多核和数据表 [英] multicore and data.table in R

问题描述

我尝试使用多核函数并行与 data.table ，我不能真正想出正确的方法来做到这一点。代码：

I am attempting to use multicore function parallel with data.table and am unable to quite come up with the right way to do this. Code:

require(multicore)
require(data.table)
dtb = data.table(a=1:10, b=1:2)
x = dtb[,parallel(a+1),by=b]

> x
   b   pid fd
1: 1 12243  3
2: 1 12243  6
3: 2 12247  4
4: 2 12247  8

我想在这里调用 collect（） parallel 对象。

I would like to call collect() on this but these are no longer parallel objects. How should one do this?

推荐答案

我认为这是沿着你想要的方式：

I think this is along the lines of what you want:

collect(dtb[, list(jobs = list(parallel(a+1))), by = b][, jobs])

之所以没有 parallel 无法运行 collect 是因为您正在将它们转换为 列表将它们存储在列表中，这是我上面做的。

The reason you didn't have parallel objects any more and couldn't run a collect is because you were converting them to a list, instead of storing them in a list, which is what I did above.

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