. And one could do a similar thing for temperature.

Thanks @jhp-lanl for reminding me of this issue.

Contributor guide

Research direction
Implement a check for rho < minimum density in the spiner table, and compute pressure as rho * Gamma(rho min, T) for extrapolation. Similar for temperature.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70