VINE --用粒子模拟天体物理系统的数字代码II：实现和性能特点
VINE -- A numerical code for simulating astrophysical systems using particles II: Implementation and performance characteristics
摘要：
我们继续介绍VINE。我们首先描述的串行和共享内存并行计算机上的VINE是打算运行的相关架构属性，并描述其对代码本身的设计的影响。我们继续详细描述对内存中粒子数据的布局以及我们用于访问该数据的二叉树的实现所做的一些优化，以用于引力计算和搜索SPH邻居粒子。我们描述了修改必要的代码，以获得部队有效地从特殊用途的“GRAPE”硬件。我们得出结论，一系列广泛的性能测试，这表明，代码可以有效地运行，无需修改，在小型工作站上的串行或并行使用OpenMP编译器指令的大规模，共享内存的并行机。我们分析了代码优化的效果，并估计它们将其整体性能提高了一个数量级以上，超过了许多其他树代码。重力和SPH计算的缩放并行性能，以及大多数模拟中最昂贵的组件，在我们可用的最大机器尺寸（Origin~3000上的120个处理器）下几乎是线性的。在类似的精度下，在GRAPE树模式下使用的VINE的性能比在仅主机模式下使用的VINE的性能慢大约两倍。GRAPE/主机通信的优化可以将速度提高三倍，但尚未在VINE中实现。
英文摘要：
We continue our presentation of VINE. We begin with a description of relevant architectural properties of the serial and shared memory parallel computers on which VINE is intended to run, and describe their influences on the design of the code itself. We continue with a detailed description of a number of optimizations made to the layout of the particle data in memory and to our implementation of a binary tree used to access that data for use in gravitational force calculations and searches for SPH neighbor particles. We describe modifications to the code necessary to obtain forces efficiently from special purpose `GRAPE' hardware. We conclude with an extensive series of performance tests, which demonstrate that the code can be run efficiently and without modification in serial on small workstations or in parallel using OpenMP compiler directives on large scale, shared memory parallel machines. We analyze the effects of the code optimizations and estimate that they improve its overall performance by more than an order of magnitude over that obtained by many other tree codes. Scaled parallel performance of the gravity and SPH calculations, together the most costly components of most simulations, is nearly linear up to maximum machine sizes available to us (120 processors on an Origin~3000). At similar accuracy, performance of VINE, used in GRAPE-tree mode, is approximately a factor two slower than that of VINE, used in host-only mode. Optimizations of the GRAPE/host communications could improve the speed by as much as a factor of three, but have not yet been implemented in VINE.
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