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发表于 2011-12-18 21:27:17
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本帖最后由 refla 于 2013-3-15 18:33 编辑
好了，终于来到条目内容了http://en.wikipedia.org/wiki/MilkyWay@Home
Contents
1 Purpose and design
2 Project details and statistics
3 Scientific results
4 See also
5 References
6 External links
Purpose and design
目标与计划
MilkyWay@home is a collaboration between the Rensselaer Polytechnic Institute's departments of Computer Science and Physics, Applied Physics and Astronomy and is supported by the U.S. National Science Foundation. It is operated by a team that includes astrophysicist Heidi Jo Newberg and computer scientists Malik Magdon-Ismail, Boleslaw Szymanski and Carlos A. Varela.
MilkyWay@home 是伦斯勒理工学院的计算机科学系、物理系（包括应用物理）与天文系的一个合作项目。该项目得到美国国家科学基金会的支持，由一个团队负责执行。这个团队包括了天体物理学家海蒂·乔·纽伯格（Heidi Jo Newberg）与计算机科学家马利克·美格登·伊斯梅尔（Malik Magdon-Ismail）、博莱斯瓦夫·斯曼斯基（Boleslaw Szymanski）、卡洛斯·瓦雷拉（Carlos A.Varela）等人。
By mid-2009 the project's main astrophysical interest is in the Sagittarius stream,[2] a stellar stream emanating from the Sagittarius Dwarf Elliptical Galaxy which partially penetrates the space occupied by the Milky Way and is believed to be in an unstable orbit around it, probably after a close encounter or collision with the Milky Way[3] which subjected it to strong galactic tide forces. Mapping such interstellar streams and their dynamics with high accuracy is expected to provide crucial clues for understanding the structure, formation, evolution, and gravitational potential distribution of the Milky Way and similar galaxies. It could also provide insight on the dark matter issue. As the project evolves it might turn its attention to other starstreams.
直到 2009 年年中，项目组在天体物理学方面的研究兴趣（interest），主要集中在射手座流（the Sagittarius stream）上。射手座流由人马座矮椭圆星系（the Sagittarius Dwarf Elliptical Galaxy）射出，其中有一段进入到银河系所属的空间。据信，射手座流的轨道并不稳定，在与银河系接近或碰撞之后，会被银河系的强大引力俘获（subject）过来。科学家对高精度地绘制出这类星际流以及它们的运动方式（dynamics），寄予了厚望。因为，这对于了解恒星流的结构、形成、演化，以及银河系的引力势分布（gravitational potential distribution），都能提供关键性线索。其研究结果还可应用到同类星系中去。这还有助于人们进一步解开关于暗物质的谜题。 随着项目进程的推进，项目的注意力将转向其他恒星流。
Using data from the Sloan Digital Sky Survey, MilkyWay@home divides starfields into wedges of about 2.5 deg. width and applies self-optimizing probabilistic separation techniques (i.e., evolutionary algorithms) to extract the optimized tidal streams. The program then attempts to create a new, uniformly dense wedge of stars from the input wedge by removing streams of data. Each stream removed is characterized by 6 parameters: percent of stars in the stream; the angular position in the stripe; the three spatial components (two angles, plus radial distance from Earth) defining the removed cylinder; and a measure of width. For each search, the server application keeps track of a population of individual stars, each of which is attached to a possible model of the Milky Way.
MilkyWay@home 使用来自斯隆数字巡天的数据，以 2.5 度角来划分星空（starfields）。划分出来的星空，称之为“工作区（wedge）”。MilkyWay@home 采用了“自优化概率分类技术（self-optimizing probabilistic separation techniques）”，即进化算法，从数据中找出一些合适的潮汐流。然后，程序在原始（input）工作区中，尝试删除掉那些潮汐流的数据，以便建立一个新的、星星密度（分布）均匀的“工作区”。被删除的潮汐流会用 6 个参数记录下它们所在的区间（cylinder）：恒星数在流中所占的比例，在数据条中的角度位置，标注被删除区间的球坐标（两个角度加上与地球距离），以及一个宽度单位。对于每次搜索，服务器程序都会持续跟踪那些单独的星群，以便加入到某个可能的银河系模型。
Project details and statistics
项目细节以及统计数据
MilkyWay@home has been active since 2007, and optimized client applications for 32-bit and 64-bit operating systems became available in 2008. Its screensaver capability is limited to a revolving display of users' BOINC statistics, with no graphical component.
