考虑到大量的输入属性可能导致复杂的BPNN，研究了用启发式方法和并行穷举方法约简属性的方法。
As complex information system usually contains large amount of attributes which can be used as the input variables of a model, it may bring about constructing a complicated BPNN.
穷举法是根据各个自变量所有可能取值相对应的函数值(输出值)寻找参数特征的一种分析方法。
Exhaustive method is an analysis method that looks for parameter property according to all obtainable corresponding function values (output values) for various independent variables.
解决这些问题的传统方法多采用解析法和穷举法，但这些方法都存在不同程度的缺点。
Analysis method and enumeration method are adopted to solve these problems traditionally, yet they have different defects in some aspects.
通过采用线性加权法、分离部分控制变量法，以及在一定范围内穷举，将问题简化，进而给出模型的求解方法。
We simplify the problems by using the linear weighted method, separate technique of partial control variables, and enumerating in certain range, then give out the solving plan of the model.
针对DES密钥空间过小而不能抵抗穷举攻击的问题，本文给出了一种基于混沌映射的密钥空间拓展方法，从而构造了一种混沌变形DES算法。
To aim at the problem that the key space of DES is too small to prevent exhaust attacks, an expanding key space method is proposed and a chaotic transformed DES algorithm is constructed.
结果表明，该方法在穷举量约为241时，能恢复出输入输出变换的子密钥信息以及密文对应的明文信息。
Result shows that this method can obtain the sub-keys and the corresponding plaintexts when the computing complexity of the improving attack is about 241.
由CPU下穷举搜索的性能较差，引出从软件方面将其并行化的改进方法。
The improvement in software was introduced due to poor CPU performance of the same search, a parallel realization was presented.
说明：搜索算法：利用计算机的高性能来有目的的穷举一个问题的部分或所有的可能情况，从而求出问题的解 的一种方法。
Search algorithm: the use of high-performance computers to have the purpose of an issue of exhaustion of some or all of the possible, and thus obtained the solutions of the problem.
说明：搜索算法：利用计算机的高性能来有目的的穷举一个问题的部分或所有的可能情况，从而求出问题的解 的一种方法。
Search algorithm: the use of high-performance computers to have the purpose of an issue of exhaustion of some or all of the possible, and thus obtained the solutions of the problem.
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