NVIDIA/AMGX

Right-hand-side of Poisson examples should be changed

Open

#30 opened on May 31, 2018

View on GitHub
 (4 comments) (0 reactions) (0 assignees)Cuda (186 forks)auto 404
enhancementgood first issue

Repository metrics

Stars
 (679 stars)
PR merge metrics
 (PR metrics pending)

Description

AMGX ships with many nice sample programs, including simple implementation of Poisson-like equations. Currently, the charge function (e.g. in A x = b, the array b) is set to 1.d0 everywhere.

This is a poor choice, since integrating a constant over larger and large volumes gives you an exponentially growing solution. As a consequence, the sample cases have terrible convergence rates and do not scale as the problem size is increased.

I suggest a better choice: set b = sin( 2 * pi * x / Lx ) * sin( 2 * pi * y / Ly ) * sin( 2 * pi * z / Lz ), which satisfies either periodic or Dirichlet boundary conditions. This is more representative of the use of a Poisson solver.

Contributor guide

Research direction
Locate the Poisson example source files in the AMGX repository, understand the current right hand side setup, then modify the charge function to use sin(2*pi*x/Lx)*sin(2*pi*y/Ly)*sin(2*pi*z/Lz) and adjust boundary conditions accordingly.
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++CUDAGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60