If more than one column is aggregated using the same grouping key or without a grouping key, then all the aggregations are computed within the same operation with a single pass over the data.

如果利用相同的分组关键字或者没有分组关键字，来聚合多个列，那么，所有的聚合都在单个数据传递中的相同操作中进行。

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For the specific implementation of PCNNs, a PCNN was forced to be a single pass network. And simplified model, look-up threshold table, and integer operation were used to decrease the time complexity.

在PCNN的具体实现中，网络被强制为单循环网络，通过简化模型、阈值查找表、整数运算等技巧，降低了PCNN的时间复杂度。

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