for the simulation sub-module. Te clients input parameters and submit computing tasks through the applet user interface, and the computing task scheduling system invokes the distributed computing object method through the CORBA mechanism. Post-Process Module—Te post-process module is designed to display the temperature field file and defect file. Because of the amount of data being transferred, displaying the result file online is difficult. So, a post-process module can generate an image of the simulation result, or the client can download post-process module software from the web and view the results on a local computer. Network Security Module—Security is one key to a
network-applied system enterprise. Te network security module authorizes the user’s privilege and prevents tamper- ing and unauthorized users from reading legal users’ files. Computing Management Module—Te computing man-
agement module manages every user’s computing process. If for some reason errors occur, the computing management module can end these processes. Account Module—Te account module computes the fee
for the computing server rental. Material Database Module—Accurate parameters of met-
alcasting material capabilities are required to obtain accurate simulation results. Tis module provides a reference material database. Clients may also input their own material database.
Finding Your Place in Line Because of limited resources, incoming tasks must be
scheduled for computer server availability. Te computing task schedule system maintains a computing server status table, computing process status table and computing task table. Te computing server status table maintains the list of servers, the task table queues computing operations with a first-in-first-out sequence, and the computing process status table maintains the list of computing process status. Te scheduling system uses one of the following algorithms
to determine when to perform a metalcaster’s simulation: Round-Robin Scheduling: Te round-robin scheduling
algorithm sends each incoming computing request to the next computer server in its list. Tus, in a three-server cluster (servers A, B and C), request 1 would go to server A, request 2 would go to server B, request 3 would go to server C and request 4 would go to server A, completing the cycling (or round-robin of servers). Tis algorithm treats all computing servers equally, whether the server is a single computer or multiple machines and the memory is large or small. Weighted Round-Robin Scheduling: Te weighted round-
robin scheduling is designed to better handle servers with different processing capacities. Each server is assigned a weight—an integer value that indicates the processing capac- ity. Te default weight is 1. For example, if the real servers A, B and C have the weights 4, 3 and 2, the scheduling sequence would be AABABCABC in a period. Weighted round-robin scheduling is better than round-robin scheduling when the processing capacity of computer servers are different. ■
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核心计算模块 该模块将CAD文件进行网格划分，指 导模拟计算子模块需要的初始数据。客户通过界面输入 参数和提交计算任务，计算任务排队系统通过CORBA 机制激活计算目标方法。 后处理模块 后处理模块用来显示温度场和缺陷文 件。由于要传递大量数据，在线显示结果文件很困难。 因此后处理模块可以生成模拟结果图像，或者用户可 以下载后处理模块然后在自己的计算机上显示并查看 结果。
网络安全模块 安全是网络系统企业的核心。网络安 全模块管理用户的权限，防止入侵和未被授权者读取用 户文件。
计算管理模块 计算管理模块管理用户的计算进程。 如果出现计算错误，计算管理模块将结束这些进程。 账户管理模块 该模块核算计算服务器的租金。 材料数据库模块 精确的计算结果需要精确的铸造材 料数据库。该模块提供参考数据库。用户也可以输入自 己的材料数据库。
在线找到自己任务的进程
由于资源有限，进来的任务必须进行排队，以利于 计算服务器的可用性。计算任务排队系统维护计算服务 状态表。
计算任务排队系统采用下面的算法决定何时开始进 行数值模拟
轮叫调度排队方法（Round-Robin）： 该算法将 各计算请求发送到下一个可用计算服务器。因此，在一 个有三个服务器的机群（服务器A,B,C）中，请求1将 会发送到服务器A，请求2发送到服务器B,请求3发送到 服务器C，则请求4发送到服务器A就实现了循环（或者 服务器循环）。不管各服务器是单机，还是多机器，也 不管其内存大小，该算法平等对待每个计算服务器。 加权轮叫调动排队系统: 该算法能够更好地处理各服 务器处理能力不同的情况。每个服务器有一个权重， 这是一个整数显示其处理能力。默认值为1。例如，如 果服务器A、B、C的权重为4、3、2，那么一个周期 内的计算排队顺序为AABABCABC。当各服务器的计 算能力不同时，加权任务排队系统比没有权重的排队 系统要好。 ■
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FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION Summer 2011
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