[Bioc-devel] reproducible with mclapply?

Dear all,

I have an issue of setting seed value when using parallel package.

library("parallel")
library("digest")

set.seed(0)
m <- mclapply(1:10, function(x) sample(1:10),

+               mc.cores=2)

digest(m, 'crc32')

[1] "4827c80c"

set.seed(0)
m <- mclapply(1:10, function(x) sample(1:10),

+               mc.cores=2)

digest(m, 'crc32')

[1] "e95b9134"

By default, set.seed() will be ignored since mclapply will set the seed
internally.

If we use mc.set.seed=FALSE to disable this feature. It works as indicated
below:

set.seed(0)
m <- mclapply(1:10, function(x) sample(1:10),

+               mc.cores=2, mc.set.seed = FALSE)

digest(m, 'crc32')

[1] "6bbada78"

set.seed(0)
m <- mclapply(1:10, function(x) sample(1:10),

+               mc.cores=2, mc.set.seed = FALSE)

digest(m, 'crc32')

[1] "6bbada78"

The problems is that the results are also depending on the number of cores.

set.seed(0)
m <- mclapply(1:10, function(x) sample(1:10),

+               mc.cores=4, mc.set.seed = FALSE)

digest(m, 'crc32')

[1] "a22e0aab"


Any idea?

Best Regards,
Guangchuang
--
--~--~---------~--~----~------------~-------~--~----~
Guangchuang Yu, PhD Candidate
State Key Laboratory of Emerging Infectious Diseases
School of Public Health
The University of Hong Kong
Hong Kong SAR, China
www: http://ygc.name
-~----------~----~----~----~------~----~------~--~---

        [[alternative HTML version deleted]]