multicore and data.table in R
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
I would like to call collect() on this but these are no longer parallel objects. How should one do this?
I think this is along the lines of what you want:
collect(dtb[, list(jobs = list(parallel(a+1))), by = b][, jobs])
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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