我的默认答案曾经是“那么不要这样做”(使用foreach),因为snow包会为您执行此操作(可靠!)。
但正如@Spacedman 指出的那样,如果您想留在/ foreach家庭,Renaud 的新doRNG就是您正在寻找的。doFoo
真正的关键是一个 clusterApply 风格的调用,用于在所有节点上设置种子。并且以一种跨流协调的方式。哦,我有没有提到蒂尔尼、罗西尼、李和塞维奇科娃的雪已经为你做了近十年了?
编辑:虽然您没有询问snow,但为了完整起见,这里是命令行中的一个示例:
edd@max:~$ r -lsnow -e'cl <- makeSOCKcluster(c("localhost","localhost"));\
clusterSetupRNG(cl);\
print(do.call("rbind", clusterApply(cl, 1:4, \
function(x) { stats::rnorm(1) } )))'
Loading required package: utils
Loading required package: utils
Loading required package: rlecuyer
[,1]
[1,] -1.1406340
[2,] 0.7049582
[3,] -0.4981589
[4,] 0.4821092
edd@max:~$ r -lsnow -e'cl <- makeSOCKcluster(c("localhost","localhost"));\
clusterSetupRNG(cl);\
print(do.call("rbind", clusterApply(cl, 1:4, \
function(x) { stats::rnorm(1) } )))'
Loading required package: utils
Loading required package: utils
Loading required package: rlecuyer
[,1]
[1,] -1.1406340
[2,] 0.7049582
[3,] -0.4981589
[4,] 0.4821092
edd@max:~$
编辑:为了完整起见,这是您的示例与doRNG文档中的内容相结合
> library(foreach)
R> library(doMC)
Loading required package: multicore
Attaching package: ‘multicore’
The following object(s) are masked from ‘package:parallel’:
mclapply, mcparallel, pvec
R> registerDoMC(2)
R> library(doRNG)
R> set.seed(123)
R> a <- foreach(i=1:2,.combine=cbind) %dopar% {rnorm(5)}
R> set.seed(123)
R> b <- foreach(i=1:2,.combine=cbind) %dopar% {rnorm(5)}
R> identical(a,b)
[1] FALSE ## ie standard approach not reproducible
R>
R> seed <- doRNGseed()
R> a <- foreach(i=1:2,combine=cbind) %dorng% { rnorm(5) }
R> b <- foreach(i=1:2,combine=cbind) %dorng% { rnorm(5) }
R> doRNGseed(seed)
R> a1 <- foreach(i=1:2,combine=cbind) %dorng% { rnorm(5) }
R> b1 <- foreach(i=1:2,combine=cbind) %dorng% { rnorm(5) }
R> identical(a,a1) && identical(b,b1)
[1] TRUE ## all is well now with doRNGseed()
R>