Collaborative Research: Abacus: A New State-of-the-Art Cosmological N-body Code

该项目将进一步开发一种新的用于宇宙N体模拟的计算机代码。算盘实现了一种计算引力的新方法，该方法比目前的方法快100倍，精度也高得多。它可以在商用图形处理器上运行，性价比得到了极大的提高。大尺度结构的观测测量依赖于宇宙学模拟来校准其统计估计器并计算准确的误差条，因此必须运行高精度模拟的大网格，以实现当前和未来宇宙学测量的潜力。算盘依靠的是一项数学突破，它实现了粒子上的近场和远场作用力的完全分开。目前的工作将增加对单个粒子时间步长、即时群体发现和合并树构建以及光锥输出的基本支持。这项研究还将把Abacus扩展到并行实现，并允许发布代码的公共版本。研究团队将使用Abacus进行第一套大型模拟，其产生的晕星表、合并树和光锥输出将公开，作为当前和未来调查项目的直接好处。算盘是游戏规则的改变者，它为更多的天体物理学家提供了进行大型模拟的能力，而此时对大型模拟的需求将会加剧。算盘的数学方法在求解椭圆型方程方面开辟了新的可能性，椭圆型方程是广泛的科学和工程学科中最常见的计算任务之一。在此过程中，该项目将培养一名博士后研究员和一名研究生。

This project will further the development of a new computer code for cosmological N-body simulations. Abacus implements a novel method for computing gravitational forces that is a hundred times faster and substantially more accurate than current methods. It can be run on commodity graphics processing units and offers a vast improvement in price-performance. Observational surveys of large scale structure rely on cosmological simulations to calibrate their statistical estimators and compute accurate error bars, making it essential to run large grids of highly accurate simulations in order to realize the potential of current and future cosmological surveys. Abacus relies on a mathematical breakthrough that accomplishes a clean split between the near-field and far-field force on particles. The present work will add essential support for individual particle time steps, on-the-fly group finding and merger tree building, and light-cone outputs. The study will also extend Abacus to a parallel implementation, and allow release of a public version of the code.The research team will use Abacus for a first suite of large simulations, whose resulting halo catalogs, merger trees, and light-cone outputs will be made public as a direct benefit to current and future survey projects. Abacus is a game-changer, opening up the ability to do large simulations to many more astrophysicists at exactly the time that the need for large sets of large simulations will intensify. The mathematical approach of Abacus opens up substantial new possibilities in the solution of elliptic equations, one of the most common computational tasks across a wide range of scientific and engineering disciplines. Along the way, the project will train a post-doctoral researcher and a graduate student.