MilkyWay@home 项目在 2007 年正式上马，优化过的客户端程序（包括 32 位和 64 位系统）也已于 2008 年发布。它的屏保程序只是简单地把用户的 BOINC 统计数据旋转显示，没有任何图形内容。
The workunits that are sent out to clients used to require only 2–4 hours of computation on modern CPUs, however they were scheduled for completion with a short deadline (typically, 3 days). By early 2010 the project routinely sent much larger units that take 15–20 hours of computation time on the average processor core, and are valid for about a week from download. This makes the project less suitable for computers that are not in operation for periods of several days, or for user accounts that do not allow BOINC to compute in the background.
起初，主流（modern）CPU 需要花费 2 ～ 4 个小时来完成一个工作单元（workunits）。因此，返还工作单元的时限很短，一般设定为 3 天。到了 2010 年初，完成工作单元的平均时间提高到 15 ～ 20 个小时。相应地，返还时间也改为 7 天左右。这次调整使得 MilkyWay@home 更不适合那些几天都不开一次机的算友，也不适合那些不允许 BOINC 以后台模式运行的算友。
The project's data throughput progress has been very dynamic recently. In mid-June 2009, the project had about 24,000 registered users and about 1,100 participating teams in 149 countries, and was operating at 31.7 TeraFLOPS. As of 12 January 2010, these figures were at 44,900 users and 1,590 teams in 170 countries, but average computing power had jumped to 1,382 TFlops,[4] which would rank MilkyWay@home second among the TOP500 list of supercomputers. MilkyWay@home is currently the 2nd largest distributed computing project behind Folding@Home which crossed 5,000 TFlops in 2009.
MilkyWay@home 的数据处理能力（data throughput）在近期得到飞速提高。2009 年 6 月中旬，分布在 149 个国家的 24,000 名算友，组成了大约 1,100 支队伍，贡献出每秒 31.7 万亿次的浮点计算能力。截止 2010 年 1 月 12 日，算友数量提升到 44,900，组成了分布在 170 个国家的 1,590 支队伍，而算力则激增至每秒 1,382 万亿次，令 MilkyWay@home 二度荣登超级计算机 500 强的名单。如今，MilkyWay@home 已经是全球第二大的分布式计算项目，紧跟在 Folding@Home 之后。名列第一的分布式计算项目 Folding@Home 在 2009 年的时候，算力就超过了每秒 5,000 万亿次。
That data throughput massively outpaced new user acquisition is mostly due to the deployment of client software that uses commonly available medium and high performance graphics processing units (GPUs) for numerical operations in Windows and Linux environments. MilkyWay@home CUDA code for a broad range of Nvidia GPUs was first released on the project's code release directory on June 11, 2009 following experimental releases in the MilkyWay@home(GPU) fork of the project. An application for ATI Technologies GPUs is also available and currently outperforming the CUDA application.[citation needed] For example, a task that requires 10 minutes using an AMD HD3850 GPU or 5 minutes using an AMD HD4850 GPU, requires 6 hours using one core of an AMD Phenom II processor at 2.8 GHz.
数据处理能力的增长速度之所以能远超算友数的增长速度，主要是因为 MilkyWay 部署了使用 GPU 作为计算工具的客户端软件（包括 Windows 和 Linux 系统）。而通常情况下，只有媒体处理和高性能计算才会用到 GPU 技术。MilkyWay@home 写的 CUDA 代码，能运行在多种英伟达（NVidia）的 GPU 上。CUDA 版本的源代码在 2009 年 6 月 11 日首次公开，放在 MilkyWay@home(GPU) 分支下。【注1】不久，基于 ATI 技术的 GPU 程序也有了，而且效率比 CUDA 还高（暂时没有具体数据）。例如，如果一个任务需要在 HD3850 上跑 10 分钟，则 HD4850 只需 5 分钟，而 2.8 GHz 的 Phenom II CPU 只能作为单线程任务跑 6 个小时。
【注1】代码位置：http://milkyway.cs.rpi.edu/milkyway/forum_thread.php?id=906#25013
Scientific results
科学成果
Large parts of the MilkyWay@home project build on the thesis of Nathan Cole which has been published in the highly reputed Astrophysical Journal.[5] Other results have been presented at several astrophysical and computing congresses.[6]
MilkyWay@home 项目取得的主要成果，大部分都作为弥敦道·科尔（Nathan Cole）的论文，刊发在享誉盛名的天体物理学杂志上。其它成果也已在多个“天体物理学与计算”大会上讨论过。 |
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发表于 2011-12-18 20:00:26
