递归函数中的 Cache

A CACHE IN RECURSIVE FUNCTIONS

由于 FFP 表达式具有引用透明性,对于给定的表达式每次计算都得到同样的结果,所以每一个值只需计算一次.然而,由于 FFP 语言支持递归程序,FC-机在处理递归结点时需要拷贝代码,运行时很难检查共享计算,因此可能导致重复计算,为此人们提出了用“记忆函数”(memo function)来解决这一问题.本文主要介绍如何在 FC-机中,利用 Cache 来实现“记忆函数”。最后给出了性能分析和在FFP 系统上的实际测试结果。

As FFP expressions have the property of reference transparent,for agiven expression,every computation gets the same result and a value is computed only once.However,because FFP language supports recursive programs,when FC-machineprocesses a recursive node,copying the node is necessary and it is difficult to check sharedcomputation and possible to cause repeated computation.For solving this problem,“memo function”is proposed.In this paper,how to use a Cache to implement“memofunction”in FC-machine is described mainly.The performance analysis and real testing re-sults in FFP system are given at the end of this paper.